Poly-(adenosine diphosphate-ribose)-polymerase (PARP) are cellular enzymes that play crucial roles in various cell processes like replication, transcription, cellular repair, and also death [224]. PARP detects single-strand breaks and triggers the activation of cellular machinery involved in the repair of the single-strand break. Studies have shown that PARP inhibitors (PARPi) exhibit enhanced radiosensitivity when combined with IR. Radiation works by damaging the DNA, which can activate the single-strand break (SSB) repair pathway like base excision repair (BER) or double-strand break (DSB) pathways like the HR and the NHEJ pathway (more details in Chap. 3). SSB, if unrepaired, gets converted to double-stranded breaks, which consequently hinder normal cellular processes. PARPi imparts radiosensitivity through the SSB and base excision pathway, which substantially increases the risk to collapsed replication fork, thereby producing a stable DSB [225]. Due to the crucial role of PARP in the DNA repair pathway, PARPi have proved as effective radiosensitizers, especially in tumors harboring DNA repair deficiencies like the BRCA mutation. The replication-reliant operations of PARPi facilitate the establishment of differential outcomes in tumor and healthy tissues. Other mechanisms that are known to induce the radiosensitization effects include inhibition of chromatin remodeling, G2/M arrest, vasodilatory effect induced by PARPi, etc. Characteristically, factors that affect radiosensitivity are the capability of tumors to repair the damage, redistribution of the cell cycle, process of reoxygenation, vascular endothelial damage process, tumor immunity, and repopulation of the tumor tissue. A radiosensitizer should have the potential not only to influence these processes but also prevent the increase in the toxicity. Since PARPi possess most of these qualities necessary for being a potential radiosensitizer (Fig. 11.26), it has gained interest in the medical community [226].

An illustration of modes of action and advantages. Mode of action: Inhibition of D N A repair and chromatin remodeling, G 2 M arrest, decrease in hypoxia, and vasodilatory effect. Advantages: Replication, protection of normal tissue, impairing synthetic lethality, and low toxicity molecules.

Fig. 11.26
The advantages and various modes of action by which PARPi enhance the radiosensitivity of tumor cells. Adapted from “Poly-(ADP-ribose)-polymerase inhibitors as radiosensitizers: a systematic review of preclinical and clinical human studies,” by [224], Licensed under CC BY 3.0


An illustration of modes of action and advantages. Mode of action: Inhibition of D N A repair and chromatin remodeling, G 2 M arrest, decrease in hypoxia, and vasodilatory effect. Advantages: Replication, protection of normal tissue, impairing synthetic lethality, and low toxicity molecules.


Nitroxides are a class of stable free radical compounds that exhibit antioxidant mechanisms, thereby safeguarding the cells from several lethal agents like superoxide and hydrogen peroxide (also described in Sect. 11.1.2). However, the rationale to use nitroxides in cancer RT comes from the role of free radicals in tumor development and capacity of inhibitors of radical reactions to suppress tumorigenesis. The underlying mode of action of nitroxyls exhibiting the radiosensitization effect can be attributed to cell signaling, enhanced blood flow to the tumor, consequences on the cellular respiration, and generation of reactive oxygen and nitrogen species that can operate as metabolite radiosensitizers. The effects of nitroxides with radiation were found conflicting, leading to uncertainty about their radiosensitizing nature.


Tempol (TPL) is a piperidine nitroxide that possesses an unpaired electron and goes through swift reversible transfer among the three forms: nitroxide, hydroxylamine, and oxoammonium cation. Based on its concentration in the cell, it can act as an oxidative or reductive agent. In cancer cells, TPL favorably inhibits growth by increasing the generation of cellular ROS [227]. When used with RT and chemotherapy, TPL exhibits a differential effect of protecting the normal healthy cells from RT and cisplatin-mediated damage, whereas in cancer cells, tempol is reduced to its hydroxylamine form that is unable to protect the cells from radiation and cisplatin-mediated damage. This differential or selective acting on cancer cells while sparing the normal cells is particularly of significance in cancer radio- as well as chemotherapy [228]. It was observed that the anticancer effects of cisplatin increased due to the prooxidant activity of TPL via the increased ROS-mediated cell apoptosis [227]. In several cancer cell lines, TPL was able to free radical-dependent apoptosis. On 24-h exposure to TPL, human promyelocytic leukemic cell line (HL-60) showed reduced levels of mitochondrial and intracellular glutathione, failure in the oxidative phosphorylation process, and diminished mitochondrial membrane potential. TPL also particularly targeted the respiratory chain complex I and showed some insignificant effects on the complexes II and IV. This can be attributed to the role of mitochondria in apoptosis and it being a free radical resource and target. In HL-60, TPL works by targeting the mitochondria, which subsequently leads to mitochondria associated with oxidative stress and apoptosis. This in turn can sensitize the tumor cells to the proapoptotic effects of cytotoxic agents [229]. When human breast cancer cells (MDA-MB 231) were treated with tempo, another nitroxide, it exhibited considerable levels of tyrosine phosphorylation of numerous unknown proteins when evaluated with the equimolar concentration, i.e., 10 mm TPL. The compounds tempo and TPL lead to the phosphorylation of tyrosine and trigger the Raf-1 protein kinase (30 min, two- to threefold) [230]. Nevertheless, TPL leads to augmented extracellular signal-regulated kinase 1 activity. Tempo also activated the stress-associated protein kinase (2 h, threefold) and induced apoptosis (2 h, >50%). The ceramide levels significantly increase (54% over control) at 30 min and (71% over control) at 1 h after treatment, prior to activation of stress-activated protein kinase and cell death via apoptosis [230]. TPL protects normal cells and tissues from oxidative damage and remarkably hampers the proliferation of cancer cells. These clearly imply that the nitroxide TPL shows the potential to be a good prooxidant and can be a potent radiosensitizing agent for cancer treatment.


Q1.
How do radioprotectors work?
 Q2.
What is the purpose of radioprotectors in RT?
 Q3.
What is TRUE: All the antioxidants are radioprotectors or all the potential radioprotectors are often antioxidants?
 Q4.
What are radiomitigators?
 Q5.
Can immunomodulators be classified as radiomitigators?
 Q6.
What is the purpose of a radiosensitizing agent in cancer RT?
 Q7.
Describe the curcumin action mechanism when administered with irradiation.
 Q8.
Generate a graph similar to Fig. 11.1 for gadolinium nanoparticles and estimate the mass attenuation coefficient ratio at 100 keV.


What is TRUE: All the antioxidants are radioprotectors or all the potential radioprotectors are often antioxidants?


What is the purpose of a radiosensitizing agent in cancer RT?


Generate a graph similar to Fig. 11.1 for gadolinium nanoparticles and estimate the mass attenuation coefficient ratio at 100 keV.


SQ1.
The detailed mechanisms are described in Sect. 11.1.1. The possible mechanisms are listed in Box 11.2 as well.
 SQ2.
Radioprotectors, which should be safe and nontoxic for human health, are used to protect the normal cells or nontumor cells from the harmful insults of ionizing irradiation and to increase survival rate in patients when administered before the exposure to radiation or at the time of RT for their effectiveness.
 SQ3.
The potential radioprotectors are often antioxidants, but not all the antioxidants are radioprotectors.
 SQ4.
Radiomitigators are used to minimize the toxicity or damage caused by ionizing irradiation in noncancerous cells even after radiation has been delivered and thus able to improve the effectiveness of radiation therapy.
 SQ5.
Yes. Radioprotective agents with potency to stimulate the proliferation and modify the function of hematopoietic and immunopoietic stem cells, often referred to as immunomodulators, can be considered as radiomitigators. The mode of action (MOA) of radiomitigators is depicted in the figure (figure number will be written).
 SQ6.
Radiosensitizer is a chemical or pharmaceutical agent which enhances the killing effect on tumor cells by making them more susceptible/sensitive to radiation therapy and at the same time having less effect on normal tissues/cells.
 SQ7.
Curcumin has been shown to have a double-face mechanism. Indeed, on the one hand, it is an antioxidant and anti-inflammatory molecule, useful in limiting the IR-induced ROS generation and IR side effects. On the other, it acts as an anticancer molecule, interacting with cellular processes, such as cell cycle, proliferation, apoptosis, and autophagy.
 SQ8.
Gd/water mass attenuation coefficient ratio @ 100 keV = 72.6.

A line graph of the decrease in mass attenuation coefficients of G d and water with an increase in photon energy.


The detailed mechanisms are described in Sect. 11.1.1. The possible mechanisms are listed in Box 11.2 as well.


Radioprotectors, which should be safe and nontoxic for human health, are used to protect the normal cells or nontumor cells from the harmful insults of ionizing irradiation and to increase survival rate in patients when administered before the exposure to radiation or at the time of RT for their effectiveness.


The potential radioprotectors are often antioxidants, but not all the antioxidants are radioprotectors.


Radiomitigators are used to minimize the toxicity or damage caused by ionizing irradiation in noncancerous cells even after radiation has been delivered and thus able to improve the effectiveness of radiation therapy.


