ML20134B351
| ML20134B351 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 01/24/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20134B349 | List: |
| References | |
| NUDOCS 9701300048 | |
| Download: ML20134B351 (6) | |
Text
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k UNITED STATES j
NUCLEAR RE2ULATORY COMMISSION 2
WASHINGTON, D.C. 20N64001
+9.....
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS.118 AND 81 TO FACILITY OPERATING LICENSE NOS. NPF-39 AND NPF-85 PHILADELPHIA ELECTRIC COMPANY LIMERICK GENERATING STATION. UNITS 1 AND 2 DOCKET NOS. 50-352 AND 50-353
1.0 INTRODUCTION
By letter dated June 28, 1996, as supplemented November 4 and 5, and December 9, 1996, the Philadelphia Electric Company (the licensee) submitted a request for changes to the Limerick Generating Station, Units 1 and 2, Technical Specifications (TSs). The requested changes would revise the TSs to incorporate performance based testing, in accordance with 10 CFR Part 50, Appendix J, " Primary Reactor Containment Leakage Testing For Water-Cooled Power Reactors," Option B.
This option allows utilities to extend the frequencies of the Type A Containment Leak Rate Test (ILRT), and Type B and C Local Leak Rate Tests (LLRTs) based on the performance of the containment and components. The November 4 and 5, and December 9, 1996, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination or the Federal Reaister notice.
By letter dated November 30, 1993, the licensee had previously proposed an extension of the test interval for the drywell bypass leakage rate test from 18 months to coincide with the Appendix J Option A Type A test interval, which the Limerick TSs specify as 40 i 10 months. The staff approved the licensee's request in a letter dated February 17, 1994. As part of the licensee's June 28, 1996 submittal, the licensee proposed maintaining the requirement to 4
perform drywell bypass leakage rate tests at the same interval as the Appendix J Type A test. However, Option B would permit, under specific conditions, increasing the Type A test interval from 40 i 10 months to 10 l
years. This issue is also addressed in this safety evaluation report. The i
proposal to extend the test interval for drywell bypass leakage rate testing was supplemented by submittals dated November 4, and 5,1996, and December 9, 1996.
2.0 BACKGROUND
2.1 Appendix J Option B
.The proposed changes would permit implementation of 10 CFR Part 50, Appendix J, Option B.
The licensee has established a " Containment Leakage Rate Testing i
Program" and proposed adding this program to the TSs.
The program references 9701300048 970124 PDR ADOCK 05000352 P
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Regulatory Guide (RG). l.163, " Performance-Based Containment Leak Test Program," which specifies a method acceptable to the NRC for complying with Option B_ dated September 1995.
i Co6apliance with 10 CFR Part 50, Appendix J, provides assurance that the l
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 Register (57 FR 4166) discussing a planned initiative to begin eliminating requirements marginal to safety which impose a significant regulatory burden. Appendix J l
.of 10 CFR Part 50 was considered for this initiative and the staff undertook a study of possible changes to this regulation. The study examined the previous performance history of domestic containments and examired the effect on risk 3
of a. revision to the requirements of Appendix J.
The results of this study are reported in NUREG-1493, " Performance-Based Leak-Test Program."
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j Based on the results of this study, the staff developed a performance-based approach to containment leakage rate testing. On September 12, 1995, the NRC i
l approved issuance of this revision to 10 CFR Part 50, Appendix J, which was subsequently published in the Federal Register on September 26, 1995, and became effective on October 26, 1995. The revision added Option B
" Performance-Based Requirements" to Appendix J to allow licensees to voluntarily replace the prescriptive testing requirements of Appendix J with i
j testing requirements based on both overall and individual component leakage rate performance.
Regulatory Guide 1.163, was developed as a method acceptable to the NRC staff for implementing Option B.
This regulatory guide states that the Nuclear Energy Institute (NEI) guidance document NEI 94-01, " Industry Guideline for j
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.
