05000285/FIN-2007007-07
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Finding | |
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| Title | SAFETY INJECTION REFUELING WATER TANK VORTEXING (Section 1R21.b.7) |
| Description | The safety injection reactor water tank provides water to the safety injection pumps during the injection phase of a design basis accident. The tank was selected for inspection to determine if it has sufficient water to satisfy the Technical Specification requirements and to provide assurance that there would not be adverse impact on the -22- Enclosure safety injection pumps due to insufficient net positive suction head or air entrainment. The team found the empty level of the tank was set at 16 inches, +0/-2 inches. The uncertainty calculation for the tank was +/- 1.25 inches which would be outside of the empty level. The licensee performed an operability assessment and determined that, based on the current instrument settings, that the tank remained operational. Early in the inspection, the licensees engineers stated that the question of vortex formation was earlier evaluated and it was determined by the licensee that the vortex eliminator would prevent the formation of the vortex. Condition Report 1998-00284 documented the evaluation results. The vortex eliminator is located at the entrance of the discharge pipe, however, the licensee did not have supporting calculations or test results to provide assurance that there would be no detrimental air entrainment during water discharge. The condition report was not acceptable because there was no supporting test or analytical evidence that the vortex eliminator would perform its function as expected. In lieu of such evidence, the NRC asked how the licensee would provide reasonable assurance that the minimum tank level was adequate. The condition report stated that the current industry methods of analysis were unreliable and that with the vortex eliminator there was no need for a vortex analysis. The team informed the licensee that without test data or an analysis available to support the function of the \\\"vortex eliminator\\\" then the team would have to consider that no vortex eliminator existed and that the licensee would have to determine the proper tank height to assure us that there were no vortices formed at the critical point of switching from the tank to the recirculation sump, and that the net positive suction head was always maintained. The licensee engaged a contractor to perform a test program to determine the acceptable minimum water height of the safety injection refueling water tank. The contractor performed a series of tests, and when questioned on the results from the first tests, elected to perform a second series of testing. Following review of the results from the vortex testing, the team had additional questions concerning the testing results, test report and correlation that is being used to determine the design basis empty water level of the safety injection refueling water tank. This issue is unresolved pending further NRC review of such supporting documents (Unresolved Item 05000285/2007007-07). |
| Site: | Fort Calhoun  |
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| Report | IR 05000285/2007007 Section 1R21 |
| Date counted | Sep 30, 2007 (2007Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | G George J Reynoso L Ellershaw P Wagner W Jonesj Kirklandj Clark A Fairbanks J Wingebach |
| INPO aspect | |
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Finding - Fort Calhoun - IR 05000285/2007007 | |||||||||||||||||||||||||
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Finding List (Fort Calhoun) @ 2007Q3
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