ML20202F603
| ML20202F603 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/26/1997 |
| From: | James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 102-04043-JML-A, 102-4043-JML-A, 50-528-97-16, 50-529-97-16, 50-530-97-16, NUDOCS 9712090135 | |
| Download: ML20202F603 (9) | |
Text
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.iamee M. Levine TEL (002)393 $300 Mail Staton 7002 Palo verde Nuclear Senor Vce Presdent F AX (602)393-0077 P o Box $2034 Generating Staton Nuclear PhoenW. AZ 85072 2034
.c2-04043 - JMlJAKK/DLK November 26,1997 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station: P1-37 Wachington, DC 20555-0001
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Units 1,2 and 3 Docket Nos. STN 50 528/529/530 i
Reply to Notice of Violation 50 529/97-16-01 Arizona Public Service Company (APS) han reviewed NRC Inspection Report 50-028/529/530/97-16 and the Notice of Violatic'i(NOV) dated October 29,1997. The violation as written was cited as a violation of Technical Specification (TS) 3/4.4.1.4.2,
" Reactor Coolant System, Cold Shi tdown Loops Not Filled." During a Reactor Coolant System (RCS) drain operation, APS operations personnel identified that shutdcwn cooling flow was less than required by TS 3/4.4 1.4.2 and took the required actions in accordance with TS Action "a."
APS believes that the requirements of the applicable TS were met throughout the duration of the event; however, we recognize that shutdowri cooling flow fell below 3780 gpm.
APS also realizes the importance of maintaining adequate shutdown cooling flow, and has implemented aggressive actions to prevent recurrencs of this event. Our investigation revealed that APS missed the opportunity to prevent this event by ineffectively addressing past industry operating experience.
Two factors were identified that contributed to the event - the closed valve position indication for the shutdown cooling warm-up bypass valve and the procedure guidance to verify cooling flow were not sufficient to provide a positive method of deterrtining or verifying shutdown cooling flow rate through the core. No previous simihr events were identified where shutdown cooling flow was inadequate to remove decay heat as a rewit of a partially opened shutdown cooling warm-up bypass valve.
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U/S. Nucle:r Regulatory Commission ATTN: Document Control Desk l
Reply to Notice of Violation 50 529/97-16-01 l
Pagd 2 This event is of minor safety significance because the Unit 2 decay heat load was below design bas!s maximums and the available shutdown cooling flow was more than adequate to ren ne decay heat under the existing conditions.
Pursuant to the provisions of 10 CFR 2.201, APS' response to the NOV is enclosed. to this letter is a restatement of the NOV. APS' response is prov!ded in.
Should you have any further questions, plear,e contect Ms. Angela K. Kralnik at (602) 393-5421.
Sincerely, Awtf AM c
JMUAKK/DI.K/mah Restatement of Neuce of Violation A+tachment 2 Reply to Notice of Violation ec:
E. W. Merschoff K. E. Perkins J. W. Clifford J. H. Moorman v
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ENCLOSURE 1 l
I RESTATEMENT OF NOTICE OF VIOLATION 50-529/97-16-01 NRC INSPECTION CONDUCTED SEPTEMBER 7 THROUGH OCTOBER 18,1997 INSPECTION REPORT NO. 50-528/529/530/97-16
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RESTATEMENT OF NOTICE OF VIOLATION 50-529/97-16-01)
During a NRC inspection conducted on September 7 through October 18,1997,one violation of NRC requirements was identified.
In accordance with the " General Statement of Policy and Procedure for NRC Enforcement Actions," NUREG 1600, the violation is listed below.
Technical Specification ?!4.4.1.4.2 requires that, with the reactor in Mode 5 and the reactor coolant loops not filled, at least one loop of shutdown cooling must be in operation with a flow greater than or equal to 3,780 gpm.
Contrary to the above, from approximately 8 p.m. on October 5,1997 until about 12 noon on Octooer 6,1997, Unit 2 was operated in Mode 5 with the reactor coolant loops not filled with less than 3,780 gpm of shutdown cooling flow.
This is a Severity Level IV violation (Supplement 1) 50-529/97-16-01.
