ML20141M354
| ML20141M354 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 08/07/1992 |
| From: | Woodard J SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20141M355 | List: |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM NUDOCS 9208110387 | |
| Download: ML20141M354 (3) | |
Text
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b4 SNthern Nucuf Operatng Ccmpany Pom OFre Bos 1295 i io har $0 BG8 66 Southern Nudcar Operating Company 2 o,,,,,,,,
Vee Prescent August '/, 1992 tre warhem eberne systern Friey Profet Docket Nos. 50-348 50-364 U. S. Nuclear elegulatory Commission ATTN: Docunent Centrol Desk Washington, DC 20555 Joseph H. Farley Nuclear Plant Response to NUREG-0737. Item II.D.1 Gentlemen:
In 1980, the Nuclear Regulatory Commission issued NUREG-0737,
- 1arification of TMI Action Plan Requirements."
Item II.D.1, " Performance Testing of BWR and PWR Relief and Safety Valves," required licensees "to conduct testing to qualify the reactor coolant system relief and safety val w under expected operating conditions for design-basis transients and accidents."
Item II.D.1 theorized that if the pressurizer safety valves opened due to high reactor coolant system pressure, the pooled yater in the loop seals might cause a water hann, 'effect that could over-stress downstream piping and supports.-
The majority of the II.D.1 items were promptly resolved. Considering the.
issues raised in II.D.1, the block valves were requalified in 1982 and the pressurizer safety valves, the ASME Class 1 portions of the related pi)ing, and the non-nuclear safety portions of the downstream piping down to tie first support past the safety valves were requalified in 1986.
Thus, only the non-nuclear safety portions of the downstream piping past the safety
- valves remain to be requalified under II.D 1.
To hasten the resolution of the issues prescated-in Item II.D.1, Alabama Power Company (APCo) participated in the PWR safety and relief valves test' program of the Electric. Power Rese r.n Institute (EPRI).
APCo determined that certain portions of the downstream pipe beyond the first support might be stressed beyond the limits of a recognized standard in certain situations. Nonetheless,.APCo concluded that-the failure of the-downstream piping would not impair.the safety function of the pressurizer rafety valves and that, if-the pipe did rupture, the consequences would not be beyond tha design basis of the plant-(i.e., the contents would spill into the containment sump and.be recirculated to the: reactor coolant-system).
The NRC responded _with a Safety Evaluation Report (SER) dated December 16,'
i 1986 that did not: accept APCo's assertion that a rupture of an over-stressed portion of the non-nuclear safety downstream piping would be acceptable.
The NRC postulated that the piping'might not simply rupture, but could possibly deform or crimp and obstruct' pressure relief.
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In response, APCo modified the insulation on the prer urizer loop seal in an attempt to raise the temperature of the loop seals to " hot loop seal," the temperature range that the EPRI study indicated would prevent pipe over-stress upon safety valve operation. APCo installed modified i
insulation on loop seal piping during the tenth refueling outage of Unit I and the seventh refueling outage of Unit 2 and measured the resulting temperatures. Although the insulation modification raised the temperature of the loop seals, the temperature did not reach the EPRI criteria for
- hot loop seal."
Since the insulation modification did not achieve " hot loop seal," Southern Nuclear Operating Company (SNC) had Westinghouse Electric Corporation conduct an elastic / plastic analysis of the pressurizer safety valves and piping system to determine whether, as the NRC had postulated, the downstream piping would deform and impair relief capability upon safety valve op.,ation.
The report. of this analysis, " Pressurizer Safety Line Piping and Support Evaluation Under Safety Valve Discharge Loading," is enclosed with this letter.
The report concludes that the insulation modification reduced the severity of the stresses on the downstream piping so that pipe deformation would not occur. Therefore, with the current insulation design, the increased loads will not affect the operability of the safety valves.
Thus, the functional capability of the pressurizer shfety valve piping system will be maintaiiod under safety valve operation.
The report also evaluated the pipe supports for the non-nuclear safety piping and determined them to be acceptable.
Ac " rdingly, SNC requests that the NRC approve the analysis and conclusions of the enclosure, " Pressurizer Safety line Piping and Support Evaluation Under Safety Valve Discharge Loading," as resolution of the outstanding 11.D.1 issues. Upon receipt of NRC approval, the analysis and conclusions of the enclosure will become the licensing basis for the non-nuclear safety portion of the pressurizer safety valve piping system.
Respectfully submitted, SOUTHERN NUCLEAR OPERATING COMPANY b
nbd Jx Woodard JMM/BHW: map 2903 Enclosure cc: Mr. S. D. Ebneter Mr. S. T. Hoffman Mr. G. F. Maxwell i
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