ML20076C766
| ML20076C766 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 07/10/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20076C764 | List: |
| References | |
| NUDOCS 9107240272 | |
| Download: ML20076C766 (5) | |
Text
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SUPPLEtTtHAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR _REGUMTION
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SUDPORTlt1G AMEt1DMEllT t;0.130 TO FACillTY OPERATING LICENSE N0. DPR-2B E
V E RiiO N T Y A.N.K.E.E..N.U.C.L.E.A.R..P.O.W.E.R..C.O.R.P.O.R.A.T.I.O N-VERFONT YAt!KEE NUCLEAR POWER STATION DOC",ET N0. 50 271 1.0 litTR000CT10H Ly letter dated April 25, 1986, Vermont Yanlee Nuclear Power Corporation (VuiPC), the licensen, requesteo a change to Section 5.5.D of the Tech ical Specification for Vermont Yankee Nuclear Power Station (VY). This change g
would it crease the number of fuel asser.blies which could be stored in the spent c
fuel pool from 2000 to 2870.
Other previously approved specificatic of Section 5.5 would remain unchanged. The change is based on the installation of new fuel racks in the spent fuel pool which can provide a closer pacting of g
teel assent liet.
Fequired crititclity margins are niaintained by incorporation ci boron containing eaterial in the rack design, This is a coanunly used
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feature foi high density ract design, ard a large number of similar dcsigns J
bcs e bu n approud t4y the f;FC.
In a letter dated tiarch 2, 1988, the licensee stated, " Vermont 'vantee has tornitted to design, install, test and make operational, a redundant seiu icelly designed Spent Fuel Fool Cooling System prior to the tir.e Vernont Yantu excevis it ( e>isting 2000 spent fuel assembly storare limit in the Vertent Yanlee spent fuel pool. This system will be operational no later than the end of Cycle 16 (Pr ojected to be 1992.)"
By Amendnent tio. 104, dated tiay 20, 1988, the Commission approved the insta:Tetion of new high density iacks in the spent fuel tool sufficiert to accommodata 2870 assettlies, and the storage of fuel assemblies in the new rac h up 's a limit of 2,000 assen;blies in the posi, but did not approve the storege of the 2870 assemblies requested.
By letter dau d July 25, 1988, the staff forwarded to VYNPC its Environn. ental Assessment and Finding of No Significant Impact. The Notice of Environmental Assesment and finding of No Significant Irpact was published in the Federal Register on agust 1, 1988 (53 FR 28925).
By letter dated October 14,7H7tFi~ staff issued the Safety Evaluation suppoi ting thc storage of Ef 70 assenblies in the storage pool, but did not issue ar, amencitent authorizing iuch storage, 1
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Ag roval to store up to 2870 assemblies in the spent fuel pool was withheld by the staff until the tf.iff reviewed and approved the spent fuel pool cooling system as enhanced by the planned improvements.
This conditic1 was made part of a stipulation entered into on fiarch 23, 1989, by the licensee, the staff, the New England Coalition on Nuclear pollution, the State of Vermont, and the Commonwealth of Massachusetts. The stipulation also required the staf' to publish its ultimate determination of the acceptability of the enhanced spent fuel _ pool cooling sys+em in a Supplement to the Safety Evaluation Report before approving storage of 2870 assembiies.
By letter dated September 28, 1990, the licensee submitted the design package for the enhanced fuel pool cooling system to the staff for review. This Safety Evaluation deals with the enhanced spent fuel pool cooling system and suppiements the Safety Evaluation issued by the staff by letter dated October 14, 1988, which is incorporated by reference.
2.0 E vat UAT10tj The enhanced fuel pool cooling and demineralizer system (FPCDS) proposed by
-the licensee consists of two subsyst ms:
(1) the normal fuel pool cooling system (NFPCS), the existing cooling system, and (2) a new additional cooling
- system designated as the standby fuel pool cooling system (SFPCS.) i.ach subsysten has two trains of pumps and heat exchangers.
