ML18101B058

LER 95-021-00:on 930403,both Reactor Vessel Level Indication Sys Trains Inoperable Due to Inadvertent CO2 Actuation Due to Water Intrusion.Completed RVLIS & Cabinet Sealing repaired.W/951016 Ltr

ML18101B058
Person / Time
Site:	Salem
Issue date:	10/15/1995
From:	Fregonese V, Warren C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-95-021-01, LER-95-21-1, LR-N95183, NUDOCS 9510230393
Download: ML18101B058 (8)

Text

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• P1.iblb~ Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038-0236 Nuclear Business Unit OCT 16 1995 LR-N95183 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 50-311 UNIT NOS. 1 and 2 LICENSEE EVENT REPORT NO. 95-021-00 This Licensee Event Report entitled "Inoperability of Both Reactor Vessel Level Indication System Trains Due to a Single Event" is being submitted pursuant to the requirements of the Code of Federal Regulation 10CFR50.73(a)

(2) (vii) (D). Attachment A contains a listing of those commitments made as a result of the investigation into this issue.

Sincerely,

~~::~

General Manager Salem Operations Attachment A Attachment LER SORC Mtg.95-117 C Distribution LER File 3.7 The power is in yuur hands.

9510230393 951015 PDR ADOCK 05000272 95-2168 REV. 6/94 S PDR

• OCT 16 1995 Document Control Desk 2 LI':'N95183 Attachment A PSE&G Commitments The following commitments have been made by PSE&G as a result of the investigation into LER 272/95-021:

1. RVLIS and cabinet sealing repairs were completed in 1993.

2. The adequacy of design, implementing and maintenance procedures will be evaluated and corrected as necessary to ensure that interactions from the C02 systems are considered. This evaluation is expected to be completed by March 31, 1996.

3. The response to the Surry event and internal operating experience will be reviewed to ensure that the issue relative to water intrusion into C02 sys~ems is adequately addressed. This review is expected to be completed prior to February 29, 1996.

4. Required actions for RVLIS as a result of the EWR review will be completed prior to Mode 3. This includes design/licensing basis review of the RVLIS System.

5. A review will be performed to identify and evaluate potential adverse effects on redundant safety related equipment due to a C02 system actuation. This review is expected to be completed by February 29, 1996.

NRCFORM 366 (4-95)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

APPROVED BY OMB NO. 3150-0104 EXPIRES 04130198 ESTIMATED BURDEN P=R RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS.

REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD

. COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH IT~ F33l. U.S. NUCLEAR (See reverse for required number of REGULATORY COMMISSION. WASHINGTON. DC 20555-0001. AND TO THE PAPERWORK REDUCTION PROJECT {3150-0104). OFFICE OF digits/characters for each block) MANAGEMENT AND BUDGET. WASHINGTON. DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE(3)

SALEM - Unit 1 05000272 1 OF6 TITLE(4) lnoperability of Both Reactor Vessel Level Indication System Trains Due to a Single Event EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL I REVISION MONTH DAY YEAR I NUMBER NUMBER Salem Unit2 FACILITY NAME 05000311 DOCKET NUMBER 04 03 93 95 - 021 - 00 10 15 95 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more) (11)

MODE (9) 6 20.2201(b) 20.2203(a)(2)(v) 50. 73(a)(2)(i)(B) 50. 73(a)(2)(viii)

POWER 20.2203(a)(1) 20.2203(a)(3)(i) 50. 73(a)(2)(ii) 50. 73(a)(2)(x)

LEVEL (10) 000 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50. 73(a)(2)(iii) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50. 73(a)(2)(iv) OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50. 73(a)(2)(v) 20.2203(a)(2)(iv) 50.36(c)(2) x 50. 73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Fregonese, V. (l&C, Supervisor) (609) 339-1607 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TONPRDS

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IP N

1.1111i111:1*i*llll*lli!j*

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION

'YES (If yes, complete EXPECTED SUBMISSION DATE). XINO DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On April 3, 1993, in Unit 2, while de fueled, an inadvertent actuation of the Cardox(C02) System occurred in the electrical penetration area. This actuation was attributed to water intrusion into the Fire Zone 98 Penetration Area C02 Relay enclosure cabinet. The water provided a bridge across the relays causing the system manual switch tag-out to be bypassed and the system actuated. Based on the post event report, this actuation caused both trains of the Reactor Vessel Level Indication System (RVLIS) to become inoperable. An Unusual Event was declared due to the discharge of toxic gas. This report is provided to discuss and report the 1993 event as it relates to the loss of RVLIS under 10 CFR 50.73(a) (2) (vii) (D) ; an event where a single cause or condition caused two independent trains or channels to become inoperable in a system designed to mitigate the consequences of an accident. This condition was determined to be applicable to both units.

Corrective actior:s include reviewing the configuration of the RVLIS equipment and determining corrective actions, and performing a review to identify and evaluating the potential for affecting other redundant safety related equipment due to a single event (i.e., C02 system actuation) .