Yes. Radioprotective agents with potency to stimulate the proliferation and modify the function of hematopoietic and immunopoietic stem cells, often referred to as immunomodulators, can be considered as radiomitigators. The mode of action (MOA) of radiomitigators is depicted in the figure (figure number will be written).


Radiosensitizer is a chemical or pharmaceutical agent which enhances the killing effect on tumor cells by making them more susceptible/sensitive to radiation therapy and at the same time having less effect on normal tissues/cells.


Curcumin has been shown to have a double-face mechanism. Indeed, on the one hand, it is an antioxidant and anti-inflammatory molecule, useful in limiting the IR-induced ROS generation and IR side effects. On the other, it acts as an anticancer molecule, interacting with cellular processes, such as cell cycle, proliferation, apoptosis, and autophagy.


Gd/water mass attenuation coefficient ratio @ 100 keV = 72.6.

A line graph of the decrease in mass attenuation coefficients of G d and water with an increase in photon energy.


A line graph of the decrease in mass attenuation coefficients of G d and water with an increase in photon energy.


Ionizing radiation and radioactive substances can be natural or human-made. Humans have always been exposed to natural ionizing radiation (background radiation), because of the exposure of the Earth’s surface to cosmic rays and the radioactivity contained in rocks that form the continental crust. The use of radiation and radioactive substances in medicine, research, industry, agriculture, and teaching, as well as the generation of nuclear power, have brought important benefits to society. Acceptance by society of the risks associated with radiation depends on the perceived relationship between these risks and the benefits to be gained from the use of radioactive sources. Logically, risks must be limited, and adequate protection provided. This does not mean that individuals or the environment must be protected from any and all effects of ionizing radiation, but rather to ensure that the amount of radiation absorbed does not have negative consequences that outweigh the benefits. The need to balance risks and benefits makes radiation a matter of science and values, meaning that in addition to technical assessments, ethical and legal issues also apply in the judgement of the acceptability of radiation risks.


After the initial and isolated observations of the first health effects of ionizing radiation (i.e., skin burns and cancers) by the pioneers at the turn of the nineteenth and twentieth centuries, two decades passed before a clear need for radiation protection was identified. One of the first signs was the leukemia epidemic that developed among radiologists after World War I, reflecting the use of X-ray radioscopy by military surgeons, without any kind of protection, to localize shrapnel in wounded soldiers. This epidemic lasted until the 1950s and affected approximately 500 radiologists [1].


To face the situation, the International Society of Radiology created the International Committee on Radiation Units (ICRU) in 1925 to develop the first concepts regarding dose quantification which were obviously needed. This was followed by the creation in 1928 of the International X-ray and Radium Protection Committee which was restructured in 1950 to take account of new uses of radiation outside the medical area and then renamed the International Commission on Radiological Protection (ICRP). Both ICRU and ICRP are still major actors of radiological protection.


Although the radiological protection (RP) system was established by ICRP, it is worth noticing the critical contribution of the United Nations Scientific Committee on the Effects of Atomic Radiations (UNSCEAR) created in 1955. The ICRP RP system is developed on the basis of the scientific knowledge gathered and synthetised by UNSCEAR.


The ICRP publishes a wide range of recommendations dealing with various aspects of radiological protection, but the current RP system with the three principles of justification, optimization, and dose limitation was first established with recommendation 26 [2]. It has been updated since then by recommendations ICRP 60 [3] and ICRP 103 [4].


ICRP has designed dosimetric factors to properly quantify the exposures to IR and then to establish links between dose and effects. The absorbed dose D is the energy deposited in the tissue: the unit of 1 J/kg is the Gray (Gy) in memory of James Gray. To take into account that different types of radiation do not produce the same biological effects for the same absorbed dose, a radiation weighting factor WR is used to convert the absorbed dose into the so-called equivalent dose HR = WR⋅D. This unit is the Sievert (Sv) in memory of Rolf Sievert. But the biological response also depends on the tissue and a tissue weighting factor WT is used to convert the equivalent dose for each organ to the so-called effective dose E by adding the contributions of all organs E = ΣR,TWTHR,T. The effective dose unit is still the Sv and when a dose is given in Sv it is mandatory to indicate if it relates to an equivalent dose or to an effective dose. Thus, only the absorbed dose is a physical parameter. Equivalent and effective doses are calculated parameters reflecting the likelihood of detriments in humans.


The effects of IR have been classified for years into two categories named deterministic and stochastic effects. Deterministic effects, e.g., skin burns, are due to high doses of ionizing radiation and the responsibility of radiation in their occurrence is clear. Deterministic effects always occur after a dose threshold is exceeded even though some individual variation exists, and the severity of the effect increases with dose. Stochastic effects, such as cancers, may occur after exposure to ionizing radiation but it is only possible to statistically express the occurrence. In other words, it is impossible to say who will develop cancer and when it will appear. One can only say that a percentage of cancers will appear in a population of persons exposed to a given dose, and the probability of developing cancer will increase with dose. Partly because of relatively high background rates of cancers in human populations, the establishment of a causal relationship between exposure to ionizing radiation exposure and the occurrence of cancer can be quite difficult (see Chap. 4).


More recently the separation between deterministic and stochastic effects does not appear to be so clear since some effects may combine both approaches, such as radio-induced cataracts. Therefore, ICRP now uses the classification tissue effect instead of deterministic effects.


Risk evaluation has resulted from epidemiologic studies that have established solid correlations (but not causality) between the frequency of cancers and the dose of IR in the dose range above 100 mGy. But ICRP recommendations are not so clear since the same numerical value is given sometimes in Sv. The calculated risk of cancer is roughly 5% per Sv of effective dose, while the risk to the developing fetus is 50% per Sv. The risk of hereditary disease has been estimated as 0.5% per Sv based on animal models, although it has not been documented so far in humans.


Epidemiologic studies have paved the way for effective management of radiation protection with the three ICRP principles of radiological protection, i.e., justification of all exposures, optimization of the justified exposures (ALARA principle), and limitation of doses for the workers and the population. Dose limitation does not apply for patients because doses need to be adapted for both diagnosis and treatment. The overarching goal was to suppress the deterministic effects and to substantially minimize the probability of the occurrence of stochastic effects.


On the basis of scientific evidence, ICRP has progressively recommended the mandatory decrease in the exposure to the level of low doses. The actual exposure of workers to ionizing radiation has clearly decreased over the years and is now in the order of or below 1 mSv/year of effective dose in most countries, although the legal limit is still 20 mSv/year for the effective dose. The dose limit of 1 mSv effective dose for the public is below the variations of natural background. At present, the dose limits of the system of radiological protection are quite low and are therefore not foreseen to be changed in the near future. However, doses from medical exposures are still steadily rising.


The ethical foundations of the system of radiological protection were reviewed by ICRP in its publication 138 [5]. This underlined that radiological protection is not only a matter of science but has been developed on ethical values either intentionally or indirectly. Four core ethical values (beneficence/non-maleficence, prudence, justice, and dignity) underpin the present system and relate to the three principles of radiological protection. This publication also addresses key procedural values (accountability, transparency, and inclusiveness) required for the practical implementation of the system (see the following section for more details).


Although the system of radiological protection developed and updated by ICRP for more than eight decades has proved robust and operational, there remain a number of ethical, legal, and social challenges
Risk evaluation is a major concern since this drives the allocation of resources for radiation protection. The majority of doses in humans are in the low-dose range with a very low risk of cancer. The effective dose should not be used for risk evaluation for a specific individual [4]. Regarding medical exposures, there is a need to develop individual risk evaluation based on doses to the organs exposed [6].

The human individual response to ionizing radiation should be included in the system in order to optimize radiological protection. This will be part of personalized and predictive medicine, for example, in persons with a high familial risk of cancer or in patients who are likely to be repeatedly exposed to ionizing radiation for medical reasons (especially children, women, prior to radiotherapy or to repeated screening).

There should be an increased focus on communication with the public and media. There is a need to understand the psychological aspects of risk perception, especially when these show diversion from the real exposures and risks.


Risk evaluation is a major concern since this drives the allocation of resources for radiation protection. The majority of doses in humans are in the low-dose range with a very low risk of cancer. The effective dose should not be used for risk evaluation for a specific individual [4]. Regarding medical exposures, there is a need to develop individual risk evaluation based on doses to the organs exposed [6].


The human individual response to ionizing radiation should be included in the system in order to optimize radiological protection. This will be part of personalized and predictive medicine, for example, in persons with a high familial risk of cancer or in patients who are likely to be repeatedly exposed to ionizing radiation for medical reasons (especially children, women, prior to radiotherapy or to repeated screening).


There should be an increased focus on communication with the public and media. There is a need to understand the psychological aspects of risk perception, especially when these show diversion from the real exposures and risks.


Discussion about the meaning and appropriateness of the acronym LNT has been central in the debate on radiation protection against low-level exposure situations. As an acronym, LNT is non-translatable; a fact that does not facilitate communication. LNT is aimed to denote an imprecise expression: “linear-non-threshold,” a short reference to the relationship between the probability of suffering a radiation health effect and the incurred radiation dose, following low doses, low dose rate, radiation exposures.


