United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9608280058

NIAGARA MOHAWK
GENERATION
BUSINESS GROUP

NINE MILE POINT NUCLEAR STATION/LAKE ROAD, P.O.  BOX 63, LYCOMING, NEW
YORK 13093/ TELEPHONE (315) 349-7263  FAX (315) 349-4753

                             August 21, 1996
CARL D.  TERRY                 NMP2L 1655
Vice President
Nuclear Engineering

U. S. Nuclear Regulatory Commission
Attn: Document Control Desk
Washington, DC 20555

RE: Nine Mile Point Unit 2
Docket No.  50-410
NPF-69

Subject.  Clow Valve Stub Shaft Dowel Pin Failure

Gentlemen:

Pursuant to 10CFR Part 21, Reporting of Defects and Noncompliance,
Niagara Mohawk is reporting a deviation which could have created a
substantial safety hazard.  Niagara Mohawk had previously notified the
Commission of this issue on July 23, 1996, via telephone and facsimile.
The attached report contains the information required by
10CFR21.21(c)(4).

                                             Sincerely,

                                             C. D.  Terry
                                   Vice President - Nuclear Engineering

CDT/JMT/kap
Attachment

xc:  Regional Administrator, Region I
     Mr.  B.  S.  Norris, Senior Resident Inspector
     Mr.  D.  S.  Hood, Senior Project Manager, NRR
     Records Management

                               ATTACHMENT

1.   Name and address of the individual or individuals informing the
     Commission.

     Mr.  Carl D.  Terry, Vice President - Nuclear Engineering
     Niagara Mohawk Power Corporation
     Nine Mile Point Nuclear Station
     P. O.  Box 63, Lake Road
     Lycoming, NY 13093

2.   Identification of the facility, the activity or the basic component
     supplied for such facility or such activity within the United States
     which fails to comply or contains a defect.

     Nine Mile Point Unit 2 (NMP2) Standby Gas Treatment System (GTS)
     discharge piping isolation valve 2GTS*MOV3B.

3.   Identification of the firm constructing the facility or supplying
     the basic component which fails to comply or contains a defect.

     2GTS*MOV3B was supplied to NMP2 by the Clow Corporation.

4.   Nature of the defect or failure to comply and the safety hazard
     which is created or could be created by such defect or failure to
     comply.

     During pre-planned maintenance activities associated with GTS valve
     2GTS*MOV3B, the valve's stub shaft dowel pin fell out of its hole
     and into the GTS discharge piping.  Although the ensuing
     investigation did not positively identify a root cause, Engineering
     conservatively dispositioned the associated Deviation Event Report
     (DER) indicating that the cause of this event was a manufacturing

     process deficiency.  (Niagara Mohawk believes this is an isolated
     event based on the number of Clow valves in service and years of
     service without a similar failure.) Specifically, this deficiency
     was identified as the failure to fully peen over the dowel pin hole
     in the valve disk.  Consequently, the valve stub shaft failed to
     rotate respective to the main shaft, thus preventing the valve limit
     switches from properly displaying valve position.  These valve limit
     switches are used as input permissives for the GTS train start
     logic.

     The GTS is designed to prevent leakage of radioactive gases and
     particulates to the environment during accidents by maintaining a
     negative pressure on the Reactor Building.  The GTS consists of two
     parallel and redundant air filtration assemblies with associated
     duct work, dampers, controls, and exhaust fans.  The discharge of
     each fan has a normally closed isolation valve (2GTS*MOV3A/3B) which
     will open upon

                                    1

     receiving a GTS start signal.  Once 2GTS*MOV3A/3B is open, the GTS
     filter train fans (2GTS*FN1A/1B) are given a permissive signal to
     start.

     In the event the GTS System was called upon to function, discharge
     valve 2GTS*MOV3B would have received an open signal.  If the dowel
     pin had already fallen out or were to fall out prior to the valve
     opening, the valve would still have opened.  However, the valve stub
     shaft, which positions the valve limit switches, would not have
     rotated as the valve moved to the open position.  Since limit
     switches indicating the discharge valve in the open position is a
     permissive to GTS system operation, the respective fan would not
     have started resulting in an inoperable GTS.  Assuming a single
     failure in the redundant GTS train, both trains could be potentially
     inoperable.  Therefore, a substantial safety hazard existed.

5.   The date on which the information of such defect or failure to
     comply was obtained.

     Niagara Mohawk identified the defect on May 23, 1996 as a potential
     Part 21 issue.  The defect was determined to be reportable on July
     22, 1996.

6.   In the case of a basic component which contains a defect or fails to
     comply, the number and location of all such components in use at,
     supplied for, or being supplied for one or more facilities or
     activities subject to the regulations in this part.

     Although there are additional Clow valves at NMP2, this defect would
     only effect GTS isolation valves 2GTS*MOV3A/3B in a similar manner
     (i.e., potentially make the associated system inoperable).  As
     previously discussed, loss of the dowel pin would have prevented the
     associated GTS fan from starting but would not have affected the
     ability of the valve to open and close.  For the remainder of the
     Clow valves, the limit switches do not provide system permissives
     but provide valve position indication only.  Therefore, the failure
     of the shaft to rotate would not have had the same safety
     significance.

7.   The corrective action which has been, is being, or will be taken;
     the name of the individual or organization responsible for the
     action; and the length of time that has been or will be taken to
     complete the action.

     Immediate corrective action by Niagara Mohawk was to reinstall the
     pin that fell from 2GTS*MOV3B and to re-peen the dowel hole.  The
     redundant GTS train was started and verified operable.  Both trains
     are subject to periodic Technical Specification required
     surveillance testing to verify operability.  2GTS*MOV3A will be
     inspected in RFO5, scheduled to begin in September 1996, to verify
     proper peening.  Niagara Mohawk does not anticipate similar problems
     in the remaining Clow valves based on the number of Clow valves and
     the years of service.

8.   Any advice related to the defect or failure to comply about the
     facility, activity, or basic component that has been, is being, or
     will be given to purchasers or licensees.

     None

                                    2

*** END OF DOCUMENT ***

LICENSEE: NIAGARA MOHAWK POWER CORP.         
SITE: NINE MILE POINT 2                     EN NUMBER:30775
DOCKET:  05000410                        EVENT DATE: 07-23-96
RX TYPE:  BWR                            EVENT TIME: 00:00
VENDORS:  GE-5                          NOTIFY DATE: 07-23-96
EMERGENCY CLASS: N/A  REGION: 1 STATE: NY      TIME: 09:00
OPS OFFICER: STEVE SANDIN             
10 CFR SECTION: CCCC  21.21               UNSPECIFIED PARAGRAPH
UNIT  SCRAM   RX   INIT  INITIAL MODE     CURR   CURRENT MODE
      CODE   CRIT  PWR                    PWR
 2    N       Y    100   POWER OPERATION  100   POWER OPERATION

DISCOVERY OF A CONDITION AFFECTING THE OPERABILITY OF CLOW       
(MANUFACTURER) VALVES INSTALLED IN THE UNIT 2 STANDBY GAS        
TREATMENT SYSTEM                                                 
                                                                 
THE LICENSEE DETERMINED THAT CLOW (MANUFACTURER) VALVES IN THE   
STANDBY GAS TREATMENT SYSTEM HAVE A DOWEL PIN INSTALLED WHICH IS 
NOT PEENED IN PLACE. SHOULD THESE DOWELS COME LOOSE, IT COULD    
INTERFERE WITH THE VALVE LIMIT SWITCHES AND PREVENT THE MAKEUP OF
CIRCUIT PERMISSIVES.                                             

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