ML20126H497
| ML20126H497 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/14/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20126H484 | List: |
| References | |
| IEIN-88-073, IEIN-88-73, NUDOCS 9301050227 | |
| Download: ML20126H497 (4) | |
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UNITED STATES 3
i NUCLEAR REGULATORY COMMISSION o
WASHINoToN, D.C. 20%6 SAFETY EVALVATION BY THE OFFICE OF NVCLEAR REACTOR REGULATIQB R[ LATED TO AMENDMEN1 NO.140 TQ FACILITY OPERATING LIC @iE NO. NPF-6 ERIMGLQPERATIONS. INC..
ARKANSAS NUCLEAR ONE. UNIT NO. 2 DOCKET NO. 50-368
1.0 INTRODUCTION
By "0CAN109102, Application for Amends to Licenses DPR-51 & NPF-6,revising Tech Specs to Add NRC Std OL Conditions for Fire Protection & Relocating Fire Protection Requirements from Tech Specs to Sars,Per [[generic letter" contains a listed "[" character as part of the property label and has therefore been classified as invalid. & 88-12|letter dated October 15, 1991]] Entergy Operations, Inc. (the licensee) submitted a request for changes to the Arkansas Nuclear One, Unit No. 2 (AND-2) Technical Specifications (TS).
The requested changes would delete two inboard containment purge isolation valves 2CV-8289-1 and 2CV-8291-1 from TS Table 3.6-1.
In addition, the licensee requested an exemption from compliance with the requirements of General Design Criterion (GDC)-56 to allow use of the redundant outboard isolation valves 2CV-8283-1 and 2CV-8285-1 to maintain containment integrity. The licensee indicated that as a fallow-up to Information Notice 88-73, it discovered that the sloped ',alve body seals of the inboard containment purge isolation valves 2CV-8289 I and 2CV-8291-1 are oriented in a direction which is less likely to seal vhen pressurized from the containmant side.
Because of the system design, it is not possible to perform traditional local leak rate testing (LLRT) of the valves with pressure applied to the valve's disc from the containment side.
Previously LLRT was conducted by pressuring the inboard isolation valves from a reverse direction.
The proposed change will allow the use of existing redundant outboard containment isolation valves in the two affected penetrations to provide essentially equivalent double isolation capability assumed in the design basis analysis.
The licensee indicated that the modifications to allow proper leak rate testing of the currently installed inboard valves or complete replacement will result in substantial cost without a significant reduction in any' safety limit.
2.0 EVALUATION The licensee indicated that the main purge supply and exhaust lines that penetrate the containment building utilize three isolation valves in series-one valve inside the containment and two valves outside the containment.
The two redundant outboard isolation valves in the purge lines are air-operated, fail closed,- 54-inch butterfly valves with resilient seals.
The valves are controlled by key operated handswitches from the control room and are maintained in a sealed closed position in operational Modes 1, 2, 3 and 4 by removing the keys from the handswitches in accordance with TS 9301050227 921214 PDR ADOCK 05000368.
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The valves also receive an automatic close signal upon initiation of the containment isolation actuation or safety injection actuation (CIS/ SIS).
The first outboard isolation valve receives a close signal from CIS/ SIS #1 and the second outboard isolation valve from CIS/ SIS #2.
Position indication for each valve is provided in the control room.
The licensee stated that the containment purge system is not credited for performing any safety-related function and is not recuired to operate during a design basis accie 'it.
The closed redundant outboarc isolation valves will provide a double barrier to the release of radioactivity for the purge lines following a design basis event. A vent line originally provided to route any potential leakage past the first outboard valve to the Penetration Rooms Ventilation System is sealed closed with a welded pipe cap to maintain a double containment isolation barrier.
Operation of either the inboard or the outboard purge isolation valves to provide containment isolation during operation Modes 5 or 6 is not required to maintain the offsite doses within the limits of 10 CFR Part 100 in accordance with the ANO-2 design basis fuel handling accident analysis.
One outboard containment isolation valve in each penetration is designed to close automatically u)on detection of high activity levels to prevent the release of radioactivity tirough the purge system.
The proposed arrangement of containment isolation valves for the containment purge system, in which both isolation valves are located outside the containment, does not conform with the explicit requirements of GDC 56.
GDC
$6 requires one inside and one outside containmerit isolation valve,-unless it can be demonstrated that isolation provisions for a specific class of lines are acceptable on some other defined basis.
