ML20059A647

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Application for Amend to License NPF-49,revising Unit 3 TS to Allow Relaxation in Setpoint Tolerance of Psv & MSSV
ML20059A647
Person / Time
Site: Millstone Dominion icon.png
Issue date: 12/17/1993
From: Opeka J
NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20059A651 List:
References
B14653, NUDOCS 9401030072
Download: ML20059A647 (7)


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' NORTHEAST UTILETIES a.nore Osces . seio.n street, seriin. Connecticut

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P.O. BOX 270 H ARTFORD. CONNECTICUT 06141-0270 L L J Z[C2.72 (203) 665-5000

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December 17, 1993 Docket No. 50-423 '

B14653 Re: 10CFR50.90 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 3 Proposed Revision to Technical Specifications Pressurizer Safety Valves and Main Steam Safety Valves lift Settina Tolerance Chance Pursuant' to 10CFR50.90,- Northeast Nuclear Energy Company (NNECO) hereby '

proposes to amend Operating License NPF-49 by incorporating - the attached proposed changes into the Technical Specifications of Millstone Unit No. 3.  ;

Backaround Overpressure protection for the reactor coolant system (RCS) and the main steam system is provided in part by the pressurizer safety valves (PSVs) and the main steam safety valves (MSSVs) located on the pressurizer and -on' the ,

four main steam lines, respectively. For the RCS, there are a total of three i' PSVs set at 2485 psig. The four main steam lines have a total of 20 MSSVs-(i.e., five per main steam line), each set at 10 psig increments which. range-  :

from 1185 psig to 1225 psig. The PSVs are Class I components, designed and ,

manufactured to meet the 1971 Edition, through the Winter 1972 Addenda, of.the ASME Code,Section III. The MSSVs are Class 2 components, designed and manufactured to meet the 1974 Edition, through the Summer 1974 Addenda, of the ASME Code,Section III. Currently, testing for the PSVs' and MSSVs is performed in accordance with ASME Section XI, every refueling outage, to assure a tolerance of 11% of the valve setpoint.  ;

Description of the Proposed Chance .

NNECO is proposing to revise the Millstone Unit No. 3 Technical -Specifications -

to allow a relaxation in setpoint. tolerance of the PSVs. and MSSVs from 11% to

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13% for the "as-found" test condition. NNEC0 will reset all PSVs and.MSSVs to 11% prior to declaring the valve operable if the "as-found" lift setting. l exceeds 11%. ,

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U.S. Nuclear Regulatory Comission B14653/Page 2 December 17, 1993 The Millstone Unit No. 3 PSVs and MSSVs were designed in accordance with ASME Section III which requires valve actuation to be within 11% of the valve's respective setpoint. However, over the course of an operating cycle, PSV and MSSV setpoints can drift. This drift for both PSVs and MSSVs, when in excess of 11%, has resulted in a reportable incident in accordance with 10CFR50.73(a)(2)(1). NNEC0 has formerly advised the NRC Staff of these incidents via License Event Reports (LER)91-002"' and 93-011:23 for the MSSVs and LER 91-023' ' for the PSVs. Each of these LERs indicate that a relaxation in PSV and MSSV setpoint tolerances to 13% be pursued to address "as-found" drift in excess of 11%. These proposed changes will revise the setpoint tolerance to assure both PSVs and MSSVs remain within technical specification tolerances and reduce the potential for filing subsequent LERs on the subject issue.

An operating history review indicates that setpoint drift of the PSVs and MSSVs is an industry-wide occurrence not unique to Millstone Unit No. 3.

Historical information provided by the Nuclear Plant Reportability Database System (NPRDS) indicates that setpoint drift is a comon industry occurrence.

Also, the NRC Staff has addressed the issue of PSV and MSSV setpoint drift as detailed by the Information Notice (IN) process; e.g., IN 86-56 and IN 89-90*'.

