ML20076E439
| ML20076E439 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 08/13/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20076E437 | List: |
| References | |
| NUDOCS 9108200108 | |
| Download: ML20076E439 (4) | |
Text
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ni NUCLEAR REGULATORY COMMISSION l
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SAf ETY EVALUAT10tl DY THE Of f1CE Of liUCLEAR kE ACTOR REGUL AT10ft
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SUPPORTING Afdt4DMEllT tiO.
5 TO FACIL11Y OPERATlflG LICEttSE I40. 14P0-86 PUBLIC SERVICE COMPAllY Of I;EW HAMPSHIRE
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SEABROOK STATION,,,UlilT 1 l
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The current Technical Specification (TS) 3.5.3.2 requires that all safety injection pumps are inoperable when the reactor coolant system (RCS) average temperature is less than 350*F.
The basic of this TS limitation is to assure i
that the cold overpressure mitigation (COM) system can adequately protect against violation of the Appendix G pressure / temperature (P/T) limits during a postulated mass addition transient when the plant is operated under low temperature conditions. The current TS 3.4.9.3 requires the C0t> sysum be I
available to protect Appendix G P/T limits considering all safety injection i
(SI) pumps are inoperable during low temperature operations which is consistent with TS 3.5.3.P.
By letters dated December 14, 1990, April 24, 1991, June 14, 1991, and July 15, 1991, the licensee made application for changes of TS 3.5.3.2 and TS 3.4.9.3 to allow one operable safety injection pump during Mode 5 and liode 6 with the reactor vessel head on and the RCS depressurized with a vent area equal to or greater than 18 square inches. This request for changes of TS addresses the reccmmendations of HRC Generic I etter 88-17 regarding the RCS makeup capability during a reduced RCS inventory condition.
2.0 EVALUATION In Section 2.6.1 of Enclosure 1 to flRC Generic Letter 88-17, the staff recommends that operating pWRs provide at least two available or operable means of adding i
inventory to the RCS that are in addition to pumps that are a part of the i
l normal decay heat removal systems. These should include at least one high pressure safety injection pump.
The water addition rate capable of being i
i provided by each of the means should be at least sufficient to keep the core covered.
The proposed changes of TS will permit one operable safety injection pump during Mode 5 and Mode 6 with the reactor vessel head on when the RCS is depressurized with a vent area equal to or greater than 18 square inches.
The licensee has performed an engineering evaluation which supports the conclusion that an 18 square inch vent area is a sufficient RCS pressure l
relief path to limit RCS presture within an acceptable range during Modes 5 and 6 operations.
The licensee's engineering evaluation addressed a number of safety concerns which are discussed below, t
9100200100 910013 ADOCK0500g3 DR
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, App,endix G p/T limits The current COM system design basis events are either:
(1) operation of a single centrifugal charging pump (CCp) or a single safety injection ($1) pump without letdown (limiting mass additien transient), or (?) inadvertent start j
of the reactor coolant pump with a 50*r temperature differential between the FCS and steam generator secondary temperatures (limiting heat addition j
j transient). A single pressurizer power operated relief valve (p0pV) with an equivalent vent area of 1.58 square inch is sufficient to protect Appendix 0 p/T limits against the above stated design basis events.
The irnplementation
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of the proposed TS change would allow one operable 51 pump in l' odes 5 and 6.
l As a result, a mass addition transient nore lit.iiting than the current COM system design basis mass addition transient beconies possible. This new limiting transient is characterized by mass addition from the simultaneous operation of both a CCp and a Si pump without letdown. The results of the licensee's study indicate that a vent area of P.97 square inch is required to orot'ect Appendix G p/T limits against this na limiting n. ass transierit. The proposed 18 square inch vent path is more than tufficient to prevent violation of the Appendix G p/T limits during such an event.
Steam Cenerator,porzic,, Dam in_tegrity The results of the licensee's evaluation indicate that the 18 square inch vent area specifisti in its proposed TS is sufficient to limit the pressure differential acrsss the steam generator norrie dams during the new limiting mass addition transient to 33 psi, which is less than the 56.8 psi design pressure differential of the nozzle den.s which may be used at Seabrook.
- Also, in the event of a loss of residual heat removal (RHR) cooling during mid-loop operation, the 18 square inch vent area provides adequate relief capacity to assure steam generator norrie dem integrity.
Graviiy feed to RCS In addition to the S1 pump and the CCp, gravity feed from the refueling water storage tank (RPST) to the RCS is available at Seat: root. The 18 square inch vent path is sufficient to pass the steaming rates associated with decay heat removal while maintaining RCS hot leg pressure:
(1) less than 45 psig, for shutdown times in excess of 7 days, and (?) less than 32 psig, for shutdown time in excess of 15 days. With a full RWST, gravity feed is achievable up to a RCS pressure of 45 psig. With a PWST level of 25i, gravity feed is possibic with RCS pressure up to 32 psig.
Therefore, gravity feed from the RWST is likely to be available in the unlitely event that both the CCp and S1 pumps are unavailabic after a complete loss of RHR cooling.
The U.censee stated that the anticipated nethod of providing the 18 square _
inch vent path is removal of a pressurizer safety valve from its flange or optionally, opening a pressurizer nanway.