NRC FORM 366 (4-95)

NRC FORM 366A (4-95)

• LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

• U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER I REVISION NUMBER Salem Unit 1 05000272 95 - 021 - 00 2 OF 6 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

PLANT AND SYSTEM IDENTIFICATION Westinghouse - Pressurized Water Reactor Reactor Vessel Level Indication System - EIIS Identifier {IP}

Fire Protection System - Cardox (C02) - EIIS Identifier {KP}

IDENTIFICATION OF OCCURRENCE Event Date: April 3, 1993 Discovery Date: August 21, 1995 Date Determined to Be Reportable: September 15, 1995 Report Date: October 15, 1995 CONDITIONS PRIOR TO OCCURRENCE Operational Mode: Defueled (Salem 2)

Reactor Power: Defueled (Salem 2)

Description of Occurrence On April 3, 1993, in Unit 2, while defueled, an inadvertent actuation of the Cardox(C02) System occurred in the electrical penetration area. The cause of the inadvertent actuation was attributed to water intrusion into the Fire Zone 98 Penetration Area C02 Relay enclosure cabinet. The water provided a bridge across the relays No. 6 and 7 contact points causing the system manual switch tag-out to be bypassed and the system actuated.

Based on the post event report, this actuation caused both trains of the Reactor Vessel Level Indication System (RVLIS) to become inoperable. An Unusual Event was declared due to the discharge of toxic gas. This report is provided to discuss and report the 1993 event as it relates to the loss of RVLIS under 10 CFR 50. 73 (a) (2) (vii) (D); an event where a single cause or condition caused two independent trains or channels to become inoperable in a system designed to mitigate the consequences of an accident. This condition was determined to be applicable to both units.

According to the post-event investigation report, the cause of the water source was believed to be related to work performed on the overhead Chiller/Condenser Service Water Supply pipe. The water found a path through conduits into the C02 relay enclosure to the RH9 holding relay.

Following the C02 actuation in Unit 2, and based on the information available, this event caused both trains of RVLIS to be inoperable.

According to the report, RVLIS Control Room Display Train A Cavity Level indication was offscale low and Train B Cavity Level indication was offscale high. On April 6, 1993, a Westinghouse representative reviewed the RVLIS equipment. To return RVLIS to operable status, a Train A leaking capillary was repaired, and a Train B transmitter was replaced.

NRC FORM 366A (4-95)

NRC FORM 366A (4-95)

• LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

• U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER I REVISION NUMBER SALEM - Unit 1 05000272 95 -- 021 - 00 3 OF 6 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Description of Occurrence (Cont'd)

RVLIS was inoperable for approximately 2 1/2 weeks. Although other testing and repairs on RVLIS occurred, these other repairs were not attributed to the C02 discharge.

The post-event investigation primarily focused on the cause and the corrective actions for the C02 inadvertent actuation. There was mention of the RVLIS issue only in that it had been repaired and returned to service and that engineering was requested to review the design and configuration. An Engineering Work Request (EWR) was issued on April 30, 1993 requesting that engineering review the configuration of the RVLIS equipment and determine the potential impact of C02 system actuations.

This EWR remains open to date.

On August 21, 1995, as a result of the PSE&G system readiness review process, this open item was re-evaluated. After researching the past C02 actuation and the attendant loss of both channels of RVLIS, it was determined on 9/15/95 that the 1993 loss of RVLIS should have been reported to the NRC.

Analysis of Occurrence The RVLIS uses three sets of differential pressure (dp) cells. All of the dp cells are located outside of the containment to minimize post-accident environmental effects. This design satisfies Regulatory Guide (RG) 1.97, category 1, type B requirements. A review was performed to determine if this event or condition had been reported in accordance with the LER rule.

The review determined that it had not been properly reported. The RVLIS is a redundant safety related system. The reporting requirements are designed to inform the NRC of single events where a single cause or condition caused two independent trains or channels to become inoperable in a system designed to mitigate the consequences of an accident. RVLIS is a monitoring system and does not provide a control function. However, RVLIS is used as a decision making data point by the operators in the Emergency Operating Procedures (EOPs) in the event of a LOCA. False indications in the RVLIS system could potentially cause an operator action which prevents mitigation of the accident condition. It is on this basis that this event is determined to be reportable.

The Design Change Packages which installed the RVLIS did not recognize that RVLIS would be affected by actuation of the CO~ system. The nearest C02 nozzle is located approximately 20 feet away from the RVLIS.

These types of events were first recognized as being significant and NRC FORM 366A (4-95)

NRC FORM 366A (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

• U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER I REVISION NUMBER SALEM - Unit 1 05000272 95 - 021 - 00 4 OF 6 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Analysis of Occurrence (Cont'd) brought to the industry's attention through the event at Surry Power Station, as described in Information Notice 86-106, Supplement 2, dated March 18, 1987. In this event, the water leaking from a failed feedwater pipe entered the fire protection control panels thruugh open conduits.

