Agenda - 11-17-1998 - 5a - Laserfiche WebLink

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19 . Nuclear Waste Dispas:,1 Cnsrs caused by stress corrosion cracking of the stainless steel. The stress corrosion cracking vas nut belie~•ed to ha~•e occurred during reactor uperatiun because the hydrogen overpressure should result in low Free oxygen levels. However, the spent fuel pool has highly oxygenated ~~•ater at low temperature that could cause cracking in the presence of high stresses and sensitized stainless steel. A total of 2? spent foe! assemblies at Prairie [slam were examined with 12 showing signs of corrosion.'" At Brunstivick in October 19y-1, while being seated on a loaded ~v03 spe L fuel shipping cask, a closure head became cocked and required realignment Durin; the lifting uperatiun, the closure head became stuck on one side of the' cask causing trvo of tour lifting cables to become overstressed and break The reactor building overhead crane was nut equipped with a load cell to indicat-''e excessive loading. ., The nuclear power industry encountered a number of fuel handling itt~; dents in the early days that compelled hardware changes and training upgrades. Once the break-in period passed, the frequency of the fuel handling inddenta decreased to approach that level defined by random equipment failures and pei~ sonnel errors. ~ _;. The risk from a fuel handling incident is limited to a single irradiated fuel assembly and whatever it strikes during transport or after being dropped Nuclear power plants analyze pustulated refueling accidents to ensure thatthe radiological consequences are within 10 CFR, Part 20 guidelines for nuclear pu~ver plant workers and 10 CFR, Part IUO guidelines Eor the public and the envi- ronment. The typical analysis assumes an irradiated fuel assembly is dropped from the maximum allowable height onto irradiated fue! assemblies in the rear fur core ur in the spent Euel pool's storage racks. The dropped assembly impacts one ur more fuel assemblies before coming to rest. The number of fuel rods dam=p aged in the event is conservatively determined from an energy balance and theme' fuel assemblies' material properties. The Eissiun products released from the dam-.; aged fuel rods are estimated and applied to ventilation and filter conf~guratio s to develop the site and off-site radiological doses. The calculated dose to the pub; lic and to the workers is generally a small Fraction of the allowable limits. ~_^ Cri~icali~y ~: Spent fuel storage racks are designed to maintain the spent Euel assemblies`-^ in a subcritical confiwratiun. This assi~•e function undertook increased si f o P ~=. once when high-density storage racks featuring irradiated fuel assemblies in. tightl~• packed arrays were introduced. ~ small number of incidents challenging this subcriticality requirement have been reported: Gaps were measured in the Buratlex material used in the high-density fuel stura,~e rack at Quad Cities l,'nits l and '_ ui Slav 1y5~ .The gap formation meeh- anum ~~•as considered to be related to large local stresses in the Buraflex from fab-, ncahun-induced restraint «•ithm the nck and to tearing and shrinkage of the r ~=• v~•' `""~=+. 1~8