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l ENCLOSURE 2 l
l REPLY TO NOTICE OF VIOLATION 50-529/97-16-01 NRC INSPECTION CONDUCTED SEPTEMBER 7 THROUGH OCTOBER 18,1997 INSPECTION REPORT NO. 50-528/529/530/97-16
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REPLY TO NOTICE OF VIOLATION I
Reason For The Violation Compliance with the Technical 3pecifications for MODE 5 shutdown cooling was maintained through this event.
On October 6,1997 Unit 2 was in the process of draining the Reactor Coolant System (RCS) to mid-loop when a level anomaly was noted between two Reactor Water Level Indicating System (RWLIS) wide range level inoicators. Even though the difference between the two indicators was within the acceptable tolerance, control room personnel stopped draining the RCS and chose not to proceed until the level indicatin problem was resolved. Shutdown cooling flow indicated 3870 gpm when operations personnel-stopped draining the RCS.
By design, the shutdown-ccoling warm-up bypass valve (SIBUV690) indicates closed before the valve is torqued closed. For this reason, the operating procedures require the hand switch to be held in the closed direction for five seconds after the valve indicates closed.
Valve indication in the control room comes from a limit switch assembly in the valve actuator as opposed to a torque switch. While troubleshooting t,te RWLIS level anomaly, a maintenance technician suggested that control room personnel check SIBUV690 closed because the RWLIS level indicators are flow compensated and diverting shutdown cooling flow through SIBUV690 affects the RWLIS level indication. Control room personnel operated the hand switch for SIBUV690 1
e in th.e closed direction to confirm the valve was fully seated. After operating the hand -
switch, the P,WLIS wide range level indicators came into agreement but shutdown cooling flow indication dropped to 3480 gpm.
Approximately 400 gpm shutdown cooling flow had been diverted from the reactor through SIBUV690.
The reason shutdown cooling flow fell below 3780 gpm was the shutdown cooling warm-up bypass valve, SIBUV690, was not fully seated, even though the valve position indicator in the control room indicated the valve was closed. APS did not thoroughly address previous industry operating experiences that identified potential problems with the shetdown cooling warm-up bypass valves and their affect on shutdown cooling flow.
While procedure guidance was provided to operations personnel to ensure full closure l
of SIBUV690, a positive means was not provided to verify SIBUV690 fully closed. As a result, the current surveillance test did not provide operations personnel with a positive method for verifying the actual shutdown cooling flow rate through the core.
The Limiting Condition for Operation in Mode 5 with the reactor coolant loops not filled (Technical Specification 3/4.4.1.4.2) requires 3780_ gpm of shutdown cooling flow.
Based on plant conditions the safety significance of this event was minor because Unit 2 had been shutdown for approximately 30 days for refuelir7 an.d the decay heat load was below design basis maximums. The reduced shutdown cooling flow did not result in an increased AT across the core because available shutdown cooling flow was more than adequate to remove decay heat urder the existing conditions.
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Corrective Steos That Have Been Taken and Results Achieved i
On October 6,1997, control room personnel fully seated SIBUV690. When indicated I
shutdown cooling flow dropped below 3780 gpm, operations personnel entered the-appropriate TS Action Statement in accordance with TS 3/4.4.1.4.2 and immediately increased shutdown cooling flow to 3900 gpm.
A significant investigation was performed in accordance with Palo Verde's corrective action program. Based on the
- results of the investigation, an independent performer is now also required to hold the valve control switch in the closed position for five seconds when initiating shutdown cooling. This is an interim action until reliable local position indication is available.
Corrective Steos That Will Be Taken To Avoid Further Violations The investigation evaluated this event, as : well as - previous mdustry operating experience, to develop corrective actions to prevent recurrence.
A reliable means of determining local valve position indication _ for SIBUV690 and --
SIAUV691 will be provioed by February 28,1998.
. Applicable surveillance procedures wi!l be revised to provide a method to accurately determine arid verify shutdown cooling flow through the core. The procedures will be revised by March 6,1998.
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Training will be provided to all operators on this event including the industry events that led up to the condition. Training will be completed by March 6,1998.
1 Date When Full Compliance Wili Be Achieved S
Full compliance with applicab!e Technical Specifications was maintained throughout the event. In accordance with the Action Statement for TS 3/4.4.1.4.2, minimum shutdown cooling flow through the core was restored on October 6,1997 when SIBUV690 was fully seated. Restoration of shutdown cooling flow was performed within the allowed TS Action time frame (i.e. corrective action was immediately initiated to return the required loops to OPERABLE status as soon as possible.)
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