It is to be noted that this imprecise acronym has been widely used with different connotations by relevant professional communities, a conundrum that can be simplistically summarized as follows:
For radiation biologists, LNT usually refers to a biological hypothesis postulating that at low radiation doses a given increment in dose will produce a directly proportionate increment in the probability of incurring malignancies or heritable effects attributable to radiation.

For radiation epidemiologists, LNT is an epidemiological conjecture by which the incidence of effects per unit dose measured at radiation exposure situations involving relatively high doses delivered at relatively high dose rates, where an epidemic of increases in malignancies have been recorded, is presumed to occur also at radiation exposure situations involving low doses and low dose rates in spite that epidemiological evidence is not achievable in such situations.

For radiation-protectionists, LNT represents a practical operational model for managing radiation protection and controlling that protection against additional doses regardless of the level of accumulated dose, and, therefore, preventing discrimination—particularly age-related labor discrimination in cases of occupational radiation protection.


For radiation biologists, LNT usually refers to a biological hypothesis postulating that at low radiation doses a given increment in dose will produce a directly proportionate increment in the probability of incurring malignancies or heritable effects attributable to radiation.


For radiation epidemiologists, LNT is an epidemiological conjecture by which the incidence of effects per unit dose measured at radiation exposure situations involving relatively high doses delivered at relatively high dose rates, where an epidemic of increases in malignancies have been recorded, is presumed to occur also at radiation exposure situations involving low doses and low dose rates in spite that epidemiological evidence is not achievable in such situations.


For radiation-protectionists, LNT represents a practical operational model for managing radiation protection and controlling that protection against additional doses regardless of the level of accumulated dose, and, therefore, preventing discrimination—particularly age-related labor discrimination in cases of occupational radiation protection.


The wide and imprecise use of the acronym LNT without clarification of its precise meaning has been a cause of serious confusion on the health effects attributable following low dose, low dose rate, and radiation exposure situations.


It could be succintly said that LNT is intended to mean a practical model rather than a sophisticated scientific theory and that it is based on the globally accepted principles of ethical prudence and on labor rights for non-discrimination—long established by international undertakings.


What are we speaking about when we speak about ethical, legal, social, and psychological aspects in relation to the radiological risk? Dealing with radioactivity in society is a complex challenge in any respect, but one can distinguish four fundamental “contexts of concern” that require different visions on complexity, and what it would mean to responsibly deal with it. When considering ethical, legal, social, and psychological aspects of radiation exposure, it is important to always do this with the context of application or “the context of concern,” in mind.


The first context is the context of “naturally enhanced” natural radiation. The second context concerns industrial practices that involve technically enhanced natural radiation. The third context is the context of peaceful applications of nuclear technology. These include applications of nuclear physics processes, such as the fission or fusion of nuclei for energy production or the use of decay radiation in medical treatment and diagnosis or for industrial purposes. The fourth context is the use of nuclear technology or material as a weapon, either as a means for political deterrence, in organized military operation or in terrorist actions.


The reason to distinguish these different contexts is motivated by a specific understanding of the ethics of radiological risk governance and its relation to the social and political aspects of governance, and this as well in theory as in practice. To put it simply, if we consider average natural background radiation as an element of our natural habitat, then any significantly enhanced level of radioactivity in the vicinity of living species represents a risk—in the sense of a potential harm—to the health of those living species. In these cases, pragmatic reasoning thus requires us to consider the possibility of protection, mitigation, or avoidance, but essentially to first evaluate why the additional radioactivity occurs in the first place, and whether we can possibly justify it. But whether that justification exercise can be done meaningfully or not depends on how we perceive the context of the occurrence of radiation.


From what the first context is concerned, whether we want it or not, natural radiation is there and any naturally enhanced occurrence (e.g., in the case of high concentrations of Radon) has a potential impact on health. Thinking in terms of justification of the presence of that radiation is meaningless, which leaves us with evaluating the justification of exposure, and thus of the possibility of protection, mitigation, or avoidance of its impact.


In the second context of technically enhanced natural radiation (for example, in the oil refinery industry or in aviation), radiation exposure manifests as a “side effect.” Practices as such may be contested (as is the case with the oil or phosphate industry), but very rarely the issue of radiation exposure will become a decisive factor in the evaluation of the justification of these practices. Similar to the case of naturally enhanced natural radiation, the radiation justification exercise thus restricts itself to the evaluation of exposure, and thus to the evaluation of the possibility of protection, mitigation, or avoidance of its impact.


In the third context, evaluation of the justification of the use of nuclear technology obviously takes the reason for that proposed use (the projected “benefits”) as a first criterion, with the aim to “balance” it with the projected risks. Despite the fact that opinions on these projected benefits and risks differ among people, in this context, an evaluation of the justification of the use of a risk-inherent technology, or thus of the presence or “creation” of radiation, remains meaningful, and this is because the application context is “neutral”; while opinions may differ on how to produce energy or perform a medical treatment, nobody is “against energy” or “against medical care” as such. The neutral context thus makes a meaningful joint evaluation of the justification of the nuclear technology application possible, and it will not affect possible outcomes (rejection or acceptance of the technology) as such.


Finally, in the fourth context, a meaningful joint evaluation of the justification of (the risk of) the nuclear technology application is not possible, and this is for the reason that the context of application itself is not neutral. A pacifist perspective does not support a principal justification of nuclear deterrence and armed conflict strategies, while, in a perspective that sees politics always as a politics of power and conflict, these strategies may be perceived as justified.


Any evaluation of the acceptability of a radiological risk is characterized by a “double” complexity. Firstly, it needs to take into account the uncertainties with regard to whether and how the risk will manifest. Science has an authoritative voice in this evaluation, but it needs to recognize that there will always be uncertainties that cannot be cleared out (stochasticity of biological effects at low radiation dose, possible delayed harm of medical diagnosis or therapy, the possibility of a nuclear accident, the fate of a radioactive waste disposal site in the far future, …). In addition, we have to accept that important factors remain to a large degree beyond control: human behavior, nature, time, and potential misuse of technology… Secondly, an evaluation of the acceptability of a radiological risk also needs to consider diverse value judgments with regard to the acceptability of the risk. In philosophical terms, one can say that the evaluation is troubled by moral pluralism: even if we would all agree on the scientific knowledge base for the assessment of the risk, then opinions on its acceptability could still differ. The reason is that evaluations of acceptability do not only rely on “knowledge” but are also influenced by references to things people value as important, such as freedom, security, the value of nature, the rights of the next generations, and their safety and that of their loved ones. In that case, science may thus inform the technical and societal aspects of options, it cannot instruct or clarify the choice to make.


Taking this complexity into account, one may understand that risk cannot be justified through a one-directional “convincing explanation” by scientific experts or political decision-makers. Ethics supports the idea that the evaluation of a possible justification of a radiological risk needs to be done in deliberation among all concerned, including those potentially affected by the risk. In that deliberation, visions from science, policy, civil society, and citizens have an equal place, bearing in mind that (quoting the philosopher Philip Kitcher) “There are no ethical experts. The only authority is the authority of conversation” [7]. Obviously, the outcome of that conversation can either be to reject or to accept the radiological risk. In other words, from an ethical perspective, the argument is that the justice of justification, ensured by the possibility of self-determination of the potentially affected, should be the central concern of risk governance. In practice, that means formal methods for decision-making and formal procedures within the organization should care for the possibility of participation of those potentially affected by the radiological risk.


Seen from a different perspective, ethics in relation to radiological protection is also about considering and recognizing the limits of the radiological protection system when it comes to providing a rationale for justification of radiation risk. In other words, we cannot question the ethical dimensions of the radiological protection system without also questioning the ethical dimensions of the “bigger” systems in which the radiological protection system operates and on which it depends. Given that the radiological protection system, in its concern for providing guidance for decision-making, relies on science but also and essentially wants to take into account human and societal values, the bigger systems that need to be questioned in terms of their ethics, are those of knowledge production (research and policy advice) and decision-making. For risks that manifest in medical diagnostic or therapeutic practices, that “system” is the possibility of deliberative dialog between the patient, the doctor, the nurse, the radiation control and protection service of the hospital, other hospital agencies, as well as regulatory and professional bodies. For risks that manifest in an occupational context, the system of decision-making is the radiation control and protection service, the management system of the organization, other relevant agencies, trade unions, and professional bodies. For risks that manifest on a societal level, that system of decision-making is the system of democracy, including input from citizens, civil society, trade unions, professional bodies, advocacy groups, and of scientific and ethical advisory committees.


The evolving ethics of the developing international system of protection against ionizing radiation could be viewed as the branch of some kind of embryonic radiological protection philosophy, which from the beginning of the profession was dealing with main protection principles and their values. It challenged questions about the morality of the protection principles—that is, concepts such as good and bad, right and wrong, virtue and vice in radiological protection. It tried to tackle issues such as the meaning and reference of moral propositions on radiological protection; the practical means of determining a moral protective action, how moral protective outcomes can be achieved in specific situations, how a moral capacity for recommending a protection paradigm develops and what its nature should be and what moral values on radiological protection people in general and stakeholders in particular should actually abide by.


