ML20155C378

SER Denying Amend to Allow Changes to Fsar.Nrc Found That NNECO Had Not Considered Diversity Provided by Switch in Control Room That Removes Power to 1 of 2 MOV in SDC Sys Flow Path in Evaluation of High Low Pressure Design

ML20155C378
Person / Time
Site:	Millstone
Issue date:	10/30/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20155C376	List: ML20155C371 ML20155C378
References
NUDOCS 9811020219
Download: ML20155C378 (5)

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j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2066m01

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PRESSURIZER PRESSURE - SHUTDOWN COOLING SYSTEM INTERLOCKS NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT NO. 2 DOCKET NO. 50-336

1.0 INTRODUCTION

By letter dated April 29,1998, the Northeast Nuclear Energy Company (NNECO/the licensee) proposed a license amendment to allow changes to the description of the Millstone Nuclear Power Station, Unit No. 2 (MNPS2) Final Safety Analysis Report (FSAR). The licensee determined that the requested changes constitute an unreviewed safety question (USQ) as defined in Title 10 of the Code of Federal Reaulations (10 CFR) Section 50.59.

The proposed changes would delete the diversity requirement in FSAR, Section 4.3.8.2.3,

" Pressurizer Pressure," for PT-103 and PT-103-1, which are the two low-range pressurizer pressure transmitters. The licensee proposes to replace PT-103 and PT-103-1 with transmitters that are more accurate in a post-accident environment to provide assurance that entry into shutdown cooling in a post accident environraent is not compromised and to provide relief for the reactor coolant system (RCS) pressure / temperature curves. The licensee further indicates that only a single model series of Rosemount transmitters meet the revised design requirements.

This request results from the licensee's determination that the existing low-range pressurizer

, pressure transmitters in the shutdown cooling (SDC) system interlocks are susceptible to high inaccuracies during harsh environment conditions following a loss-of-coolant accident or a main steamline break inside the containment. The replacement of these transmitters will result in the elimination of transmitter diversity as described in the MNPS2 FSAR, Section 4.3.8.2.3,

" Pressurizer Pressure." The licensee has determined that this deviation involves a USQ, as defined in 10 CFR 50.59. Therefore, in accordance with 10 CFR 50.59(c), the licensee requests that the staff review and approve this change to the FSAR through an amendment to Facility Operating License DPR-65, pursuant to 10 CFR 50.90.

2.0 EVALUATION The NRC's Branch Technical Position HICB 1, " Guidance on isolation of Low-Pressure Systems From the High-Pressure Reactor Coolant System," states in part, that where both valves in a high/ low pressure system interface are motor-operated, the valves should have independent and diverso interlocks to prevent both from opening unless the primary system pressure is below the subsystem design pressure, in the MNPS2 FSAR, credit is presently taken for diversity achieved through the use of diverse pressure transmitters in each of the two channels for the motor-operated valves that isolate the low-pressure SDC system from the high-pressure RCS.

9811020219 981030 PDR ADOCK 05000336 P PDR Enclosure

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The licensee indicates that replacement of the low-range pressurizer pressure transmitters is necessary to provide sufficient accuracy so that entry into SDC in a post accident l environment is not compromised. To resolve the problem, the existing transmitters, PT-103 and i PT-103-1, will be replaced with transmitters that exhibit greater accuracy in post-accident l environments. Of the qualified transmitters available, only one model series manufactured by l Rosemount exhibits a post-accident accuracy that meets the revised design requirements.

! Therefore, both PT-iO3 and PT-103-1 must be replaced with identical Rosemount, Model 1154, i l Series H transmitters. As previously noted, the replacement would eliminate the transmitter l diversity presently credited in the FSAR and the licensee has determined that the change is a l

USQ as defined in 10 CFR 50.59. Thus, the licensee has requested that the NRC staff review and approve the change prior to implementation.

The NRC staff has reviewed the diversity aspect of the licensee's submittal and finds that the l design change proposed by NNECO is similar to the change implemented by Southern Califomia Edison Company (Edison) for the same problem at San Onofre Nuclear Generating Station (SONGS), Units 2 and 3. Edison had similarly submitted a request to the staff for approval of the design before its implementation. However, in a phone conference held on January 11,1995, Edison informed the staff that one valve in each SDC system flow path has power removed whenever primary plant pressure is greater than the SDC design pressure. These valves have power removed to prevent inadvertent opening caused by failures that could defeat the keylock

! feature or other safety interlocks. On the basis of this discussion, it was agreed that having i power removed from one valve in each SDC flow path meets the staff's diversity criteria for j assurance that the high/ low pressure interface would not be inappropriately opened. (See letter l

from Walter C. Marsh, Southem Califomia Edison Company, to U.S. Nuclear Regulatory Commission, dated March 28,1995.)

! On the basis of that agreement, Edison perfomled a 10 CFR 50.59 evaluation for the proposed design change. The evaluation supported replacing the existing low-range pressurizer pressure isansmitters at SONGS, Units 2 and 3, with ar, improved model supplied by one manufacturer and providing a diverse means of assuring SDC system isolation by the removal of motive power from one of the motor-operated valves in each SDC system flow path when RCS pressure is greater than SDC system design pressure.

