ML20097D758
| ML20097D758 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/04/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20097D754 | List: |
| References | |
| NUDOCS 9206110114 | |
| Download: ML20097D758 (6) | |
Text
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i NUCLEAR REGULATORY COMMISSION o
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SAFETY EVALVATION BY TEL.9EFICE 0.E NVCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 158 TO FALILITY 00ERATING LICENSE NO. DPR-65
@RTHEAST NUCLEAR ENERGY COMPANY. ET L MILLSTONE NVCLFAR POWER STATION. UNIT N U h
DOCKET N0, 50-336
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^ INTRODUCTION yp %
q 1etter dated April 16, 1992, as supplemented by letter d
'ay 7, 1992,
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Northeast Nuclear Energy Company (the licensee) proposed chai.,
to the
' 11 stone Unit 2 Technical Specifications (TS) which would modify the existing ao-region spent fuel poi design to a three-region configuration.
The May 7, s92, letter provided information that did not change the initial proposed no significant hazards consideration determination.
7 These changes ce proposed as a result of errors discovrired in the spent fuel rack criticalny analysis as reported to the NRC in 1.icensee Event Report 92-003-00, dated March 13, 1992. These calculational errors were due primarily to the incorrect treatment of thin, bhhly absorbing Boraflex panels and were discavered while performing critica'it( reanalyses associated with the Boraflex degradation. This prompted the issuance of NRC Informai. ion Notice 92-21 and its Supplement.
~ resent 13. Ran.n I of the Hilletone Unit 2 spent fuel pool is designed to
- tore up to M4 fuel assemblies with an initial enrichment of up to 4.E weight percent (w/o) U-235. Region I is comprised of five (5) rack modules and fuel assemblie can be stored in every location. The Region I racks contain
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Boraflex and have a nominal center-to-center distance between storage
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Iccations of 9.8 inches.
Region II is designed to store up to 726 fuel assemblies which have sustained a minimum required burnup as specified in-TS Figure 3.9-3.
Fuel assemblies tre stored in a three-out-of-four array, witi-blocking dev!ces installed to prevent inawertent placement of a fuel assembly in the fourth location. The Region II storage racks have a non.inal center-to-center distance between storage locations of nine (9) Sches acd centain no Boraflex.
The proposed changes woula result in a three-regLn configuration, described by alphabetic lettcrs rather than the previous numeric convention.
Region A would utilize three of the existing Region I poisnn rack modules.
Region A ic de:iqned to Fore up to 224 fuel assemblies, which will be qualified for storage by verification of adequate assembly average burnup versus fuel assembly initial enrichment.
Fuel assemblies can be stored in every location in Region A.
These racks would be used for immediate storage of fuel discharged from the reactor.
Region B would utilize the remaining two existing Reofon I rack modules. Region B is designed to store up to 120 fresh 4
9206110114 920604 PDR ADOCK 05000336 ri PDR
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(unirradiated) fuel assemblies with an initial enrichment of up to 4.5 w/o U-235 and other assemblies which do not satisfy the burnup versus initial a
enrichment requirements of e; 'er Region _ A or Region C. - _ Fuel assemblies will be stored in a three-out-of-tu array in Region B, with blocking devices installed to prevent inadvertent placement:of a fuel: assembly in the fourth location.
Region C is the new designation for the existing Region lI storage-racks, designed for fuel assemblies which have sustained their design burnup.
Since this group of racks do not contain Boraflex, a reanalysis due to o
Boraflex degradation or due to previous calculational errors was not required.
2.0 Ey&UATION i
On September 8,1987, the NRC-issued Information Notice No. 87-43 alerting all operating licensees that gaps had been found:in the Boraflex panels of the-sient fuel storage racks at Quad Cities Unit 1.
In response to this, the L
licensee initiated blackness testing on-the Boraflex panels in-the Millstor.c j
Unit 2 spent' fuel storage racks. To date, approximately half of the poisonad rack cells in Region I'have-ocen tested. These_ measurements confirmed the presence _ of gaps in about -16% of-the irradiated panels with the largest
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observed -gaps at a.2% shrinkage rate,- resulting in a maximum gap size oi approximately 2.825 irches. -The licensee has,-therefore, performed criticality analyses to demonstrate the safety of the storage er.cks accounting for gap formation.
I The criticality analysis assumed 4% shrinkage result'ing in 5.65-inch gaps at' the observed test locations.
The analysis also assumed a '4%-gap formation with a random distribution in all of the other Eoraflex. panels. - The staff-considers these assumptions to be acceptable-since'the test _ data has only-l identified a maximum shrinkage of 2% and existir.g industly-wide data supports a 4% maximum shrinkage rate.
In addition,; the _ random distribution. of _ gap l
formation is also supported by the licensee's test _ data.
