ML20246P169
| ML20246P169 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 08/29/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246P161 | List: |
| References | |
| NUDOCS 8909110062 | |
| Download: ML20246P169 (6) | |
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WASHINGTON, D. C. 20555 NUCLEAR REGULATORY COMMISSION y%./
SAFETY EVAIUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 39 TO FACILITY OPERATING LICENSE NO. NPF-49 NORTHEAST NUCLEAR ENERGY COMPANY, ET AL.
MILLSTONE NUCLEAR POWER STATION, UNIT NO. 3 DOCKET NO. 50-423 1.0 It:TRODUCTION By application for license amendment dated April 20, 1989, Northeast Nuclear Energy Company, et al. (the licensee) requested changes to MillsteneUnit'3.TechnicalSpecifications(TS}.
The proposed amendment would change the Millster.e Unit 3 Technical Specif.ications (TS) to allow storage of fuel with an enrichment of up to 5.0 nominal weight percent U-235 as follows:
(1) Section 1.0,
" Definitions," would be changed by adding new TS 1.40 and 1,41 to define the fuel regional storage pattern, (2) A new TS 3/4.9.13 " Spent' Fuel Pool
- Reactivity," would be added to limit the fuel K to less than or equal to.95, (3) A new TS 3/4.9.14, " Spent Fuel f[b1 - Storage Pattern,"
would be added to implement the fuel storage pattern, (4) TS 5.6.1.1,
'" Criticality" would be changed and expanded to address the storage of fuel ' utilizing a regional storage systen, and (5) A new TS 5.6.3,
" Capacity" would be added to address the use of cell blocking devices in the storage of fuel.
In addition to'the above, the licensee has requested that TS 5.6.1.2 be deleted.
2.0 DISCUSSION AND EVALUATION The purpose of the licensee's April 20, 1989 application is to seek approval for storage of fuel in the spent fuel storage pool with an initial enrichment of up to a nominal 5.0 weight percent (w/o) U-235.
The criticality and accident considerations addressed reflect the effects of storage of 5.0 w/o enriched fuel. The thermal hydraulic and certain structural effects, however, only reflect conditions associated with the present Cycle 3 fuel. Accordingly, certain analyses must be reperformed on a cycle-by-cycle basis or bounding analyses must be submitted for
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2.1 Criticality Millstone Unit 3 spent fuel racks are designed to limit the effective neutron multiplication factor (k
) to less than, or equal to,.95 providedthatthestoredfuelenfi[hmentisnotgreaterthan3.85 weight percent (w/o)U-235.
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The licensee has now proposed to store fuel with an enrichment of up to 5.0 w/o U-235. The increased enrichment would be compensated by use of cell blocking devices, which would limit the proximity of high enrichment fuel (up to 5.0 nominal w/o U-235).
The Millstone Unit No. 3 spent fuel pool (SFP) storage racks were reanalyzed by ' Westinghouse utilizing a two-region storage scheme to accommodate a nominal 5.0 w/o U-235 fuel.
Region I was reanalyzed to show that fresh 5.0 w/o (nominal) U-235 fuel can be stored in the racks in a three-out-of-four storage scheme.
Region II was reanalyzed to take into consideration the changes in fuel and fission product inventory resulting from depletion in the reactor core of fuel with nominal enrichments up to 5.0 w/o U-235.
The Region I rack reanalysis was based on maintaining K less than or equalto0.95forstorage-ofWestinghouse17x17OFAa8bfSTD fuel at a nominal 5.0 w/o U-235 utilizing three-out-of-four storage cells in the array. The Region II spent fuel rack reanalysis was based on maintaining K
less than or equal to 0.95 for storage of Westinghouse 17 x 17 0FA a8bfSTF fuel at a nominal 5.0 w/o U-235 with an initial enrichment /burnup combination in the acceptable area of proposed TS Figure 3.9-1 with utilization of every cell pennitted for storage of the fuel assemblies.
of less than or equal to.95 is the acceptance criteria for AK subN{ticalitycontainedinStandardReviewPlan9.1.2,"SpentFuel Storage,"Section III.2.a.
