ML20128D486

Requests That Licensee Meet W/Nrc Staff on 921215 to Provide Justifications for Continued Operability of HHSI at Plant Following Issuance of Info Notice 92-061

ML20128D486
Person / Time
Site:	Millstone
Issue date:	11/25/1992
From:	Calvo J Office of Nuclear Reactor Regulation
To:	Opeka J CONNECTICUT YANKEE ATOMIC POWER CO., NORTHEAST NUCLEAR ENERGY CO.
References
IEB-80-18, IEIN-91-029, IEIN-91-064, IEIN-91-29, IEIN-91-64, IEIN-92-059, IEIN-92-061, IEIN-92-069, IEIN-92-070, IEIN-92-071, IEIN-92-072, IEIN-92-073, IEIN-92-59, IEIN-92-61, IEIN-92-69, IEIN-92-70, IEIN-92-71, IEIN-92-72, IEIN-92-73, TAC-M84948, NUDOCS 9212070290
Download: ML20128D486 (9)

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Docket No. 50-423 Mr. John F. Opeka Executive Vice President, Nuclear Connecticut Yankee Atomic Power Company Northeast Nuclear Energy Company Post Office Box 270 Hartford, Connecticut 06141-0270

SUBJECT:

OPERABILITY OF THE ALTERNATE MINIMUM FLOW PATHS FOR THE HIGH-HEAD SAFETY INJECTION PUMPS (TAC NO. M84948)

On August 20, 1992, the staff issued Information Notice 92-61, and on September 1, 1992, the NRC staff issued special team inspection report No. 50-400/92-201 detailing staff findings and inspection activities pertaining to the effect and circumstances of a reported loss of high-head safety injection (HHSI) at the Shearon Harris Nuclear Power Plant (SHNNP) o)erated by Carolina Power & Light Company (CP&L). This event was reported to tie NRC in Licensee Event Report (LER) 50-400/91-008 on May 3, 1991. The LER was supplemented on May 15, 1991. On November 6, 1992, the NRC issued Supplement I to NRC Information Notice 92-61 (Enclosure 1).

This event was examined in an Oak Ridge National Laboratory accident sequence precursor study of 1991 reactor operational events. In that study, the event was assigned a conditional core damage frequency of 6.3x10E-3 per year. The special team inspection centered around the alternate minimum flow !AMF) system piping and valves. The AMF system was installed after a Westinghouse 10 CFR Part 21 report and NRC Bulletin 80-18 were issued.

On October 13, 1992, CP&L submitted LER 50-400/91-008, Rev. 2, reporting additional system failure during the performance of an integrated functional test on the AMF system. In this LER, CP&L also stated that the as-designed AMF system at SHNPP is being modified to remove the system weaknesses that have been previously identified.

During the course of staff review of the reported loss of HHS1 at the SHNPP, the staff identified that a similarly designed AMF system is installed at Millstone Nuclear Power Station, Unit 3.

Because of the high safety significance of this issue, we request that you meet with the staff on December 15, 1992, to provide your justifications for the continued operability of the HHSI at Hillstone 3. Please be prepared to describe the AMF system configuration in detail, as well as your surveillance EO0l%

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testing experience to demonstrate that the A4f system will perform its  :

functions as designed for all reactor pres:,ure conditions. You should also be -

prepared to discuss any planned modifications to the AMF system.  ;

Sincerely, l Original signed by

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Jose A. Calvo. Assistant Director i for Region 1 Reactors-Division of Reactor Projects -l/II Office of Nuclear Reactor Regulation

Enclosure:

As stated cc w/ enclosure:

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Mr. John F. Opeka Millstone Nuclear Power Station Northeast Nuclear Energy Company Unit 3 Cci Gerald Garfield, Esquire R. M. Kacich, Director Day, Berry and Howard Nuclear Licensing Counselors at Law Northeast Utilities Service Company City Place Post Office Box 270 Hartford, Connecticut 06103-3499 Hartford, Connecticut 06141-0270 W. D. Romberg, Vice President D. O. Nordquist Nuclear, Operations Services Director of Quality Services Northeast Utilities Servico Company Northeast Utilities Service Company Post Office Box 270 Post Office Box 270 Hartford, Connecticut 06141-0270 Hartford, Connecticut 06141-0270 Kevin McCarthy, Director Regional Administrator Radiation Control Unit Region I Department of Environmental Protection U.S. Nuclear Regulatory Commission State Office Building 475 Allendale Road Hartford, Connecticut 06106 King of Prussia, Pennsylvania 19406 Allan Johanson, Assistant Director First Selectmen Office of Policy and Management Town of Waterford Policy Development & Planning Division Hall of Records 80 Washington Street 200 Boston Post Road Hartford, Connecticut 06106 Waterford, Connecticut 06385 S. E. Scace, Nuclear Station Director P. D. Swetland, Resident inspector Hillstone Nuclear Power Station Millstone Nuclear Power Station Northeast Nuclear Energy Company c/o U.S. Nuclear Regulatory Commission Post Office Box 128 Post Office Box 513 Waterford, Connecticut 06385 Niantic, Connecticut 06357 C. H. Clement, Nuclear Unit Director M. R. Scully, Executive Director Millstone Unit No. 3 Connecticut Municipal Electric Northeast Nuclear Energy Company Energy Cooperative Post Office Box 128 30 Stott Avenue Waterford, Connecticut 06385 Norwich, Connecticut 06360 Burlington Electric Department David W. Graham c/o Robert E. Fletcher, Esq. Fuel Supply Planning Manager 271 South Union Street Massachusetts Municipal Wholesale Burlington, Vermont 05402' Electric Company Post Office Box 426 Nicholas S. Reynolds Ludlow, Massachusetts 01056 Winston & Strawn 1400 L Street, NW Washington, DC 20005-3502

'. UNITED STATES l NUCLEAR REGULATORY CortilSSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 I

l November 6, 1992 NRC INFORMATION NOTICE 92-61, SUPPLEMENT 1: LOSS OF HIGH HEAD {

SAFETY INJECTION Addressees l All holders of operating licenses or construction permits for nuclear power reactors.

Purcose The U.S. Nuclear Regulatory Comission (NRC) is issuing this information notice to alert addressees to additional developments relating to the loss of high head safety injection (HHSI) function because of anomalies in the associated alternate minimum flow (AMF system. It is expected that recipients will review the information)for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action or written response is required.

Descriotion of Circumstances On April 3, 1991, Carolina Power & Light Company (the licensee) determined that the HHS! system for the Shearon Harris Nuclear Power Plant had been in a degraded condition during the previous operating cycle. The degraded condition resulted from relief valve and drain line failures in the AMF system for the charging / safety injection pumps (CSIPs) which would have diverted a significant amount of safety injection (SI) flow away from the reactor coolant i system (RCS). Additional description of the existing AMF system and l

additional discussion regarding the specifics of this event are contained in Information Notice 92-61, " Loss of High Head Safety Injection," dated August 20, 1992, and in NRC Special Inspection Report 50-400/92-201, dated September 1, 1992. In addition, Figurc 1 provides a schematic of the existing HHS! system at Shearon Harris.

To address NRC staff concerns regarding long-term operability of the existing HHSI system, the licenses comitted to im)lement procedures to minimize the potential for gas or air intrusion into tie AMF system and to perform additional testing of the AMF system.

On September 17, 1992, the licensee tested the HHS! AMF system. When the 105-746 motor-operated isolation valve was opened to test train 'A' of the HHS! AMF system (1C5-746 will stroke fully open in approximately 7 seconds),

relief valve 105-744 chattered slightly for several seconds and then 9211020211"

e 4 IN 92-61 Su November 6,1992 pplemeht 1 Page 2 of 3 successfully opened. When the 105-752 motor-operated isolation valve was opened (also requiring approximately 7 seconds) to test train 'B' of the HHS!

a AMF system, relief valve 105-755 chattered significantly, the valve bellows failed, and the test was halted. Additional-discussion regarding these tests '

is contained in NRC Inspection Report 50-400/92-17, dated October 1, 1992.

