ML20077D470
| ML20077D470 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/16/1991 |
| From: | Ray H SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9105300270 | |
| Download: ML20077D470 (5) | |
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Southom Califomia Edison Company 8 3 P A,p f H B T R f f T invlbf, C ALIF O8tiv6A Witte
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~..... c. o May 16, 1991 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50 362 Reply to a Notice of Violation San Onofre Nuclear Generating Station, Unit 3
Reference:
Letter from Mr. S. A. Richards (USNRC) to Mr. Harold B. Ray (SCE),
dated April 12, 1991.
The referenced letter forwarded a Notice of Violation resulting from the routine NRC resident insaection conducted between January 27 through March 9, and March 15, 1991, at tie San Onofre Nuclear Generating Station Units 1, 2, and 3.
The inspection report addresses a violation concerning the untimely corrective action for deficiencies associated with Crosby model JMBU relief valves.
The inspection was documented in NRC Inspection Report No.
50 362/91-03.
In accordance with 10 CFR 2.201, the enclosure to this letter provides Southern California Edison's (SCE) reply to the Noti (.e of Violation.
As was discussed with Mr. Phil Johnson (NRC) on May 10, 1991, this response was delayed in order to provide a complete response.
if you have any questions regarding SCE's response to the Notice of Violation or require additional information, please call me.
Sincerely, 6 t%dd(A O, 7' 4
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r Enclosure cc: J, B. Martin, Regional Administrator, NRC Region V C. W. Caldwell, NRC Sr. Resident inspector, San Onofre Units 1, 2, and 3
'h l'I b k 9105300270 910516 PDR ADOCK 05000362
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r ENCLOSURE Reply to a Notice of Violation The enclosure to Mr. Richard's letter dated April 12, 1991, stated in part:
"10 CFR S0, Appendix B, ' Quality Assurance Criteria for Nuclear Power Plants', Criterion XVI, ' Corrective Action,' states in part:
'Heasures shall be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations defective material and eculpment, and nonconformanccs arepromptlyidentifiedandcorrectec.
In the case of significant conditions adverse to cuality, the measures shall assure that the cause of condition is cetermined and corrective action taken to preclude repetition...'
"SCE Topical Ovality Assurance Manual, Chapter 1-f, paragraph 1.0 states in part:
' Systems shall be established, implemented, and controlled by written procedures to assure that conditions adverse to quality are identified, documented, evaluated, and corrected in a timely manner and that action is taken to prevent recurrence of the condition...'
" Contrary to the above, the licensee failed to take aparopriate corrective actions to prevent improper operation on fe;ruary 11, 1991,
[ sic] of the relief valve c.n Safety Injection Tank (SIT) T-10.
On that date, this relief valve lif ted but failed to properly reset, causing the SIT to be depressurized and become inoperable.
This model of relief valve had caused similar depressurization of a Unit 2 Sli in 1988, and its excessive blow-down characteristics had also been discussed in a 10 CFR Part 21 Report received by the licensee in early 1990.
"This is a Severity Level IV violation (Supplement I), applicable to Unit 3."
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REPLY TO NOTICE Of VIOLATION Hay 16, 1991
Background
On August 22, 1988, during the routine pressurization of a Safety injection Tank (SIT) on San Onofre Unit 2, 2PSV-9356, a Crosby model JMBU-S relief valve, lif ted prematurely and depressurized (blew-down) the SIT.
Investigation at that time identified roughly machined internal surfaces in the valve assembly which likely caused binding in the valve, resulting in the premature lift.
No previous instances of premature lifting of these Crosby relief valves had occurred.
The relief valve was repaired, re-tested to verify satisfactory lif t setpoint, and returned to service.
Corrective action from the event did not address the blow-down if the valve, which was in excess of that specified in the procurement specification.
Seventeen months later, on January 4,1990, SCE received a Cooper Industries, Energy Services Group, 10 CFR 21 report applicable to San Onofre Unit I concerning smaller Crosby relief valves (of similar design to those on the SONGS 2&3 SITS) installed on the air starting receiver of the diesel generators at the Perry plant.
The report described an incident of smaller relief valves spuriously lifting when physically impacted.
The report also noted blow-down in excess of that specified.
Upon receipt by SCE, the report was promptly reviewed to determine if the smaller Crosby relief valves were installed in any of the San Onofre units in applications similar to that described in the report.
Crosby relief valves were determined to be installed in air receivers of the Unit 1 Diesel Generators, and this location was promptly barricaded and posted to preclude personnel from inadvertently impacting the valves.
Additionally, 27 other similar Crosby relief valves, including those on the SONGS 2&3 SITS, were identified in service at each of SONGS 2&3.