Based upon the above, we conclude that the use of regional fuel storage together with the cell blocking devices will effectively limit K,ff to less than.95, for nominal 5.0 w/o enriched fuel, and is thus acceptable.
2.2 Structural / Seismic Considerations From a seismic /structur.a1 standpoint, the change of nominal enrichment-from 3.8 w/o U-235 to a nominal enrichment 5.0 w/o U-235 does not affect the current licensing analysis due to the fact that the total weight of the fuel assembly remains the same. The enrichment change is in the distribution of U-235 versus U-238 that comprises the fuel pellet. Thus, there is no effect on the mechanical load bearing or seismic resistance of the spent fuel racks or associated structures.
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.. l The proposed storage of irradiated 5.0 w/o fuel does result in higher thermal loads when compar?d with 3.8 w/o fuel. The licensee, however performed thermal load analyses for Cycle 3 - specific conditions which resulted in the FSAR analy;is for a nominal 3.8 w/o fuel being bounding, The analyses address thermal loads on concrete structural members and the i
spent fuel pool liner. With regard to the s' pent fuel racks, the increased decay heat of the 5.0 w/o feel increases the cell / axial and cell-to-grid weld shear stresses; however, the stress increases are small and are well within allowable values.
Based upon the above, we conclude that storage of 5.0 w/o fuel does not effect the mechanical load bearing or seismic resistar '.e capability of the spent fuel racks or asso:iated structures.
In adoition the thermal stresses associated with 5.0 w/o fuel, with regard to the spent fuel.
racks are acceptable during Cycle 3 operation. The thermal loads for the spent fuel pool liner and structural concrete members have been shown to be acceptable for Cycle 3 - specif!: conditions. Additional calculation for subsequent cycles, or bourding analyses, must be submitted for approval.
2.3 Spent Fuel Pool Coolina The licensee has performed Cycle 3 - specific calculations to determine the adequacy of the spent fuel pool cooling system. The original design calculation was revised to reflect actual maximum reactor plant component cooling water temperature. Heat loads for an end of Cycle 3 core off-load, for a Cycle 3 emergency full core off-load, and for plant operation with a normal refuel load (one-third core) in the SFP, were determined.
These heat loads were used as the basis for detennining the i
SFP cooling system fluid temperatures under a variety of operating scenarios.
For all cases except an emergency core off-load, the predicted temperatures were lower than those described in the SFP cooling safety evaluation in the Millstone Unit No. 3 Final Safety Analysis Report (FSAR) (Section 9.1.3.3).
All temperatures were based on only one 100 percent capacity train of SFP cooling in operation. The second train of SFP cooling is either in standby or out of service. Under no scenarios did the SFP fluid boil or the fluid temperature exceed 200*F.
For an emergency core off-load occurring during Cycle 3, the pool temperature was predicted to reach 163*F. This temperature exceeds the predicted temperature of 149'F for this event in the FSAR. A review of the design conditions of the equipment and piping confirmed that 163'F is acceptable since it is below the design temperature of the SFP cooling system which is 200'F.
We conclude that the Millstone Unit 3 spent fuel pool cooling system is adequate for Cycle 3 operation in that heat load calculations, except for an emergency core off-load, are bounded by the existing FSAR calculations.
For the emergency core off-load case, boiling in the spent
.. l fuel pool does not occur and thus meets the guidance in Standard Review Plan 9.1.3, " Spent Fuel Pool Cooling and Cleanup System,"Section III.1.d and is acceptable.
Additional calculations of spent fuel pool cooling capability for subsequent cycles, or bounding analyses, must be submitted for approval.
3.0 ACCIDENT ANALYSES The licensee has considered the potential consequences of various accidents that could result from storage of fuel with increased enrichment /burnup.
Fuel Handling Accident - The source term for the fuel handling accident is insensitive to increased enrichment or burnup of the spent fuel. Accordingly the radiological consequences of the fu?1 handling accident do not increase.
Criticality - As described in Setion 2.1 herein, the proposed spent fuel storage strategy utilizes a regional scheme with cell blocking devices. The proposed strategy acceptably limits K to less than or equal to.95.
