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

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12 Chapter Eight • Spent Fuel Rtsks Loss of Water Inventory The principal spent fuel accident concern is losing spent fuel pool ~.•ater end the capability to caul the irradiated fuel assemblies. [f the spent fuel pool drams, the spent fuel assemblies discharged within the past three to four veirti ,till pr~- duce sufficient decay heat to cause meltdown. in addihun, the htel'~ cla~idin could initiate and sustain rapid oxidation (often referred to as "fire' uut~id~~ the nuclear power industry) during heatup prior to melting. The resultiti, .la~idin~ fire in a spent fuel pool equipped with high-density storage rark~ ruul~i :pre~d to every spent fuel assembly. The probability that the cladding would catch urrfire after the spent fuel pool completely drains has been estimated at 100~'~ for PWRs and 2~=.'. fur B~~'Ps.' The BWR probability is significantly lower because it was assumed that tl~e BtVR spent fuel assemblies are stored with their fuel channels in place, thus acting as barriers preventing the fire from spreading. Storing BWR spent fuel assemblies kith the fuel channels in place significantly reduces spent fuel risk, vet the SRC dues nut require or even recommend that BWR plants implement thu ine~pen- sive safety precaution. The loss of spent fuel pool water inventory e~•ent has the potential fur c~nt- aminating the environment tivorse than would occur from a reactor core accident due to the significantly la der quantity of radioactive material a. ~ilable fur release.' Additionally, the loss of spent foe! pool ~.•ater im•entun• r~•~•nt i~ inher- ently worse than the reactor cure accident because the fuel d.ima~__• ,utd radiuar- tivity release urcvr outside the major barrier protecting the pubic,. the prtman~ containment. Therefore, it is mute likely that radioactive material r~•lriwd in a spent fuel pool accident would reach the environment. Several failure mules causing spent fuel puuTweter in~•enturv to be lust were considered during the design process. The predominant fai!t;r,: [nude is structural integrity damage that drains the spent fuel pool ~.•ater at ,t r,~te e~ceed- ing makeup capability. The events producing this failure mo~i~ , r!• quakes, heavy loads dropping into the pouf ur onto its wall, and ti: . ed missiles. The secondary failure mule im•olves fuel pool cuolin warm mil- htnrhuns enabling accelerated water loss from the pool. Thy e.•ent> prudurin this failure mule include a fuel pool cooling system pipe break and a failure of the system's heat removal function. Another failure mud e, typically nut run~id- ered dunng the design process but pru~•ing to be rather troublesome nonetheless. in~•ul~•es sell failure that allu..-s water to leak from the pool into ,t~ii,t:eni .tr~a, Sorb as the containment, the shipping cask pit, and the fuel tran.t~ r tuh~~ The spent Fuel pools at nuclear power plants to the t_ rit~•~1 ~t.lte•. are de~t~ned to withstand earthquakes without loss ut inte~rtt~' Thy \l:C ~~. ,~lu.tted the spent fuel pooh at the ~'ermunt Yankee an~i the H. B R~~i•r•~~m hl,tnt~ t., ~irt~•rnunr thetr.ulnerabilit~' to earthquakes more ~r.•ert~ thin ~~•~•.;,I~~r~•.i .lurut ~i~~~i~n Th~•~~ runrludrd that the spenc fuel pool, ~.~ouid prol~,ti~l~ •ur. n u .ut