Ethics was the primordial earliest concept for judging human actions such as those involved in radiological protection and provides its fundamental basis. Radioprotectionists had been (and continue to be) very keen on exploring and reassessing the rules and standards governing their professional conduct. They have had an unusual curiosity to self-inspect whether they hold the right behavior and what is the set of principles for self-ensuring that such behavior is right. This interest in self-appraisal of conduct correlates with the notion of ethics.


The ethical basis of radiological protection was early recognized by the profession’s forefathers [1]. The primordial radiation protection principle related to individuals (in fact these individuals were at the beginning just radiologists; it would take a number of years to incorporate individual members of the public, and some more to incorporate individual patients undergoing radiodiagnostic or radiotherapy), as follows:
The principle of individual dose restrictions, which was aimed at ensuring that the total dose incurred by any individual should be restricted to protect the individual exposed. Although not explicitly, it was implicitly based on an ethics of duty, the so-called deontological ethics, which is usually expressed with the aphorism “One should do unto others as they would have done unto them.”


The principle of individual dose restrictions, which was aimed at ensuring that the total dose incurred by any individual should be restricted to protect the individual exposed. Although not explicitly, it was implicitly based on an ethics of duty, the so-called deontological ethics, which is usually expressed with the aphorism “One should do unto others as they would have done unto them.”


Over time it became clear that the protection of individual was a necessary but not necessarily a sufficient condition, and the system of collective ethical requirements evolved. Two basic principles would fill this gap, as follows:
The principle of justification, which was aimed at ensuring that any decision that alters the radiation exposure situation should do more good than harm—meaning that by introducing new radiation sources or by intervening for reducing existing doses, sufficient individual or societal benefit should be achieved to offset the detriment such actions may cause. This principle was based on the ethics of consequence or teleological ethics, which is usually expressed with the aphorism “The ends justify the means.”

The principle of optimization, which aimed at ensuring that the level of protection would be the best under the prevailing circumstances, maximizing the margin of benefit over harm, and thus the number of people exposed and of their individual doses be kept as low as reasonably achievable, taking into account economic and societal factors. This was based on the ethics of efficacy or utilitarian ethics, which is usually expressed with the aphorism “Provide the greatest good for the greatest number of people.”


The principle of justification, which was aimed at ensuring that any decision that alters the radiation exposure situation should do more good than harm—meaning that by introducing new radiation sources or by intervening for reducing existing doses, sufficient individual or societal benefit should be achieved to offset the detriment such actions may cause. This principle was based on the ethics of consequence or teleological ethics, which is usually expressed with the aphorism “The ends justify the means.”


The principle of optimization, which aimed at ensuring that the level of protection would be the best under the prevailing circumstances, maximizing the margin of benefit over harm, and thus the number of people exposed and of their individual doses be kept as low as reasonably achievable, taking into account economic and societal factors. This was based on the ethics of efficacy or utilitarian ethics, which is usually expressed with the aphorism “Provide the greatest good for the greatest number of people.”


These two principles and their ethics are the basis of the radiation protection paradigm recommended by the ICRP.


In addition, there was an intrinsic value of these principles, or de facto principle in its own right, which unfortunately was not specifically declared as such by ICRP, but which is implicitly referred to in many statements and underlines most of the ICRP recommendations and it was recognized in subsequent international standards. It could be formulated as follows:
The principle of intergenerational prudence, also termed principle of protection of present and future generations in international standards, is aimed at ensuring that protection extends to all humanity and its environment, regardless of where and when people live, and which implies that all humans, present and future, and their environment shall be afforded with a level of protection that is not weaker than the level provided to those populations causing the protection needs. It can be construed that this important principle is mainly based on the ethics of virtue or ethics of arête, which is usually expressed with the aphorism “No return should be expected from good actions, as goodness is an ideal that transcends human nature.”.


The principle of intergenerational prudence, also termed principle of protection of present and future generations in international standards, is aimed at ensuring that protection extends to all humanity and its environment, regardless of where and when people live, and which implies that all humans, present and future, and their environment shall be afforded with a level of protection that is not weaker than the level provided to those populations causing the protection needs. It can be construed that this important principle is mainly based on the ethics of virtue or ethics of arête, which is usually expressed with the aphorism “No return should be expected from good actions, as goodness is an ideal that transcends human nature.”.


Teleological and utilitarian ethics belong to a family of “social-oriented” ethics; deontological and arête ethics belong to a family of “individual-oriented” ethics. In relation to radiation protection, teleological and utilitarian ethics aim at protecting society as a whole, while deontological and virtue ethics are more focused on individual protection and individual rights. Teleological, utilitarian, and deontological ethics have evolved in a mainly anthropocentric framework. Conversely, arête ethics is able to deal with more general ethical issues such as intergenerational and environmental protection.


The start of the twenty-first century saw a growing criticism of the anthropocentric focus of the system of radiological protection, exemplified by the statement that “… the standard of environmental control needed to protect man to the degree though desirable will ensure that other species are not put at risk” [3]. Critics noted that there were cases where human doses could be low and doses to wildlife high (e.g., waste disposal), that the approach was not in line with management of other environmental stressors, and that there was a need to demonstrate explicitly that non-human species were being protected [8–10]. The IAEA published a report on “Ethical Considerations in protection of the environment from the effects of ionising radiation,” exploring ethical principles that might underlie a system of protection and stressing the need to be compatible with international legal instruments such as those related to sustainability and protection of biodiversity [11]. The requirement to address the impacts of ionizing radiation on the environment is now included in international radiation protection recommendations and standards [4, 12, 13].


Previous writers have compared the ICRP principles with ethical theories, highlighting the similarities between the principle of justification with teleological or contractarian ethics, the principle of optimization with utilitarian approaches, and the principle of dose limitation with deontological ethics [14, 15]. In its recent work on the ethical foundations of radiological protection, ICRP has focused on commonly recognized ethical values, rather than overarching ethical theories such as utilitarianism or deontology [5]. This is in line with approaches to ethical assessment applied in biomedical and public health ethics [16], as well as work on cross-cultural ethics [17], underlining that it is easier to find agreement on fundamental values than on ethical doctrines. ICRP highlights four core values underpinning the system of radiological protection: beneficence/non-maleficence, justice, dignity, and prudence [5].


Examples of how these values can be applied in the analysis of ethical challenges are given in the following sections. But briefly, beneficence and non-maleficence refer to the principles of promoting well-being and avoiding the causation of harm. In radiological protection, this is clearly related to the reduction of radiation exposures, and the avoidance of resultant harms, but can also include a range of different costs and benefits, including economic and societal aspects. There will always be questions about how to measure consequences and who or what should count in such an evaluation (e.g., animals and future generations). Dignity is concerned with respect for autonomy and the self-determination and choice of affected populations and includes issues related to privacy, human rights, as well as individual and community empowerment. The ethical principles of fairness and justice stress the importance of addressing the way in which risks, costs, and benefits are distributed (distributive justice), as well as the way in which decisions are carried out (procedural justice). Prudence is the ability to make discerning and informed choices without the full knowledge of the scope and consequences of our actions. While precaution and prudence are rarely alluded to in general medical ethics and bioethics, the precautionary principle is well recognized in environmental ethics. The ICRP also introduces the procedural values of transparency and accountability, in the practical application of radiological protection, especially in the need to engage stakeholders in decision-making processes [5]. While there has been a general consensus on the fundamental values proposed by ICRP, there have been proposals that the system should include additional values such as empathy and honesty [18].


The public’s aversion to radiation—and especially that associated with nuclear power rather than natural or medical exposures—is often cited as an example of irrationality or misunderstanding, and is best combated by improved education. But to understand risk perception, we need to recognize that risk is in part quantifiable but also a social construct that is interpreted differently by people in various situations, environments, and cultures. It is true that people misunderstand probabilities; however, numerous studies of the psychological and psychometric factors that influence risk perception show that the situation is more complex than this alone. Public or lay perceptions of risk vary widely between people and can differ from the calculated, technical approach to the assessment of risks. Whereas an expert will often tend to rank risks as being synonymous with the size or probability of harm, risk tolerance or aversion is dependent on many additional characteristics [19, 20]. Many of the characteristics have strong psychological as well as societal and ethical relevance (such as control, voluntariness, and distribution of risks and benefits).


People tend to be less tolerant of risks that are imposed without their choice or personal control. The phenomenon applies to a range of different risks and actions, such as driving a car compared with flying. Personal control is closely related to the fundamental ethical value of autonomy (i.e., respect for the free will of individuals), dignity, integrity, and individual rights. It is also linked to the requirement for free informed consent within medical ethics and can explain why people are less concerned over medical radiation exposures (which are largely voluntary and for an obvious personal benefit). People often feel a lack of personal control over radiation exposure [19], particularly those associated with accidents. They are dependent on information from authorities or media and have to deal with both the risks from the exposure as well as the consequences of measures to reduce exposure such as relocation or agricultural bans.


