The condition of the fuel debris has not yet been identified in any reactor except
estimations by severe accident analysis codes. Study of the TMI-2 fuel debris [6],
however, suggests that various kinds of fuel debris may also be produced in the
1FNPS reactors, such as hard and loose debris. Especially, loose debris may show a
wide variety of composition including structural materials such as Zircaloy and
Fig. 21.1 Benchmark model of the BWR STEP3 fuel assembly
21 Options of Principles of Fuel Debris Criticality Control in Fukushima. . .
253
estimations by severe accident analysis codes. Study of the TMI-2 fuel debris [6],
however, suggests that various kinds of fuel debris may also be produced in the
1FNPS reactors, such as hard and loose debris. Especially, loose debris may show a
wide variety of composition including structural materials such as Zircaloy and
Fig. 21.1 Benchmark model of the BWR STEP3 fuel assembly
21 Options of Principles of Fuel Debris Criticality Control in Fukushima. . .
253