Seabrook Station procedures will include administrative controls to ensure that a vent path of at least 18 square inches is established prior to maling the S1 punp available for use in a reduced inventory condition per tne requirements of TS 3.5.3.2 and TS 3.d.?.?.
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, Tempora,ry _ Thimble Tube Seals e o Regarding potential failure of tcmporary thimble tube seals caused by I
pressurization of the RCS while a safety injection pump was operable in Mode 5 l
or 6, the licensee in its letters dated June 14, and July 15, 1991 stated that r
the Seabrook Major plant Evaluation procedure 051000.09 "kefueling Operations" l
will specify that (1) the reactor vessel head must be detensioned before the RC$ boundary is broken at the seal table and the installation of the temporary seal begins, and (2) the temsorary seals must be removed and the permanent RCS pressure boundary reestablished at the seal table prior to beginning the l
tensioning of the reactor vessel head. The plant procedures 151090.816 "Incore Instrumentation Thimble Installation" and 151690.815 "Incore Instrumentation Thimble Withdrawal" will specify the same sequencing for the i
installation and removal of the temporary sea.s to assure that the temporary thimble seals will exist only while the plant is in Mode 6 with the reactor
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vessel head detensioned. During the preoperational testing period of Seabrook l
Station, the reactor vessel head was lifted from the reactor vessel with approxinately 1 to 11 inch gap by the internal spring forces, from the above 1
experience, the licensee conside.s that a substantial vent area in the RCS will be available after the reactor vessel head is detensioned and a failure t
of temporary thimble tube seals caused by pressurization of the RCS will be
. prevented. The temporary thimble tube seals are designed to withstand the
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static head of ap?roximately 10 psig. However, one of the temporary seals, of the same design t1at will be utilized during the refueling outage, has been informally bench tested to approximately 60 psig without catastrophic failure. Additionally, the temporary seals will be installed with a metal t
backing device so that the expected failure mechanism will be seal leakage and i
not a catastrophic failure of the temporary seal.
Since the seal table and i
the location of the _ temporary thimble tube seals is 11 inches below the elevation of the reactor vessel flange, the worst case of postulated temporary thimble tube seal leakage may reduce the reactu vessel level to.the reactor vessel flange which is well above the to) of the core. With the plant i
design and operating procedures available at Sea) rook plant it is unlikely that a failure of temporary thimble tube seals could occur due to a pressurization of the RCS while a safety injection pump was operable.
The staff has evaluated the licensee's engineering evaluation.and agrees-with its conclusion that the 18 square inch vent path during Modes 5 and 6 operation would provide sufficient relief capability to protect Appendix G p/T limits and steam generatar nozzle dam integrity, and to assure the capability of gravity feed to the RCS from the RWST. Also, the integrity of the temporary l
thimble tube seals will'be protected by the design of the seal, by the vent from the gap under the-reactor vessel head when the vessel head is detensioned, and by plant operating procedures.-
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3.0 STATE. CONSULTATION j
in accordence with the Consnission's regulations, the New Hampshire State official was notified of the proposed issuance of the amendment. The State official had ec ::cc,nents.
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1he amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in l
10 CFR Part P0. The NRC staff has determined that the amendment-involves no significant increase in tha 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 Connission has previously issued a proposed finding that the amendment i
involves no significant hazards consideration, and there has been no public comment on such finding (56 FR 24217). Accordingly the amendment meets the i
eligibility criteria-for categorical exclusion sct 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.
5.0 CONCLUSION
Based on the staff evaluation in Section P.0 above, the staff concludes that the licensee's proposed TS 3.5.3.2 and TS 3.4.9.3 are acceptable.
i The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will i
not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the connon defente and security
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or to the health and safety of the public.
0.0 REFERENCES
1.
Letter from T. C. Feigenbaum, New H wpshire Yankee, to USNRC, " Request for License Amendment:
Safety injection Pump Operability in a Reduced Inventory Condition," December 14, 1990.
2.
Letter from T. C. Feigenbaum, New Hampshire Yankee, to USNRC, " Request for License-Amendment:
Safety injection Pump Operability in Modes 5 and 6," April 24, 1991, 3.
Letter from T. C. Feigenbaum, New Hampshire Yankee, to USNRC, " Request for Additional Information Regarding Safety injection Pump Operability-in tiodes 5 and 6," June 14,:1991.
4 Letter from T. C. Feigenbaum, New Hampshire Yankee, to USHRC, " Request for Additional Information Regarding Safety injection Pump Operability in 1
Modes 5 and 0," July 15,1991.
principal Contributor:
Chu-Yu Liang Date:
August 13, 1991
A! 7*14Etil 110. 5 TO I;PF-86 SEA 0 ROOK STA110N DA1ED August 13. 1991 OlSTRIBUTION:
Fo'cWtTiWE0-443 k-IIRC PDR Local PDR PDl-3 Reading S. Varga J. Calvo M. Rushbrook S. Shaninen G. Edison 000 - 15 D10 Dennis Hagan - MilBB 3206 E. Jordan - itN00 3701 D. Griras - 9 A3 G. Hill (4) PI 37 Wanda Jones - 7103 i>NBB C. Grin:es - 11 f?3 ACRS (10) P - 315 GPA/PA - 2 G5-OC/LFt1B - I'l BB J. Linville, Region 1 K. Brocknian Chu-Yu Liang - 8E23 i
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