ML13331A353
| ML13331A353 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/31/1990 |
| From: | Nandy F SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-89-002, IEB-89-2, NUDOCS 9002070476 | |
| Download: ML13331A353 (2) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE. CALIFORNIA 92718 F. R. NANDY TELEPHONE MANAGER OF NUCLEAR LICENSING January 31, 1990 714 587-5400 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 NRC Bulletin No. 89-02 San Onofre Nuclear Generating Station Unit 1 This letter provides the Southern California Edison response for San Onofre Unit 1 to NRC Bulletin 89-02, "Stress Corrosion Cracking of High-Hardness Type 410 Stainless Steel Internal Preloaded Bolting in Anchor-Darling Model S350W Swing Check Valves or Valves of Similar Design."
As requested in Action I of the Bulletin, a design review of applicable safety related check valves at San Onofre Unit 1 has been performed as defined below. This review found no Anchor-Darling Model S350W or swing check valves of similar design with internal preloaded type 410 stainless steel bolting.
Bulletin 89-02 requests identification, disassembly and inspection of all safety related Anchor Darling Model S350W swing check valves or check valves of similar design with internal preloaded type 410 stainless steel bolting.
The specific failures which led to this Bulletin occurred in Anchor Darling Model S350W swing check valves with type 410 stainless steel retaining block studs. These studs, which retain the blocks that attach the valve disk assembly to the valve body, were cracked from stress corrosion cracking (SCC) because improper heat treating resulted in high hardness and an increased susceptibility to SCC.
Our review involved all 158 safety related check valves in the In-Service Testing (IST) program. This included both active and passive safety related check valves. An active valve must change position in order to accomplish a specific function. Thus, a safety related active valve must either swing open or closed to perform its safety function and could be in either position during normal plant operation. A passive valve is not required to change position in order to accomplish a specific function. The passive safety related check valves are closed during normal operation and are required to remain closed to perform their safety related function.
,UQZQM:7C)'
))O
_1C OK$
pDR AL '
PLIC
Document Control Desk January 31, 1990 Our design review has determined that neither Anchor-Darling Model S350W swing check valves nor any other check valves of similar design with internal preloaded type 410 stainless steel bolting are used in active or in passive safety related applications as described above.
There are other safety related passive check valves at San Onofre Unit 1 which are not in the IST program and were not included in the scope of this review.
These valves are classified as safety related because the external pressure boundary of the VaTe-forms part of the safety related piping system pressure boundary. These valves are normally closed but are able to perform their safety function regardless of disc position because the check function of these valves is not safety-related.
These valves are not required to perform any other safety function, following a design basis event. The safety function of these valves would not be affected by the bolting material failures which are the subject of this Bulletin and these valves are therefore excluded from the scope of the review.
Based on our review, no further actions pursuant to this Bulletin are required for Unit 1.
Respectfully submitted, By :
F. R. Nandy Manager of Nuclear Licensing Subscribed and sworn to before me this 3/
day of
-r'OFFICIAL SEAL
//
YOMAR V. CLEARY Notary Public-Califomia ORANGE COUNTY My Comm. Exp. May 8, 1992 Notary /ublic in the State
(
of California cc:
J. B. Martin, Regional Administrator, NRC Region V C. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3