ML18100A621

Special Rept 93-4:on 930910,radiation Monitoring Channels 2R45B & 2R45C Inoperable Greater than Seven Days.Caused by Design Deficiency.Corrected by Separating Monitors Reference & Chassis Grounds

ML18100A621
Person / Time
Site:	Salem
Issue date:	09/17/1993
From:	Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
93-4, NUDOCS 9309280150
Download: ML18100A621 (3)

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Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station September 17, 1993 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 SPECIAL REPORT 93-4 This Special Report addresses the inoperability of the Radiation Monitoring System (RMS) channels 2R45B and 2R45C Plant Vent medium and high range noble gas monitors for greater than seven (7) days.

This report is submitted for informational purposes in accordance with Technical Specification 3.3.3.1 Action 26 pursuant to Specification 6.9.2.

sincerely yours,

c. A. Vondra General Manager -

Salem Operations MJPJ:pc Distribution 9309280150 930917 PDR ADOCK 05000311

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SPECIAL REPORT NUMBER*-4 i PLANT IDENTIFICATION:

Salem-Generating Station - Unit 2 Public Service Electric & Gas Company Hancock's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

Radiation Monitoring Channels 2R45B and 2R45C inoperable for greater than seven days Event Date(s): 9/10/93 Report Date: 9/17/93 This report was initiated by Incident Report No.93-372 which identifies a September 3, 1993 failure of the 2R45 Radiation Monitoring System (RMS) channels. The 2R45 RMS channels have not been returned to service within seven days; therefore, this Special Report is required in accordance with Technical Specification 3.3.3.1.b Table 3.3-6 Action 26 which 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 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 schedule for restoring the system to OPERABLE status."

CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 (Power Operation) Reactor Power 100% Unit Load 1130 MWe DESCRIPTION OF OCCURRENCE:

On September 3, 1993, at 0810 hours0.00938 days <br />0.225 hours <br />0.00134 weeks <br />3.08205e-4 months <br />, the 2R45B and 2R45C RMS channels (medium and high range Plant Vent noble gas monitors) were declared inoperable due to spurious *actuations-of the CT-2B "HIGH" (radiation) alarm. The channels were removed from service_and troubleshooting was initiated.

APPARENT CAUSE OF OCCURRENCE:

The root cause of th.is event is design deficiency. The monitors' chassis and reference grounds are tied together through the annunciator card mounting screws and metal standoffs. This results in susceptibility of the monitors' annunciator card to noise-induced spikes, causing inadvertent "HIGH" alarm relay actuations. These spikes were observed during manipulation of the CT-2B control panel

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\ APPARENT CAUSE OF OCCURRENCE: (cont'd) arawer. Following discussion with the ven~or, it was recognized that the symptoms our equipment displayed could be ~orrected utilizing*

circuitry card nylon standoffs to separate the monitors' chassis and reference grounds~

ANALYSIS OF OCCURRENCE:

The 2R45B and 2R45C channels monitor the Plant Vent radioactive noble gas releases via representative sampling. The 2R45B monitor is a medium range monitor and the 2R45C channel is a high range monitor.

They are both required in operating modes 1 - 4 (power operation to Hot Shutdown). Their purpose is to monitor significant releases *of radioactive materials in compliance with the Updated Final Safety Analysis Report (UFSAR) and federal regulation.

CORRECTIVE ACTION:

This problem will be corrected by separating the monitors' reference and chassis grounds. Per vendor recommendation, non-conducting (nylon) standoffs have been ordered and will be installed in place of the metal standoffs on both Salem units. This should eliminate susceptibility of the monitors to noise-induced spikes. Following receipt and installation of necessary repair parts, the Unit 2 monitors will be returned to service within a week.

~~~

General Manager -

_Salem Operations MJPJ:pc SORC Mtg.93-084