ML20195B442

Safety Evaluation Supporting Amend 74 to License NPF-12

ML20195B442
Person / Time
Site:	Summer
Issue date:	10/28/1988
From:	Office of Nuclear Reactor Regulation
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ML20195B431	List: ML20195B426 ML20195B435 ML20195B442
References
NUDOCS 8811020020
Download: ML20195B442 (4)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTINGAMEN0MENTNO.74TOFACILITYOPERATINGLICENSENO.NPFg SOUTHCAR0lRAELECTRIC&GASCOMPANY SOUTH CAROLINA PUBLIC SERVICE AUTHORITY VIRGIL C. SUMMER NUCLEAR STATION, UNIT 00. 1 DOCKET NO. 50-395

1.0 INTRODUCTION

In a letter dated March 8, 1988, South Carolina Electric & Gas Company (the licensee) schmitted a request for changes to the Virgil C. Sumer Nuclear Station, Unit No. 1, Technical Specifications (TS), Section 3.9.12. "Spent Fuel Assembly Storage," Section 5.3.1, "Fuel Assemblies,"

and Section 5.6, "Fuel Storage." The changes to these TS Sections were submitted as a result of the proposed changes in reactor fuel from Westinghcuse's LOPAR (low parasitic) fuel to Westinghcuse's enhanced burnup fuel (Vantage 5).

By letters dated August 31, 1988 and September 30, 1988, the licensee provided revised source term inputs and radiological analyses of postu-lated accidents to support the utilization of the Vantage 5 fuel.

The purpose of the proposed arendment is to modify Figures 3.9-1 and 3.9-2 of Section 3/4.9.12. These figures depict the acceptable and the unacceptable values of fuel assembly exposure (i.e., burnup), as a function of fuel enrichment, to permit storage in Regions 2 and 3 of the spent fuel pool. The proposed changes to Technical Specifications 5.3.1 and 5.6.1.1 limit the maximum enrichment to 4.25 weight percent (w/o) lj-235 and require a minimum burnup of 19,000 MWD /MTU (megawatt-days per metric ton uranium) for fuel stored in Region 2 of the spent fuel pool and 39,750 MWD /MTU for fuel stored in Region 3 of the spent fuel pool.

The proposed changes to TS 3.9.12, 5.3.1, and 5.6 are to reflect revised storage limitations for the mix of LOPAR and the Westinghouse Vantage 5 fuel to be utilized in the core during the fif th cycle at the Sumer Station ind for the Vantage 5 fuel that will be used in all subsequent cycles.

2.0 EVALUATION The ifcensee has proposed that fresh fuel racks used for Vantage 5 fuel assemblies be limited to a maximum enrichment cf 4.25 w/o U-235. The present TS allow fuel with an enrichment of 4.3 w/o U-235. The spent fuel racks are divideo into three regions. All regions contain stainless 8811020020 DR 001020 p ADOCK 05000395 PNV

2 steel cells, one for ea:h stored assembly. The licensee has proposed that Region 1 accept freshly discharged fuel assemblies with enrichments up to 4.25 w/o U-235 while Regions 2 and 3 accept assemblies with up to 4.25 w/o U-235 initial enrichment provided they have burnups sufficient to meet criticality limits. These burnups are proposed as 19,000 MWD /MTV and 39,750 MWD /MTU for Regions 2 and 3, respectively. Regions 1 and 2 are poisoned, i.e., contain fixed boron absorbers. Present TS Section 5.6 allows fuel with an enrichment of 4.3 w/o U-235 and requires a minimum burnep of 20,000 MWO/MTV for Region 2 and 42,000 MWD /MTV for Region 3 of the spent fuel ecol.

The licensee has performed criticality analyses for Regions 1, 2 and 3 for standard Westinghouse and Vantage 5 fuel assemblies using approved computer codes. The results meet the NRC criteria of a spent fuel peak of k,ff less than 0.95 (for unborated water) including uncertainties.  ;

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The licensee also pcrformed criticality analysis of fresh fuel racks in a l full range of moderator densities using approved computer codes. The i results shew that rack k,ff values are less than 0.95 inclu: ling uncertain- l ties.

The staff tas reviewed the criticality analyses for both the spent fuel racks of Regions 1, 2 and 3 and for the fresh fuel racks. Since the results mest the staff's criteria for a spent fuel peak of k less than 0.95(forunbaratedwater)includinguncertaintiesandthesbf's less than or equal to 0.98 in the low criteriamoderator density for fresh fuel racks region and k(k,f,less than or equal to 0.95 in the high densityregion),thestaffconbdesthattheproposedchangestoFigures 3.9-1 and 3.9-2 of TS 3.9.12 and the proposed changes to TS 5.3.1 and 5.6 are acceptable.

