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Features of Fugen's Core |
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Because fission neutrons are moderated sufficiently down to the thermal neutron energy range in heavy water, they are relatively unsusceptible to resonance absorption by plutonium, making the nuclear worth of fissile plutonium and fissile uranium almost equal. Therefore, even if the isotopic composition of the plutonium recovered from spent fuels varies, fuels can be burnt approximately the same as long as the sum of fissile plutonium and fissile uranium are maintained. Additionally, even if uranium and MOX fuel coexist, those fuel assemblies' independency in the core makes the effect of spectral hardening, results from MOX fuel's thermal neutron absorption, on the uranium fuel scarce. The other feature is that MOX fuel loading has little influence on control rod worth because MOX fuels are inserted into heavy water rich in thermal neutron. Consequently, full loading of MOX fuel is possible without the design change of the reactor. |
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Neutron Moderation by Heavy Water
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 Pressure Tubes View from Reactor Bottom |
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