PSV and MSSV testing will continue to be performed in accordance with ASME Section XI. The 13% tolerance will be used for the "as-found" test acceptance criterion in lieu of the current 11% tolerance for setpoint drift. For the resetting of the PSVs and MSSVs, a 11% tolerance will Le required prior to ,

declaring the valve operable in instances where the 11% tolerance was i exceeded. -

NNECO notes that a similar amendment request on relaxing PSV and MSSV setpoint tolerances has been accepted by the NRC Staff for New Hampshire Yankee on behalf of the Seabrook Station, Unit No.1 (Docket No. 50-443, Amendment 15, dated September 3,1992). The proposed changes contained herein are similar l

(1) S. E. Scace letter to the U.S. Nuclear Regulatory Commission, " Licensee .l Event Report 91-002-00," dated March 4, 1991.

(2) S. E. Scace letter to the U.S. Nuclear Regulatory Commission, " Licensee Event Report 93-011-00," dated August 30, 1993.

(3) S. E. Scace letter to the U.S. Nuclear Regulatory Commission, " Licensee )

Event Report 91-023-00," dated September 30, 1991.

(4) U.S. Nuclear Regulatory Commission Information Notice 86-56, " Reliability of Main Steam Safety Valves," dated July 10, 1986.

(5) U.S. Nuclear Regulatory Commission Information Notice 89-90 " Pressurizer Safety Valve Lift Setpoint Shift," dated December 28, 1990.

U.5.NuclearRegula6cryCommission B14653/Page 3 December 17, 1993 in nature to those approved by the NRC Staff for New Hampshire Yankee on behalf of the Seabrook Station, Unit No. I docket.

Safety Assessment NNECO is proposing to relax the "as-found" lift setting for the PSVs and MSSVs from 11% to 13%. This relaxation is applicable for PSV and MSSV drift which occurs during the operating cycle. NNECO will continue to require both PSV and MSSV setpoint tolerances to be restored to 11% when the "as-found" lift setting exceeds 11%, prior to declaring the PSVs and MSSVs operable. These changes will have no affect on ASME Code compliance. In addition, a prior analysis for the transition to VANTAGE SH fuel examined the effects of a relaxed PSV and MSSV lift setting on the plant safety analysis."" Each of these issues is further addressed as follows:

The 1989 edition of the ASME Code Section III, Subarticle NB-7410/NC-7410 specifies "The set pressure of at least one of the pressure -relief devices connected to the system not be greater than the design pressure of any component within the pressure retaining boundary of the protected system."

NNECO notes that the RCS design pressure is 2485 psig which corresponds to the PSVs setpoint. The main steam system design pressure is 1185 psig. This value corresponds to the Group 1 MSSVs which have the lowest opening setpoint.

Therefore, the proposed relaxation in setpoint tolerance to 13% is in compliance with the 1989 ASME Code,Section III requirements.

In addition, the 1989 edition of the ASME Code,Section XI, requires that PSVs and MSSVs be tested in accordance with ASME/ ANSI OH-1987, Part 1,

" Requirements for Inservice Performance Testing of Nuclear Power Plant Pressure Relief Devices." This standard allows a testing lift pressure to vary from the stamped pressure by more than 13% before declaring a test failure. This standard also includes guidelines for testing additional valves when a valve exceeds the 13% tolerance. Therefore, increasing the PSV and MSSV setpoint tolerance to 13% for the "as-found" test acceptance criterion is -

in compliance with the 1989 ASME Code,Section XI requirements.

The proposed changes have been reviewed to determine any effect cn the PSV and MSSV inlet piping and discharge piping. Based on this review, it has been determined that there is a linear relationship between both the PSV and MSSV discharge pressure and the safety valve steam hammer discharge segment forces.

Therefore, a maximum increase in the PSV and MSSV steam hammer discharge loads of 3% would be expected as a result of increasing the maximum allowable test tolerance to 3%. This increase has an insignificant affect on the structural integrity for the previously noted. sections of piping. The structural integrity review considered the impact to pipe stress analysis, pipe support (6) E. J. Mroczka letter to the U.S. Nuclear Regulatory Commission, " Proposed Change to the Technical Specifications Cycle 4 Reload Submittal," dated November 1, 1990.

U.S. Nuclear Regulatory Commission B14653/Page 4 December 17, 1993 '

analysis and nozzle load summaries. This review has determined that these components have sufficient margin to accommodate a 3% increase in PSV or MSSV steam hammer discharge loads.