In risk management, measures that increase personal control and understanding, such as the provision of dosimeters or counting equipment, and participation in decision-making are considered positive and can help populations in coping. Provision of counting equipment and independent monitoring are methods that have been successfully applied in both Chernobyl- and Fukushima-affected communities [21–23]. When combined with access to experts to help interpret results, such actions can help empower populations. Ethically, procedures that involve the populations themselves can help promote the principle of informed personal control over radiation risks.


The Chernobyl and the Fukushima accidents both resulted in a wide range of social and economic consequences. Many evacuees lost their jobs, social network, and connection to places of a particular community or historical value like graveyards or places where they played as children [24]. Resettlement and long-term evacuation in Fukushima have changed the social structure of the villages and city districts [25]. After Chernobyl, the emigration of young people impeded the whole social and economic development of the region, including a shortage of teachers and doctors [26]. Similar demographic changes have been seen after Fukushima, with young families more likely to evacuate and less likely to return [25]. These lead in turn to a variety of social and health effects such as alcoholism, obesity, and depression in affected populations.


The economic costs of accidents are complex and wide-reaching. Loss of consumer trust in food from a contaminated area can have economic consequences that go beyond the loss of food production. Stress, ill-health, and even suicide can accompany job loss and bankruptcy. Loss of consumer trust can have profound consequences both for a range of industries (particularly food or tourist industries) and for the local identities of people and groups. This has been well-documented in Fukushima with price drops for produce from the entire region, including areas not affected by the accident, as well as impacts on tourism [25]. Negative economic side effects can arise from rural breakdown and stigma of contaminated communities. Discrimination and stigmatization of the Hiroshima and Nagasaki Hibakusha and their children have an important historical dimension in Japan [27] and is a particular concern for Fukushima evacuees. Hibakusha is a Japanese term referring to the survivors of the Hiroshima and Nagasaki atomic bombs, which translates literally as “bomb-affected people.” TEPCO workers also cited discrimination as one of the main causes of psychological stress [28]. In addition to experienced prejudice, concerns of the populations affected by Fukushima Daiichi accident include worries about whether their children would be able to find partners or marry in the future and reports of discrimination against Fukushima children after moving to new schools.


The aftermath of an accident can also be economically beneficial to parts of the community, for example, through the generation of local employment opportunities. This may lead to some sections of the population making a profit from remediation (such as selling or hiring equipment), which can lead to further social inequity and division.


Distribution of the costs, risks, and benefits of radiation exposure relate to the fundamental ethical values of equity, justice, and fairness. After an accident, doses received by individuals can vary widely, and the risks of those exposures differ between adults and children. The consequences of remediation can impact different members of the affected communities. Some may lose their livelihood, while others can continue more or less as before the accident. For example, after Fukushima the situation was particularly harsh for the elderly evacuees, particularly those living in temporary housing who experienced greater isolation from family and communities [25].


The potential for increased health risks from radiation in children means that the risk perceptions go beyond consideration for personal risks, as is seen by anxiety over thyroid cancer in Fukushima populations [35, 36]. The fear that your child could be affected in the future can overshadow any personal concern [24]. Such concerns create challenges for health surveillance, particularly thyroid screening of children. While parents may, understandably, request screening, the procedure can lead to unnecessary surgery (e.g., 4000 thyroid surgeries in Chernobyl children may explain most of 15 deaths attributed to exposure), and without a carefully thought communication plan may raise anxiety (Shamisen 2020). Some measures to reduce exposures could result in an equitable distribution of cost and dose reduction, such as investment by taxpayers to reduce activity concentrations in public areas; while others are less equitable, for example, when a reduction of dose to the majority is only possible at the expense of a higher dose, cost, or welfare burden, on a minority (e.g., banning all farm production in a small community).


To conclude, public reaction to disasters is the result of complex and intrinsic features of risk perception, many of which have strong ethical and societal relevance. A holistic approach to disaster management should integrate economic, ecological, and health measures. Risk management strategies should be designed to accommodate varied needs. For nuclear accidents, it is not sufficient to simply focus on the dose reduction aspects of radiation protection as societal aspects will play a major role in how individuals cope with, and communities recover from the disaster. Engaging with the affected population with regard to increasing their understanding and personal control and involving them in decision-making processes respects people’s fundamental right to shape their own future. In addition to increasing trust and compliance, such approaches can lead to significant improvements in the effectiveness and acceptability of disaster management in communities.


Testing for radiosensitivity has the potential to improve patient treatment and diagnosis or protect workers. Assays might be applied prior to radiotherapy, to avoid adverse reactions in radiosensitive individuals, or to avoid enhanced cancer risk in connection with radiodiagnoses such as CT scans or mammography [31]. While not yet applied in medicine or worker protection, assays are currently under development, and their potential application raises a number of ethical and legal challenges. These go beyond the simple question of whether the assay will “do more good than harm” to include, for example, questions about how the costs and benefits might be distributed in society, concerns about privacy and data protection, and considerations of the potential for discrimination.


Radiosensitivity and radiosusceptibility assays have a clear potential to provide physical health benefits by improving cancer treatment, avoiding negative side effects, and enhancing worker protection. There are also economic aspects, such as balancing the cost of the assays against the opportunity to save money through tailored treatment. Psychosocial consequences could include reassurance but might also cause worry about sensitivity to other stressors. Information on the magnitude of the effect, its relation to other potential risk factors, and indeed any dose–response relationship, as well rates of false positives and false negatives would be needed to be able to balance the physical harms and benefits. But this would also have knock-on effects on economic, psychological as well as legal assessments. Could doctors be sued for the negative effects of not carrying out a test?


Information on individual radiosensitivity and radiosusceptibility could clearly enhance patient or worker empowerment and personal control, but this would depend strongly on the context in which this information was used. The issues are similar to other challenges with personal health information, such as conforming to data protection laws and the increasing commercialization of genetic testing [32]. For example, the degree to which data from patients undergoing an assay as part of radiotherapy would be stored, anonymized, and made available for further research would need to be addressed. A debate on the implications of these issues would need to include engagement with the various stakeholders but could also play an important role in risk communication, by putting the risks of ionizing radiation in context with other environmental and genetic risk factors.


Increased understanding of the differences in radiosensitivity within populations is relevant to an assessment of justice. Other questions would include whether the assays would provide equal access to health care and support or have any impact on health insurance (would sensitive populations have to pay higher premiums?) or compensation claims (will it change the balance of probabilities that cancers were caused by radiation exposure?). Even in countries with national health insurance, there is the question of whether people should be obliged to disclose the results of genetic testing before taking out private health or life insurance schemes. If sensitivity or susceptibility was linked to a genetic trait, there would be additional issues associated with implications for children or other family members. While identification of increased radiosusceptibility in workers could be used for protective purposes, it might also lead to discrimination, or raise questions about “responsibility” for any diseases or negative side effects (lifestyle, predisposition, occupational exposure, etc.). These issues could be linked to broader debates on the implications for radiological protection of populations with different risk factors such as whether children or women should be treated differently on the basis of increased radiation cancer risks.


To conclude, many of the ethical challenges associated with the field of radiosensitivity and radiosusceptibility have parallels with existing challenges in medical, occupational, and public health. They also raise important questions about the implications for radiological protection. For example, will population-level differences in radiation susceptibility impact the assessment of health risk? Will they lead to a change in dose constraints? These questions can only be addressed with the participation of a wide variety of stakeholders. Assessing the implications for well-being requires knowledge from experts in radiation biology, medicine, occupational health, health economics, social scientists, etc., as well as transparency about uncertainties and assumptions. Respecting both the principles of dignity and fairness in the procedure requires the participation of affected persons (workers, patients, the public, etc.) in decision-making.


Looking at the societal impacts of science and technology, nuclear technology probably represents the most extreme case of how science and technology can serve both cure and destruction. While medical applications of nuclear technology save individual lives every day, nuclear weapons have enormous destructive potential. Nuclear energy is a low-carbon source of electricity, but a nuclear accident can have dramatic impacts on the environment and on the physical and psychological health of a whole population for a long time. In addition, disposal of radioactive waste unavoidably requires taking responsible action toward future generations thereby taking into account time dimensions longer than ever faced before in human history.


The case of nuclear energy technology is also an example of how technology assessment can be troubled by the fact that “benefits and burdens” of a technology are essentially incomparable. Referring to the general considerations related to the radiological risk and the need to include values in its assessment above, we can say that, taking into account the specific character of the nuclear energy risk, also the societal justification of nuclear energy is troubled by moral pluralism. That is, even if we would all agree on the scientific knowledge base for the assessment of the risk, then opinions on its acceptability could still differ. The matter becomes even more complex if we take into account the fact that science can only deliver evidence to a certain extent. Nuclear science and engineering are mature, but we have to acknowledge that the existence of knowledge-related uncertainties puts fundamental limits to understanding and forecasting technological, biological, and social phenomena in the interest of risk assessment and governance. Last but not least, we have to accept that important factors remain to a large degree beyond control. These are human behavior, nature, time, and potential misuse of technology.


