ML20207A709
| ML20207A709 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/07/1986 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20207A713 | List: |
| References | |
| FOIA-86-862, REF-GTECI-A-01, REF-GTECI-PI, RTR-NUREG-1190, TASK-A-01, TASK-A-1, TASK-OR NUDOCS 8607160399 | |
| Download: ML20207A709 (2) | |
Text
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July 7, 1986 rii,0RAWDUM FOR:
Victor Stello, Jr.
Executive Director for Operations FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
REVIEW AND ASSESSMENT OF WATER HAMMER OCCURREhCES SINCE CY 1981 This memorandum is our response to staff action Item No. 2 enclosed with your February 4, 1986 memorandum:
" Staff Actions Resulting from the Investigation of the November 21, 1985 San Onofre Nuclear Generating Station, Unit 1 Event (NUREG-1190)." The principal reason for this reassessment was the Chairman's question during the San Onofre IIT's briefing on January 22, 1986 regarding the need to reopen USI,A-1.
We reviewed the reported water hammer occurrences and find that the frequency of water hamer occurrence has decreased since last reviewed in 1981 as part of the resolution of USI A-1 and that no new underlying causes have emerged.
i We do not expect to achieve a total elimination of water hamer occurrences (as noted previously in the resolution of USI A-1) nor do we see a stronger safety implication than was previously derived.
We find the San Onofre Unit I water hamer attributable to grossly failed check valves in the feedwater system and not a basis for reopening the water hamer safety issue. Moreover, the resolution of USI A-1 recognized that t
water hamer events, such as that which occurred at SONGS-1, would continue to occur, and that such events would not produce unacceptably high contributions to core melt frequency or public risk. The water hamer event at SONGS-1, in and of itself, did not result in a "near miss" to a core melt accident.
Finally, we reconfirm our original conclusion that the imposition of new requirements related to further reducing water hammer events is not supportable by current cost-benefit guidelines.
A brief review and assessment of such water hamers has been prepared by A. W. Serkir of my staff, with assistance from Eric Leeds (AEOD), and is ranclosed.
OriginalSigned l1
_J&95!I85J Harold R. Denton, Director Office of Nuclear Reactor Regulation
Enclosure:
Review & Assessment of Water cc: See next page Hamer Occurrences - CY 1981 through CY 1985 Distribu ion: See next page
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