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13 <br />Nuclear 'Haste Disposal Cnsis <br />earthquake three tunes la der than they were de>>gned to handle. Then also con- <br />cluded that it •••uuld take an earthquake nearly ten times greaten than the design <br />basis earthquake to cause the spent fuel pools to fail catastrophically.'° .. <br />Spent Fuel pools are nut designed to withstand a shipping cask weighing T <br />to 110 turn dropping onto their flours ur .valls. A dropped cask will probably <br />cause the spent fuel pool to fail catastrophically. Although the consequences from <br />a cask dropping into the spent fuel pool are significant, the probability that such ; <br />an e.•ent .will occur has been considered to be sufficiently low as to effectively ;: <br />manage this risk factor. "~ <br />While the nuclear pu•ver industry has nut experienced the prototypical cask `' <br />drug event, there have been precursors. On December 28, 1994, a core shroud w <br />head bolt dropped into the Unit 1 spent Euel pool at Georgia Power Company's.: ~: <br />Edwin I. Hatch Nuclear Plant from one foot above the water surface when the ` <br />sling holding the butt broke. The bolt, 17 feet lung by three inches in diameter and <br />weighing 36~ pounds, glanced off the side wall and fell to the bottom of the spent • . <br />fuel pool v`•ithuut hitting the storage racks or irradiated fuel assemblies. The bolt <br />tore a three inch gash in the 3/16 inch thick stainless steel liner. Approximately <br />2,000 gallons leaked through the hole and through a drain line to the radwaste <br />system before valves in es eind31minlutes, causing the fuel p~l coolulgFsystem <br />dropped nearly t<vo Inch <br />pumps to trip un low suction pressure. Operators restored level after the leakage <br />path was isolated, then returned the fuel pool cooling system to service. Georgia <br />Po.••er removed the bolt and placed a larje rubber mat (i.e., a nuclear-sized sink <br />stopper) over the hole to limit leakage until underwater welding repairs were <br />completed. <br />The Hatch incident occurred less than a vear after a screwdriver dropped <br />into the spent fuel pool at a foreign nuclear pu•ver plant with similar results. On <br />January 31, 1994, workers at Tricastin Unit 1 in France were removing the control <br />rod duster ;aide tube from a spent fuel assembly. A 15 foot long screwdriver <br />..•eighing -4-4 pounds fell into the spent fuel pool and punctured the stainless steel <br />liner. The le.•el in the spent fuel pool dropped nearly four inches. A stainless steel <br />plate .vas ••'elded over the lwle. <br />Spent fuel pools are nut designed to .yithstand the impact from a turbine <br />venerated missile. A turbine generated missile can result from the main turbine's <br />gross failure. The detached blading ur shroud from a large turbine spinning at <br />1,50(1 rpm can be extremely detrimental to .vhatever it impac~• The probability <br />that a turbine generated missile will cause spent fuel pool integrity failure has <br />been estimated to be •i.ix10~ per reactor vear. This prubability is predicated on a <br />l~lU' per reactor year prubability that a turbine failure event generates a missile <br />cuinbined ~.'itlt a -4.1x10 `prubability that such a missile strikes the spent fuel pool <br />~.•tth suffi~tel~t enemy to be ~iestruchye. ' 1993, <br />Full~~~• ul~ the marl turbine failure at Fermi l; nit ? un Christm~N Dr~[ed by <br />Drtnnt Edi>~m Company determu~e~i th,it .~ hi:;h trajectory missile ~_ <br />Ill <br />