05000454/FIN-2011015-01
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Finding | |
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| Title | Design of Auxiliary Feedwater System Included Voids in Safety-Related Alternate Suction Flowpaths |
| Description | A URI was identified by the inspectors during the review of voided sections of AF alternate suction piping affecting all AF trains at Braidwood and Byron. Specifically, the inspectors questioned the acceptability of the voids and the potential impact on the AF systems, and an adequate technical justification from the licensee was not readily available. The AF system provides decay heat removal by cooling the steam generators following a reactor shutdown. The normal supply of water to the AF system is from the non-safety related condensate storage tank (CST), which contains chemically treated water. In the event the CST becomes empty or damaged, the alternate water source is the safety related SX system, which provides lake water at Braidwood and river water at Byron. The design of the AF systems at Braidwood and Byron included a section of SX supply to AF piping that was maintained voided between two valves with a partially open drain. The purpose of this configuration was to prevent SX water intrusion into the steam generators through valve leak-by, which would have an adverse chemical effect since SX water is not chemically treated to the same standards as CST water. On January 31, 2011, NRC inspectors at Byron questioned the existence of voided sections of piping in the SX supply to the AF system. At Byron, the NRC questions were entered into the CAP as IR 1172938. In response to the question identified in the subject IR, the Byron licensee concluded that the AF system was operable with the voids present based on a 1993 Byron Engineering letter addressed to the Braidwood and Byron Station Managers. This letter documented that the AF pumps would not be adversely affected by the ingestion of the assumed voids through the pumps following a swap-over from the CST to the SX water supply. As a basis for this conclusion, the letter referenced a 1987 telephone conversation with the pump vendor and a Duke Engineering Services letter, neither of which were attached to the Byron Engineering letter. The inspectors at Byron questioned whether this conclusion was valid since no formal documentation supporting the conclusion was included with the 1993 Byron Engineering letter. Despite an exhaustive effort at Byron, neither a record of the telephone conversation with the pump vendor or a copy of the Duke Engineering Services letter that provided the basis for the conclusion in the Byron Engineering letter could be found. At Byron, in the absence of formal documentation supporting the conclusion that the AF pumps would not be adversely impacted by the ingestion of the voids following a swap over from the CST to the SX water supply, previously installed vent valves in the voided piping sections were used to fill the voids in all four AF trains on Unit 1 and Unit 2 on February 15, which eliminated current operability questions. Event Notification (EN) 446708 for Byron was submitted to the NRC on March 30, 2011, in accordance with 10 CFR 50.72(b)(3)(ii)(B). |
| Site: | Byron  |
|---|---|
| Report | IR 05000454/2011015 Section 4OA5 |
| Date counted | Jun 30, 2011 (2011Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 93812 |
| Inspectors (proximate) | E Duncan J Gilliam J Nance R Ng C Thompson B Bartlett J Robbins J Cassidy T Bilik B Metrow D Jonesc Zoias Sheldon A Garmoe S West |
| INPO aspect | |
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Finding - Byron - IR 05000454/2011015 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Byron) @ 2011Q2
Self-Identified List (Byron)
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