Trc existing NFPCS provides for the normal cleaning of the spent fuel pool.
Thu MfPCS is r teu as ncnseismic Categcry !, with one 450-gpm centrifugal pump and one 2.23 tGtu/hr tube-and-stell heat exchanger in each train. The NFPCS cools the spent fuel pool by transferring the decay heat from the spent
-fuel through heat exchangers(s) to ine closed cooling water system in the reactor building. - The t1FPCS cleens the pool water by circulating the watcr through the filters and domineralizers that clear and purify the pool water.
One train of the NFPCS norndly operates during plant operationt to maintain pool temperatures'within specified limits.
The SfPCS will only be used to cool the spent fuel pool when a high spent fuel
-decay heat load is placed in the pool or if a seismic event occurs that disables the !!TPCS. The Sf0CS is rated as seismic Category 1, with one 700-gpm pump and one 11.0 PBtu/hr tube and-shell heat exchanger in each train. The SFPCS equipment receives electrical power from safety-related Class 1E power sources.
For normal refueling heat loads, each train has sufficient capacity I
to maintain the pool water temperature below 150*F for a full core discharge.
In addition, the SFPCS has-been designed to perform the following:
1.
Continue functioning even af ter a single active f ailure or the failures of nonsafety class components or systems, 2.
Maintain the pocl water level by detecting and isolating the nonseismic i
portion of the NTPCS, 3.
. Fulfill the design tascs without effecting other existing systems such as tre service water syster ar.d emergency power sources, and
--3 4.
Provide instrumentatiert and control to initiate, mon: tor, and shut down the systera from the control ruom.
Following the guidelines of Standard Review Plan (SRP) Section 9.1.3, " Spent Fuel Pool Cooling and Cleanup Systems," the staff evaluated two types of spent fuel pool heat generation conditions. The first conoition was the normal maximum heat load, which is the beat generated by spent fuel when the pool is filled (2870 assemblies) with successive regular refuelings (1/3 of the core for each refueling interval) assuming a failure of one train of the SFPCS.
The second condition was the ebnormal maximum heat load, which is similar to the normal maximum heat load except that it assumes that the last 368 spaces are filled by a full core off-load and that both trains continue to operate.
The licensee calculated the decay heat loads from normal refuelings with the assurption that the spent fuel was discharged to the storage pool at 6 days and 10 days followinc shntdown from normal o?eration. The licensee calculated the abnorroal decay hv. load assuming that t1e full core was discharged to the storage pool 10 days following shutdown from normal operations for refueling.
Table 10.5.? of the design package provides data on the decay heat generation rate that is identical to the data in Table A.2 of the licensee's submittal of June 7, ISf$, which wes the basis of the staff's October 14, 1988, Safety Evaluation supporting the storage of P870 assemblies in the pool. This data indicated that the decay heat generation rate for normal refueline discharge varies frora 7J9 MBtu/hr to 10.33 MEtu/hr, and that the rate for the abnormal refueling discharge varies frora 16.84 MBtu/hr-to 18.26 MBtu/hr.
In the SER issued by the staff by letter dated October 14, 1988, tt.e staff stated that these heat ger.cration rates are sirailcr to the values calculated independently by the staf f. Furthermore, the staff compared these calculated heat loads and
+he heat removal capability of the cooling systems, and concluded that the
.uel pool cooling and demireralizcr syst.em has sufficient capacity to remove
- the chiculated rnaximum norrnal ar.d abnormal teat generated by the spent fuel.
