ESTABLISHMENT AND DEMONSTRATION OF



　Achievements of Plutonium(MOX) Fuel Utilization

The average utilization factor in the past 24 years after starting the practical operation is approximately 62%. Fugen's basic operation cycle consists of six months operation, a month shutdown for refueling, six months operation and three months periodical inspection. The average utilization factor, 62%, based on this cycle is favorable and is compatible to other LWRs constructed in the same period.
For the past 25 years since the reactor attained the first criticality with 22 MOX fuels in March 1978, Fugen has been operating loading 772 MOX fuels (including approximately 1850kg of plutonium, metal weight) and 687 uranium fuels. Although Fugen has experienced one leak from a uranium fuel in April 2002, no other leak has been detected on MOX fuels.
At Fugen, it is possible to load full MOX fuels in the core. But the loading ratio has been flexibly controlled according to the supply and demand status of plutonium. The loading ratio ranges from 34% to 72% and that figure shows the core flexibility in the plutonium utilization. Additionally, the percentage of plutonium fission almost corresponds to the MOX fuel's loading ratio. The maximum plutonium fission in the past performance is 70% of power generation.
As for the disposition of MOX fuels in the core, 96 MOX fuels were loaded in the center of the core in the early stage of operation to confirm the characteristics of plutonium core. Subsequently, MOX fuel and uranium fuel were loaded dispersed and demonstrated the validity of usage equality in the core.
The maximum burnup of regular MOX fuel at Fugen is approximately 20GWd/t (assembly's average), which is half of uranium fuel's burnup at recent LWRs. However, the experimental MOX fuels irradiated at Fugen as part of the ATR demonstration plant's fuel development, marked approximately 38GWd/t. Currently, those fuels are under postirradiation examination and the results are expected to be exploited in the plutonium utilization in LWR (plutonium-thermal) project.

Fugen Nuclear Power Station