Discussion The licensee has indicated that the chattering of the 1C5-755 relief valve is believed to have been caused by hydraulic effects associated with opening the 105-752 motor-operated isolation valve. The NRC staff believes that the fluid frictional and dynamic pressure loss characteristics of the long inlet piping 4

upstream of 105-752 may have also contributed to the chattering. The licensee indicated that the testing, disassembly, and examination of the 1C5-755 relief valve identified that the valve lift setpoint (2300 psi) had not changed, and that the bellows failure was caused by cyclic fatigue of an inside weld.

Static testing to verify the valve lift setpoint had been routinely performed, during the plant lifetime, whereas testing to simulate flow through the valve to assure proper operation and reseating apparently never was performed.

The Crosby relief valve technical manual states that chattering can affect the life, operation, and performance of a relief valve. The manual reconssends that relief valves not have restricted inlets because restricted inlets can cause valve chatter. The opening and closing of the motor-operated isolation

valve in the existing HHSI AHF design at Shearon Harris restricts the inlet to the relief valve. In addition, relief valves are generally designed to provide system overpressure protection and are not designed for continuous fluid throttling purposes.

The licensee also indicated that modifications will be made to the HHS! AMF system before restarting the plant from the current refueling outage. Figure 2 provides a schematic of the proposed modifications to the HHS! AMF system at Shearon Harris. The licensee intends to install flow restricting orifices upstream of the motor-operated isolation valves and to remove the relief valves. The motor-operated isolation valve actuation logic will also be modified so that the isolation valves will open when a safety injection signal is present coincident with RCS pressure above approximately 2300 psi.

! The NRC staff is aware that other facilities may employ an HHS! AMF design i similar to the existing system at Shearon Harris. These include, but may not '

be limited to, Millstone Unit 3, Comanche Peak Units I and 2. Beaver Valley- i

, Unit 2, and Vogtle Units 1 and 2. In addition, systems other than the HHS!  ;

AMF system may contain relief valves with restricted inlets, thus also making l - these valves potentially susceptible to chatter.

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IN 92-61, Supplement 1 November 6,1992 4

Page 3 of 3 This information notice requires no specific action or written response. If  !

you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate Office of Nuclear '

Reactor Regulation (NRR) project manager.

Brian K. Grimes Director '

Division of Operating Reactor Support Office of Nuclear Reactor Regulation  ;

Technical contact: J. Ramsey, NRR -

(301) 504-1167 Attachments:

1. Figure 1. Existing Shearon Harris High Head Safety injection System

2. Figure 2. Modified Shearon Harris High Head Safety Injection System

3. List of Recently issued NRC Informat<on Notices E

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' IN 92-61, Supplement 1 November 6 1992

, Page1ofI LIST OF RECENTLY ISSUED NRC INFORKATION NOTICES Information Date of

• Notice No. Subject Issuance Issued to 92-73 Removal of A Fuel All holders of OLs or cps 11-04/92-Element from A Re- for nuclear power reactors, search Reactor Core While Critical 92-59, Horizontally-installed 11/04/92 -

- All holders of OLs or cps Rev. 1 Motor-Operated Gate for nuclear power reactors.

Valves 92-72 Employee Training and 10/28/92 All U.S. Nuclear Regulatory Shipper Registration Commission Licensees.

Requirements for Trans-porting Radioactive Materials 64, Site Area Emergency 10/07/92 All holders of OLs or cps Supp. 1 Resulting from A Less for nuclear power reactors, of Non-Class IE Uninterruptible Power Supplies-92-71 Partial Plagging of 09/30/92 All holders of OLs or cps Suppression Pool for nuclear power reactors.

Strainers At A foreign BWR 92-70 Westinghouse Motor-Operated 09/25/92 All- holders of OLs or cps Valve Performance Data for nuclear power reactors.

Supplied to Nuclear Power Plant Licensees 92-69 Water Leakage from Yard 09/22/92 All holders of OLs or cps Area Through Conduits for nuclear power reactors..

Into Buildings 91-29, Deficiencies Identified 09/14/92 All-holders of OLs or cps Supp. 1 During Electrical Dis- for nuclear power reactorst tribution System Func-tional Inspections DL = Operating Licen~te CP = Construction Permit-