prompt: A civil reactor experiences a step reactivity insertion of +100 pcm. Using six-group thermal U-235 kinetics, what is the stable (asymptotic) reactor period? Non-operational.

reference_answer: The dominant inhour root gives a stable reactor period of about 53.59 s.


prompt: A -145 pcm step reactivity is inserted into a civil reactor. What asymptotic period does six-group U-235 kinetics predict?

reference_answer: The asymptotic period is about -107.4 s; the negative sign means the neutron population is decaying.


prompt: For a +100 pcm step below prompt critical, what prompt-jump factor n_after/n_before does beta/(beta - rho) give for thermal U-235?

field: ratio

reference_answer: The prompt jump raises the neutron population by a factor of about 1.185.


prompt: Convert -145 pcm to dollars for a core with beta_eff = 0.0064. Show the value in dollars.

from_unit: pcm

to_unit: dollars

field: value

reference_answer: At beta_eff = 0.0064, -145 pcm is about -0.2266 dollars.


prompt: Express 250 pcm as a dimensionless dk/k reactivity.

to_unit: dkk

reference_answer: 250 pcm equals 0.0025 in dk/k.


prompt: Compute the fuel (Doppler) reactivity feedback in pcm for alpha_f = -2.5e-5 /K and a fuel temperature rise of 42 K. Define all variables.

reference_answer: The Doppler feedback is rho = alpha_f * dT_f, about -105 pcm.


prompt: A civil reactor sees a fuel rise of 42 K (alpha_f = -2.5e-5 /K) and a moderator rise of 5 K (alpha_m = -3.0e-4 /K). What is the total temperature feedback in pcm? The contributions add.

reference_answer: Adding fuel and moderator contributions gives about -255 pcm total.


prompt: A civil reactor operates at thermal flux 2.0e13 n/cm^2/s with Sigma_f = 0.043 1/cm. What is the equilibrium Xe-135 reactivity worth in pcm? Non-operational.

reference_answer: Equilibrium Xe-135 is worth about -1949 pcm, always a poison.


prompt: At thermal flux 2.0e13 n/cm^2/s and Sigma_f = 0.043 1/cm, what is the equilibrium Xe-135 concentration in atoms/cm^3?

reference_answer: The equilibrium Xe-135 concentration is about 7.6867e+14 atoms/cm^3 (xenon saturates because burnout removes it).


prompt: At thermal flux 2.0e13 n/cm^2/s and Sigma_f = 0.043 1/cm, what is the equilibrium I-135 concentration in atoms/cm^3?

reference_answer: Equilibrium I-135 is about 1.8752e+15 atoms/cm^3 (linear in flux, no burnout).


prompt: After tripping from equilibrium at flux 2.0e13 n/cm^2/s (Sigma_f = 0.043 1/cm), how many hours after shutdown does the Xe-135 peak occur?

reference_answer: The post-shutdown xenon peak occurs about 7.452 hours after trip.


prompt: At thermal flux 3.0e13 n/cm^2/s with Sigma_f = 0.2 1/cm, what is the equilibrium Xe-135 reactivity worth in pcm?

reference_answer: Equilibrium Xe-135 worth is about -2154 pcm at this flux and Sigma_f.


prompt: Roughly what percent of full thermal power is civil decay heat one hour (3600 s) after shutdown, using the Way-Wigner correlation for long irradiation?

field: percent

reference_answer: One hour after shutdown, decay heat is about 0.9617% of full power.


prompt: Using Way-Wigner for long irradiation, about what percent of full power is decay heat one day (86400 s) after shutdown?

reference_answer: One day after shutdown, decay heat is about 0.3933% of full power.


prompt: A 3400 MWt civil core is shut down. Using Way-Wigner, about how many MWt of decay heat must be removed one hour (3600 s) later?

reference_answer: About 32.7 MWt of decay heat must be removed one hour after shutdown.