ML20216C271

Safety Evaluation Supporting Amend 159 to License DPR-28

ML20216C271
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	04/10/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20216C255	List: ML20216C251 ML20216C271
References
NUDOCS 9804140377
Download: ML20216C271 (3)

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4 UNITED STATES g

j NUCLEAR REGULATORY COMMISSION

%*****/g WASHINGTON, D.C. 20666-0001 o,,

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.159 TO FACILITY OPERATING LICENSE NO. DPR-28 l

VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271

1.0 INTRODUCTION

By letter dated December 11,1997, as supplemented by letter dated March 3,1998, the Vermont Yankee Nuclear Power Corporation (VYNPC or the licensee) submitted a request to amend the Vermont Yankee Nuclear Power Station Technical Specifications (TSs). The proposed amendment would revise the TSs to correctly specify the values for the safety limit minimum critical power ratio (SLMCPR) for Cycle 20 operation.

Section 1.1 of the technical specification (TS) establishes the SLMCPR for single or double recirculation loops in operation. Section 6.0 of the TS references NRC-approved topical reports

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used to determine the thermallimits. " General Electric Standard Application for Reactor Fuel

• (NEDE-24011-P-A-13), GESTAR ll delineates the approved analytical methodologies and requirements for determining the SLMCPR and the operating limit minimum critical power ratio j

(OLMCPR). The operating limit MCPR and the cycle specific thermal limit parameters are j

specified in the Core Operating Limit Report (COLR), which is reissued every reload.

The licensing basis document, GESTAR 11 delineates, in part, that: (1) for every new fuel design, a generic MCPR will be calculated for a large high power density plant, assuming a bounding equilibrium core; (2) for each new fuel design the applicability of the generic i

equilibrium core SLMCPR will be confirmed for each operating cycle or a plant specific. analysis i

will be performed; and (3) critical power ratio correlation will be reconfirmed or a new one j

established whenever there is a change in the wetted parameters of the flow geometry (e.g.,

fuel, water rod diameter, channel sizing, spacer design.)

In addition, NRC and General Electric Nuclear Energy (GENE) instituted interim implementing procedures which were developed as corrective actions to issues identified in GENE's Part 21 l

reporting and in the notice of noncompilance (NOV) issued to GENE during the May 1996 NRC inspection. Amendment 25 to GESTAR 11, which is under staff review, incorporates the l

corrective actions and the interim procedures which require, in part, that the licensees perform core-specific SLMCPR evaluation during each reload.

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For the part length GE13 fuel, GENE, the fuel vendor, determined the generic equilibrium SLMCPR to be 1.09. However, for the cycle-specific SLMCPR analysis, Vermont Yankee Cycle 20 yielded bounding and higher SLMCPR in comparison to the GE13 equilibrium core SLMCPR. Consequently,in this amendment, VYNPC proposes to revise Section 1.1.A of the TS and to adapt the cycle specific MCPR safety limit.

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' The information provided on March 3,1998, had no effect on the original proposed no significant hazards consideration determination.

2.0 EVALUATION VYNPC proposed changes to the technical specifications and the co#Tesponding evaluations are provided below.

i Proposed Change a specification 1.1 - Reactor Core Safety Limits (SLs)

VYNPC proposes to change the SLMCPR specified in the TS 1.1.A from 1.10 to 1.11 for two '

recirculation loops in operation and from 1.12 to 1.13 for a single loop in operation.'

Attachment five to the amendment request cordains the GENE evaluation which discusses the basis for the Vermont Yankee cycle-specific SLMCPR, including the mixed (GEg and GE13) core-specific input parameters, the corresponding assumptions and a comparative discussion of why the cycle-specific SLMCPR calculations yield higher values than the generic equilibrium core GE 13 SLMCPR.

VYNPC stated that the core-specific safety limits were evaluated in accordance with the NRC approved methodology specified in the topical report, " General Electric Standard Application for Reactor Fuel "(NEDE-24011-P-A-13, dated August 1996), and supplemented by " Proposed Amendment 25 to GE Licensing Topical report NEDE-24011-P-A- (GESTAR ll) on cycle-specific safety limit MCPR."

The sta# reviewed the R-factor calculation method for the GE13 fuel product line, and Amendment 25 to the topical report GESTAR 11, which is under sta# review. The proposed cycle-specific SLMCPR analysis is based on the NRC approved methodologies specified in GESTAR ll (NEDE-24011-P-A-11, Sections 1.1.5 and 1.2.5, which references NEDO-10g85-A, January 1977), for two loop operations. Because the R-factor methodology referenca j in i

NEDE-24011-P-A-11 is not applicable to the part length GE13 fuel, a revised R-factor methodology described in NEDC-32505P, "R-Factor Calculation Method for GE11, GE12 a ed

- GE13 Fuel," November 1995 was used. The revised R-factor calculation method uses the same NRC approved equation stated in GESTAR (NEDE-24011-P-A) except that it substitutes rod integrated powers for the lattice peaking factors to account for the effects of the part length rod design.

The Vermont Yankee Cycle 20 core specific SLMCPR was derived using cycle-specific fuel and core parameters such as the actual core !cading, conservative variations of projected control blade pattoms, the actual bundle parameters, and the cycle exposure range. The key parameters for the SLMCPR calculations developed by GE indicate that the core-specific safety

. limit is based on flatter radial power distribution than the generic GE13 calculations. Vermont

-Yankee core also has higher core enrichment for Cycle 20, and the analysis covered a di#erent range of cycle exposures. The flatter radial power distribution, the higher core enrichment and the diNerer;t range of cyde exposures, all contributed to the higher core-specific SLMCPR.

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' The licensee experienced leaking fuel for the current operating Cycle 19 and VYNPC locally suppressed the power in the vicinity of the leaking bundle in order to minimize degradation of leaking fuel assembly. Power suppression could potentially 6ffect the end of cycle fuel depletion, which may etter the preliminary reference core loading and the key assumptions used in the Cycle 20 SLMCPR. By letter dated March 3,1998, the licensee indicated that they had concluded that there was no impact on the SLMCPR values for cycle 20 operation.

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Yankee technical specification ~ acceptable, because the SLMCPRs: (1) are based on core-Based on the review, the staff finds the proposed changes to Seebon 1 1.A of the Vermont l

l specific inputs and analysis; (2) were obtained using NRC-approved methods and procedures; -

and (3) provide higher margins of safety to ensure that 99% of the rods in the core will not -

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experience the boiling transition during normal, or anticipated operational occurrence. Since the SLMCPRs were derived using cycle-specific inputs and parameters, this amendment applies only to Cycle 20 reload.

l 3.0 STATE CQNSULTATION l

In accordance with the Commission's regulations, the Vermont State official was notifed of the

. proposed issuance'of the amendment. The State official had no comments.

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4.0 ENVIRONMENTAL CONSIDERATION

- The amendment changes a requirement with respect ic hstallation or use of a facility component located within the restricted area as define:I in 10 CFR Part 20..The NRC staff has.

determined that the amendment involves no significam increase in amounts, and no significant

. change in the types of any effluents that may be released offsite, and that there is no s gnificant -

- increase in individual or cumu%tive occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and thefte has been no public comment on such finding (63 FR 7000).

Accordingly, the arr,endment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmentalimpact statement or environmental assessment need be prepared in connection with the issuance of the amendment.'

5.0 CONCLUSION

- The Commission has concluded, based on the considerations discussed above, that: (1) there -

3 is reasonable assurance that the health and safety of the public will not be endangered by

operation in the proposed manner, (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 to the health and safety of the public.

Principal Contributor: Z. Abdullahi Date: April 16, 1998

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