L The NITAWL-KENO-5a con,puter code package -was used in a three-dimensional mode-with the:27-group. SCALE neutron cross:section_ set. This model'has:been benchmarked against experimental data and has been found to-adequately reproduce the critical values. The original calculations for the Millstone Unit'2 spent fuel pool used the DOT two-dimensional',' discrete-ordinates t.ansport code with cross sections; generated:by the CEPAK tode..a synthesis of l-FORM, THERMOS, and. CINDER. As prev 1ously mentioned, the originc1 calculations were found:to be'in error. The reactivity of the Region I spcnt= fuel storage racks was underpredicted ducLto inaccuracies in predicting Boraflex:
absorption, thus resulting' in a 'nonconservativeLanalysis. - A more_ recent analysis of. the' original Region I design using1the NiTAWL-KENO-Sa package
. resulted in a k-eff. of 0.3812, assuming' fully loaded racks of-4.5 w/o fuel and rot accounting =for Boraflex shrinkage.
This does not_ meet:the NRC'95/95 upper limitt k-eff criterion of no greater than= 0.95.
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The licensee has, therefore, reanalyzed the Region I rack design witt NITAWL-KENO-5a assuming a three-out-of-four storage configuration (new Regier B designation) with 4.5 w/o fresh fuel and 5.65-inch gaps at the locations observed in the Hillstone 2 blackness tests and a random = rial distribution of 5.65-inch gaps in all otbe.' Boraflex panels.
The result., maximum k-eff, including all appropriat' hisses and uncertainties, was 0.9179 for ANF fuel, 0.9252 for Westinghouse hel, and 0.9201 or CE fuel, all well wittJ.. the 0.95 limiting criterion.
The calculations also assumed a conservative shrinkage of 4% in width even though such shrinkage was not evident from visible inspections of Boraflex panels.
The old Cegion I rack design was also reanalyzed utilizing all of the cells in a four-out-of-four cell arrangement with credit f(
fuel burnup (new Region A designation).
The same Boraflex gap Jistribution,
umed in the Region B ana!ysis was used. As seen from TS Figure 3.9-4, fuel with an initial enrichment of 4.5 w/o U-235 and minimum burnup of 8670 MWD /MTV is equivalent to unirradiated fuel enriched to 3.3 w/o U-235.
The resulting maximum (95/95) k-eft was 0.9317 for ANF fuel, 0.9381 for Westinghouse fuel, and 0.9335-for CE fuel, all within the 0.95 limiting criterion.
It is possible to postulate events, such as the inadvertent mistoading of an assembly with a burnup and enrichment combination outside. of the acceptable area or the placement of a fresh assembly in the fourth cell of the three-out-of four configuration, which could lead to an incretse in reactivity.
However, for such events, the Double Contingency Principle allows credit for the presence of approximately 800 ppm of boron in the pool water required by TS whenever a fuel assembly is being moved in the spent fuel pool.
The reduction in k-e'r cau'if by the boron more than offsets the reactivity addition caused by credible accidents.
The following TS changes have beca proposed as a result of the reanalysis of the Millstone Unit 2 spent fuel pool. The staff finds these changes acceptable as well as the associated Bases changes.
(1)
Definiticn 1.39, STORAbt PATTERM is currently defined for Region II.
This is being : hanged to define the three-out-of-four array to be-used in Regions B and C.
(2)
TS 3.9.17 is currently concerned with fuel movement over Region 11 racks (due to the dropped assembly accident and misplaced fuel assembly event).
This is being changed from any fuel movement over the Region II racks to any fuel movement it, the spent fuel pool.
(3)
TS 3.9.18 is'being modified to change the wording in the'surve nl wce requirements from Region 11 to Region C, and adds a surveillance requirement to ensure that fuel assemblies to be placed in Region A are within the enrichment and burnup limits of a new Figure 3.9-4.
(4)
Figure 3.9-1 is being modified to change the references from Region II to Region C.
d
.- (3)
Figure 3.9-2 is being modified to delete the references from Regions I and II and add Regions A, B, and C.
(6)
Figure 3.9-3 is being modified to change the references from Region II
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to Region C.
(7)
A new Figure 3.9-4 is being added to specify the allowable enrichment and burnup limits for fuel assemblies to be stored in Region A.
(8)
TS 3.9.19 is teing split into two parts:
(a) TS 3.9.19.1 is the old TS 3.9.19, changing the references from Region 11 to Region C.
(b) TS 3.9.19.2 is a new requirement for the STORAGE PATTERN requirements of Region B.
(9)
The Design Features section for Fuel storage Criticality and Capacity 4
are being changed to describe the design features for the newly defined regions (A, B, and C), as well as tu change the storage capacity numbers to reflect the blocked locations in Regions B and C.