Within a few minutes, shorting of the fire protection control circuits caused the contents of the C02 storage tank to discharge into the cable tray rooms leaving the station without carbon dioxide in the event of a fire.

During the construction phase at Hope Creek, an inadvertent actuation of the C02 system occurred as a result of water intrusion through unsealed conduits. Other C02 discharge events have occurred but are attributed to different and unrelated reasons. None of these events resulted in the loss of both trains of equipment necessary to mitigate the consequences of an accident. The actuation of the C02 system at Salem in 1993 due to water intrusion demonstrates that actions taken in response to the Surry event were not effective. The lessons learned from the Surry and Salem 1993 event are being reviewed to determine if additional corrective actions are required.

According to the post-event investigation report, RVLIS operability was restored and sealing recommendations were made for all Salem C02 fire protection cabinets. Engineering is reviewing the effect of C02 actuation on the RVLIS system to determine if additional corrective actions are required.

As was previously stated, an EWR was issued to address the configuration of the RVLIS equipment and determine the potential impact of C02 system actuations. Investigation revealed that the EWR remains open and is indicative of untimely corrective action implementation. The cause of the untimely corrective actions was the low priority given to resolving the EWRs and the allowance for the Incident Report to close on the basis that an EWR was generated. In regard to the untimely action on the EWR, the closure of the initial Incident Report, and the failure to identify this condition as reportable, the following actions were taken. In July, 1995, the corrective action program was significantly revised to ensure that conditions adverse to quality (CAQ) are documented and that operability and reportability are promptly assessed. Further, the program requires that deficiencies be corrected in a timely manner commensurate with their importarce to safety. The CAQ may not be closed without resolution of attendant work requests.

Screening of existing EWRs is underway. This screening include~ a review of open EWRs to ensure that items affecting equipment are properly NRC FORM 366A (4-95)

NRC FORM 366A (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

• U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER I REVISION NUMBER SALEM - Unit 1 05000272 95 -- 021 - 00 5 OF 6 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Analysis of Occurrence (Cont'd) prioritized and dispositioned, as appropriate, prior to restart.

Prior Similar Occurrences There have been no other similar reportable occurrences identified relative to C02 discharge and systems interaction.

Safety Significance Actual The RVLIS is a post accident monitoring system. Disabling of redundant RVLIS trains occurred while the plant was in an outage condition. At the time of the event, RVLIS was not required to be operable per the Technical Specifications since the unit was defueled. Therefore, the event had no significant safety consequences.

Potential In the event of a LOCA, RVLIS is used as a decision making data point by the operators in the Emergency Operating Procedures (EOPs). False indications in the RVLIS system could potentially cause an operator action which prevents mitigation of the accident condition.

Should both channels of RVLIS become inoperable at power, other instrumentation is available for monitoring inadequate core cooling.

• Reactor Coolant System(RCS) ~T less than full load ~T,

• RCS or core exit thermocouple temperatures constant or decreasing,

• Steam Generator pressure constant or decreasing at a rate of decrease of RCS temperatures while maintaining steam generator level with continuous auxiliary feedwater.

A further guide for recognition of inadequate core cooling is a computerized subcooling monitor. The EOPs were revised to address the use of this processor output.

Cause of the Event The cause of the event was inadvertent C02 actuation due to water intrusion. A contributing cause was the failure to adequately evaluate the Surry operating experience as it relates to C02 actuation due to water intrusion.

NRC FORM 366A (4-95)

NRC FORM 366A (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

• U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER I REVISION NUMBER SALEM - Unit 1 05000272 95 - 021 - 00 6 OF 6 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Cause of the Event (Cont'd)

The cause of the untimely corrective actions was attributed to the low priority given to EWRs. A contributing cause was also determined to be an inadequate corrective action program in that the Incident Report was broughL to closure status on the basis that an EWR was generated.

Corrective Actions

1. RVLIS and cabinet sealing repairs were completed in 1993.

2. The adequacy of design, implementing and maintenance procedures will be evaluated and corrected as necessary to ensure that interactions from the C02 systems are considered. This evaluation is expected to be completed by March. 31, 1996.

• 3. The response to the Surry event and internal operating experience will be reviewed to ensure that the issue relative to water intrusion into C02 systems is adequately addressed. This review is expected to be completed prior to February 29, 1996.

4. Required actions for RVLIS as a result of the EWR review will be completed prior to Mode 3. This includes design/licensing basis review of the RVLIS System.

5. A review will be performed to identify and evaluate potential adverse effects on redundant safety related equipment cue to a C02 system actuation. This review is expected to be completed by February 29, 1996.

A supplement to this LER will be provided in the event that additional modifications are identified due to system interactions with the C02 system.

NRC FORM 366A (4-95)