The licensee indicated that although no explicit guidelines are provided for alternate containment isolation design provisions for lines such as containment purge lines, the guidance contained in Standard Review Plan (SRP) Section 6.2.4, item 116.d is relevant to the proposed ANO-2 design. The above guidance states that both isolation valves may be located outside containment if the isolation valve nearest containment and the piping between the containment and the valve is conservatively designed to preclude a breach of piping integrity.
The design t
of the ANO-2 outboard containment isolation valves and associated piping complies with this criterion.
The licensee stated that the outboard I
containment isolation valves and the associated piping are designed to Seismic Category I standards and have a design temperature and pressure rating of 300'F and 65 psig, respectively, t-These design ratings exceed the calculated peak design basis accident containment conditions. The valves and piping associated with the containment purge supply and exhaust are classified as Safety Class 2 and are protected from the dynamic effects of potential pipe ruptures.
The outboard isolation valves and associated piping will be tested in accordance with the other TS requirements for isolation valves. Additionally, periodic replacement of the valve's resilient seal is included in the plant preventive maintenance i-program.
Therefore, the use of the redundant outboard isolation valves in i
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. each of these containment senetrations which are sealed closed during operational Modes 1 througi 4 will provide acceptable isolation provisions for purge system penetrations.
The only potential concern resulting from the use of redundant outboard valves to provide containment isolation is the possibility of tornado missile damage.
The licensee stated that the outboard isolation valves are located in close aroximity to each other.
The >hysical arrangement minimizes the piping setween the isolation valves w11ch could be subjected to potential tornado missile damage. These valves are located at high elevation and are significantly shielded from horizontal tornado missiles by the containment and auxiliary buildings.
Using the techniques of NUREG/CR-4713, the likelihood of any size tornado generating a missile that impacts any part of the outside containmentpurgepipingorvalveswitgin30daysfollowingaLOCAofanysize is calculated to be much less than 10' per year.
Therefore, the possibility withaLOCAisnotconsideredcredible,solationvalvesorpipingconcurrent of tornado missile damage to the purae i in a telephone conversation with the staff, the licensee also stated that the nature of the LLRT of the outboard containment purge isolation valves will require that the inboard containment purge isolation valves continue to be maintained. The test is performed by pressurizing between the inboard purge isolation valve and the outboard purge isolation valve being tested and measuring the pressure decay.
The decay rate is equated to valve leakage, all of which will se attributed to the outboard isolatinn valve.
The licensee indicated that it will continue to maintain the inboard containment purge isolation valves as safety related equipment and will keep them sealed closed during operational Modes 1 through 4, and the existing containment isolation signal will be maintained as an additional impediment to the release of radioactivity through the containment piping.
The staff has reviewed the licensee's submittal as discussed above and finds that the containment isolation provisions for the two penetrations associated with the containment purge supply and exhaust lines are acceptable on the basis that the use of redundant outboard contair. ment isolation valves on each penetration, which are designed tc the acceptance criteria of 11 6.d of SRP 6.2.4 and are tested per 10 CFR Part 50, Appendix J, provide an equivalent degree of containment isolation as that assumed in the design basis accident analysis. With the additional impediment to the release of radioactivity provided by the inboard isolation valves, which will be kept sealed closed during operational Modes 1 through 4, the proposed change does not involve a significant reduction in margin of safety.
3.0
SUMMARY
Based on the above evaluation, the staff finds that the proposed TS change, to remove the inboard containment isolation valves 2CV-8289-1 and 2CV-8291-1-from the listing of the containment isolation valves,;is acceptable because the redundant containment purge isolation valves provide an essentially equivalent degree of double containment isolation assumed in the design basis analysis.
y 4-In addition, the licensee will maintain the inboard purge isolation valves as safety-related equipment and keep them sealed closed during operating Modes 1 through 4 with the existing containment isolation signals, for additional impediment to the release of radioactivity.
The staff also concludes that an exemption from GDC 56 is not needed in that GDC 56 provides that the isolation provisions for a s)ecific class of lines may be demonstrated acceptable on some other defined ) asis.
Containment isolation provisions for the containment purge supply and exhaust lines are acceptable on the basis described in this evaluation.
4.0 STATE CONSVLTATION in accordance with the Commission's regulations, the Arkansas State of ficial was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change-in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding _that the amendment involves no significant hazards consideration, and there has been no public comment on such finding-(57 FR 40211). Accordingly, the amen #ent meets the eligibility criteria for categorical 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 amendment.
6.0 f_0NCLUSION The Commission has concluded, based on the considerations discussed above, 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 activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be. inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
R. Goel, SPLB Date: December 14, 1992 i
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