ML18096B351

Special Rept 93-2:on 930310,RMS Channels 2R45B & 2R45C Removed from Svc to Functionally Test Low Flow Differential Pressure.Test Results Showed That Switch Inoperable.Caused by Design Deficiency.Design Mod Being Prepared

ML18096B351
Person / Time
Site:	Salem
Issue date:	03/23/1993
From:	Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
93-2, NUDOCS 9303260147
Download: ML18096B351 (3)

Text

f 0 Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 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 SPECIAL REPORT 93-2 March 23, 1993 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. MJP:pc Distribution 9303260147 930323 PDR ADOCK 05000311 S PDR Sincerely yours, tc. A. Vondra General Manager -Salem Operations 95-2189 REV 7-92 SPECIAL REPORT 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): 3/17/93 Report Date: 3/23/93 This report was initiated by Incident Report No.93-193. CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 (Power Operation)

Rx Power 100% Unit Load 1170 MWe* DESCRIPTION OF OCCURRENCE:

On March 10, 1993, at 1034 hours0.012 days <br />0.287 hours <br />0.00171 weeks <br />3.93437e-4 months <br />, Radiation Monitoring system (RMS) channels 2R45B and 2R45C (medium and high range Plant Vent noble gas monitors) were removed from service to functionally test the low flow differential pressure switch (2PD6866 manufactured by Ashcroft) . Test results showed that the switch was inoperable.

The switch low flow alarm could not be adjusted (i.e., External Fail alarm). Therefore, the channels were not returned to service and remain out of service pending design modifications.

Since the channels have not been returned to service within seven days, 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." The differential pressure switch functional test was performed as a result of information obtained during investigation of a Salem Unit 1 R45 channel External Fail alarm occurring on January 14, 1993 (reference Special Report 272/93-1).

Recent discussion with the manufacturer revealed that the switch is not designed to function under vacuum conditions.

UNIT 2 SPECIAL APPARENT CAUSE OF OCCURRENCE:

The root cause of this event is design deficiency.

The pressure switch, which measures flow through the R45 RMS channels is not designed to work in a vacuum. Technical Specifications required effluent release composite sampling is obtained via hard line connections to the R45 RMS channel tubing. Two (2) 40-liter/minute sample pumps draw effluent release samples from the R45 RMS channel tubing. This creates a vacuum condition affecting the functioning of the differential pressure switch. 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.

At the time of discovery, flow through the Unit 2 R45 RMS channels was found to be within the design requirements.

Therefore, the R45 RMS channels were functioning within their design specifications.

CORRECTIVE ACTION: A design modification is being prepared to remove the differential pressure switch and cap its 2 pressure taps. Its input to the microprocessor External Failure Alarm will be eliminated.

Low flow alarm indication will be wired into the Control Room annunciator alarm system. MJP:pc SORC Mtg.93-025 (;/i3VcL:r Manageg- ll Salem Operations