The Safety Evaluation issued by the staff by letter dated Octaber 14, 1988, concludes that "the Vermont Yanket high density racks and fu(1 pool, including i
the enhanced system for spent fuel pool cooling is acceptable for the proposed expanion to 2870 "semblies, provided that the enhanced system as described in the licensee's.ae 7, 1988, submittal has been installed and tested to denonstrate operability." The licensee's March ?, 1980, letter committed the licensee to " install, test, and make operational" the new fuel pool cooling system " prior to the time Vermont Yankee exceeds the existing 2000 spent fuel-
-assen.bly storace linit in the Vernont Yankee spent fuel pool." This review finds that the design of the standby fuel pool cooling system for the Vermont Yankee Nuclear Power Station conforms to the guidance described in SRP Section 9.1.3, " Spent Fuel Pool Cooling and Cleanup System." This review also finds that the design is "as described in the licensee's June 7, 1988, submittal."
Therefore, the systeni is acceptable.
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3.0 fjp,AL,y0,,$JGpj[JCAp,1,HA7ARDSCONSIDEPATIONDETERMINATION The licensee's request for amendment to the operating license _for Vermont Yankee including a proposed determination by the staff of a no significant hazards consid-eration was_ individually noticed in the Faderal Pegister on slune 18, 1986, followed by a notice on December 31, 1986, pertaining specifically to the hybrid hearing
- provisions of the Commission's regulations.
When the staff prepared these notices the licensee had not proposed to add the SFPCS. The staff has now reviewed the design of the SFPCS and' found that it does not change the staff's determination of no significant hazards consideration.
The Commission's regulations in 10 CFR 50.92 include three standards used by the tiRC staff so arrive at a determination that a request for amendment
- nvolves no significant hazards consideration. These regulations state that the Comraission n.ay make such a final deternination if operation of a f acility in accordance with the proposed aniendrent would not (1) invohe a significant increase in the prchabili, or consequences of an accident previously evaluated; or (?) create the possibility of a new or different kind of accident from ary accident previously evaluated; or (3) involve a significant reduction in a nargin of safety.
The Safety Evaluation accompanying Amendu.ent tio.104 included an analysis that showed that each one of these standards was met for Amendnent f:e. 104 The Amendn ent tlo 104 analysis remains valid and_ is referred to for this amendnent, with one exception.
In discussing the third standard (involve a tignificant reduction in a margin of safety), three areas were addressed:
- 1. Nuclear criticality considerations.
P. Therraal-hydraulic considera t ions.
- 3. Fechanical, material and strutturcl considerations.
The fitst and third erecs are not relevant here..Fowever, the analysis sup-porting the conclusion that there was no significant reduction in the n:argin of safety for thermal-hydraulic considerations relied on the f act that Amendment 104 did not authorize an increase in heat load.
The staff has now reviewed and approved the acceptability of the enhanced spent fuel pool cooling system.
(Jnder worst case conditions, the initiation of the stand-by fuel pool cooling systen. nay slightly reduce the available service water systen flow to specific accident r,itigetion systen si ^ port equipitent.
However, the licensee's analysis, as confirmed by the staff, shows no detrin; ental ef fect:, to the performance of these systec s.
The staff concludes that approval of spent fuel pool storage capacity for 2870 assemblies, with the enhanced fuel pool cooling system installec' and operable, does not involve a significant reduction in the oargin of saf ety for thcrnal-hydr aulic consider ctions. Therefore, Lased on the analysis accompanying Anendnent No.104 and the above analysis, this amendnent does no' involve significant hazar ds considerations, i
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t 5-4.0 EtlVIRONMEliTAL ASSESSMENT j
The staff published an issuance of Environment Assessment and finding Significant Impact with respect to the proposed action (53 FR 28925) or.
ist 1, 1988. Although subsequent submissions by the licensee provided detaiis that were not available at the time the staff prepared its Environmental Assessment, these details do not change the determinations reached in the staff's assessment.
5.0 C0f1CLUS10H Based on the above considerations, the proposed change to Section 5.5 D. of the Technical Specifications for Vermont Yankee, to increase froc 2000 to 2870 the nun;ber of assernblies which could be stored in the spent fuel it.orage pool, is acceptable.
Principal Contributors:
D. Shuir and V. Rooney Dated:
July 10, 1991 l
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