The design for MNPS2 is similar to that at SONGS in that one valve in the SDC system flow path has power removed whenever RCS pressure exceeds the SDC system design pressure. This design change was implemented by NNECO in 1983 to improve operator control over one of the SDC suction valves and to prevent inadvertent or unauthorized operation of that valve. The design change included the installation of a manual power disconner t switch in the control room.

When open, this switch removes power to one of the two motor-operated valves. This switch is maintained open in accordance with operating procedures whenever the pressure of the RCS exceeds 265 psia, in order to better preclude the possibility of connecting the high-pressure system to the low-pressure system. An annunciator is provided to wam the operator whenever the manual power disconnect switch is closed.

Thu5, the NRC staff finds that the existing design at MNPS2 provides a diverse means of assuring SDC system isolabon by the removal of motive power from one of the motor-operated valves whenever the RCS pressure exceeds the SDC system design pressure.

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3.0 CONCLUSION

The NRC staff has reviewed NNECO's submittal and finds that NNECO had not considered the )

diversity provided by the switch in the control room that removes power to one of the two motor-operated valves in the SDC system flow path in its evaluation of the high/ low pressure interface design. The NRC staff has determined that the licensee should perform a new safety evaluation under the provisions of 10 CFR 50.59 to determine if a USQ exists with this design consideration included. Depending on its findings, NNECO may be able to withdraw the April 29,1998, amendment application and proceed to change the MNPS2 licensing basis and associated FSAR revision under the provisions of 10 CFP 50.59. If NNECO determines that a USQ still exists, it may supplement the current application b,' providing the results of the new safety evaluation to support a license amendment.  ;

l Principal Contributor: K. Mortensen Date: October 30, 1998 l i

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l. Millston3 Nuclxr Ptwer Station Unit 2 cc:

Lillian M. Cuoco, Esquire Mr. F. C. Rothen

! Senior Nuclear Counsel Vice President - Work Services l Northeast Utilities Service Company Northeast Utilities Service Company P. O. Box 270 P. O. box 128 Hartford, CT 06141-0270 Waterford, CT 06385 l Mr. John Buckingham Emest C. Hadley, Esquire l Department of Public Utility Control 1040 B Main Street l Electric Unit P.O. Box 549 l 10 Liberty Square West Wareham, MA 02576 New Britain, CT 06051 .

l Mr. John F. Streeter Edward L. Wilds, Jr., Ph.D. Recovery Officer - Nuclear Oversight Director, Division of Radiation . Northeast Utilities Service Company Department of Environmental Protection P. O. Box 128

!* 79 Elm Street Waterford, CT 06385 l

Hartford, CT 06106-5127 Mr. John Carlin Regional Administrator, Region l Vice President - Human Services U.b. Nuclear Regulatory C >mmission Northeast Utilities Service Company l 475 Allendale Road P. O. Box 128 King of Prussia, PA 19406 Waterford, CT 06385 First Selectmen Mr. Allan Johanson, Assistant Director Town of Waterford Office of Policy and Management 15 Rope Ferry Road Policy Development and Planning Waterford, CT 06385 - Division 450 Capitol Avenue - MS# 52ERN Mr. Wayne D. Lanning, Director P. O. Box 341441 Millstone Inspections Hartford, CT 06134-1441 Office of the Regional Administrator

' 475 Allendale Road Mr. M. H. Brothers i King of Prussia, PA 19406-1415 Vice President - Operat!ons Northeast Nuclear Energy Company Charles Brinkman, Manager P.O. Box 128 Washington Nuclear Operations Waterford, CT 06385 ABB Combustior. Engineering 12300 Twinbrook Pkwy, Suite 330 Mr. J. A. Price Rockville, MD 20852 Director - Unit 2

Northeast Nuclear Energy Company Senior Resident inspector P.O. Box 128 L Millstone Nuclear Power Station Waterford, CT 06385 l- clo U.S. Nuclear Regulatory Commission l . P.O. Box 513 i Niantic, CT 06357 1-t 1

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.,, Millstona Nucle:r Power Station

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cc. 3 Mr. Leon J. Olivier Attomey Nicholas J. Scobbo, Jr.  ?

Chief Nucler Officer- Millstone Ferriter, Scobbo, Caruso, Rodophele, PC Northeast Nuclear Energy Company i Beacon Street,11th Floor _

P.O. Box 128 Boston, MA 02108 j Waterford, CT 06385 4 Mr. J. P. McElwain Citizens Regulatory Commission Recovery Officer - Millstone Unit 2 ATTN: Ms. Susan Peny Luxton Northeast Nuclear Energy Company 180 Great Neck Road P. O. Box 128 Waterford, CT 06385 Waterford, Connecticut 06385 Deborah Katz, President  :

Citizens Awareness Network j P. O. Box 83 j Shelburne Falls, MA 03170 The Honorable Terry Concannon Co-Chair Nuclear Energy Advisory Council Room 4035  ;

Legislative Office Building Capitol Avenue l Hartford, CT 06106 3 i

Mr. Evan W. Woollacott  !

Co-Chair l Nuclear Energy Advisory Council 1 128 Terry's Plain Road i Simsbury, CT 06070 j Little Harbor Consultants, Inc. i Millstone -ITPOP Project Office  !

P. O. Box 0630 Niantic, CT 06357-0630 Mr. Daniel L. Curry Project Director Parsons Power Group inc.

2675 Morgantown Road Reading, PA 19607 ,

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