The resulting room for interpretation complicates the evaluation of risk-inherent technologies in general and of nuclear technology in particular and puts a specific responsibility on science and technology assessment as a policy-supportive research practice. And this is the point where ethics come in. In simple terms, that responsibility comes down to acknowledging and taking into account uncertainty and pluralism as described above, and the consequences thereof for research and policy. That “responsible attitude” does not only apply to scientists but to everyone concerned with applications of science and technology in general and with the issue of nuclear technology in particular. The idea is that this responsible attitude can only be enabled and stimulated in “interaction methods” for policy and scientific research that are able to generate societal trust by their “method.” Today we know that this in principle translates as doing politics differently by involving the potentially affected and other stakeholders in deliberative decision-making, and as doing science differently, namely as transdisciplinary science advancing from a holistic perspective and enriched with insights and ideas from the social sciences and the humanities, from lay knowledge and the arts and from civil society and citizens (see, among other [33–35]). For science in particular, confronted with the need to deal with incomplete and speculative knowledge and value pluralism in providing policy advice on issues of social well-being, its challenge is no longer the production of credible proofs but the construction of credible hypotheses [33]. From an ethical perspective, in the general interest of rendering hypotheses with credibility (and the potential to generate societal trust), one could say science has no choice but to “open up its method” for transdisciplinarity and public involvement, in addition to the “traditional” quality criteria of objectivity and independence and the need to recognize uncertainty, value pluralism, contingency, and potential misuse. Obviously, the aim of this ethically inspired “reflexivity” is not to undermine the credibility of science but to stimulate dialog and (self) critical thinking, and to make science more resilient against pressure from politics and the market to deliver evidence it cannot (yet) deliver.


The complex dimensions of radiological risk, particularly after large-scale accidents raise particular challenges for cost-benefit analysis of post-accident response. Emotional descriptions of such emergencies seem more common than quantitative cost-effectiveness considerations. Noteworthy, a few weeks before the first atomic bomb test in July 1945, an official report warned that “civilization would have the means to commit suicide at will” [36]. Kahn [37] considered a full-scale 10,000,000 kiloton nuclear exchange between the Soviet Union and the USA, and deliberated in detail why the above statement is far from being based on evidence.


Quantitative considerations show that the direct health consequences—radiation sickness, carcinogenesis, etc.—of any past (or future practically probable) radiological accident are much less far-reaching than those which are usually perceived. In each scenario, direct health effects are only a small part of the damage caused by fear and anxiety. For example, the two major humanitarian disasters after the Chernobyl and Fukushima nuclear accidents turned out to be such disasters not because of their radiogenic effects, either actual or averted. The main health consequences could be attributed to countermeasures by the authorities, and socio-psychosomatic problems among the public. The relocation of hundreds of thousands of people created very real suffering, morbidity, and mortality [38]. Rational decision-making should have quantitatively compared the human cost of evacuation and long-term relocation with the human cost of radiation exposure. Such comparison was performed only decades later. For example, Yanovskiy et al. [39] estimated that in Fukushima the evacuation was not justified at all, and in Chernobyl the evacuated zone could have been repopulated after 1 month.


The human cost of evacuations should be considered as follows. First, there is always a direct loss of life due to the temporary loss of medical care, psychosomatic disorders, and even suicides; After Fukushima, e.g., 1% of the evacuees died during the first 2 years due to evacuation-related causes (on top of the natural mortality). Second, evacuees’ quality of life deteriorates by about 20% [39]. Last but not least, evacuation is expensive. While associating human life with monetary value is psychologically difficult and may seem ethically challenging, it is actually an ethical necessity since extraneous expenditure leads to a statistical shortening of life. A cost-effectiveness analysis is routinely performed when formulating health policies [40]. Safety expenditures should be treated in a similar way since both healthcare and safety deal with life extension [41].


In this context, it is worth mentioning that life expectancy varies considerably not only for different countries but also for different locations of each country: the main reasons are probably socioeconomic and environmental. This disparity in life expectancy across countries is typically of several years; in the extreme case of Calton in the UK it was 25 years below the country average [42]. It is needless to mention that evacuation of less-successful locations is nowhere considered as a viable option.


The purpose of nuclear law is to establish a legal framework for the safe management of all sources and types of radiation and endeavors involving exposure to ionizing radiation [43]. Nuclear law should thus ensure the adequate protection of individuals, society, and the environment, both present and future, against radiological hazards. Specifically, nuclear law should cover the exposure of the general public—i.e., any individual in the population—of workers—i.e., any person who works, whether full-time, part-time, or temporarily, for an employer and who has recognized rights and duties in relation to occupational radiation protection—as well as exposures related to medical uses of radiation, situations in which a patient is voluntarily exposed for therapeutic purposes (radiodiagnostic or radiotherapy) and who may incur high doses of radiation, possibly with unwanted side effects as a result. Radiation protection rules and regulations should always include special provisions relating to the way in which the application of fundamental principles of justification of actions involving radiation exposure, optimization, or protection, and limitation of individual radiation risk is applied.


The general principles of nuclear law broadly apply to all nuclear-related activities and facilities where ionizing radiation is used or produced.


Section 12.4 will first define nuclear law. Important principles will then be covered followed by a summary and explanation of relevant legislative frameworks. Certain specific potential exposure situations and how the law treats them will also be expanded upon such as employer and medical liability, as well as the legal framework for airline personnel and astronauts.


Legal attribution and imputation of radiation harm to radiation exposure situations, a topic that has distinct epistemological elements, will be discussed in Sect. 12.5 after the more formal legal aspects.


The scope of nuclear law can be succinctly defined as any issue or matter relating to the use of, production of, or exposure to ionizing radiation in specific situations.


In more detail, nuclear law can be defined as “The body of special legal norms created to regulate the conduct of legal or natural persons engaged in activities related to fissionable materials, ionizing radiation, and exposure to natural sources of radiation” while its primary objective is “To provide a legal framework for conducting activities related to nuclear energy and ionizing radiation in a manner which adequately protects individuals, property, and the environment” [44].


This definition has four key elements. Firstly, nuclear law is a body of special legal standards and norms. These are recognized as a part of general national legislation. Since it is a sovereign right of countries to choose how they enact laws, national legislations may differ when it relates to nuclear issues.


Secondly, nuclear law serves a regulatory purpose. The use of and exposure to radiation needs to be regulated given that whilst there is a potential benefit to social and economic development, there also a potentially detrimental effects.


Thirdly, nuclear law relates to the conduct of legal and natural persons. These persons could be commercial, academic, scientific, governmental, or natural. A legal person is a body corporate (or corporate organization) such as a company while a natural person is an individual human being [45].


Fourthly, nuclear law primarily relates to radioactivity, ionizing radiation, and the products of nuclear fission, with the clarification that in this context, it means those that have potentially unwanted biological effects. We could add to the definition that the effects of fusion reactions—still largely in a developmental phase at the time of the redaction of this work—should also be included under the umbrella of nuclear law. The property of protection of the population from the adverse effects of radioactivity and radiation is considered to be the defining aspect justifying the need for a special legal regime.


A number of basic concepts, often expressed as fundamental principles, distinguish nuclear law from other aspects of law. These principles and various theories are crucial to understand because they help understand why the law exists in the form it does.


The safety principle is arguably the central concept in nuclear law [43]. Within the safety principle, there are a number of other principles. These include the prevention principle that postulates that, given the special nature of the risks associated with the use of nuclear energy, the primary objective of nuclear law is to promote the exercise of caution and foresight to prevent damage and minimize adverse effects. Another principle is the protection principle which postulates that when the risks associated with an activity are found to outweigh the benefits, priority must be given to protecting public health, safety, security, and the environment. The precautionary principle also prioritizes protection and the prevention of foreseeable harm as fundamental requirements.


Fundamental safety principles codified in legislation may be applied to a wide variety of activities and facilities that pose very different types and levels of risk. Activities posing significant radiation hazards will obviously require stringent technical safety measures and, in parallel, strict legal arrangements. Activities posing little or no radiation hazard will need only elementary technical safety measures, with limited legal arrangements.


The security principle [43] is an underlying principle of the special legal measures that are required to protect and account for the types and quantities of nuclear material that may pose security risks. These measures should protect against both accidental and intentional diversion from the legitimate uses of these materials and technologies. Lost or abandoned radiation sources can cause physical injury to persons unaware of the associated hazards. The acquisition of radiation sources by terrorist or criminal groups could lead to the production of radiation dispersion devices to be used to commit malevolent acts. The diversion of certain types of nuclear material could contribute to the spread of nuclear weapons to both subnational and national entities. It is for these reasons that legal measures regarding physical protection, emergency preparedness, response, and transport, import and export of radioactive material have been adopted.


While safety is of the utmost importance, it is important to carry out a balancing of both the risks and the benefits of exposure. There are situations in which the benefits clearly outweigh the risks, and it is important to not dismiss outright any and all exposure based solely on hazard.


The aforementioned principles are not the only ones used in a nuclear law context. For example, the IAEA Basic International Safety Standards (BSS, infra, Sect. 12.4.4.1) represent a broad international consensus on the appropriate handling of radioactive sources to ensure that nuclear-related activities can be conducted in a safe, secure, and environmentally acceptable way. The BSS consists of three sets of publications: the Safety Fundamentals, the Safety Requirements, and the Safety Guides. The Fundamentals establish the fundamental safety objectives and principles of protection and safety, the Requirements set out the requisite conditions that must be met to protect the population and the environment and the Safety Guides provide practical recommendations and guidance on how to comply with the requirements.


