05000530/LER-1998-001

LER-1998-001,

Event date:	9-8-0909
Report date:	50-10-0151
5301998001R00 - NRC Website

DOCKET NUMBER LER NUMBER PAGE FACILITY NAME

015101010151310 == 1. REPORTING REQUIREMENT: ==

This LER 530/98-001-00 is being written to report an event that resulted in the operation in a condition prohibited by the technical specifications. (50.73(a)(2)(i)) Specifically, on July 30, 1998, at approximately 1135 MST, Palo Verde Unit 3 was in Mode 1 (POWER OPERATION), operating at approximately 100 percent power when control room personnel (utility-licensed operator) determined that all four flow transmitters (FT) for the high pressure safety injection system (HPSI) (BQ) were isolated and out of service. The transmitters had been isolated earlier in the shift in support of planned maintenance on the B train HPSI pump and injection valves (4). At approximately 1212 MST the Shift Manager (utility-licensed operator) determined that with all four of the transmitters isolated the condition constituted operation outside the associated emergency core cooling system technical specification limiting condition for operation 3.5.2 and the associated action statement. Technical Specification 3.0.3. was entered and concurrent action was initiated to restore the transmitters to OPERABLE status. At 1242 MST Technical Specification 3.0.3 was exited after the transmitters had been aligned and independently verified.

2. EVENT DESCRIPTION:

On July 30, 1998 at approximately 0500 MST Unit 3 was operating at 100% reactor power when the B train HPSI injection valves and pump were removed from service and tagged for planned maintenance. In support of the planned maintenance a separate clearance had previously been generated to ensure compliance with Technical Specification (TS) 3.6.3 action requirements since the injection valves are also containment isolation valves. This course of action had been discussed by the Shift Manager and the work control senior reactor operator (SRO) (utility-licensed operator) the previous day and both agreed that the clearance would ensure compliance with the containment isolation TS. At approximately 0645 MST on July 30, an operator (utility- licensed operator) isolated the four HPSI flow transmitters in accordance with the clearance and as directed by control room personnel.

At approximately 1135 MST, during a daily operations crew briefing, I&C personnel (other utility personnel) began performing instrument loop calibrations for HPSI cold leg injection transmitters, SIB-FT-311, SIB-FT- 321 which provide HPSI flow indication to the control room. During this performance a computer alarm was received in the control room and an LICENSEE EVENT REPORT (LER) TEXT CONTINUATION == PAGE LER NUMBER ==

DOCKET NUMBER

015101010151310 9I8 I- 010J1 - 010 operator noticed that an A train HPSI flow indicator was "bouncing" The system design for HPSI flow indication includes a flow transmitter in each of the four HPSI injection lines. Each of these injection lines combines flow from both the A and B HPSI trains. Each flow transmitter supplies flow indication to the train A and B safety injection portion of the main control board in the control room.

The Shift Manager and Work Control SRO were contacted and a review of work activities in progress was performed. During this review it was identified that all four HPSI flow transmitters were isolated under the TS 3.6.3 clearance and that the A train HPSI may also be impacted. At approximately 1212 MST the Shift Manager determined the condition constituted operation outside the associated emergency core cooling system TS limiting condition for operation (LCO) and action statement. TS 3.0.3. was entered and concurrent action was initiated to restore the four transmitters to OPERABLE status. At 1242 MST TS 3.0.3 was exited after the transmitters had been aligned and independently verified.

There were no safety system actuations and none were required.

3. ASSESSMENT OF THE SAFETY CONSEQUENCES AND IMPLICATIONS OF THIS EVENT:

The HPSI flow indicators are a related support system for the emergency core cooling system (ECCS) and are required to support the operability of the ECCS. During the initial injection phase of a loss of coolant accident (LOCA), flow indication is not required since the associated cold leg injection header orifices ensure proper cold leg injection flow balance.

However, approximately 2 hours after a large break LOCA simultaneous hot and cold leg flow is initiated. Hot and cold leg flow indication is required at that time so that average cold leg flow can be measured and hot leg injection valves can be throttled so that total hot leg flow equals total cold leg flow. This flow split is required to provide core flushing in order to prevent possible precipitation of boron in the core which would adversely affect heat transfer. The methodology used in the emergency operating procedures to establish this flow split accounts for one or two failed HPSI cold leg flow transmitters by averaging only those transmitters which are indicating flow. Since flow is actually balanced between cold legs by surveillance testing, which sets a limit for the open travel of the injection valve, averaging three or four indicators would essentially yield the same result.

Since the initial injection flow is determined by the mechanical characteristics of the system, the flow indicators are not required for the initial HPSI injection phase.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION == DOCKET NUMBER ==

LER NUMBER PAGE

or result in any release of radioactive materials. Therefore, there were no adverse safety consequences or implications as a result of this event.

This event did not adversely affect the safe operation of the plant or health and safety of the public.

4. CAUSE OF THE EVENT:

An independent investigation of this event is being conducted in accordance with the APS Corrective Action Program. As part of the investigation, a determination of the cause of the event will be performed. A preliminary evaluation has determined that the apparent root cause is attributed to cognitive personnel error (SALP Cause Code: A:

Personnel Error) on the part of the individuals involved with preparing, reviewing, and authorizing the clearance used to ensure compliance with the TS for containment isolation. These individuals concentrated on the containment penetration aspect of the clearance and did not consider other ramifications of isolating the four HPSI transmitters. If the evaluation results differ from this determination, a supplement to this report will be submitted to describe the final root cause determination.

No unusual characteristics of the work location (e.g., noise, heat, poor lighting) directly contributed to this event. No procedural errors contributed to this event.

5. STRUCTURES, SYSTEMS, OR COMPONENTS INFORMATION:

There are no indications that any structures, systems, or components were inoperable at the start of the event that contributed to this event. No component or system failures were involved.

6. CORRECTIVE ACTIONS TO PREVENT RECURRENCE:

An independent investigation of this event is being conducted in accordance with the APS Corrective Action Program. Actions to prevent recurrence are being developed based upon the results of the investigation. Actions identified include a lessons learned briefing, of the results from the investigation, to all Work Control personnel. In addition, changes to the work control process, to more clearly define responsibilities for reviewers regarding TS impacts caused by clearances, will be made.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION == FACILITY NAME LER NUMBER PAGE ==

i YEAR SEQUENTIAL REVISION ! == DOCKET NUMBER ==

015101010151310 No other previous events, in the last three years, have been reported pursuant to 10 CFR 50.73 where entry into TS 3.0.3 occurred when equipment was removed from service.

8. ADDITIONAL INFORMATION:

None CATEGORY 1 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS) ACCESSION NBR :9809090266 DOC.DATE: 98/08/28 NOTARIZED: NO DOCKET # FACIL:STN-50 -530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH.NAME AUTHOR AFFILIATION MARKS,D.G. . Arizona Public Service Co. (formerly Arizona Nuclear Power OVERBECK,G.M ▪ Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION SUBJECT: LER 98-001-00:on 980730,entered TS 3.0.3 due to safety injection flow instruments being removed from svc.Caused by personnel error.Transmitters were unisolated & returned to svc.W/980828 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR l ENCL I SIZE: 61) TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:Standardized plant. 0500053a 0 C A T E == RECIPIENT ==

ID CODE/NAME

PD4-2 PD INTERNAL: ACRS == AEOD/SPD/RRAB ==

RES/DET/EIB

EXTERNAL: L ST LOBBY WARD NOAC POORE,W.

LTTR ENCL

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FIELDS,M

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