Agenda - 02-02-1999 - 9e1 - Laserfiche WebLink

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Official estimates indicate that this exposure will cause 50-100 thousand extra cancer fatalities worldwide over the next 70 yeazs.19 28. The core of the Harris reactor contains 157 PWR fuel assemblies. At shutdown, this core contains about 155,000 TBq (47 kg) of cesium-137.20 When a spent fuel assembly is discharged from the reactor, it will contain more cesium-137 than the average assembly at shutdown. CP&L plans an eventual, aggregate capacity in the Harris pools of 3,080 PWR assemblies and 5,304 BWR assemblies. Note that the cesium-137 content in each BWR assembly will be about one. quarter the cesium-137 content in each PWR assembly, if both assemblies have been dischazged for an equal period.21 After dischazge, the content of cesium-137 in a fuel assembly will decay exponentially with ahalf--life of 30 years. 29. As a simplified illustration, assume that all fuel assemblies in the Harris pools have been discharged for an equal period. Further assume that all four pools are full and contain 3,080 PWR assemblies and 5,304 BWR assemblies. The pools will then contain as much cesium-137 as 4,406 PWR assemblies. (3,080 + 5,304 x 1/4 = 4,406) Note that 4,406 PWR assemblies represent 28 cores of the Harris reactor. 30. If an accident can be postulated that releases to the environment a significant fraction of the cesium-137 in the Harris pools, then it is clear that the consequences of this accident would be large. The offsite radiation exposure could be an order of magnitude larger-than the exposure from the Chernobyl accident. Activation of pools C and D could lead to an accident which creates offsite radiation exposure as much as two times higher than the exposure that would arise from a similar accident involving only pools A and B. H. Loss of Water from Spent Fuel Pools at Harris 31. Loss of water from one or more of the Harris pools could initiate a release to the environment of a significant fraction of the cesium-137 in the pools. This potential exists because the cladding of PWR or BWR fuel is a zirconium alloy which can react exothermically with air or steam. Thus, if the water in a fuel pool is removed and the fuel is partially or totally uncovered, one must be concerned about the possibility of a runawayair-zircomum or steam-zirconium reaction. Such a reaction could release cesium-137 and other radioisotopes from affected fuel-into the fuel building. That building was not designed to contain radioisotopes released during a vigorous exothermic reaction in the pools, and it can be assumed that most of the volatile radioisotopes entering the building from the affected fuel would be released from the building as an atmospheric plume. 32. Several reports prepared by or for the NRC have examined the conditions under which a runaway zirconium reaction might occur.22 However, these reports have ~9 Allan S Krass, Consequences of the Chernobyl Accident (Cambridge, Massachusetts: Institute for ~ Resource and Security Studies, December 1991). 20 NRC, Final Environmental Statement, page 5-50. 21 The ratio of one quarter derives from the parameters shown in the license amendment application, ~ Enclosure 7, page 5-15. 22 Relevant reports include: V L Sailor et al, Severe Accidents in Spent Fuel Pools in Support of Generic Safety Issue 82, NUREG/CR-4982, July 1987; E D Throm, Regulatory Analysis for the Resolution of Generic Issue 82, "Beyond Design Basis Accidents in Spent Fuel Pools", NUREG-1353, April 1989; and R