ML18096A218

LER 91-010-00:on 910723,ESF Actuation Signals Initiated. Caused by High Channel Spike on Channel 2R1B & Noble Gas Monitor 2R45C Due to Faulty Equipment Design.Detector Assembly Replaced & Design Mods underway.W/910815 Ltr

ML18096A218
Person / Time
Site:	Salem
Issue date:	08/15/1991
From:	Pollack M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-010-02, LER-91-10-2, NUDOCS 9108260024
Download: ML18096A218 (6)

Text

Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Je.rsey 08038 Salem Generating Station

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

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO.. 50-311 UNIT NO. 2 LICENSEE EVENT REPORT 91-010-00 August 15, 1991 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations lOCFR so;73(a) (2) (iv). This report is required within thirty (30) days of discovery.

• MJP:pc Distribution

... : 1 i e En er o * .. * :-!_*, * . .} t c 910815 PDR ADOCK 05000311 c PDR Sincerely yours, 1/CJ-V4r;, C. A. Vondra tr7 G-'(./ General Manager -Salem Operations 95-2189 (10MJ 12-89 NRC FORM 366 (6-89) U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMS NO. 3150-0104 EXPIRES: 4/30/92 LICENSEE EVENT REPORT (LERI ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. FACILITY NAME (1) Salem Generating Station -Unit 2 'DOCKET NUMBER (21 I PAGE 131 o I 5 I o I o I o I 3 1 1 1 1 I 1 OF n I ') TITLE (4) 2 ESF Actuation Signals: Cont. Vent. Isol. & Auto Switch *6f Control Rm Vent. EVENT DATE (5) LER NUMBER (61 REPORT DATE (7) OTHER FACILITIES INVOLVED (81 MONTH DAY YEAR YEAR ::::::::::

SEQUENTIAL)'::::::::.

REVISION MONTH ::::::::'.:

NUMBER NUMBER DAY YEAR FACILITY NAMES DOCKET NUMBER(SI q 7 213 9 1 9 I 1 -o 11 10 -o 10 o 1 s 115 9 I 1 01s1010101 I I OPERATING MODE (9) 1 THIS REPORT IS SUBMITTED PURSUANT TO THE OF 10 CFR §:(Check one or more of the following}

(111 20.402(bl 20.405(c) x 50,73(o)(2)(iv)

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LICENSEE CONTACT FOR THIS LEA (121 NAME AREA CODE M. J. Pollack -LER Coordinator CAUSE SYSTEM COMPONENT COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (131 REPORTABLE

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I I I I I I I SUPPLEMENTAL REPORT EXPECTED 1141 MONTH DAY YEAR n YES (If yes, complete EXPECTED SUBMISSION DATE} bl NO ABSTRACT (Limit to 1400 spsctJs, i.e., approximately fifteen single-space typewritten Unes} 116) EXPECTED SUBMISSION*

DATE (151 I I This Licensee Event Report addresses two (2) Engineered Safety Feature (ESF) signals initiated through the Radiation Monitoring System (RMS}. One ESV signal was for the automatic switching of the Control Room ventilation from normal to the emergency mode of operation (100% recirculation}

and the other for a Containment Purge/Pressure-Vacuum Relief (CP/P-VR)

System isolation.

Both events occurred on July 23, 1991. The cause of the Control Room Ventilation switch was a high channel spike on the 2R1B RMS channel (Control Room Ventilation Intake Duct monitor).

The cause of the Containment Ventilation Isolation signal was a high channel spike on the 2R45C (Plant Vent High Range Noble Gas monitor) channel which caused the Plant Vent Noble Gas RMS channels (2R41C respectively) to de-energize.

The root cause of the 2R1B channel spike is equipment design. The 2R1B RMS channel monitor is a Victoreen 843-22, Beta Scintillator.

Periodic problems with the Victoreen system have been experienced, as indicated in prior LERs (e.g., 311/90-040-00).

