ML20135C164
| ML20135C164 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 02/24/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20135C160 | List: |
| References | |
| NUDOCS 9703030392 | |
| Download: ML20135C164 (3) | |
Text
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j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30086 0001 o%...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 49 TO FACILITY OPERATING LICENSE NO. NPF-86 NORTH ATLANTIC ENERGY SERVICE CORPORATION SEABROOK STATION. UNIT NO. 1 l
DOCKET NO. 50-443
1.0 INTRODUCTION
On September 12, 1995, the U.S. Nuclear Regulatory Commission (NRC) approved issuance of a revision to 10 CFR Part 50, Appendix J, " Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors" which was subsequently published in the Federal Reaister on September 26, 1995, and became effective on October 26, 1995. Tho NRC added Option B " Performance-Based Requirements" to allow licensees to voluntarily replace the prescriptive testing requirements of 10 CFR Part 50, Appendix J, with testing requirements based on both overall leakage rate performance and the performance of individual components.
By application dated June 4,1996, North Atlantic Energy Service Corporation (North Atlantic /the licensee) requested changes to the Technical Specifications (TS) for Seabrook Station, Unit No.1 (Seabrook).. The proposed changes would permit implementation of 10 CFR Part 50, Appendix J, Option B.
North Atlantic has established a " Containment Leakage Rate Testing Program," and has proposed adding this program to the TS..The program references Regulatory Guide (RG) 1.163, " Performance-Based Containment Leak Test Program," which specifies a method acceptable to the NRC for complying with Option B.
Supplemental information to tile application for license amendment was submitted by letter dated January 8, 1997. The supplement provided information related to leak rate testing of the containment purge and vent valves and did not change the initial proposed no significant hazards consideration determination.
2.0 BACKGROUND
Compliance with 10 CFR Part 50, Appendix J, provides assurance that the primary containment, including those systems and components which penetrate the primary containment, do not exceed the allowable leakage rate specified in the TS and Bases. The allowable leakage rate is determined so that the leakage assumed in the safety analyses is not exceeded.
On February 4,1992, the NRC published a notice in the Federal Reaister (57 FR 4166) discussing a planned initiative to begin eliminating requirements l
marginal to safety which impose a significant regulatory burden. Appendix J of j
10 CFR Part 50 was considered for this initiative and the staff undertook a 9703030392 970224 PDR ADOCK 05000443 P
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study of possible changes to this regulation. The study examined the previous i
performance history of domestic containments and examined the effect on risk of a revision to the requirements of Appendix J.
The results of this study are reported in NUREG-1493, " Performance-Based Leak-Test Program."
Based on the results of this study, the staff developed a performance-based 4
approach to containment leakage rate testing. On September 12, 1995, the NRC approved issuance of this revision to 10 CFR Part 50, Appendix J, which was i
i subsequently published in the Federal Register on September 26, 1995, and i
became effective on October 26,.1995. The revision added Option B' i
"Perfomance-Based Requirements" to Appendix J to allow licensees to voluntarily replace the prescriptive testing requirements of Appendix J with testing requirements based on both overall and individual component leakage
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rate perfomance.
1 Regulatory Guide 1.163, was developed as a method acceptable to the NRC staff l,
for implementing Option B.
This regulatory guide states that the Nuclear Energy Institute (NEI) guidance document NEI 94-01, " Industry Guideline for Implementing Performance-Based Option of 10 CFR Part 50, Appendix J" provides methods acceptable to the NRC staff for complying with Option B with four exceptions which are described therein.
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Option B requires that the RG or other implementation document used by e i
licensee to develop a performance-based leakage rate testing program must be i
included, by general reference, in the plant TS. The licensee has referenced j
RG 1.163 in the Seabrook TS.
Regulatory Guide 1.163 specifies an extension in Type A test frequency to at j
least one test in 10 years based upon two consecutive successful tests. Type B tests may be extended up to a maximum interval of 10 years based upon j
completion of two consecutive successful tests and Type C tests may be j
extended up to 5 years based on two consecutive successful tests.
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By letter dated October 20, 1995, NEI proposed TS to implement Option B.
After some discussion, the staff and NEI agreed on final TS which were attached to a letter from C. Grimes (NRC) to D. Modeen (NEI) dated November 2, 1995. These TS are to serve as a'model for licensees to develop plant specific TS in preparing amendment requests to implement Option B.
For a licensee to determine the performance of each component, factors that are indicative of or affect performance, such as an administrative leakage limit, must be established. The administrative limit is selected to be indicative of the potential onset of component degradation. Although these limits are subject to NRC inspection to assure that they are selected in a reasonable manner, they are not TS requirements. Failure to meet an administrative limit requires the licensee to return to the minimum value of the test interval.
Option B requires that the licensee maintain records to show that the criteria for Type A, B and C tests have been met.
In addition, the licensee must
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. maintain comparisons of the performance of the overall containment system and the individual components.to show that the test intervals are adequate. These records are subject to NRC inspection.
3.0 EVALUATION North Atlantic proposes to establish a Containment Leakage Rate Testing Program and to add this program to the TS. The program would reference RG 1.163, which specifies a method acceptable to the NRC for complying with Option B.
This requires a change to existing TS 1.7, 3/4.6.1, and 3/4.6.5, and the addition of a new Section 6.15 relating to the Containment Leakage l
Rate Testing Program. The corresponding bases were also modified.
l Option B permits a licensee to choose Type A; or Type B and C; or Type A, B and C; testing to be done on e performance basis. North Atlantic has elected to perform Type A, B and C testing on a performance basis.
The TS changes proposed by North Atlantic are in compliance with the i
requirements of Option B and consistent with the guidance of RG 1.163, and the generic TS of the November 2,1995, letter and are, therefore, acceptable to the staff.
The existing Seabrook TS 4.6.1.7.1 requires the containment purge supply and exhaust valves to be leak rate tested at least every 92 days to demonstrate that the leak rate does not exceed the specified limit. North Atlantic also I
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has proposed to modify TS 3.6.1.7 and 4.6.1.7.1 by moving the specified leak l-rate acceptance criterion to TS 6.15 and adding reference to the Containment Leak Rate Testing Program. The valves then would be tested in accordance with l
RG 1.163 which specifies a test interval of 30 months. The current requirement to test these valves at least every 92 days is not an Appendix J requirement, but instead is based upon the findings of Generic Issue B-20, j
" Containment Leakage Due to Seal Degradation," that valves with resilient l
seals should be tested more frequently than required by Appendix J.
The background for this conclusion is discussed in IE Circular 77-11
" Leakage of l
Containment Isolation Valves with Resilient Seals" (issued September 6, 1977).
i By letter dated January 8,1997, North Atlantic submitted the results of containment purge supply and exhaust valve leak rate testing and the maintenance performed on these valves from Nay 1986 to November 1995. Thirty-eight tests were performed on the containment purge supply valves, COP-V1 and COP-V2, and thirty-nine tests were performed on the containment purge exhaust valves, COP-V3 and COP-V4. None of the test leakage results exceeded the Technical Specification acceptance limit of 0.01 L,, or 7.4 SCFH for these valves (where L, is the maximum allowable containment leakage rate). The L
combined leakage rate for valves COP-V1 and COP-V2 has exhibited a small increasing trend over time, but the largest test leakage obtained to date has not exceeded 35 percent of the acceptance criterion. The combined leakage rate for valves COP-V3 and COP-V4 has exhibited a more stable rate, and the largest test leakage obtained to date has not exceeded 38 percent of the acceptance criterion. North Atlantic has not had to perform any maintenance on the valves that affect leaktightness of the valves.
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