The Fundamental Safety Principles are the basis of international and intergovernmental standards of radiation and nuclear safety. They have been established under the aegis of the IAEA and are jointly sponsored by the European Atomic Energy Community (Euratom), the Food and Agriculture Organization of the United Nations (FAO), the International Atomic Energy Agency (IAEA), the International Labour Organization (ILO), the International Maritime Organization (IMO), the OECD Nuclear Energy Agency (OECD/NEA), the Pan American Health Organization (PAHO), the United Nations Environment Programme (UNEP), and the World Health Organization (WHO).


The fundamental safety principles are more detailed elements of the safety principle previously discussed:
The first principle is the responsibility for safety: The prime responsibility for safety must rest with the person or organization responsible for facilities and activities that give rise to radiation risks.

The second safety principle relates to the role of the government: An effective legal and governmental framework for safety, including an independent regulatory body, must be established and sustained.

The third safety principle relates to the leadership and management for safety: Effective leadership and management for safety must be established and sustained in organizations concerned with, and facilities and activities that give rise to, radiation risks.

The fourth safety principle calls for the justification of facilities and activities: Facilities and activities that give rise to radiation risks must yield an overall benefit.

The fifth safety principle refers to the optimization of protection and safety: Protection must be optimized to provide the highest level of safety that can reasonably be achieved.

The sixth principle requests the limitation of risks to individuals: Measures for controlling radiation risks must ensure that no individual bears an unacceptable risk of harm.

The seventh principle calls for the protection of present and future generations: People and the environment, present and future, must be protected against radiation risks.

The eighth principle refers to the prevention of accidents: All practical efforts must be made to prevent and mitigate nuclear or radiation accidents.

The ninth principle relates to emergency preparedness and response: Arrangements must be made for emergency preparedness and response for nuclear or radiation incidents.

The tenth and final principle refers to protective actions to reduce existing or unregulated radiation risks: Protective actions to reduce existing or unregulated radiation risks must be justified and optimized.


The first principle is the responsibility for safety: The prime responsibility for safety must rest with the person or organization responsible for facilities and activities that give rise to radiation risks.


The second safety principle relates to the role of the government: An effective legal and governmental framework for safety, including an independent regulatory body, must be established and sustained.


The third safety principle relates to the leadership and management for safety: Effective leadership and management for safety must be established and sustained in organizations concerned with, and facilities and activities that give rise to, radiation risks.


The fourth safety principle calls for the justification of facilities and activities: Facilities and activities that give rise to radiation risks must yield an overall benefit.


The fifth safety principle refers to the optimization of protection and safety: Protection must be optimized to provide the highest level of safety that can reasonably be achieved.


The sixth principle requests the limitation of risks to individuals: Measures for controlling radiation risks must ensure that no individual bears an unacceptable risk of harm.


The seventh principle calls for the protection of present and future generations: People and the environment, present and future, must be protected against radiation risks.


The eighth principle refers to the prevention of accidents: All practical efforts must be made to prevent and mitigate nuclear or radiation accidents.


The ninth principle relates to emergency preparedness and response: Arrangements must be made for emergency preparedness and response for nuclear or radiation incidents.


The tenth and final principle refers to protective actions to reduce existing or unregulated radiation risks: Protective actions to reduce existing or unregulated radiation risks must be justified and optimized.


The central underlying principle of nuclear law is safety. If a situation arises in which a law’s interpretation is unclear, it is useful to ask which interpretation would lead to the safest outcome. This should of course take into account the beneficial impacts relating to the exposure, but it is a good starting point if confusion arises.


An international regime based on broad international consensus has produced over time a set of recommendations and standards that govern radiation protection. These are not set in stone but have evolved and will still evolve over time as new fundamental scientific insights develop. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) compiles, assesses, and disseminates scientific information on the causal link between incurred doses of radiation and possible adverse health effects outcomes. Its findings are periodically reported to the UN General Assembly (UNGA) and are made available to the public on its website. Since 1950, the International Commission on Radiological Protection (ICRP), a private nongovernmental charity, has been developing internationally agreed-upon recommendations in all areas of radiation protection. The Annals of the ICRP are mostly freely available to the general public.


International radiation protection standards are established under the aegis of the International Atomic Energy Agency (IAEA) with the cosponsoring of other relevant international organizations. Since 1962, the IAEA takes into account UNSCEAR publications as well as ICRP recommendations in order to establish and issue Basic Safety Standards (BSS), which provide fundamental principles, requirements, and recommendations to ensure nuclear safety. The IAEA considers these standards as a global reference for protecting people and the environment and a main contribution to a harmonized high level of safety worldwide. Scientific and technical publications are issued annually and include international safety standards, technical guides, conference proceedings, and scientific reports. They cover the breadth of the IAEA’s work, focusing among other topics on nuclear power generation, the use of sealed radioactive sources in medicine, radiation therapy, agriculture, nuclear safety and security, and nuclear law.


The publications by UNSCEAR, the ICRP, and the IAEA are comprised of general principles, mandatory requirements, and binding rules, recommendations, and guidelines. In addition, a growing structure of international treaty obligations and accepted rules of best practices have been developed. Important to note are that these recommendations and standards, while broadly recognized on an international level, are not adopted by all countries in a uniform way. Almost all ICRP recommendations and most IAEA standards are considered to be “soft law” meaning that countries and institutions are encouraged to implement them in regulations and national legislation, without an actual legal obligation to do so.


It is important to note that the national variations in the implementation of nuclear law do not vary from country to country simply due to varying levels of scientific understanding, but is also influenced by political motives and public perception. For example, states that are generally wary of the use of nuclear energy may have a notably different legal framework than states that generally favor the use of nuclear energy, despite these states having essentially the same access to the same scientific information.


There are few hard laws at the international level. Nation states generally retain a large measure of self-determination in regulating nuclear activities within their borders. There is however a substantial international consensus in many areas of radiation protection and consequently in the basic concepts of nuclear law, expressed on the one hand in binding treaties and on the other in rules of soft law, i.e., quasi-legal instruments such as recommendations or guidelines that are strictly speaking not legally binding but are nevertheless widely adopted and may become legally binding in the future.


Adherence to international instruments (e.g., conventions and treaties) has both an external and an internal aspect. As a matter of international law, states that take the necessary steps under their national laws to approve (or ratify) such instruments are then bound by the obligations arising out of that instrument in their relations with other States Parties. When this is the case, states need to establish legal arrangements for implementing those obligations internally. Most States require that the provisions of international instruments be adopted as separate national laws. This approach is, for example, reflected in Article 4 of the Convention on Nuclear Safety [46], which states that: “Each Contracting Party shall take, within the framework of its national law, the legislative, regulatory and administrative measures and other steps necessary to implement its obligations under this Convention.”


When analyzing nuclear law on a national level, there are basic concepts shared by different states and thus large overlaps in national public law even though national laws remain territorial, meaning only applicable to the state or its nationals. It would be impossible to even summarize, let alone provide a comprehensive overview and compare various nuclear laws in different countries.


The EU is a notable exception to the fragmented incorporation of international binding regulations into national legislation. This is because EU regulations provide a legislative framework that is directly applicable within the EU. The most recent regulatory framework is the consolidated version of the 2013 Directive laying down the basic safety standards for protection against the dangers of ionizing radiation. The Directive establishes uniform basic safety standards for the protection of the health of individuals subject to occupational, medical, and public exposures. It applies to any planned, existing, or emergency exposure situation that involves a health risk from exposure to ionizing radiation. The Directive does not apply to natural levels of background radiation, aboveground exposure to radionuclides present in the undisturbed Earth’s crust, exposure of members of the public, or exposure of workers other than air or space crew to cosmic radiation in flight or in space. Exposure to naturally occurring radioactive material (NORM), e.g., in the context of industry or mining activity is regulated if it leads to exposure of workers or members of the public which cannot be disregarded from a radiation protection point of view.


Whether national or regional, it is important to recognize that nuclear law must take its place within the national legal hierarchy. The legal framework in which most states operate consists of several levels. The constitutional level establishes the basic institutional and legal structure governing all relationships within the state. Immediately below the constitutional level is the statutory level, at which specific laws are enacted by the legislative branch of government in order to establish other necessary bodies and to adopt measures relating to the broad range of activities affecting national interests. The third level comprises regulations, detailed and often highly technical rules issued by regulatory bodies to the nuclear industry.


A fundamental element of any national nuclear framework is the creation or maintenance of regulatory bodies with the legal powers and technical competence necessary to ensure that operators of nuclear facilities and users of nuclear material and ionizing radiation operate and use them safely and securely. For example, article 7 of the Convention on Nuclear Safety (CNS) [46] and article 19 of the Joint Convention [47] require the establishment and maintenance of a legislative and regulatory framework to govern the safety of, respectively, nuclear installations and radioactive waste management, identifying a number of functions to be performed by a regulatory body within such a framework.


