05000269/FIN-2010004-02
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Finding | |
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| Title | Potential inoperability of condenser off gas radiation monitors |
| Description | An Unresolved Item (URI) was identified when water was observed in the 1-RIA-40 and 2-RIA-40 rotameters. The rotameters were downstream of the detectors indicating that the monitors had been affected by the presence of condensed water. Units 1 and 2 were operating at or near 100% RTP and the mechanical vacuum pumps were not in operation. At full power, the N-16 detectors near the main steam lines were used to determine primary-to-secondary leakage. However, these detectors cannot be relied on when the reactor was at low power or shutdown due to the absence of significant N-16 production. The condenser off-gas monitoring system served to detect primary-to-secondary leakage during operation at low power and when the unit was shut down. The inspectors identified that the condenser off-gas monitors for both Units 1 and 2 had water in the rotameters downstream and approximately three feet above the elevation of the noble gas monitor chamber and detector. Gas Bubbles were passing through the water and it was believed that the monitors detection chamber was also partially filled with water due to their location below the rotameters. The monitor had a horizontally oriented, fixed volume gas measuring chamber with a beta sensitive detector mounted at the end of the chamber. The fixed volume allowed quantification of noble gas entrained in the effluent stream in the event of primary to secondary side leakage. The presence of water in the chamber would reduce the sensitivity to any radioactive noble gases that may be present. Also water would shield the detector from beta particles further reducing the monitors sensitivity. The response due to noble gases adsorbed into the water should be dampened due to the time lag between changes in the gas concentration and the time it takes for the water to reach the new equilibrium. The licensee was performing an analysis on the operability of the detectors and the impact on the ability of the monitor to provide timely detection and quantification of a primary to secondary leak at shutdown and low power conditions. This issue is identified as URI 05000269, 270/2010004-02: Potential Inoperability of Condenser Off-Gas Radiation Monitors. |
| Site: | Oconee  |
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| Report | IR 05000269/2010004 Section 2RS6 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71124.06 |
| Inspectors (proximate) | R Hamilton B Bonsern Merriweathera Nielsen R Hamilton R Rodriguez A Sabisch G Kuzo G Ottenberg J Hamman K Ellis L Suggs M Mcconnell P Shemanski T Koshy |
| INPO aspect | |
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Finding - Oconee - IR 05000269/2010004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Oconee) @ 2010Q3
Self-Identified List (Oconee)
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