ML20024J511
| ML20024J511 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/12/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20024J509 | List: |
| References | |
| NUDOCS 9410180371 | |
| Download: ML20024J511 (4) | |
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NUCLEAR REGULATORY COMMISSION f
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TEMPORARY EXEMPTION FROM 10 CFR PART 50. APPENDIX J TYPE B AND C LOCAL LEAK RATE TESTING OF CONTAINMENT PENETRATIONS NORTHEAST NUCLEAR ENERGY COMPANY THE CONNECTICUT LIGHT AND POWER COMPANY THE WESTERN MASSACHUSETTS ELECTRIC COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT N0. 2 DOCKET NO. 50-336
1.0 INTRODUCTION
By letter dated September 26, 1994, the Northeast Nuclear Energy Company (NNECO or the licensee) requested a one-time schedular exemption from the requirements of 10 CFR Part 50, Appendix J, Sections II.D.2(a) and III.D.3.
The temporary schedular exemption would extend the interval for Type B and C local leak rate testing (LLRT) of containment penetrations at the Millstone Nuclear Power Station, Unit No. 2 beyond the 2-year limit of 10 CFR Part 50, Appendix J until the end of the current refueling outage (12th refueling outage).
Appendix J requires these tests to be performed at every refueling outage, but with the interval not to exceed 2 years.
On September 23, 1994, NNECO discovered that Type B and C containment leak rate tests for certain containment penetrations had not been performed within the 24 months as required by Technical Specification (TS) SetMilance Requirement (SR) 4.6.1.2.d.
The specific Action Statement for Limited Conditions for Operations 3.6.1.2 applies and requires that containment integrity to be restored within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or place the plant in hot standby within the next 6 1
hours, and in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Since SR 4.6.1.2.d was inadvertently missed, SR 4.0.3 was invoked at approximately 1:00 p.m. on i
September 23, 1994. This SR permits the action requirements to be delayed for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to permit the completion of a missed surveillance when the allowable outage time limits of the action requirements are less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Since the Type C test cannot be performed while at power and the Type B tests that have exceeded the 24-month period cannot be completed within the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> window, Millstone Unit 2 would be forced to shutdown to comply with the requirements of the Hillstone Unit 2 TS.
9410180371 941012 ADOCK0500g6 DR
e 4 NNEC0 determined that the 24-month testing requirement had been exceeded for a number of Type B and Type C components by up to approximately 4 months.
3.0 EVALUATION As justification for the requested exemption, NNEC0 provided the following rationale:
1.
One of the conditions of all operating licenses for water-cooled power reactors, as specified in 10 CFR 50.54(o), is that primary reactor containments shall meet the containment leakage test requirements set forth in 10 CFR Part 50, Appendix J.
More specifically the following sections require that:
10 CFR Part 50. Accendix J.Section III.D.2(a)
Type B tests, except tests for air locks, shall be performed during reactor shutdown for refueling, or other convenient intervals, but in no case at intervals greater than 2 years.
10 CFR Part 50. Anoendix J. Section 111.0.3 Type C tests shall be performed during each reactor shutdown for refueling but in no case at intervals greater than 2 year.
By letter dated September 26,1994, NNEC0 requested schedular exemptions from the above requirements. NNEC0 recently conducted a review of the Type B and Type C test data and on September 23, 1994, determined that a number of components, for which Type B and Type C testing is required, have exceeded their respective 24 month interval by up to approximately four months. On September 23, 1994, NNEC0 discovered that Type B and C tests for certain containment penetrations had not been performed within the last 24 months.
i Previously, Millstone Unit 2 considered the Type B and Type C tests to constitute one group such that the 2 year surveillance window began shortly after the last component test was completed during the refueling outage. A review of this rationale and discussions with industry counterparts and the NRC staff determined that this was not the appropriate interpretation.
Rather, each Type B or C test of a penetration or valve should be considered unique, each with its own 2 year surveillance window. Using this interpretation, NNECO determined on September 23, 1994, that a number of Type B and Type C tests had not been conducted in accordance with the requirements of SR 4.6.1.2.d and 10 CFR Part 50, Appendix J.
Since the Type C tests cannot be performed while at power and the Type B tests that have exceeded the 24 month period cannot be completed within a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> window, Millstone Unit 2 would be forced to shutdown to comply with the Millstone Unit 2 TS.
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, 2.
Historical results of previous Type A, B and C tests have demonstrated the leak-tightness of the containment and the reliability of the penetrations / valves.
NNEC0 stated in their submittal that they had completed the second Type A test for the present 10-year service period successfully on December 24, *992.
The "As-Found" and "As-Left" integrated leakage rate test ILRT remits were 0.2809 weight percent per day and 0.2577 weight percent per day respectively.
Each ILRT result was below the Technical specifications limit which demonstrates the overall leak-tightness of the containment.
In addition, as of December 1992, the total Type B and C "As-Found" and "As-Left" leakage results were 0.049 weight percent per day and 0.008 weight percent per day. These values represent approximately 16.3% and 2.7% of the Technical Specification limit respectively. The results of these tests demonstrate that Millstone Unit No. 2 has maintained control of containment integrity by maintaining a conservative margin between the acceptance criterion and the "As-Found" and "As-Left" leakage rates. Subsequent to this ILRT, during Cycle 12, maintenance on several containment isolation valves was performed. The post-maintenance retest requirements were accomplished by successful performance of Type C tests. Thus, the previous Type A, B and C tests and prior post-maintenance retests of selected valves have demonstrated the leak-tightness of the containment and the reliability of the penetrations / valves.
3.
If Millstone Unit 2 was required to shutdown prematurely, it would severely impact activities planned to occur during the week before the scheduled shutdown and during the planned shutdown. Such activities were planned to reduce worker exposure during the refueling outage.
These include reactor coolant system (RCS) cleanup to reduce RCS activity and degassification of the RCS prior to shutdown to reduce containment activity during shutdown. Also, avoiding an early shutdown of Millstone Unit 2 would allow NNECO to test motor-operated valves and main steamline isolation valves during shutdown that would preclude the additional transients if these valves were tested during startup due to the potential for discovery of valve conditions that would require resolution.
In addition, as a result of NNECO shutdown risk analysis to minimize risk, NNEC0 has developed plans to maximize safe controlled operation during service water system outages and reduced inventory conditions.
The staff notes that the 2 year interval requirement for Type B and C components is intended to be often enough to prevent significant deterioration a
from occurring and long enough to permit the tests to be performed during the plant outages.
Leak rate testing of the penetrations during plant shutdown is preferable because of the lower radiation exposures to plant personnel.
Moreover, some penetrations cannot be tested at power.
For penetrations that
s s cannot be tested during power operation, or for which testing at power is inadvisable, the increase in confidence in containment-integrity following a successful test is not significant enough to justify a plant shutdown specifically to perform the tests within the 2 year period.
Based on the above evaluation, the staff has determined that the proposed Exemption is acceptable.
Principal Contributor:
G. Vissing Date:
October 12, 1994 l
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