ML20237B540
| ML20237B540 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/14/1987 |
| From: | Ebneter S NRC OFFICE OF SPECIAL PROJECTS |
| To: | |
| Shared Package | |
| ML20237B542 | List: |
| References | |
| NUDOCS 8712160336 | |
| Download: ML20237B540 (7) | |
Text
6 7590-01
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of
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TENNESSEE VALLEY AUTHORITY Docket Nos. 50-327
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50-328 (Sequoyah Nuclear Plant, Units 1 and 2)
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EXEMPTION I.
l The Tennessee Valley Authority (the licensee) is the holder of Facility i
Operating Licenses No. DPR-77 and DPR-79 which authorize operation of the Sequoyah Nuclear Plant, Units 1 and 2, respectively. These licenses provide I
that, among other things, the facility is subject to all rules, regulations 1
and Orders of the Comission now or hereafter in effect.
The Sequoyah facility consists of two pressurized water reactors located at the licensee's site in Hamilton County, Tennessee.
j II.
l General Design Criterion (GDC) 55 of Appendix A to 10 CFR Part 50 l
requires that each reactor coolant pressure boundary line penetrating the l
l primary reactor containment be provided with containment isolation valves.
l The combination of valves is to be one inside and one outside containment and 1
either automatic or locked closed. The GDC does allow for a demonstration of acceptability on some other defined basis.
As part of the original design of Sequoyah Nuclear Plant, Units 1 and 2, i
TVA relied upon certain closed systems as the outside containment isolation barrier to meet the Comission's regulations, specifically GDC-55 and 56, on some "other defined basis." The NRC staff issued NUREG-0011, dated March l
8712160336 871214' DR ADDCK 0500 7
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7590-01 1979, which documents the acceptability of TVA's compliance with the GDC; however, the staff did not specifically address the acceptability of an "other defined basis" for any containment isolation configurations.
Subsequent to the development of the TMI Action Plan, NRC staff policy has been established that closed systems outside containment are not generally acceptable as an isolation barrier for lines covered by GDC 55 and 56.
As a result of an NRC staff inspection conducted at Sequoyah in March 1986, apparent discrepancies in system compliance with the containment iso-lation requirements were identified. These findings led to a general reassess-i ment of the containment isolation design and the "other defined basis" assumr, tions made for the Sequoyah Nuclear Plant, Units 1 and 2.
I Subsequent to discussions with TVA, by letter dated January 2, 1987 TVA redesignated certain existing system line isolation valves as containment isolation valves. The Commission's requirements, however, could not be met in every isolated case.
In most of the cases evaluated, the_ explicit require-ments of GDC 55 or 56 could be satisfied by valve predesignation, thereby imposing them to the associated operability, surveillance, and testing require-ments.
For those cases where the staff requirements could not be met, TVA has requested an exemption from the GDC.
This exemption addresses the Seouoyah Nuclear Plant, Units 1 and 2, con-tainment isolation valves in the Residual Heat Removal (RHR) System loop supply line with respect to the valve location requirements only.
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7590-01,
The containment isolation provisions for the Sequoyah Nuclear Plant, Units 1 and 2 RHR System reactor coolant loop supply (discharge line) through penetration X-17 utilizes a check valve and a motor-operated remote manual valve inside containment and a water seal and closed system outside contain-ment. The licensee has designated this inboard remote manual valve as a containment isolation valve. This valve, therefore, is subject to appropriate operability, surveillance and testing requirements, and thereby, in combination with the inboard check valve, satisfies the redundancy requirements of GDC 55.
While the designation of the motor-operated valve as a containment isolation valve is necessary, this change does not bring the isolation design into compliance with the requirements of GDC 55.
Although the licensee has provided an isolation design which satisfies the GDC in terms of redundancy of valves, it is not in compliance with the requirement of GDC 55 concerning valve location. The location of both contain-ment isolation valves inside containment clearly does not satisfy the criteria of GDC 55 which specifies a valve inside and outside containment. Allowances for valve location are made in cases where it is impractical to locate valves on either side of the containment, e.g., in a situation where location of an isolation valve inside containment would mean it could be submerged following an accident.
Consequently, by letter dated February 3,1987, supplemented by letter dated April 8,1987, the licensee requested an exemption from the valve location requirement of GDC 55 for the RHR loop supply line. The licensee
v 7590-01 -
contends that an exemption is warranted on the basis that the isolation
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i capability for this line was technically adequate and that further modification to the design was not cost effective.
