ML19324C327

LER 89-014-00:on 891010,primary Containment Isolation Sys Group 5 Isolation Occurred Due to Opening of Valve 1G31-D002A.Caused by Personnel Error.Personnel Counseled & Memo Issued Re Confirming commands.W/891108 Ltr

ML19324C327
Person / Time
Site:	Hatch
Issue date:	11/08/1989
From:	Hairston W, Tipps S GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
HL-814, LER-89-014-02, LER-89-14-2, NUDOCS 8911160137
Download: ML19324C327 (7)

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OPERATING LICENSE DPR-57 i LICENSEE EVENT REPORT l PERSONNEL ERROR LEADS TO GROUP 5 ISOLATION  :'

OF PRIMARY CONTAINMENT ISOLATION SYSTEM ,

Gentlemen: (

In accordance with the requirements of 10 CFR 50.73(a)(2)(iv),

Georgia Power Company is symitting the enclosed Licensee Event Report (LER) concerning the unanticipated actuation of an Engineered Safety l Feature. This event occurred at Plant Hatch - Unit 1. '

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Enclosure:

LER 50-321/1989-14 l c: (See next page.)

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Mr. L. P. Crocker, Licensing Project Manager - Hatch U.S. Nuclear Reaulatory Commission. Reaion II Mr. S. D. Ebneter, Regional Administrator Mr. J. C. Henning, Senior Resident Inspector - Hatch I

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On 10/10/89, at approximately 1020 CDT, Unit I was in the Run mode at an approximate power level of 2436 MWT (approximately 100% of rated thermal f power). At that time, plant equipment operators (PE0s), in accordance with procedure, opened valve IG31-F052A to place into service the Reactor i Water Cleanup (RWCV) system filter /demineralizer (F/D) 1G31-D002A.

Opening the valve caused a pressure transient which actuated the RWCV system high differential flow alarm. A Primary Containment Isolation System (RCIS) Group 5 isolation then occurred per design.

The root cause of this event was personnel error. Miscomunication resulted in the inability to quickly recognize and mitigate the differential flow condition, in that the PE0 who opened the valve mistakenly believed communication had been established with the Main Control Room prior to the attempt to place the F/D into service. A contributing factor is the non-fault tolerant design of the RWCV system F/Ds. in that opening the F/D isolation valve can result in a pressure / flow transient.

Corrective actions for this event include counselling the involved personnel, issuing a memorandum emphasizing the need to use the verbal repeat back technique for confirming comands before executing actions, and scheduling a design change to the RWCU system.

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SUM!%RY OF EVENT On 10/10/09, at approximately 1020 CDT, Unit I was in the Run mode at an approximate power level of 2436 MRT (approximately 100% of rated thermal power). At that time, plant equipment operators (PEOs) opened valve 1G31-F052A to place into service the Reactor Water Cleanup' system (RWCU, Ells Code CE) filter /demineralizer (F/D) 1G31-0002A. Opening the valve precipitated a pressure transient which actuated the RWCU s differential flow alarm of the RWCU Leak Detection SystemLOS. (ystemEIIShigh Code BD). The PE0 who opened the valve mistakenly believed procedurally required communication with the Main Control Room had been established -

via a second PEO. Because communication had not been established, the PEOs did not know the high differential flow alarm had actuated, and hence did not close valve 1G31-F052A to mitigate the differential flow condition. A Primary Containment Isolation System (FCIS EIIS Code JM)

Group 5 isolation then occurred per design.

The root cause of this event was personnel error. Specifically, miscommunication between the two PEOs at the remote F/D panel resulted in the inability to quickly recognize and mitigate the differential flow condition. A contributing factor to the event is the non-fault tolerant design of the RWCU system F/Ds, in that opening the F/D isolation valve can result in a pressure / flow transient. i Corrective actions for this event include counselling the involved personnel, issuing a memorandum from the Manager of Operations emphasizing the need to use the verbal repeat back technique for confirming commands before executing actions, and scheduling a design change to the RWCU system.

RSCRIPTION OF EVENT h

On 10/10/89, at approximately 0700 CDT, plant operations personnel began a backwash and precoat cycle on the Unit 1 RWCU F/Ds. At 1020 CDT, plant operations personnel were returning a F/D to service in accordance with procedure 34S0-G31-003-15. "RnCU System." To accomplish this task, two PE0s were stationed at a remete F/D panel, and licensed plant '

operators were stationed in the Main Control Room (ICR). At the remote l

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instruct the PEOs to isolate the F/D should the LDS annunciator actuate due to a RWCU system high differential flow signal. .

