ML16341F328
| ML16341F328 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 09/07/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16341F327 | List: |
| References | |
| NUDOCS 8909210084 | |
| Download: ML16341F328 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION
.+p,R 4cQy CgP Cy v
~ b O
4 O
,sII <
WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON POWER PLANT - UNIT 1 DOCKET NO. 50-275 SCHEDULAR RELIEF FROM CERTAIN INSERVICE INSPECTION RE UIREMENTS
1.0 INTRODUCTION
2.0 By letter dated September 7, 1989, Pacific Gas and Electric Company, the licensee for Diablo Canyon Power Plant Units 1 and 2, requested schedular relief for Unit 1 from certain ASME Code Section XI Inservice Inspection requirements.
It was only recently realized that these tests are required by the current ISI program to be performed by September 7, 1989, before the end of the current operating cycle, October 13, 1989.
To perform the tests otherwise, plant shutdown would be necessary, involving cycling of systems and corresponding wear and plant life cost which would exceed the insignificant increment in safety gained by performing the tests within the current schedule as opposed to deferring the tests for 60 days as requested.
The licensee therefore requested a one-time schedular relief of 60 days in order to perform the tests during the upcoming refueling
- outage, currently scheduled to begin October 13, 1989.
Our evaluation of the licensee's relief request is provided below.
EVALUATION The licensee proposed a one-time relief request, a 60-day extension of the ASME Boiler and Pressure Vessel Code Section XI 3 1/3 year (plus one year extension allowed by IWA-2400) time period requirement to allow performance of visual inspection of piping and welds in portions of several systems that are inaccessib'ie while the reactor is operating.
The relief would allow the inspections to be performed during the upcoming refueling
- outage, scheduled to begin October 13, 1989.
The continued safe operation of the plant is not significantly affected by granting of the 60-day schedular exemption.
The slightly increased interval on the first inservice inspection period is not significant in the context of the 40-year design probability of accident occurrence or the accident consequences.
Surveillance tests pressurize this piping sufficiently such that leakage would be detected as an indicator of piping integrity.
The surveillance testing history of the affected sections of the system piping demonstrates that there has been no evidence of degradation or maintenance problems.
The effect of increasing the interval of the first inservice inspection period does not increase any loading or other input to the piping systems.
Therefore, continued operation of Unit 1 for an additional 60 days would not result in an increased probability of occurrence or an increased consequence of an accident or malfunction of eq'uipment important to safety previously analyzed in the FSAR Update.
89092i0084 S90907 PDC PDR ADOCK 05000275
I e
\\
-2>>
In like manner, the requested 60-day extension of time for performing the tests will not affect any previously evaluated accident or malfunction.
The operation of these piping systems for an additional 60 days without the Code-required ISI Program inspection does not require physical altera-tion to any plant system or cause changes in the method by which any safety-related system performs its function.
In the highly unlikely event that a piping degradation should occur during this period, it would result in leakage rather than a catastrophic failure of the piping system to perform its intended safety function.
The requested schedule extension will not create the possibility of an accident or malfunction of a different type other than any evaluated previously in the FSAR Update.
In like manner the requested 60-day extension of time for performing the tests will not compromise any margin of safety.
The margin of safety with respect to the design and analysis of the subject piping systems is provided, in part, by the safety factors inherent in the ASME Code, and the increase in the first inservice inspection period does not reduce the margin of safety.
Further, alternate inspections which meet the intent of the ASME Code have already been completed and confirm the adequacy of margins in the lines.
Consequently, extending the ISI Program surveillance requirement for an additional 60 days will not reduce the margin of safety as defined in the basis for the DCPP Technical Specifications.
Further consideration in granting of the requested schedular relief is that alternate testing/inspecting of the affected lines have been completed successfully without any indication of reasons for concern.
Although the staff has not made a finding regarding the equivalency of these tests/
inspection to those requirements by ASME Code Section XI and the Diablo Canyon Inservice Inspection
- Program, the tests/inspection do confirm the adequacy of the inspected/tested piping.
The staff has reviewed the licensee's schedular relief request and finds that the granting of the requested relief is authorized by law, will not present an undue risk to the public health and safety, will not endanger life or property and is consistent with the common defense and secur ity, and is otherwise in the public interest giving due consideration to the adverse consequences of not granting the relief.
The staff finds also that the requested 60-day extension is not a significant deviation from Code requirements based on the fact that the licensee has found no history of problems or failures with similar piping and welds.
- 3. 0 CONCLUSION Based on the above discussion, the staff concludes that, consider ing the burden on the licensee of shutting down the plant and the minimal safety implications of extending the test interval a maximum of 60 days, the one-time schedular relief for the affected four systems should be granted as requested.
The requested relief is granted.
Princi al Contributor:
Roby Bevan Date:
September 7,
1989
(a
+ ~
4