ML20137X144

Safety Evaluation Supporting Proposed Rev to RPV Surveillance Capsule Withdrawal Schedule

ML20137X144
Person / Time
Site:	Beaver Valley
Issue date:	04/09/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20137X135	List: ML20137X131 ML20137X144
References
NUDOCS 9704210170
Download: ML20137X144 (4)

Text

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 3060H001

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED REVISION TO THE RPV SURVEILLANCE CAPSULE WITHDRAWAL SCHEDULE BEAVER VALLEY POWER STATION. UNIT NO. 2 DOCKET NO. 50-412 DUOVESNE LIGHT COMPANY FACILITY OPERATiMG LICENSE NO. NPF-73

1.0 INTRODUCTION

By letter dated March 27, 1996, as supplemented by letters dated January 2.

February 10, and February 13, 1997. Duquesne Light Company (the licensee) submitted for NRC review and approval o proposed change to the Beaver Valley Pcwer Station Unit No. 2 (BVPS-2), reactor vessel material surveillance arogram withdrawal schedule, a program required by Title 10 of the Code of rederal Peaulations Part 50, (10 CFR Part 50) Appendix H. In this request.

the licensee proposed to update their withdrawal schedule in BVPS-2, Updated Final Safety Analysis Report (UFSAR) Table 5.3-6, to reflect changes in the

)rojected vessei and capsule fluences due to the use of the state-of-the-art ENDF/B-VI cross section library.

Title 10 of the Code of Federal Reaulations, Part 50, Appendix H, requires licensees to withdraw surveillance capsules periodically according to the capsule withdrawal schedule in the American Society for Testing and Materials (ASTM) E185, " Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels."Section III.B.1. of Appendix H further explains that "...the withdrawal schedule must meet the requirements of the edition of ASTM E185 that is current on the issue date of the ASME Code to which the reactor vessel was purchased. Later editions rray be used but including only those editions through 1982."

Additional guidance on the processing of changes to an existing withdrawal schedule has recently been published in the U.S. Nuclear Regulatory Commission's (USNRC) Commission Memorandum and Order, CLI-96-13, dated December 6,1996 in which the Commission reversed the decision of the Atomic Safety and Company Board (ASLB) in the matter of The Cleveland Electric Licensing's Illuminating 3roposed change to the Perry Nuclear Power Plant's withdrawal schedule. T1e Commission states that, " Contrary to the assumption made by the Licensing Board, we do not find that all such approvals [f.e. ,

withdrawal schedule changes, reviewer's note] are de facts license amendments," The Commission affirmed that, "Only those actions falling

'beyond the ambit of prescriptive authority granted under the license' 9704210170 970409 PDR P

ADOCK 0500o412 PDR

necessitate a license amendment," and that "the key consideration should be:

did the agency action " supplement" the existing operating authority prescribed in the license?" The staff understands these comments and the remainder of the Commission's Order indicates that changes to a facility's withdrawal schedule which do not conflict with the requirements in the facility's licensing basis (as established to meet the conditions of 10 CFR Part 50, Appendix H) do not require a license amendment.

In its February 13, 1997 letter, the licensee noted that they had considered CU-96-13 and requested that the staff continue its r'eview based on the licensee's submittal referenced herein. The licensee therefore concluded that it was only required to request the staff's review and approval of this request and that no license amendment was necessary.

2.0 EVALUATION Tne staff has evaluated the licensee's submittal to verify two aspects of the proposed change. The staff first sought to confirm that they agreed with the licensee's technical basis for revising the withdrawal schedule. Next, the staff was required to determine if the licensee's conclusion that a license amendment was not required in this case to support the requested change was valid.

The basis for the changes to the withdrawal schedule proposed by the licensee was the result of updated fluence (E > 1.0 MeV) calculations performed by Westinghouse for the BVPS-2' reactor vessel and surveillance capsules. The staff-has recently examined the Westinghouse methodology in detail in conjunction with its review of the updated Palisades Pressurized Thermal Shock (PTS) assessment in a letter dated December 20, 1996 to Consumers Power Company. In Reference 6 of that letter, the staff noted that validity of the modifications to the neutron group-fluxes as a result of the FERRET log-normal least-squares fitting routine had not yet been confirmed by the staff. In fact it is noted that, "A major concern with the application of the FERRET adjustment is that, while the adjustment does provide a best fit of the measured data, the dosimeter cross sections, measured reaction rates and calculated spectrum adjustments are made without any physical basis." The staff has not completed its review of the FERRET code and does not approve its use in calculating absolute fluence values at this time. Furthermore, for the purposes of this review, the staff has not stLrnoted to resolve other issues regarding the use of a measured fluence-to-calcubted fluence bias or

" weighing factor". Therefore, the determination telow by the staff regarding the acceptability of the fluence values for BVPS-2 g1en in WCAP-14484 for revising the Appendix H withdrawal schedule is not an approval of these values for other applications, i.e., PTS assessment or the def;nition of pressure-temperature limit curves.