The central consideration is that a regulatory body should possess the attributes necessary to correctly, self-sufficiently, and independently apply the national laws and regulations designed to protect public health, safety, and the environment. Its tasks can be roughly grouped into four categories: preliminary assessment (establishing requirements and determining whether regulatory control is needed); authorization (licensing and registration, including the prohibition of operations without a license); inspection of nuclear installations and assessment through periodical reviews and enforcing compliance through issuing administrative orders or prohibitions, fines or other penalties. A fifth category, not mentioned in the two aforementioned conventions but considered essential by most regulatory bodies, is the provision of information, including consultation, on regulated activities with the public, the media, the legislature, and other relevant stakeholders. Finally, a regulatory body should be permitted to coordinate its activities with the activities of international and other national bodies involved in nuclear safety.


An example of successful regulation within these parameters can be found in the UK—although the UK is no longer a member of the EU since January 1, 2021—they remain compliant with both article 7 of the CNS and article 19 of the Joint Convention.


A crucial area of nuclear law is nuclear liability. This area is especially important in the context of unplanned emergency exposure to radiation. The occurrence of nuclear and radiological accidents cannot be completely excluded even in situations in which the highest standard of safety has been achieved. All states that engage in nuclear-related activities have generally concluded that general tort law is not an appropriate instrument for providing a liability regime adequate to the specifics of nuclear risks. Tort law is the branch of the law that deals with civil suits alleging negligence, intentional harm, and strict liability, with the exception of disputes involving contracts and is considered to be a form of restorative justice since it seeks to remedy losses or injury from the wrongful acts of others by providing awarding monetary damages to provide full compensation for proved harms. Since civil law is generally designed to cope with large-scale catastrophes, special measures are required, and states have enacted specific nuclear liability legislation.


The Paris Convention [48], the Vienna Convention [49], the Brussels Supplementary Convention [50], the Joint Protocol [51], the Convention on Supplementary Compensation [52], and the Revised Vienna Convention [53] (hereafter “the Conventions”) establish comprehensive regimes for civil liability for nuclear damage. Application of the international nuclear liability regime created by the conventions and the corresponding national legislation will be triggered if an installation or activity causes a nuclear incident.


A nuclear installation must have a person in charge: the operator. In the nuclear liability conventions, the operator is the person—whether this is an individual or any other private or any public entity having a legal personality—designated or recognized as the operator of a nuclear installation by the installation state. The operator, most often the license holder but possibly the owner of the installation, will always be the person responsible (and thus liable) for safety.


The term “nuclear incident” means any occurrence, or any series of occurrences having the same origin, that causes nuclear damage or, but only with respect to preventive measures, creates a grave and imminent threat of causing such damage. Since the occurrence has to cause or threaten nuclear damage, the definition of what constitutes “nuclear damage” is paramount. In general tort law, the concept of compensable damage is well established. If states seek to obtain the benefits of the Conventions, they must accept the definitions.


“Nuclear liability” is understood to be the legal regime based upon the following principles:
“Exclusive liability of the operator of the nuclear installation concerned;

“Absolute” or “strict” liability, so that the injured party is not required to prove fault or negligence on the part of the operator;

Minimum amount of liability;

Obligation for the operator to cover liability through insurance or other financial security;

Limitation of liability in time;

Equal treatment of victims, irrespective of nationality, domicile, or residence, provided that damage is suffered within the geographical scope of the convention;

Exclusive jurisdictional competence of the courts of the contracting party in whose territory the incident occurs or, in case of an incident outside the territories of contracting parties (in the course of transport of nuclear material), of the contracting party in whose territory the liable operator’s installation is situated);

Recognition and enforcement of final judgments rendered by the competent court in all Contracting Parties.” (IAEA Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management [47]).
According to Article 1 of the Paris Convention (Third Party Liability), a “nuclear incident” is considered to be “any occurrence or series of occurrences having the same origin which causes nuclear damage.”


“Absolute” or “strict” liability, so that the injured party is not required to prove fault or negligence on the part of the operator;


Obligation for the operator to cover liability through insurance or other financial security;


Equal treatment of victims, irrespective of nationality, domicile, or residence, provided that damage is suffered within the geographical scope of the convention;


Exclusive jurisdictional competence of the courts of the contracting party in whose territory the incident occurs or, in case of an incident outside the territories of contracting parties (in the course of transport of nuclear material), of the contracting party in whose territory the liable operator’s installation is situated);


Recognition and enforcement of final judgments rendered by the competent court in all Contracting Parties.” (IAEA Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management [47]).


Furthermore, there must be a causal link between a certain nuclear installation, a certain nuclear incident, and the damage suffered. The burden of proof of the causal link is on the person claiming compensation. The Conventions do not contain any provisions regarding causality. This issue is left to the law of the competent court (i.e., to national law), so states may apply the principles of causality applied in their national law. In most states not all causes of damage are legally relevant; for example, remote causes may not be considered. In many states, the law requires “adequate causality,” which means that a cause is only legally relevant if that cause is likely to have directly caused the damage for which compensation is claimed.


The operator of a nuclear installation is held liable, regardless of fault. This concept is sometimes referred to as the channeling of liability. This kind of liability is called strict liability, or sometimes absolute liability or objective liability. It follows that the claimant does not need to prove negligence or any other type of fault on the part of the operator and the simple existence of causation of damage is the basis of the operator’s liability. Furthermore, the operator of a nuclear installation is exclusively liable for nuclear damage. No other person may be held liable, and the operator cannot be held liable under other legal provisions (e.g., tort law). Liability is legally channeled solely onto the operator of the nuclear installation. This concept is a feature of nuclear liability law unmatched in other fields of law. With the exceptions of Austria and the USA, all states party to the Conventions that have enacted nuclear liability laws have accepted the concept of legal channeling. Exonerations from this strict liability are limited; the operator being held liable even if the nuclear incident is caused by force majeure (i.e., “an act of God”).


It is also important to note that the financial compensation which results from the liability may be limited in amount because legislators feel that unlimited financial liability would discourage people from engaging in nuclear-related activities. It is important to note that not all states have chosen to limit liability. In the Conventions, claims for compensation for nuclear damage must be submitted within 30 years in the event of personal injury and within 10 years in the event of other damage.


The nuclear liability conventions require that the operators maintain insurance or provide other financial security covering liability for nuclear damage in such amount, of such type, and in such terms as the installation state specifies. Insurance against nuclear risks is quite different in that there are not many nuclear clients in the insurance industry and while the risk is low in frequency, it is potentially very high in severity, resulting in very high amounts to be covered. On an international level international nuclear pools of insurance exist, where insurance companies net their capacity in order to bring together the financial capacities of the entire pool, which is then used to insure domestic civil nuclear risks and to provide inter-pool reinsurance (reciprocation). This pooling principle trickles down to the national level, where the domestic insurance industry is also organized into nuclear insurance pools.


With regard to the compensation rights of those affected by nuclear energy accidents, the Protocols to amend the Paris Convention on Third Party Liability in the Field of Nuclear Energy and the Brussels Convention Supplementary to the Paris Convention have entered into force on 1 January 2022. The revised conventions combined ensure that those suffering damage resulting from an accident in the nuclear energy sector will be able to seek more compensation—the operator liability will be of at least EUR 700 million under the Paris Convention and the public funds provided under the Brussels Supplementary Convention will complement up to EUR 1.5 billion, a sharp increase from the previous 5 million Special Drawing Rights (SDR) (approximately EUR 6 million as of 13 December 2021) and SDR 125 million (approximately EUR 155 million as of 13 December 2021), respectively. The revised Paris Convention also provides now for a minimum of EUR 70 million and EUR 80 million in case of accidents at low-risk installations and during the transport of nuclear substances, respectively. A total of 16 countries will be parties to the amended Paris Convention, covering 105 operating reactors and 7 under construction, out of a total of 442 operating reactors worldwide and 51 under construction. Of those countries, 13 are also parties to the amended Brussels Supplementary Convention (NEA COM 2021).


Finally, with regard to jurisdiction, national procedural law(s) across countries may indicate several courts to have jurisdiction when dealing with claims arising out of a nuclear incident with transboundary or international effects—meaning several courts could be allowed to claim competence to seize proceedings. The more complicated the different causes and effects, the more parties internationally involved and the larger the effects of the contamination, the greater the selection of potentially competent courts. For this reason, the Conventions provide, firstly, that only courts of the state in which the nuclear incident occurs, have jurisdiction and, secondly, that each member state party to the Conventions shall ensure that only one of its courts has jurisdiction in relation to any one nuclear incident. The concentration of procedures within a single court not only creates legal certainty but also excludes the possibility that victims of nuclear incidents will go “forum shopping” and seek to submit claims in states where their claims are likely to receive more favorable treatment.


If an activity or facility could cause public exposure in neighboring states through the release of radioactive substances to the environment, the regulatory body in the state of the licensee should take steps to ensure that the activity or facility will not cause greater public exposure in neighboring states than in the state of the licensee [55]. The concept of neighboring states does not require that these states share a border.