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The team identified a violation of 10 CFR … The team identified a violation of 10 CFR 50, Appendix B, Criterion III, Design Control, associated with TVAs failure to use appropriate assumptions in design calculations at the Sequoyah Nuclear Plant. TVAs failure to use appropriate assumptions in design calculations resulted in a significant increase in the calculated maximum room temperatures for the Emergency Core Cooling System pump rooms as well as the TDAFW pump room. This increase in the calculated maximum room temperatures led to a reasonable doubt about the operability of components in the affected rooms. Description. Design Criteria Document SQN-DC-V-13.9.3, Auxiliary Building Ventilation and Cooling, Table T1.34 established the design temperatures for the TDAFW pump room for normal and abnormal conditions. This document established a maximum room temperature of 110 F for an abnormal operational event. TVA calculation SQN-31CD053- EPM-RG-060987, Revision 2 was developed, in part, to determine if the capacity of the installed direct current (DC) fan equipment for the TDAFW pump was adequate to maintain the maximum design temperature of 110 F specified in the design criteria document. The calculation determined the air temperature needed to maintain the abnormal design temperature based on the heat input load calculated in SQN-31CD053- EPM-DLM01-030887, HVAC Cooling Load Calculation: Aux. Bldg. TDAFW pump, Revision 2 and determined an inlet air temperature of 80 F. Based on a preliminary calculation, the installed fan would maintain the TDAFW pump room at 131 F instead of 110 F. This issue was entered into the CAP as PER 126928. A review of the environmental qualification (EQ) list of equipment inside that room indicated that the equipment is qualified to at an ambient temperature of 215 F which is higher than the 110F specified in the design criteria document. Another design calculation with inappropriate assumptions was Engineered Safety Features (EFS) room cooler calculation, 30-DO53-EPM-BVC-052788, Emergency Raw Cooling Water (ERCW) River Water Temperatures Effect on ESF Coolers, Rev. 7. The incorrect assumption was the use of input cooler air flow rates that were higher than the minimum design flow rate. In this case, the non conservative nominal value of 4933 cubic feet per minute (CFM) was used as opposed to the minimum design airflow rate of 4439 CFM in order to calculate maximum accident room temperature. Deficient assumptions included using an ERCW supply temperature and flow rate that were not worst case for the calculations. As a result of the use of non conservative input values in the ESF maximum room temperature calculations, the installed room coolers were not capable of maintaining the analyzed temperatures for the ESF rooms. The licensee performed a preliminary calculation which showed a significant reduction in margin between the calculated maximum room temperatures and design limits. In the case of the 1B-B Centrifugal Charging Pump (CCP) room, the design temperature limit was exceeded by .6 degrees. The team determined the 1B-B CCP to be operable because of additional margin available with respect to environmental qualification. Analysis. The TVA\'s failure to use appropriate assumptions for ESF and TDAFW pump maximum room temperature calculations is a performance deficiency associated with the Mitigating Systems cornerstone. This finding is more than minor because if left uncorrected problems in Design Control could lead to a more serious safety concern as many other safety-related design calculations rely upon these design outputs. This finding was reviewed for cross-cutting aspects and none were identified.-cutting aspects and none were identified.
23:59:59, 30 September 2007 +
23:59:59, 30 September 2007 +
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00:34:21, 21 February 2018 +
23:59:59, 30 September 2007 +