The BVPS-2 vessel's withdrawal schedule is based on the 4-capsule withdrawal scheme given in ASTM E185-82 The first two capsules have already been withdrawn and, as such, the proposed schedule modifications only apply to the third and fourth capsules. These capsules are designated in the licensee's

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l request as capsule W and capsule X. respectively. Table 1 in E185-82 re uires that the third capsule be withdrawn at 15' Effective Full-Power Year (EFP ) or "at the time when the accumulated neutron fluence of the capsule corresponds to the approximate E0L fluence at the reactor vessel inner wall location.

whichever comes first."  ;

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Likewise, the standard would require that the fourth capsule be withdrawn no later than E0L. but with the proviso that it accumulates a fluence "not less than once or greater than twice the Jeak E0L vessel fluence. The licensee's fluence evaluation

! wouldbe3.85x10',deterginedthattiepeakvesselinnerwallE0Lfluence '

n/cm (E > 1.0 MeV). Thelicenseehasdetermipe scheduling capsule W to be removed at 10 EFPY (fluence 2 n/cm )- 3.g x 10 ' d and ca)sule X to be removed at 13 EFPY (fluence - 5.77 x 10 n/cm ) would i 4

meet t1ese requirements. '

4 While the staff's concerns regarding the Westinghouse methods for determining the absolute fluence values have not yet been resolved, the staff concurs with the licensee's assessment in this submittal. The adjustments made by the  ;

i application of the dosimetry information and the FERRET code to the values i determined from the forward neutron trans) ort calculation are applied to both the fluences at the capsules and at the R3V wall. These adjustments are in the form of a multiplicative bias or " weighing factor" based on the ratio of the measured-to-calculated fluence values. Since all fluences (and the flux i

_ values for projecting the accumulated fluence at some point in the future) are ,

subject to the same multiplicative " weighing factor" (0.94 in this case) their  !

values relative to each other do not change. Therefore, while the absolute i

. value of the fluences would be higher if this " weighing factor" were not

i included, the EFPY value at which the two remaining surveillance capsules

would reach the appropriate fractions of the RPV E0L fluence would not be expected to change. Based on these considerations and the a) plication of the l requirements of ASTM E185-82, the staff finds the technical 3 asis for the i

proposed revision to be acceptable.

The staff has also examined the issue of whether a license amendment is required to implement the changes requested by the licensee. BVPS-2 Technical Specification (TS) 4.4.9 notes that the program's withdrawal schedule will be  !

conducted in accordance with Appendix H to 10 CFR Part 50 and the bases for  !

this TS reference Table 5.3-6 of the BVPS-2 UFSAR. Although the withdrawal I schedule of the original licensing basis was based on the 1973 edition of ASTM l Standard E 185. licensees are permitted by 10 CFR Part 50. Appendix H.Section III.B.1.' to update their withdrawal schedules to comply with editions of the E 185 up to and including the 1982 edition. As noted previously, the current withdrawal schedule in UFSAR Table 5.3-6 is based on ASTM E185-82 and was ,

submitted by the licensee and approved by the staff with the analysis of the l first surveillance capsule in 1990. Therefore, the staff has determined that the current licensing basis for the BVPS-2 withdrawal schedule references ASTM E 185-82. that the changes pro)osed by the licensee are consistent with their ,

current licensing basis and, t1erefore, per CLI-96-13. do not require a license amendment.

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3.0 CONCLUSION

The staff has concluded that notwithstanding the reservations noted above i

regarding the absolute fluence values for the surveillance capsule and the l i RPV, a technical basis exists for the withdrawal schedule changes proposed by l the licensee. The staff has also concluded that the licensee need not submit 4

' a licensee amendment to request the staff's approval to implement these changes. Therefore, the staff concludes that the licensee may implement the changes to Table 5.3-6 of the BVPS-2 UFSAR as requested in the original

submittal dated March 27, 1996, which is shown in Table 1 of this SE.

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TABLE 1 Recommended Surveillance Caosule Removal Schedule for the j Beaver Vallev Unit 2 Reactor Vessel i

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i l Capsule Capsule Location Lead Factor Withdrawal EFPY Fluence l l (azimuthal degree) (n/cm', E > 1.0 i 4 MeV) l

(* = Removed) '

U 343 3.27 1.24 6.01 x 10* I i V 107 3.67 5.98 2.64 x 10

• W 110 3.22 10 3.85 x 10 ' 1 !

X 287 3.67 13 5.77 x 10

I Y 290 3.22 Standby -----------

Z 340 3.22 Standby -----------

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. Principal Contributor: M. Mitchell

Date

April 9, 1997

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