By letter dated November 1, 1990,* NNECO submitted proposed technical specification changes for refueling and operation of Millstone Unit No. 3 with the VANTAGE 5 Hybrid (5H) improved fuel design. In support of these changes, a Plant Safety Evaluation (PSE) was performed for the transition to the VANTAGE SH fuel design and was included in the November 1,1990, submittal.

The PSE was reviewed and approved'8' by the NRC Staff as part of the license amendment request dated November 1, 1990. The PSE included mechanical, nuclear, thermal and hydraulic, and accident evaluations. As part of this.

analysis, use of a 13% PSV and MSSV setpoint tolerance was examined.

Specifically, Section 5.05 of the PSE examined the impact of' increased MSSV and PSV setpoint tolerance on the safety analysis. The following is a summary of the PSE analyses, and a basis as to why no changes to the safety analysis will result from relaxing PSV and HSSV setpoint tolerance to 13%:

  • The non-LOCA safety analyses performed for the VANTAGE 5H transition includes revisions in the treatment of both PSVs and MSSVs. -The PSVs were modeled so as not to open until the pressurizar pressure reaches 2575 psia. Flow through the PSVs was modeled with 3% accumulation; i.e.,

it ramps up from zero to full rated flow over the range of 2575 to l 2652 psia (2500 x 1.03 x 1.03). Previously, the PSVs were modeled as opening with the pressurizer pressure at 2500 psia and full rated flow being reached at 2575 psia.

  • For secondary system pressure protection, the PSE non-LOCA analysis 1 employed a model that allowed steam generator pressure to reach l 1320 psia. At this pressure it was assumed that sufficient MSSV capacity <

exists to stabilize pressure and prevent further increases. The l 1320 psia figure was selected as a conservative bounding value; i.e., '

1320 psia is equal to 110% of the steam generator design pressure. Prior analyses used a model that allowed steam generator pressure to reach  ;

1236 psia. This represented design pressure with a 3% ' allowance for i accumulation.  ;

i

  • Existing FSAR auxiliary flow rates, which are based on assumed MSSV- l capability, correspond to a steam generator pressure of 1236 psia. The PSE analysis for the transition to VANTAGE SH used a more conservative model which allows steam generator pressure to reach 1320 psia.

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(7) Ibid (8) D. H. Jaffe letter to E. J. Mroczka, " Issuance of Amendment No. 60 (TAC No. 77924," dated March 11, 1991.

U.S. Nuclear Regulatory Commission B14653/Page 5 December 17, 1993

  • The current Millstone Unit No. 3 LOCA analyses are not affected by an increase in setpoint tolerance for the PSVs and MSSVs. A 3% MSSV drift from the setpoint was considered for both the large and small break LOCA analyses.

Sionificant Hazards Consideration NNECO has reviewed the proposed changes in accordance with 10CFR50 and has concluded that the changes do not involve a significant hazards cons,Jeration (SHC). The basis for this conclusion is that the three criteria of i 10CFR50.92(c) are not compromised. The proposed changes do not involve an SHC .

because the changes would not: 1

1. Involve a significant increase in the probability or consequences of an accident previously evaluated.

The proposed changes revise the "as-found" setpoint tolerances for the PSVs and MSSVs from 11% to 13%. For the resetting of the PSVs and MSSVs, a 11% setpoint tolerance will be required prior to declaring the valve operable for those instances where the 11% tolerance was exceeded. The proposed changes involve no hardware modifications to plant structures, systems, or components. The proposed setpoint tolerance of 13% for the "as-found" condition was previously evaluated as part of _the PSE report for the transition to VANTAGE SH fuel. The PSE was reviewed and approved by the NRC Staff as a part of a prior license amendment."" In addition, '

since the proposed changes have previously been evaluated by the PSE report, the calculated radiological release associated with the PSE remain unaffected. In addition, the proposed changes are in compliance with applicable sections of the ASME Code and will not significantly_

affect structural integrity of either the reactor coolant system or the main steam system. Therefore, the proposed changes will have no effect on the probability or consequences of previously evaluated accidents.

