Calculating Number Density in a Sodium-Uranium Mixture

[clynne21]

Homework Statement

Consider a mixture of sodium and 20 atomic percent enriched uranium (20 % U-235 and
80 % U-238). If there are 49 moles of sodium for every mole of uranium and the density
of the mixture is 1.1 g/cc

This is only the first part of the information- I need the number density to calculate fuel and moderator cross sections for reactor calcs in the rest of the problem

Homework Equations

The Attempt at a Solution

Tried numerous different ways to calculate the number density, but no matter what I've tried I keep getting the wrong answer in the rest of the work. This is just one attempt.

49mol x ((1.1x(6.022x10²³)0/22.99) (number density for sodium)

1mol x .2((1.1x(6.022x10²³)0/235.0439) (number density for U-235)

 

[jbsteele]

+.8((1.1x(6.022x1023)0/238.0289) (number density for U-238)I'm really stuck and would really appreciate any help. Thanks!