Because the 27 relief valves were either considered not accessible and therefore unlikely to be physically impacted 'e.g., the S!T relief valves are located inside containment),orthevalveswereinnon-criticalapplications,immediate action on these valves was not considered to be necessary.
Therefore, the remaining 27 valves were identified for evaiuation to determine whether the valves were suitable for their intended service, or if long term remedial action, such as replacement at the next outage, should be taken.
These actions were completed within approximately a tix-week period from receipt of the 10 CFR 21 report on January 24, 1990.
On February 8, 1991, relief valve 2PSV-9376 on San Onofre Unit 3 SIT T-010 spuriously lifted and blew-down the S!T to a pressure below the technical specification lower limit in a similar fashion as described in the 10 CFR 21 report for the smaller valves.
Following this event, the root cause investigation, RCE 91-005, concluded that mis event was likely the result of a generic design flaw in all similar model Crosby nlief valves, in addition, this root cause evaluation also found that the valve blew-down in excess of the procurement specification requirement. Action was initiated to identify a suitable replacement valve to be installed at the next refueling outage.
The remaining 23 Crosby relief valves in each of San Onofre Units 2 and 3 were determined to be non-critical and to not need further action.
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e REPLY 10 NOTICE OF V10LA110N May 16, 1991 1.
Reasons for the violation Insufficient Root Cause Evaluation Nonconformance Report (NCR) 2R-0059 was generated on August 22, 1988, for a root cause evaluation of the premature lifting condition of relief valve 2PSV-9356 which occurred during a routine pressurization of the SIT on Unit 2.
The NCR evaluation indicated that upon valve disassembly, it was determined that the premature lifting was due to the sharp top edge of the spindle rubbing against the roughly machined inside surface of the spring adjusting bolt.
The NCR did not explicitly discuss the relief valve's excessive blow-down, e.g., that the blow-down was in excess of that specified in the procurement specification.
Subsequent to repairs, the valve tested satisfactorily for lift setpoint.
The reset pressure and design blow-down specification were not noted in the NCR. Therefore, the excessive blow-down was not identified during this repair effort.
The NCR corrective actions included inspection of all remaining SIT valves for similar machining deficiencies.
The inspections found similar machining deficiencies in all remaining SIT relief valves which were subsequently refurbished.
This event was reported to the NRC in Licensee Event Report No. 2-88-22 on September 20, 1988.
A more thorough root cause evaluation (similar to that performed in RCE 91-005) might have identified that the valve blow-down was in excess of that s)ecified in the procurement specification.
Failure to fully determine tie root cause o' this event in 1988 is considered the primary contributor to this violation.
CJ01_rhutina Cause to Late Corrective Action on SIT Aelief Valve Prior to October 1990, the SCE 10 CFR 21 Program did not provide specific provisions or instructions to address potential operability issues of all affected plant equipment, within a specified time, for Vendor initiated 10 CFR 21 reports. As a result, a backlog of Vendor 10 CFR 21 Report peading evaluations occurred. When the February 8, 1991, SIT relief vahe event occurred, SCE had not completed the Cooper Industries 10 CFR 21 Report evaluation.
2.
Corrective steos that have been taken and the results achieved Root Cause Evaluation Proaram Corrective Actions i
l When NCR 2R-0059 was generated in 1988, there was no centralized program and overview responsibility to ensure consistent, high quality root-cause determinations. SCE has since formalized the overall root cause program and assigned dedicated resources.
Program res)onsibility was assigned to the Manager of Safety Engineering within tie Nuclear Oversight Division.
Since implementation of the new program, the quality and consistency of the root-cause determinations have improved
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REPLY TO NOTICE Of VIOLATION May 16, 1991 such that in today's environment, the excessive blow-down of the Sli-relief valve would have been identified early-on and evaluated.
10 CFR 21 Proarne Corrective Actions in October 1990, SCE recognized the need to manage the Vendor 10 CFR 21 backlog and consolidated the 10 CFR 21 Program.
SCE now reviews the Vendor initiated 10 CFR 21 reports more promptly.
3.
Corrective steps that will he taken to avoid further violations
$1T Relief Valves Corrective Actions SCE will replace the relief valves (Crosby Model JHBU-S safety relief valves) used on the Safety injection Tanks, 2(3)T-007 through 2(3)T-010, during the upcoming Cycle 6 refueling outages for Units 2 and 3 with valves that are not subject to the problems noted in the 10 CFR 21 report.
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Eate when full compliance will be achieved.
Full compliance was achieved on February 8, 1991, when NCR No. 91-020075 was issued to document the excessive blow-down of the SIT relief valve, and initiate the evaluation and formulation of appropriate corrective actions.
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