3.0 DESP.GN BASIS ACCIDENT ANALYSIS RELAT!VE TO EXTENDED FUEL BURNUP The licensee's intent to utilize Vantage 5 fuel will result in the lead fuel rod having an average burnup as high as 60,000 MWO/MTU. In an August l 31, 1988 submittal, the licensee provided their evaluation of the reactor I

roolant and core source terms for the vantage 5 fuel. In the licensee's September 30, 1988 submittal, they provided their assessment of the radiological consequences, based upon the utilization of Vantage 5 fuel, for the design basis accidents presented in Chapter 15 of the licensee's FS3 The licensee concluded that the radiological consequences of postulated accidents as a result of the utilization of the Vantage 5 fuel, when compared to operation with the present LOPAR fuel, would result in a decrease in the gamma and' beta skin doses but an increase in the thyroid dose.

The staff reviewed the licensce's subms.tals and also reviewed a publica-tion which was prepared for the NRC entitled, "Assessment of'the Use of Extended Burnup Fuel in Light Water Reactors," NUREG/CR 5009, February 1988. The NRC contractor, the Pacific Nortnwest Laboratory (PNL) of Battelle Memorial Institute, examined the changes that conld result in the

NRC Design Basis Accident (DBA) assumptions, described in the various Standard Review Plan (SRP) sections and/or Regulatory Guides, that could result from the use of extended burnup fuel (up to 60,000 MWD /MT). The staff agrees that the only DBA that could be affected by the use of extended burnup fuel, even in a minor way, would be the potential thyroid doses that could result from a fuel handling accident. PNL estimates that I-131 fuel gap activity in the peak fuel rod with 60,000 MWD /MT burnup could be as high as 12%. This value is approximately 20% higher than the value normally used by the staff in evaluating fuel handling accidents (Regulatory Guide 1.25. "Assumptions Used for Evaluating the Potential Radiological Consequences of a Fuel Handling Accident in the Fuel Handling and Storage Facilities for Boiling and Pressurized Water Reactors").

PNL concluded in their report that for fuel damage accidents, "The percentage of fission-product inventory released from the fuel would not likely change as a result of the extended burnup; however, the fission-

, product inventory in the fuel would change for the long half-life fission l products and actinides ...." PNL also concluded that the actinides would only minimally contribute to doses compared to the fission products and that the main concern for thr! actinides would be from the long-term effects of inhalation (vegetables, (lung) milk, and meatdose) andin,ingestion raised or fed onoffood foodgrown products in, con-taminated soil. PNL concluded that the inventory of fission products, cesium-137 and strontium-90 would iecreasa by a factor of almost 2 in the extended burnup fuel. However, the staff has concluded that their contribution to dose would be minimal.

For the fuel handling accident, PNL concluded that the use of Regulatory l Guide 1.25 procedures for the calculation of accident doses for extended burnup fuel may be utilized. These procedures give conservative estimates for noble gas release fractions that are above calculated values for peak rod burnups of 60,000 MWD /MTV. lodine-131 inventory, however, may be up to 20% higher than that predicted by Regulatory Guide 1.25 procedures.

l The staff, therefore, reevaluated the fuel handling accidents for the Summer Station assuming an increase in iodine gap activity in the fuel damaged in a fuel handling accident which was 20% higher than that assumed using Regulatory Guide 1.25. Table 1 presents the fuel handling accident thyroid doses. The assumptions, which were utilized in the staff's evaluation, were the see as those presented in Table 15-5 of the V. C.

Sunser NW1 ear Station. Unit No.1 Sa'ety Evaluation Report (NUREG-0717),

February 1951, with the following oceptions:

pcwer Peaking Factor l = 1.68 Number of fuel rods assumed failed a 264 l

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Table 1 Thyroid Doses as a Consequence of DBA Fuel Handling Accidents r

Exclusion Area low Fopulation Zone Thyroid Dose (Rem) Thyroto Dose (Rem) I Fuel Handling Accident ,

In Fuel Building 17 2.1 In Reactor Building 115 14 The staff concludes that the only potential increased doses potentially resulting from OBA with extended fuel burnup to 60,000 MWD /MT is the thyroid dose resulting from fuel handling accidents and these doses I remain well within the 300 Rem thyroid exposure guideline values set forth in 10 CFR Part 100 and that this small calculated increase above '

i the present calculated dose presented in Table 15-4 of the V. C. Suseer SER (NUREG-0717) is not significant.

4.0 ENVIRONMENTALCONS10 ERAT!g Pursuant to 10 CFR 51.21, 51.32, and 51.35, an environmental assessment and finding of no significant impact have been prepared and published in the Federal Register (53 FR 43486) on October 27, 1988. Accordingly, based upon the enITUonmental assessrent, the Cossission has determined that the issuance of this amendrent will not have a significant effect on -

the quality of the human environment.

5.0 CONCLUSION

The Commission has issued a "Notice of Consideration of Issuance of r Amendment to Facility Operating License and Proposed No Significant .

Hazards Consideration published in Determination the FEDERAL REGISTER and1,Opportunity on Jur,*/ 1988 (53 FR 20046) andfor Hearin consulted with the State of South Carolina. No public coceents or  ;

requests for hearing were received, and the State of South Carolina did not have coseents.

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 not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Coesnission's regulations and the issuance of this amendment will not be inimical to the conson defence and security or to the health and safety of the public.

Principal Contributors: John J. Hayes, Jr.  :

Shi Liang Wu  !

Dated: October 28, 1988 i

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