ML18096A083

LER 91-007-00:on 910522,channel Failure Occurred.Caused by Equipment Design Concerns.Failed Channel Control Module Replaced & Channel Functional Test Successfully Completed. W/910620 Ltr

ML18096A083
Person / Time
Site:	Salem
Issue date:	06/20/1991
From:	Pollack M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-007-02, LER-91-7-2, NUDOCS 9106260244
Download: ML18096A083 (6)

Text

Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station June 20, 1991 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 91-007-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a) (2} (iv). This report is required within thirty (30) days of discovery.

Sincerely yours,

1. Pc. A. Vondra General Manager -

Salem Operations MJP:pc Distribution Ths EnerQY People 9106260244 910620

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• PDR ADOCK 05000:311 f'., JU ~I. *:-.; F'DF<

• .111RC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION 16-89) APPROVED OMB NO. 3150*0104 .

EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP*530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT 13150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER 12) I PAGE (3)

TITLE (4)

Salem Generating Station - Unit 2 I0 I5 I 0 I0 I 0 I 3 1 1 1 1 I 1 IOF 5 I ESF Actuation Signals for CVI: 2Rl2B and lRi:\lC Channel Failures EVENT DATE (5) LER NUMBER 16) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR JJ: SE~~~~~~AL (( ~~~~~~ MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERIS)

Salem Unit 1 o 15 Io 1 o 1 o 12 17 12 oIs 2 2I 9 1 911 - oIo 17 - o lo o16 2 Io 911 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE R~QUIREMENTS OF 10 CFR §: (ChBck ono or morB of th* following) (11)

MODE (9) 2 I

20.402(b) 20.40510) 50.731o)(2)(iv) 73.71(b)

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50.38(c)(1) 50.73(o)(2)(v) 73.71(c)

POWER 20.405(0)(1 )(i)

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..._ 50.73(o)(2)(vii)

,___ OTHER (Spscify in Abstract

~ bolow snd in Tt1xt, NRC Form 20.405(0)(1 )(iii)

- 50.73(o)(2)(i) 50.73(o)(2)(viii)(A) 366AI l!lifliilll!lf1111=

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LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER AREA CODE M. J. Pollack COMPLETE ONE LINE 'FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC-TURER R~6o~;:giE  ::::l'*ili.:_*.*.j:j*:::::*1*1:.._,.:1:.:*:*111...::: CAUSE SYSTEM COMPONENT MANUFAC*

TUR ER I I I I I I I I I I I I I I 1*1:1.:...**1*1::::.:1*:1.*:11:,...:1=1*.. 1:,:J:l*'..

I I I I I I I I I I I I I I SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED h YES 1/f v*s. compl*t* EXPECTED SUBMISSION DATE! El ABSTRACT (Limit to 1400 spaces, i.e., approximately fiftet1n single-space typewrittt1n linos) (16)

NO SUBMISSION DATE 115)

I I I This LER addresses Containment Purge/Pressure-Vacuum Relief System (CP/P-VRS) isolation signals (3 events} (an Engineered Safety Feature (ESF)). Once from the Salem Unit 2 2R12B Containment Iodine Radiation Monitor Radiation Monitoring System (RMS} channel and twice from the Salem Unit 1 1R41C Plant Vent Radioactive Noble Gas Monitor RMS channel. Both RMS channels are manufactured by Victoreen. On May 22, 1991, the 2R12B RMS channel failed low. On May 29, 1991, the 1R41C RMS channel failed low. Tech. Spec. Table 3.3-13 Action 31 was entered.

Investigation of this actuation did not identify the specific cause of the event. Upon successful completion of functional testing, the channel was returned to service (and Tech. Spec. Table 3.3-13 Action 31 exited) on June 3, 1991 at 1735 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.601675e-4 months <br />. On June 3, 1991 at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, during normal power operations, the 1R41C RMS channel again failed low. The channel was declared inoperable and Tech. Spec. Table 3.3-13 Action 31 was re-entered. The root cause of the actuation of the CP/P-VRS isolation signals is attributed to equipment design concerns.