Option B requires that the RG or other implementation document used by a licensee to develop a performance-based leakage rate testing program must be a
included, by general reference, in the plant TSs. The licensee has referenced RG 1.163 in the Limerick Unit 1 and Unit 2 TSs.
Regulatory Guide 1.163 specifies an extension in Type A test frequency to at 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
' completion of two consecutive successful tests and Type C tests may be 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 J
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 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.
2.2 Drywell Bypass Leakage Rate Testing During a postulated loss-of-coolant accident (LOCA) inside containment, the drywell is pressurized with steam and air.
The resulting large pressure difference between the drywell and the wetwell forces the steam through the.
suppression pool where it is condensed, resulting in a lower containment pressure.
If the steam were to bypass the suppression pool and pressurize the wetwell, containment design pressure may be exceeded.
Consequently, a test is performed to ensure that the leakage between the drywell and the wetwell is less than a specified amount.
The leakage is specified as A//K, where A is the flow area of the leakage path and K is the geometric and frictional loss a
coefficient.
For Limerick Units 1 and 2 the design value of A//K is 0.05 ft,
The technical specifications limit is 10% of this value for conservatism.
The licensee's November 30, 1993 submittal provided a technical basis for extending the test interval from 18 months to the same test interval as the Appendix J Type A test.
This interval is 40 i 10 months. As part of the licensee's proposal, a vacuum breaker leakage rate test was required to be performed during those refueling outages when the drywell bypass leakage test i
was not performed.
As discussed above, Appendix J Option B would allow the Type A test interval to be extended to 10 years.
Therefore, the staff j
reviewed the licensee's November 30, 1993 submittal again and requested additional information to determine the acceptability of the 10-year drywell bypass leakage rate test interval. Our evaluation is given below.
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. 3.0 EVALUATION 3.1 Evaluation of Licensee's Proposal to Adopt Appendix J Option B for Containment Leakage rate testing The licensee's June 28, 1996, letter to the NRC proposes to establish a
" Containment Leakage Rate Testing Program" and proposes to add this program to the TSs. The program references RG 1.163, which specifies a method acceptable to the NRC for complying with OptSn B.
This requires a change to existing Limerick Unit I and Unit 2 TS Sections 4.6.1.1, 3.6.1.2, 4.6.1.2, 3.6.1.3, 4.6.1.3, 4.6.1.5.1, 4.6.2.1 and the addition of the " Containment Leakage Rate Testing Program" to Section 6.8.4.g.
Corresponding bases were also modified.
Option B permits a licensee to choose Type A; or lype B and C; or Type A, B and C; testing to be done on a performance basis. The licensee has elected to perform Type A, B and C testing on a performance basis.
The licensee's June 28, 1996 submittal discusses three exemptions from Appendix J.
TS LC0 3.6.1.2.b identifies an exemption which permits MSIV leakage to be considered separately from other Type C leakage and for testing the MSIVs at a lower pressure than that specified in Appendix J.
Pursuant to paragraph V.B.1 of Option B, this exemption will be retained with editorial changes to reflect its continued applicability.
TS surveillance requirement 4.6.3.5 identifies a Traversing Incore Probe (TIP) system explosive isolation valve surveillance test which is performed in place of an Appendix J Type C test.
Pursuant to pararaph V.B.1 of Option B, this exemption will also be retained. TS surveillance requirement 4.6.1.3.a.2 identifies an exemption to i
the Appendix J requirements for air lock leakage rate testing. Appendix J Option A states:
" Air locks opened during periods when containment integrity is not required by the plant's Technical Specifications shall be tested at the end of such periods at not less than P." The exemption allows a 10 psig leakage rate test of containment air lock seals prior to establishing primary containment integrity when the air lock has been used and no maintenance has been performed on the air lock that could affect its sealing capability.
This exemption is no longer required since Option 8 does not specify detailed requirements for air lock testing.
The details for thic, test are now included in NEI 94-01 Revision 0 which is endorsed by RG 1.163.
