A nuclear reactor is loaded at the start of the year with 40 tons of fuel containing 4 percent uranium-235 and 96 percent uranium-238. During power production over the course of three years (a typical fuel burn-up period), three-fourths of the uranium-235 is fissioned; further, 2% of the fuel is converted from uranium-238 to various plutonium isotopes. Find:

1) The percentage of fission products and uranium-235 remaining in the reactor's spent fuel at the end of three years.

2) The weight of fission products, uranium-235, uranium-238, and plutonium isotopes remaining in the reactor's spent fuel at the end of three years.

Note: In an actual reactor, some of the plutonium produced from uranium-238 would fission and produce energy. For simplicity, we have not included this aspect in the numerical calculations suggested above.

Institute for Energy and Environmental Research

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Last updated: September 1996