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9 <br /> modelling . The modelling should consider both partial and complete uncovering and the <br /> transition from one of these states to the other . Also , the modelling should cover : ( 1 ) <br /> thermal radiation, conduction, and steam or air convection ; (2) air-zirconium and steam- <br /> zirconium reactions ; (3 ) variations along the fuel rod axis ; and (4 ) radial variations within <br /> a representative fuel rod, including effects of the pellet-cladding gap . Experiments will <br /> probably be required to support and validate the modelling . <br /> 37 . Until the problem of water loss is re - analyzed in this manner, there is no basis for <br /> determining when fuel has been discharged for a sufficiently long period that it will not <br /> suffer a runaway zirconium reaction in the event of water loss . If the problem were to be <br /> properly analyzed through validated models , such a determination could be made within <br /> some margin of error, but the determination should consider site- specific factors . For <br /> example , the detailed design of a rack might be an important site-specific factor . <br /> 3 8 . No determination of this kind has been made for pools C and D at Harris , nor does <br /> the methodology now exist to make such a determination. In any case , there is nothing in <br /> the license amendment application and its proposed modifications to the Harris Technical <br /> Specifications which prohibits the placing of freshly discharged fuel in pools C and D . <br /> Reports previously prepared for the NRC concede that freshly discharged fuel can <br /> experience a runaway air-zirconium reaction in the event of complete water loss . <br /> 39 . A variety of events, alone or in combination, could lead to partial or complete <br /> uncovering of spent fuel in the Harris pools . This class of events should be subjected to <br /> the kind of systematic analysis that is performed in an IPE and an IPEEE . Relevant <br /> events include : ( 1 ) an earthquake, cask drop , aircraft crash, human error, equipment <br /> failure or sabotage event that leads to direct leakage from the pools ; (2) siphoning of <br /> water from the pools through accident or malice ; (3 ) interruption of pool cooling, leading <br /> to pool boiling and loss of water by evaporation ; and (4) loss of water from active pools <br /> into adjacent pools or canals that have been gated off and drained . Interactions with the <br /> Harris reactor should be considered . For example, a reactor. accident might release <br /> radioactivity that precludes personnel access to the plant for purposes of maintaining or <br /> restoring pool cooling . <br /> I. Increased Probability or Consequences of Accidents Previously Evaluated <br /> 40 . The Federal Register notice of this license amendment application claims that the <br /> probability of a spent fuel assembly drop or a misloaded fuel assembly is not significantly <br /> increased if the license amendment is approved and pools C and D are activated . This <br /> claim is false , because activation of pools C and D will roughly double the total number <br /> of fuel handling operations to be conducted at Harris . Assuming that the general nature <br /> of fuel handling operations continues as before, the probability of a fuel assembly drop or <br /> misloaded fuel assembly, integrated over the entire period of the Harris operating license , <br /> will increase significantly, by a factor of two . This point has been made by David <br /> Lochbaum of the Union of Concerned Scientists , in a 22 January 1999 letter to the NRC <br /> Commissioners . A •copy of his letter is provided here as Attachment F . If probability is <br /> integrated over the remaining period of the Harris operating license, rather than over its <br /> total duration, then activation of pools C and D will more than double the probability of a <br /> fuel assembly drop or a misloaded fuel assembly. <br /> 41 . A spent fuel assembly drop or a misloaded fuel assembly are members of a broader <br /> class of accidents that could arise during the movement of fuel from other CP &L stations <br /> to Harris , and during fuel movement within Harris . This class of accidents will include <br /> design-basis accidents and severe accidents . Assuming that the general nature of fuel <br /> movement continues as before, the probability of accidents in this class , integrated over <br />