Consider a sphere of uranium (density 19.1 g=cm3) with the following composition: 235U97.6 at% and 238U 2.4 at%. Use the diffusion theory to determine:

(a) the critical radius of the sphere with vacuum boundary conditions;

(b) the reflector saving when the sphere is surrounded by water (1.0 g=cm3)—assume infinite reflector. 

 

Use the following data.

Element   Sigma_cap(b)   Sigma_f (b)   Sigma_tr (b)    v
235U             0.15                    1.25             5.03            2.60
238U             0.10                     0.21            5.73            2.80
H2O               0.13                       -               16.68             -