The PE0s at the remote F/D panel were aware of the requirement to establish communication with the ICR before opening the valve to the F/D  ;

to return it to service. Therefore, the PE0 assigned to the comunication function went to a nearby plant telephone and dialed the ,

MCR. As the PE0 assigned the comunication function waited for the ICR '

to answer the phone, the PE0 assigned to equipment operation misinterpreted a gesture made by the other PE0 as a comand to proceed.

When he opened the isolation valve (1G31-F052A) to the F/D, a pressure / flow transient actuated the LDS annunciator in the KR. Thus, at approximately the same moment as the telephone began ringing in the <

MCR, the LDS annunciator also alarmed in the ER. KR licensed plant operators responded to the annunciator rather than answering the telephone. Therefore, because comunication was not established, the ICR operators were not aware that the F/D isolation valve had been  :

opened, and the PEOs were not aware that the high differential flow annunciator had sounded. When the LDS 45-second time delay expired, the PCIS Group 5 valves isolated per design. ,

Following the event, PEOs inspected the RWCV system to verify that no leaks existed from piping or valves. The REV system was then returned  !

to service without further incident. .

CAUSE OF THE EVENT The root cause of this event was personnel error. Specifically, miscomunication between the two PEOs at the remote REV tystem F/D panel resulted in the inability to quickly recognize and mitigate the differential flow condition. The PE0 who opened the F/D isolation valve at the remote panel misinterpreted a gesture made by the other PE0 as the latter was attempting to telephone the KR. Therefore, the F/D -

isolation valve was opened before comunication was established with the MCR operators. A contributing factor to the event is the non-fault tolerant design of the F/Ds, Opening the F/D isolation valve can result in a pressure / flow transient potentially of sufficient duration to activate a PCIS Group 5 isolation due to RWCU system high differential flow,

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REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT This report is required per 10 CFR 50.73 (a)(2)(iv) because an event occurred which resulted in the unplanned actuation of an Engineered Safety Feature (ESF). Specifically, the R)CU system isolation valves, 1G31-F001 and 1G31-F004 (Group 5 PCIS valves), closed in response to an  ;

indication of high differential flow between the lines entering and 1 caving containment.

The purpose of the RWCU LDS is to detect leakage from the RWCU system ,

outside primary containn.ent and to mitigate the consequences of that leakage. This system uses leak detection instrumentation which initiates closure of Primary Containment Isolation Valves (PCIVs) upon detecting a parameter indicating a leak. One of the instruments used for detecting leakage compares RWCU system influent and effluent. A high differential flow condition exists when the influent exceeds the effluent by at least 56 gpm for 45 seconds. This condition will initiate closure of the Group 5 PCIVs. ,

In the eve 9t addressed in this report, an actual high differential flow condition existed resulting in the isolation of the Group 5 PCIVs. The miscommunication between the PEOs who were stationed at the remote location and the operators who were in the ICR ied to the premature opening of a F/D isolation valve. This causet' a pressure transient which activated the RWCU LDS. The LDS annune. tors, in turn, led liCR operators to deal with the task of silencing the alarms rather than establishing conrnunication with the PE0s because they did not realize the PE0s had opened the isolation valve to the F/D. Thus the F/D was not isolated to mitigate the high differential flow condition as directed by the procedure. There was no leakage of reactor coolant outside the RWCU system.

Based on the above analysis, it is concluded that this event had no adverse impact on nuclear safety. Since the isolation occurred at rated thermal power, it is concluded tnat this event would not have been more severe under other operating conditions.

CORRECTIVE ACTIONS Corrective actions for this event include:

1. The personnel involved will be counselled by 11/24/89 regarding the significance of this event and the need for constant attention to detail.

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2. Issuing a memorandum from the Manager of Operations to all operations personnel emphasizing the importance of using the repeat back technique of verifying verbal commands before executing them.

This action will be completed by 12/15/89. '

3. Implementing a design change to provide a small bypass valve around the outboard inlet 1 solation valves to the F/Ds. This will permit slow F/D pressurization and mitigate the pressure transient which was the immediate cause of this event. This action will bc

, completed by the end of the next Unit 1 refueling outage, currently scheduled to begin 2/28/89. '

ADDITIO;4AL INFORMATION

1. Other Affected Equipment:

No plant systems other than the RWCU system and the Grcup 5 PCIVs were affected by this event.

2. Previous Similar Events:

Similar events in which the RWCU system isolated due to high differential flow were previously reported in the following LERs:

50-321/1989-001, dated 03/06/89 50-321/1989-012, dated 10/31/89 50-366/1983-021, dated 09/28/88 50-366/1988-015, dated 08/26/88 The corrective actions for these events included revising defective procedures, repairing and replacing valves, and counseling involved personnel. These corrective actions would not have prevented the event addressed in this report because no procedural deficiencies were involved, there were no failed components in this event, and different personnel were involved in this event.

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