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Jan23-08, 04:11 PM
P: 925
They sort of do already. In a fission reaction, there is about 170 MeV of instantaneous energy deposited in the reactor per fission event. In PWR/BWR reactors, cooling the reactor provides the steam that is diverted to a turbine which generates the electricity. There is about 18 or so MeV in the delayed energy from decay product and neutron capture gammas which also is deposited in the reactor, so in a sense the decay products are adding a little extra power to the reactor. This is why when the reactor is shut down and there are no fissions, there is still some of this decay heat which needs to be removed from the reactor. However, after some time, the SNF acts like a poison to the reactor and the neutrons are absorbed into fission fragments, which reduces the effectiveness of the fuel (meaning fewer fissions, meaning less MeV deposited in the reactor). So, basically, a little bit of byproduct material is good, but too much is bad.