Also, the Salem Unit 2 RMS is susceptible to voltage transients.

Investigation of the 2RlB channel CP/P-VRS isolation signal did not identify any failed components.

The root cause of the 2R45C channel spike is equipment failure. A resistor in the detector assembly was found to have one of its connections broken. The assembly was subsequently replaced.

NRC Form 366 (6-891 I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION . Salem Generating Station Unit 2 DOCKET NUMBER 5000311. PLANT AND SYSTEM IDENTIFICATION:

Westinghouse

-Pressurized Water Reactor LER NUMBER 91-010-00 PAGE 2 of 5 Energy Industry Identification System (EIIS) codes are identified in the* text as {xx) IDENTIFICATION OF OCCURRENCE:

2 Engineered Safety Feature signals initiated from the Radiation Monitoring System Event Date: 7/23/91 Report Date: 8/15/91 This report was initiated by Incident Report *Nos.91-502 and 91-503. CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 Reactor Power 100% -Unit Load 1120 MWe DESCRIPTION OF OCCURRENCE:

This Licensee Event Report addresses two (2) Engineered Safety Feature (ESF) signals initiated through the Radiation Monitoring System (RMS) {ILi. One ESF signal was for the automatic*

switching of the Control Room ventilation

{VII from normal to the emergency mode of operation (100% recirculation) and the other for a Containment Purge/Pressure-Vacuum Relief (CP/P-VR)

System {BF) isolation.

Both events occurred on July 23, 1991. On Jtily 23, 1991, at 1236 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.70298e-4 months <br />, the Control Room Ventilation Intake Duct RMS channel (2R1B) spiked high. This resulted in Control Room ventilation switching to the emergency mode of operation for both Salem Units (by design). On July 23, 1991 at 1732 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.59026e-4 months <br />, the high range Plant Vent noble gas radiaiion monitor (2R45C) channel spiked high. This caused the Plant Vent Noble Gas RMS channel (2R41C) to de-energize resulting in a CP/P-VR System isolation signal (by design). Technical Specification 3.3.3.1 Action b26 (for 2R45C channel inoperability) was entered at the time of the event. It states: "With the number of OPERABLE Channels less than required by the Minimum Channels OPERABLE requirements, initiate the preplanned alternate method of monitoring the appropriate parameter(s), within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and: 1) either restore the inoperable Channel(s) to OPERABLE status within 7 days of the event, or 2) prepare and submit a Special Report to the Commission LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 2 DESCRIPTION OF OCCURRENCE:

DOCKET NUMBER 5000311 (cont'd) LER NUMBER 91-010-00 PAGE 3 of 5 pursuant to Specification 6.9.2 within 14 days following the event outlining the action taken, the cause of the inoperability and the plans and restoring the system to OPERABLE status." The Nuclear Regulatory Commission (NRC) was notified of each ESF actuat_ion in accordance with Code of Federal Regulations lOCFR 50.72(b) (2) (ii) on July 23, 1991 at 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> and 1932 hours0.0224 days <br />0.537 hours <br />0.00319 weeks <br />7.35126e-4 months <br />, respectively.

APPARENT CAUSE OF OCCURRENCE:

The root cause of the 2RlB channel spike is equipment design. The type of detector system used for the majority of the Salem Unit 2 RMS channels is manufactured by Victoreen.

The 2R1B RMS channel monitor is a Victoreen 843-22, Beta Scintillator.

Periodic problems with the Victoreen system have been experienced, as indicated in prior LERs (e.g., 311/90-04"0-00).

Aiso, the Salem Unit 2 RMS is susceptible to voltage transients.

Investigation of the 2R1B channel CP/P-VRS isolation signal did not identify any failed components.

Detailed visual inspections were conducted.

No *concerns.were noted (e.g., backplane pins appeared and detector connections were intact). A channel calibration was performed and successfully completed.