Thus, probability of a criticality b8Ng achieved in the spent fuel pool will not increase with storage of fuel with an enrichment of up to 5.0 w/o.
Loss of Spent Fuel Pool Integrity - The integrity of spent fuel pool structures and systems are judged to be adequate in light of the increased heat load associated with the higher enrichment and burnup of the spent fuel. This conclusion is somewhat limited in that it only reflects Cycle 3 conditions in the spent fuel pool.
Based upon the above, we conclude that the consideration of potential failures and accidents associated with storage of fuel assemblies with higher enrichment and burnup is acceptable.
4.0 TECHNICAL SPECIFICATIONS The licensee has proposed several changes to the Millstone Unit 3 TS which reflect the proposed storage of fuel, in the spent fuel pool, with a nominal enrichment of up to 5.0 w/o.
In addition, TS 5.6.1.2 would be deleted.
Section 1.0--Definitions 3
i New definitions, proposed Sections 1.40 and 1.41, would be added to
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define the required fuel storage patterns. Section 1.40 would define i
the fuel storage pattern of Region I fuel, and Section 1.41 would J
delineate the fuel storage requirements of Region II fuel. The I
reason for this change to a regionalized storage pattern is to account for the required three-out-of-four storage pattern required for criticality considerations of fuel assemblies with no burnup or j
minimum burnup and with nominal enrichments less than or equal to 5.0 w/o U-235 and greater than 3.8 weight percent U-235.
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-. I Section 3/4.9--Refueling Operations New Sections, 3/4.9.13 and 3/4.9.14, Spent Fuel Pool, would be added, with new accompanying Limiting Conditions for Operation 3.9.13 and 3.9.14 and Surveillance Requirements 4.5.15 and 4.9.14.
The reason for these changes is to provide the specific conditions and criteria for SFP reactivity and regionalized fuel storage, with the accompanying applicability and verification requirements.
In addition, a new figure 3.9 I would be added to provide the fuel burnup versus enrichment criteria, and a new Figure 3.9-2 would be added to provide the Region I fuel assembly loading schematic.
The accompanying new Bases 3/4.9.13 and new Bases 3/4.9.14 would be added to provide the bases for new Sections 3/4.9.13 and 3/4.9.14.
Additionally, new Bases 3/4.9.13 makes reference to administrative controls to verify fuel assembly burnup. These controls are currently being formalized and will be in place prior to the issuance of this amendment request.
Section 5.6--Fuel Storage Section 5.6.1.1 would be modified and expanded in order to address the storage of fuel utilizing a regionalized storage scheme.
Section 5.6.1.2 would be deleted. The reason for this change is that this section was only applicable to storage of new fuel stored dry in the spent fuel racks, during the first reload, and is no longer applicable.
Section 5.6.3, Capacity, would be changed from specifying the specific number of fuel assemblies allowed to be stored in the SFP to specifying only the number of storage locations available. The reason for this change is to account for the varying number of cell blockers which may now occupy various fuel storage locations in support of the regionalized storage scheme. Utilizing celi blockers, it may not be possible to fill all possible storage locations with spent fuel.
Therefore, the number of storage locations, not fuel assemblies, need be addressed.
The proposed changes to the TS implement the two region fuel storage system addressed in Section 2.1, herein. The proposed TS, which provide will be maintained at less than or equal to.95 under assurancethatK*kstulatedconditions,areacceptable.
the most adverse With regard to cycle fuel to.98 when stored, dry, in the spent fuel racks.ff of first TS 5.6.1.2, this TS can be deleted since it restricts the K e Since the spent fuel pool will remain water-filled for the life of the facility, the potential overmoderating effects of aqueous fire-fighting foam are no longer a concern.
5.0 ENVIRONMENTAL CONSIDERATION
This 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 and changes surveillance requirements. We have determined
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.6 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 staff has previously published e proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding.
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set'forth in.10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b),
4 no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
6.0c' CONCLUSION We have: 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, and (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 toLthe health and safety of the public.~
Dated: August 29. 1989 Principal Contributor: David H. Jaffe
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