Periodic problems with the Victoreen system have been experienced, as indicated in prior LERs (e.g., 311/90-040-00). Investigation of the second 1R41C channel failure identified the specific cause of the two (2) channel failures. The control module had failed. It was subsequently replaced. Several system design modifications will be implemented.

NRC Form 366 16-89)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 91-007-00 2 of 5 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xxJ IDENTIFICATION OF OCCURRENCE:

Salem Unit 1 and Unit 2 Containment Purge/Pressure-Vacuum Relief System Isolation Signals Due To Equipment Design Concern Event Dates: 5/22/91, 5/29/91 and 6/3/91 Report Date: 6/20/91 This report was initiated by Incident Report No.91-375.

CONDITIONS PRIOR TO OCCURRENCE:

Unit 2: Mode 2 Reactor Power 2% - Unit Load 0 MWe Maintenance Outage completed; Unit restart in progress Unit 1: Mode 1 Reactor Power 100% - Unit Load 1140 MWe DESCRIPTION OF OCCURRENCE:

This LER addresses Containment Purge/Pressure-Vacuum Relief System (CP/P-VRS) fBFJ isolation signals (3 events). Once from the Salem Unit 2 2R12B Containment Iodine Radiation Monitor Radiation Monitoring System (RMS) {IL} channel and twice from the Salem Unit 1 1R41C Plant Vent Radioactive Noble Gas Monitor RMS channel. Both RMS channels are manufactured by Victoreen.

At the time of the three (3) signals, the valves associated with CP/P-VRS were closed. Also, at the time of the 1R41C signal actuations, the 1WG41 valve (Waste Gas Decay Tank Vent Control Valve) was closed, i.e., a Waste Gas Decay Tank relief was not in progress.

On May 22, 1991, 0345 hours0.00399 days <br />0.0958 hours <br />5.704365e-4 weeks <br />1.312725e-4 months <br />, during normal startup operations, the 2Rl2B RMS channel failed low. This resulted in an actuation signal for CP/P-VRS isolation. The channel was declared inoperable.

On May 29, 1991, at 0815 hours0.00943 days <br />0.226 hours <br />0.00135 weeks <br />3.101075e-4 months <br />, during normal power operations, the 1R41C RMS channel failed low resulting in an actuation signal for CP/P-VRS isolation and a closure signal for the 1WG41 valve. The channel was declared inoperable and Technical Specification Table 3.3-13 Action 31 was entered. Investigation of this actuation did not identify the specific cause of the event; therefore, it has been attributed to design concerns as identified by previous LERs (e.g.,

311/90~019-00). The channel was left on (but not returned to service) for two (2) days with no observed problems. Upon successful completion of functional testing, the channel was returned to service (and Technical Specification Table 3.3-13 Action 31 exited) on June 3, 1991 at 1735 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.601675e-4 months <br />.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 91-007-00 3 of 5 DESCRIPTION OF OCCURRENCE: (cont'd)

On June 3, 1991 at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, during normal power operations, the 1R41C RMS channel again failed low resulting in an actuation signal for CP/P-VRS isolation. The channel was declared inoperable and Technical Specification Table 3.3-13 Action 31 was re-entered.

The CP/P-VRS isolation signal is an Engineered Safety Feature (ESF).

The Nuclear Regulatory Commission was notified of the actuation of the CP/P~VRS isolation signals, on May 22, 1991, at 0611 hours0.00707 days <br />0.17 hours <br />0.00101 weeks <br />2.324855e-4 months <br />, on May 29, 1991 at 0916 hours0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.48538e-4 months <br />, and on June 3, 1991 at 2145 hours0.0248 days <br />0.596 hours <br />0.00355 weeks <br />8.161725e-4 months <br /> (respectively),

in accordance with Code of Federal Regulations 10CFR 50.72(b) (2) (ii).

Technical Specification Table 3.3-13 Action 31 states:

"With the number of channels OPERABLE less than required by the Minimum Channels OPERABLE requirement, the contents of the tank(s) may be released to the environment provided that prior to initiating the release:

a. At least two independent samples of the tank's contents are analyzed, and

b. At least two technically qualified members of the Facility Staff independently verify the release rate calculations and discharge valving lineup; Otherwise, suspend release of radioactive effluents via this pathway."

