05000282/FIN-2010006-06
Finding | |
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| Title | No Full Flow Testing of PORV Air Supply Check Valves |
| Description | The inspectors identified an unresolved issue (URI) related to full flow testing of a safety-related air supply check valve to demonstrate that it will perform satisfactorily in service. Specifically, the licensee has not performed initial or periodic flow testing of the opening function of a check valve installed as part of a backup air supply system for operating pressurizer PORVs.
The pressurizer PORVs are spring loaded closed. The PORVs were designed to fail closed upon loss of power or control air to prevent loss of RCS inventory. Air to open the valves was normally supplied by a control air source. To assure the ability of the valves to open on loss of control air, a backup air supply was provided. It consisted of a passive air accumulator for each PORV, which was supplemented by temporary compressed air bottles when the plant was in the LTOP mode of operation. In 2004, Westinghouse performed an analysis Westinghouse COMS Transient Analysis, Report. No. NSP-04-189 which determined that the PORVs would need to stroke 143 times in ten minutes in order to provide sufficient LTOP protection during mass addition transient. In 2005, the licensee installed Temporary Modification 04T175, Pressurizer PORV Air Accumulator Supplementation. The inspectors reviewed Temporary Modification 04T175, and noted that no post modification testing of the system was performed to ensure the system would deliver the required amount of air flow rate assumed in the analysis. Calculation ENG-ME-584, Sizing of Supplemental Air Supplies for Pressurizer PORV Air Accumulators, Revision 0 determined how much air would be needed to stroke the PORVs during the LTOP licensing basis mass injection event (143 strokes in ten minutes). The calculation stated that approximately 2430 standard cubic feet per hour (scfh) of air, or about 41 standard cubic feet per minute (scfm) was needed for ten minutes. A check valve was installed in the piping system between the temporary air supply, after the air regulator, and the PORVs. The inspectors questioned if the check valve was initially tested, or periodically tested to ensure the valve would pass full design flow. The inspectors were informed that the valve was never tested to ensure it could pass full flow. Subsequently, the licensee entered this issue into their corrective action program as CAP 01242980 to develop test criteria to full flow test the system to ensure the design flow rate assumed in the analysis would be available to the PORVs. On August 30, 2010, the licensee performed a flow testing of the LTOP temporary modification check valve per work order WO 0411821 to demonstrate that the check valve was able to open and pass flow under simulated LTOP design basis conditions. During testing, the test rig was unable to establish a differential pressure across the check valve that was high enough to demonstrate the required flow because the 3/8 to 1/4 ID tubing used in the test rig resulted in higher system resistance than the actual LTOP backup air system. However, the licensee concluded that the flow tests demonstrated that the valve was capable of passing at least as much air as an open in-line fitting in the test rig line. The licensees conclusion was based on the check valve manufacturer data and discussion with the site check valve Program Engineer. The inspectors reviewed the test results and the licensees conclusion and determined that the licensees justification for operability was inadequate. Specifically, the licensee performed six tests/scenarios for the backup air supply system, two tests with the check valve installed, and 4 tests with the check valve removed. During all six tests, the licensee was not able to establish the design flow value of 2430 scfh required per the design calculation to support the operability of the pressurizer PORV under simulated LTOP design basis conditions. This issue is considered unresolved pending the licensees further evaluation or retesting of the check valve to demonstrate that the valve is able to open and pass the required flow under simulated LTOP design basis conditions. (URI 05000282/2010006-06; 05000306/2010006-06, No Full Flow Testing of PORV Air Supply Check Valves). |
| Site: | Prairie Island  |
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| Report | IR 05000282/2010006 Section 1R21 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | J Jandovitz M Mitchell C Brown M Phalen K Stoedter D Betancourt J Corujo-Sandin E Sanchez N Feliz-Adorno S Lynch S Shahj Chiloyand Betancourt M Munir A Dahbur D Szwarc C Brown B Sherbin |
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Finding - Prairie Island - IR 05000282/2010006 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Prairie Island) @ 2010Q3
Self-Identified List (Prairie Island)
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