The licensee has designed the remote manual valve in the FHR loop supply line l
to the loop 1 and 3 hot legs as a containment isolation valve. This line has multiple isolation provisions; a remote manual valve and two missile-protected check valves inside containment and a closed system outside containment.
The licensee has stated that in addition to the check valve and the remote manual isolation valve there are other isolation barriers that provide protection against leakage to the environment from these penetrations.
- First, the system outside containment is a closed system designed to seismic Category l
l 1 standards and meets at least Safety Class 2 design requirements.
- Secondly, i
these lines are supplied by two RHR pumps which are interconnected to provide a water seal at a pressure sufficient to preclude containment atmospheric J
leakage.
l The NRC staff recognizes that both the water seal and the closed system l
outside containment are eauivalent to a valve as an isolation barrier since both of these barriers can withstand a single active failure. The staff has evaluated the Sequoyah isolation design and exemption request for the RHR loop supply line and concludes that the exemption is justified on the grounds that the existing redundant isolation capability, in consideration of both the.
water seal and closed system outside containment, provides reasonable assurance against offsite releases and, therefore, application of GDC 55 in these particular circumstances is not necessary to achieve the purpose of the criterion.
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J 7590-01.
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Accordingly, the Comission has' determined that, pursuant to 10 CFR 50.12, the exemption is authorized by law, will not present an undue risk to the public health and safety, and is consistent with the comon defense and security. The Comission further determines that special circumstances, as provided in 10 CFR 50.12(a)(2)(ii), are present justifying the exemption--namely, that application of the regulation in the particular circumstances is not necessary to achieve the underlying purpose of the rule in that the licensee's design meets the underlying intent of GDC 55 which is to provide a redundant means of isolation. The design does this by providing a spring-loaded check valve in series with a remote manual isolation combined with a water seal and a closed system outside containment.
The Commission hereby grants an exemption from the requirements of GDC 55 of Appendix A to 10 CFR Part 50 to the licensee for operation of the Sequoyah Nuclear Plant, Units 1 and 2, in that the RHR loop supply line to the loop 1 and 3 hot legs can be isolated using two check valves and a remote manual valve all of which are located inside containment.
Pursuant to 10 CFR 51.32, the Comist. ion has determined that the issuance of this exemption will have no significant impact on the environment (52 FR 46869, December 10,.1987.
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7590-01 6-For further details with respect to this action, see the request for exemption dated February 3,1987, as supplemented April 8,1987, which are available for public inspection at the Commission's Public Document Room, 1717 H Street, NW, Washington, D.C., and at the Chattanooga-Hamilton County Library, 1001 Broad Street, Chattanooga, Tennessee 37402.
This exemption is effective upon issuance.
Dated at Bethesda, Maryland this 14th day of December, FOR THE NUCLEAR REGULATORY COMMISSION fas/
M Stewart D, Ebneter Director Office of Special Projects l
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i e
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DISTRIBUTION Docket File Projects Reading CJamerson December 14, 1987 DOCKET NO.
Rules and Procedures Branch MEMORANDUM FOR:
Division of Rules and Records Office of Administration FROM:
yQggggggfygggnggg OffjCe of Special Projects
SUBJECT:
TEMESSEE VALLEY AUTHORITY, SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 One signed original of the Federal Register Notice identified below is enclosed for your transmittal to the Office of the Federal Register for publication. Additional conformed copies (
) of the Notice are enclosed for your use, Notice of Receipt of Application for Construction Permit (s) and Operating License (s).
Notice of Receipt of Partial Application for Construction Permit (s)and Facility License (s): Time for Submission of Views on Antitrust Matters.
Notice of Consideration of issuance of Amendment to Facility Operating License.
Notice of Receipt of Application for Facility License (s); Notice of Availability of Applicant's Environmental Report; and Notice of Consideration of issuance of Facility License (s) and Notice of Opportunity for Hearing.
Notice of Availability of NRC Draf t/ Final Environmental Statement.
Notice of Limited Work Authorization.
Notice of Availability of Safety Evaluation Report.
Notice of issuance of Construction Permit (s).
Notice of issuance of Facility Operating License (s) or Amendment (s).
Order.
Exemption.
Notice of Granting Exemption.
Environmental Assessment.
Notice of Preparation of Environmental Assessment.
Other:
bh HXIXMXIXNDEX5tGHH Office of Special Projects i
Enclosure:
[XHIMXIXXMdB As stated
Contact:
Carol Jamerson Phone:
49-28749 M cE>
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