APPARENT CAUSE OF OCCURRENCE:

The root cause of the actuation of the CP/P-VRS isolation signals is attributed to equipment design concerns. The type of detector system used for the Salem Unit 2 RMS channels and the Salem Unit 1 1R41 RMS channels is manufactured by Victoreen. Periodic problems with this system have been experienced, as indicated in prior LERs (e.g.,

311/90-040-00). Also, the Salem Unit 2 RMS is prone to voltage transients.

Investigation of the 2R12B channel and the first 1R41C channel CP/P-VRS isolation signals did not identify any failed components.

Detailed visual inspections were conducted. No concerns were noted (e.g., backplane pins appeared intact). A channel functional test was performed and successfully completed.

Investigation of the second 1R41C channel failure identified intermittent operation of the control module. The module would operate properly part of the time. This failure mechanism is believed to be the cause of the first 1R41C channel failure. It was subsequently replaced.

ANALYSIS OF OCCURRENCE:

The 2R12B RMS channel monitor's the radioactive iodine gas content of

• 1 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 91-007-00 4 of 5 ANALYSIS OF OCCURRENCE: (cont'd) the Containment atmosphere. By design, either a "high" alarm signal or a low channel failure will cause the automatic isolation of the CP/P-VR System.

Air samples are pulled from the Containment atmosphere through a filter paper which continuously moves past the 2RllA (Containment Radioactive Particulate Monitor) detector. The air sample then passes through a charcoal cartridge (monitored by the 2R12B monitor) and is then mixed into a fixed shielded volume where it is viewed by the 2Rl2A (Containment Radioactive Noble Gas Monitor) monitor. The air sample is then returned to the Containment.

The 2Rl1A and 2Rl2A monitors are used to corroborate the 2R12B channel's indications. Neither of these channels indicated any abnormal activity during this event.

The 2R12A Containment Radioactive Noble Gas monitor is the channel taken credit for by the accident analysis for monitoring Containment airborne activity in order to mitigate the consequences of an accident. The 2Rl2A monitor has the capability of automatic isolation of the CP/P-VR System. It remained operable during the course of this event and did not indicate any abnormal Containment airborne activity.

• Isolation of the CP/P-VRS is an ESF. It mitigates the release of radioactive material to the environment after a design base accident.

The 1R41C channel monitor's plant vent effluent releases for radioactive noble gasses. The ESF actuation feature of CP/P-VRS isolation, associated with this channel, is redundant to the 1Rl2A channel. In addition to its ESF function, this channel isolates the 1WG41 valve. During the 1R41C CP/P-VRS isolation signal events, the 1R12A monitor remained operable.

The 1R41C detector is a Victoreen Model 843-22 Beta Scintillator and the 2R12B detector is a Victoreen Model 843-34 Scintillator.

During this event, RCS leakage within the Unit 2 Containment did not increase nor was there any indication of increasing Containment activity as indicated by the 2R12B corroborating RMS channels. Also, no indication of significant Unit 1 plant vent releases were identified at the time of the 1R41C channel failures. Therefore, these events did not affect the health or safety of the public.

However, due to the automatic actuation of an ESF system, they are reportable in accordance with Code of Federal Regulations 10CFR

50. 73 (a) (2) (iv).

On June 10, 1991 at 1930 hours0.0223 days <br />0.536 hours <br />0.00319 weeks <br />7.34365e-4 months <br />, upon completion of 1R41C channel repairs and channel functional testing, the 1R41C channel was returned to service and Technical Specification Table 3.3-13 Action 31 was exited.

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 91-007-00 5 of 5 CORRECTIVE ACTION:

The failed 1R41C channel control module was replaced and a channel functional test was successfully completed.

Upon completion of channel functional testing, the 2Rl2B RMS channel was returned to service.

As indicated in LER 311/90-040-00, Engineering has investigated the concerns with the Victoreen RMS channels. Several system qesign modifications are being investigated to eliminate the spurious ESF actuation signals. These modifications include installation of an uninterruptable power supply {UPS) for Unit 2 and RMS channel equipment replacements. Plans for completion of these modifications have been developed.

General Manager -

Salem Operations MJP:pc SORC Mtg.91-070