The root cause of the 2R45C channel spike is equipment failure. A resistor i'n the detector assembly was found to have one of its connections broken. 2R1B -ANALYSIS OF OCCURRENCE:

The 2R1B channel continuously monitors air from the HVAC intake duct into the Unit 2 Control Room. This monitor consists of four parallel Geiger-Mueller (GM) tubes. When any of the four GM tubes reaches the alarm setpoint the monitor actuates an alarm and initiates closure of the duct intake valve to prevent contaminated air from entering the Control Room. During the time the 2R1B channel was inoperable, the 2R1A Control Room General Area Monitor RMS channel remained operable.

It did not indicate any significant increase in radiation levels. The 2RlA RMS channel also has the same automatic ESF function for Control Room ventilation isolation.

Upon receipt of the 2R1B .high channel spike, a Control Room air sample was initiated by Radiation Protection.

No significant increase in airborne activity was identified.

As indicated previously, automatic switching of the Control Room ventilation system to the accident mode of operation, was not caused LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 2 2R1B -ANALYSIS OF OCCURRENCE:

DOCKET NUMBER 5000311 (cont'd) LER NUMBER 91-010-00 PAGE 4 of 5 by an actual high radiation

• Therefore, the health and safety of the public was not affected by this event. However, since the switching to the accident mode of operation by the control room ventilation system is an ESF actuation, this event is reportable in accordance with the Code of Federal Regulations lOCFR 50. 7 3 (a) ( 2) (iv)

• 2R45C -ANALYSIS OF OCCURRENCE:

Isolation of the CP/P-VRS is part of the design Engineered Safety Features (ESFs) . mitigates the release of excessive quantities of radioactive material to the environment after a design base accident.

The 2R45C channel is interlocked with the 2R41 detectors and sample pump to cause them to de-energize upon reaching the high radiation level setpoint.

This is to protect the 2R41 channel detectors.

When the 2R41C detector is de-energized, an ESF CP/P-VRS isolation signal is generated, as per conservative design. The 2R41C channel monitors plant vent effluent releases for radioactive noble gas via representative sampling.

The ESF actuation feature of CP/P-VRS isolation, associated with this channel, is of conservative design. It is redundant to the 2R12A channel. In addition to its ESF function, the channel closes the 2WG41 valve (Waste Gas Decay Tank Vent Control Valve). At the time of this event, neither Containment Purge, Containment Pressure/Vacuum Relief nor Waste Gas Decay Tank release was in progress.

The valves associated with these functions were already in the closed position.

The 2R45C channel detector is an Eberline SA-15 energy compensated GM tube. The inadvertent CP/P-VRS isolation signal was caused by an equipment failure, not the result of high activity.

Therefore, this event did not affect the health or safety of the public. However, due to the actuation of an ESF function, this event is reportable in accordance with Code of Federal Regulations lOCFR 50.73(a) (2) (iv). CORRECTIVE ACTION: As identified in the Apparent Cause of Occurrence section, the investigation of the 2R1B channel CP/P-VRS isolation signal did not identify any failed components.

Detailed visual inspections were conducted and a channel calibration was performed and successfully completed.

On July 24, 1991, the channel was returned to service. After a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> observation period, the channel was declared operable.

Periodic problems with Victoreen RMS equipment have been experienced, as indicated in prior LERs (e.g., 311/90-044-00).

Due to those other LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating.Station Unit 2 r CORRECTIVE ACTION: (cont'd) DOCKET NUMBER 5000311 LER NUMBER 91-010-00 PAGE 5 of 5 events, design modifications are being considered to eliminate the spurious ESF actuation signals. These design modifications include a proposal for RMS channel equivalent replacement.

The 2R45C detector assembly was replaced.

The channel was declared operable and Technical 3.3.3.1 Action b26 was exited on July 26, 199i at 0430 hours0.00498 days <br />0.119 hours <br />7.109788e-4 weeks <br />1.63615e-4 months <br /> upon successful completion of a functional test. MJP:pc SORC Mtg ..91-084 /'

-( 7r General Manager &°'--" Salem Operations