(10) The Bases sections for TS 3.9.17, 3.9.18, and 3.9.19 are being changed to reflect the changes introduced by the new spent fuel storage-rack criticality design basis.
4 Based on the review described above, the staff finds the criticality aspects of the proposed Millstone Unit 2 spent fuel storage pool changes acceptable.
Specifically, with the ccnservatively postulated maximum 5.65-inch gaps in all Boraf4x panels, the spent fuel storage racks can safely accommodate spent fuel arom Millstone Unit 2 of the burnup-enrichment combinations indicated in TS Figure 3.9-4 (Region A) or Figure 3.9-1 (Region C) using all cells in a four-out-of-four arrangement.
In addition, Region B can safely accommodate fresh 4.5 w/o U-235 Millstone Unit 2 fuel in a three-out-of-four loading pattern with the fourth cell empty.
3.0 STATE CONSULTA110'!
In accordance with tha t,ommission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 PUBLIC COMMENTS Ms. Patricia R. Nowicki, representing Earthvision, Inc., by letter dated May 27, 1992, requested a public hearing on'this matter citing that "...it would be in the best interest of both Northeast Utilities as'well the welfare of the citizeiis of this area that the licensee provide background information to the public as to the need for-and the safety-of said-amendment." - The staff has considered Ms. Nowicki's comments and has concluded that there is nothing in
. 4 them that would cause the staff to change the proposed no ignificant hazards consideration determination.
Ms. Mary Ellen Marucci of New Haven, Connecticut, by letter postmarked May 28, 1992, requested a hearing and a wish to intervene and an implied request for a 10 day delay in the issuance of the amendment citing a concern that "...there is significant unacceptable hazards risk if the spent fuel pool were to be utilized under planned conditions to oc u r on June 14, 1992, and that the design question cf criticality calculations in that pool may not have been resolved. Also the removal of criticelity monitors as allowed by the NRC in an experimental fuel consolidation program that is on-going may not have bet.n grudent." The NRC staff has considered Ms. Harucci's comments and has co.1cluded that there is nothing in them that would cause the st. f to change the proposed no significant hazards consideration determination.
3 In a telephone conversation Mr. Michael Pray of New London, Connecticut, on hy 28, 1992, indicated that he would file a request for a hearing. That request has not yet been receiveo nor have Mr. Pray's comments.
5.0 FINAL NO SIGNIFICAr4T HAZARDS CONSIDERATION DETEfiMINAT103 The Commission's regulations in 10 CFR 50.92 state that the Commission may m?ke a final determination that the license amebant involves no significant hazards consideration if operation of the facility, in accordarice with the amendment, would not:
1.
Involve a s1gnificant increase in the probability or consequences of an accident previously evaluated.
Radiological consequences of the fuel handling accident are not impacted by the formation of Regions A and B because the fuel assembiy design is unchanged. Howver, the probability of occurrence of a fuel misplacement error has increased slightly. The-increase is not significant because the types of controls being put into place in Regions A and B are of the same type as already in place in Region C.
Furthermore, a fuel assembly misplacement error is not considered an accident, as defined in the Final Safety Analysis Report.
2.
Create the possibility of a new or different kind 07 accident from any previously evaluated.
No changes are being made to the fuel assemblies or the storage racks, and controls used in the fuel pool will be of the same type as are no, in j_
place. As such, there is no possibility of a new or different kind of accident being created, The existing design basis m9 s t.! 6essible accider,t scenarios in '.he spent fuel pool.
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a significant-reduction in a margin of safety.
There is no reduction in the margin of safety since K.,,50.95 is met under-all analyzed conditions using conservative assumptions which do not credit the soluble boron in the spent fuel pool except under some accident conditions, as allowed by NRC guidelines. The original mechanical analyses are unchanged for thermal and seismic / structural considerations.
Accordingly, the NRC staff concludes that the proposed amendment involves no significant hazards considerhtions.
6.0 ENVIRONMENTAL CONSIDERATION
l 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 occupationa1Lradiation exposure. The Commission has made a-final no significant hazards consideration determination with respect to this amendment. Accordingly,-the amendment meets the eligibility criteria for categorical-exclusion set forth i
Pursuant to 10 CFR 51.22(b).no environmental impact statement or environmental assessment need be prepared in connection with the issuance'of the atendment.
7.0 {ANCLUSION The Commission has concluded, based on the considerations discussed above,.-
that:
public w(1) there is reasonable assurance that the health and safety of the' ill not be endangered by operation in the proposed manner -(2) such activities wil1 ~ be conducted in compliance with the Connission's _ regulations, and (3) the issuance of the amendment will not' be inimical toLthe: common.
defense and security _ or to the health and safety of the public.
Principal Contributor:
L. Kopp Date: June-4, 1992' i
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