However, the licensee requests that the exemption be retained in the Limerick Generating Station Unit I and Unit 2 licenses in order to document that the test is performed at a pressure lower than P (10 psig). The licensee has included the air lock testpressureinTSSecIion6.8.4.g,thePrimaryContainmentLeakageRate Testing Program, as specified by Section 10.2.2.1 of NEI 94-01, Revision 0.
1 The TS changes proposed by the licensee are in compliance with the requirements of Option B and consistent with the guidance of RG 1.163, and the generic TSs of the November 2,1995, letter and are, therefore, acceptable to the staff.
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5-i 3.2 Evaluation of Licensee's proposal to D: tend Drywell Bypass Test Interval f m 40 ? 10 months to 10 years, t
The must protas s hakage paths between the drywell and the wetwell of a BWR Mark II containee t are through the four sets of vacuum breakers. The licensee's November 30, 1993 submittal proposed adding a surveillance requirement to leak test this leakage path during those refueling outages when the drywell bypass leakage rate test was not performed. The staff approved 3
this proposal in a safety evaluation report which was transmitted to the licensee by letter dated February 17, 1994. The licensee has not performed j
any drywell bypass leakage tests since that time. The licensee has performed vacuum breaker leakage rate tests.
In a letter dated December 9, 1996, the i
licensee stated that the measured leakage rates have been below the acceptance l
criteria specified in TS 4.6.2.1.f.
The other leakage paths are diaphragm floor penetrations such as the downcomer and main steam safety / relief valve (SRV) discharge line penetrations, cracks i
in the diaphragm floor and liner plate and cracks in the downcomers and SRV i
discharge lines that pass through the suppression chamber air space.
Isolation valves in lines which are cross-connected between the drywell and the wetwell are another possible leakage path. The staff's February 17, 1994 safety evaluation report considered all these flow paths and found that an extension in the test interval would not result in a significant increase in F
the leakage through any of these leakage paths.
The staff has again reexamined these leakage paths and concludes that a further extension of the test interval to 10 years would not result in significant leakage through any b
of these paths.
In addition to the vacuum breaker tests which are performed j
at all refueling outages during which a drywell bypass leakage rate test is 4
not performed, the licensee indicated in the November 4, 1996 letter in response to a staff question that the liner plate over the diaphragm slab is j
visually inspec.ted at every refueling outage.
j In addition, the staff requested that the licensee assess any possible increases in risk associated with the increased interval. The licensee j
responded in the November A, 1)96 letter to the staff by outlining the actions i
that could be taken according to the emergency operating procedures if an increase in containment drywell pressure were to occur. The operator would ba i
directed to use wetwell and drywell sprays or to d' pressurize the reactor vessel if these sprays were to be unavailable.
In addition, the licensee pointed out that risk studies for Limerick have demonstrated that the primary contributors to containment overpressure failure are due to failure of the i
vacuum breakers and failure of decay heat removal equipment. The frequency of loss of vapor suppression is only a minor contributor to the containment overpressure failure frequency.
The staff therefore finds the licensee's proposal to increase the drywell bypass test interval to 10 years to be acceptable.
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The licensee proposed some minor editorial changes to the TSs in a telephone conference dated January 9, 1997, that did not change the context of the TSs
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and, therefore, are acceptable to the staff.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments. The State
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l official had no comments.
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5.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with resptet to installation or use of a i
facility component located within the restricted area as defined in 10 CFR 1
Part 20 and change surveillance requirements.
The NRC staff has determined i
that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released 3
offsite, and that there is no significant increase in individual or cumulative i
occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, ar.d there has been no public comment on such finding (61 FR 550?R). Accordingly, the amendments meet the t igibility criteria for catege,rical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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6.0 CONCLUSION
l The Commission has concluded, based on the considerations discussed above, i
that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such 4
activities will be conducted in compliance with the Commission's regulations,
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and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
R. Lobel Date: January 24, 199'i
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