2. Create the possibility of a new or different kind of accident from any accident previously evaluated.

The proposed changes will not create the possibility of a new or different kind of accident from those previously analyzed. The changes revise the technical specifications so that setpoint tolerance for the PSVs and MSSVs can be 13% for the "as-found" condition. These changes have no effect on plant operation. The PSV and MSSV setpoint drift in excess of the 11% lift setting is an occurrence which has previously and may subsequently occur. The analyses for the transition to the _ VANTAGE SH fuel have examined the effects on the plant accident analyses for relaxation in PSV and MSSV setpoint tolerance to 13%. Also, these (9) Ibid

U.S. Nuclear Regulatory Commission B14653/Page 6 December 17, 1993 changes will have no effect on ASME Code compliance. These changes do-not introduce any new failures.

3. Involve a significant reduction in the margin of safety.

In support of the transition to the VANTAGE 5H fuel, a PSE was performed which assumed _ a 13% setpoint tolerance for both the PSVs and MSSVs.

Therefore, the effects of relaxing the PSV and MSSV setpoints are already accounted for in the existing analyses of record and will not affect the plants accident analyses. Additionally, the proposed changes will have no significant effect on the structural integrity of the reactor coolant system or the main steam system. Also. for. those occurrences where the "as-found" setpoint of the PSV or MSSV is in excess of 11%, a resetting ,

to within 11% of the valve setpoint will be required prior to declaring the valve operable. Therefore, the proposed changes will not involve a significant reduction in a margin of safety.

Moreover, the Commission has provided guidance concerning the application of standards in 10CFR50.92 by providing certain examples (March 6, 1986,- ,

51 FR 7751) of amendments that are considered not likely to involve an SHC.

The proposed changes are not enveloped by a specific example. However, the i changes would not involve a significant increase in the probability or-  !

consequences of an accident previously evaluated, and therefore, the proposed changes do not involve an SHC. The proposed changes relax the setpoint tolerance for PSVs and MSSVs to 13% for the "as-found" condition. If a PSV or.

MSSV should exceed the 11% tolerance, it will be required to be reset prior to  ;

declaring the valve operable. The effects of a 13% -setpoint tolerance were '

used in the VANTAGE SH PSE report and were shown to be acceptable. Structural integrity of the reactor coolant system and the main steam system will not be significantly affected by the proposed changes. Section 5 of the PSE is provided as Attachment 3.

The mark-up of the existing technical specifications is contained in i Attachment 1. The retype of the proposed changes to the technical  !

specifications are contained in Attachment 2 and reflects the currently issued ,

version of technical specifications. Section 5 - of the PSE is provided in Attachment 3. .j NNECO has reviewed the proposed license amendment against the criteria of -

10CFR51.22 for environmental considerations. The proposed changes do not increase the type and amounts of effluents that may be released off site, nor significantly increase individual or cumulative occupational radiation i exposures. Based on the foregoing, NNECO concludes that the proposed changes meet the criteria delineated in 10CFR51.22(c)(9) for categorical exclusion from the requirements for an environmental impact statement.

The Millstone Unit No. 3 Nuclear Review Board has reviewed and approved the proposed changes and has concurred with the above determination.

U.S. Nuclear Regulatory Commission B14653/Page 7 December 17, 1993 In accordance with 10CFR50.91(b), we are providing the State of Connecticut with a copy of this proposed amendment.

Regarding our proposed schedule . for this amendment, we request issuance at your earliest convenience with amendment effective as of the date of issuance, to be implemented within 30 days of issuance.

Should the Staff require any additional information, please contact my staff.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY J. F W ka U Executive Vice President 1

cc: T. T. Martin, Region I Administrator V. L. Rooney, NRC Project Manager, Millstone Unit No. 3 '

P. D. Swetland, Senior Resident Inspector, Millstone Unit Nos. 1, 2, ,

and 3  ;

Mr. Kevin T.A. McCarthy, Director Monitoring and Radiation Division l Department of Environmental Protection i 79 Elm Street P.O. Box 5066 i Hartford, CT 06102-5066 Subscribed and swcrn to before me this /'/M day of ,d s l o ) , 1993

/z n u t b . / h ? // n u A f w V Date Commission Expires: 3 3/,