ML13331A281
| ML13331A281 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/18/1988 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| IEB-85-003, IEB-85-3, NUDOCS 8811220438 | |
| Download: ML13331A281 (2) | |
Text
Southern California Edison Company P 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M.O.MEDFORD TELEPHONE MANAGER OF November 18, 1988 (818) 302-1749 NUCLEAR REGULATORY AFFAIRS U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 IE Bulletin No. 85-03, Request for Additional Information San Onofre Nuclear Generating Station Unit 1
Reference:
- 1) Letter from R. J. Kiessel (NRC) to M. 0. Medford (SCE) dated May 10, 1988
- 2) Letter from M. 0. Medford (SCE) to NRC dated September 27, 1988 Enclosed with reference 1 was a request for additional information on SCE's response to IE Bulletin 85-03.
By reference 2 we indicated that additional information which was not previously available could facilitate our review of the request for additional information. We have reviewed this information and discussed our conclusions with Mr. Richard 3. Kiessel of the NRC staff. In summary, our review confirms that water hammer is not a concern that should be considered in determining switch settings of MOV's in safety systems at San Onofre Unit 1. Our response to the request for additional information reflects this conclusion and is enclosed.
Respectfully submitted, By:
M. 0. Medford v
Manager of Nuclear Regulatory Affairs Subscr ed and sworn to before me this T_.
day of OFFICIAL SEAL
/f C. SALLY SEBO
(. Aa%
Notary Public-California Notary Public in d for the County of LOS ANGELES COUNTY Los Angeles, State of California MyCorn.Exp.Apr.20,1990 8811220438 881118 PDR ADOCK 05000206 Enclosure QPDC cc: 3. B. Martin, Regional Administrator, NRC Region V Richard J. Kiessel, Division of Operational Events Assessment F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3 C. M. Trammell, NRR Project Manager, San Onofre Unit 1
SCE RESPONSE TO NRC RAI FOR IEB 85-03 SAN ONOFRE UNIT I Request for additional information:
"Revise your response of 10-23-87 to Question No. 1 about waterhammer to indicate that factors such as valve closure times, piping lengths, flow conditions, procedures and experience have been considered."
Ouestion 1 "Has waterhammer due to valve closure been considered in the determination of pressure differentials? If not, please explain."
Response
Waterhammer was not considered in the original determination of pressure differentials for MOV operation. Waterhammer is a shock wave resulting from rapid changes in fluid velocity. The magnitude of the pressure change depends on valve closure time, piping length, and flow velocity. MOV's at Unit 1 have stroke times of at least 5 seconds which is much longer than the sonic transit times of system pipelines, and thus waterhammer from valve closure is not a concern.
A method for calculating pressure rise due to flow velocity decrease is given in Marks' Handbook 7th edition page 3-72.
For a typical MOV with cool water traveling at 30 feet per second and a pipe length of 500 feet between source and discharge point (which envelopes SONGS 1 configuration),
a valve closure time of 0.2 seconds or less would be necessary to produce an excessive differential pressure - commonly referred to as waterhammer.
Since SONGS 1 MOVs operate much more slowly, waterhammer due to flow changes is not considered to be a significant factor in their design.
During full flow testing of certain MOVs in response to Bulletin 85-03, waterhammer was not encountered.