[ultima_5]

Any help would be greatly appreciated.

1) For a gram of uranium having this isotopic mixture, what is the decay rate of the u-238 in the fuel?
Possible answers
a. 32 micro-curie
b. 2.1 micro-curie
c. .23 micro-curie
d. 3.1 Ci
e. 2000 Ci

Additional Assumptions:
~two isotopes U-235 and U-238
~For one reactor design, we might have 97% by weight U-238 and 3% by weight U-235.
~The half-life of U-238 is 4.5x10^9 years, while the half-life for U-235 is 7.1x10^8 years.

I'm assuming on this one I should use the equation A=N x (ln(2) / half-life) but I'm really confused on how to use the percentages.

2) If all the energy were from the fission of the U-235 isotope, what is the mass (in metric tons) of the uranium atoms that undergo fission to produce power?

a. 0.96 tons
b. 12 tons
c. 180 tons
d. 3500 tons
e. 0.10 tons

Additional Assumptions:
~A reactor designed to produce power at a rate of 3,000 MW (3x10^9 watts)operates at a capacity factor of 80% for a period of one year (365 days)
~1 watt = 1 J
~1055 J = 6.584x10^15 MeV
~1 Fission produces 193 MeV

I was able to get answer (a), by converting 3x10^9 J/s into MeV / s then finding out how many there are in a year (5.89x10^29 MeV/Year) then finding 80% of that (4.712x10^29), but from there I'm lost.