A typical thermal reactor contains about 100 tons of uranium with an average enrichment of 2% (do not confuse it with the enrichment of the fresh fuel). If the reactor power is 3000MWth, determine the reaction rate and the average core thermal flux.
The amount of fissile 235U per the volume of the reactor core.
m235 [g/core] = 100 [metric tons] x 0.02 [g of 235U / g of U] . 106 [g/metric ton]
= 2 x 106 grams of 235U per the volume of the reactor core
The atomic number density of 235U in the volume of the reactor core:
N235 . V = m235 . NA / M235
= 2 x 106 [g 235 / core] x 6.022 x 1023 [atoms/mol] / 235 [g/mol]
= 5.13 x 1027 atoms / core
The microscopic fission cross-section of 235U (for thermal neutrons):
σf235 = 585 barns
The average recoverable energy per 235U fission:
Er = 200.7 MeV/fission