ML18106A859

Special Rept:On 980816,RMS Channel 1R15 Inoperable for Greater than Seven Days.Cause Is Under Investigation. Replacement of Detector Assembly W/Higher Temperature Rated Detector to Mitigate Effects to Be Completed by 981019

ML18106A859
Person / Time
Site:	Salem
Issue date:	08/31/1998
From:	BAKKEN A C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LR-N980422, NUDOCS 9809090222
Download: ML18106A859 (3)

Text

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• Publ!c Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038-0236 Nuclear Business Unit U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:

AUG 311998 LR-N980422 SALEM GENERATING STATION UNIT NO. 1 LICENSE NO. DPR-70 DOCKET NO 50-272 SPECIAL REPORT The attached special report addresses the inoperability of Unit 1 Radiation Monitoring System Channel 1R15 for greater than seven days. This report is submitted pursuant to Technical Specification 6.9.2 and is in accordance with Technical Specification Table 3.3-6 ACTION 23, item 2. Attachment C Administrator

-Region I Sincerely, 1 /J'r:J A. C. Bakken..::zzL General Manager Salem Operations Unit States Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 /PJD Distribution LER File 3.7 9809090222 980831 PDR 05000272 S PDR 1111' 1 '1 *\\ t'r ism 1,*l iur h.mds. I *. / ; I , I , .r ; 95-2168 REV. 6194

• AUG311998 ATTACHMENT TO LR-N980422 Radiation Channel 1R15 continuously monitors ttie discharge from the condenser air removal exhaust header for gaseous radioactivity.

The monitor is also used to provide an indication of steam generator primary system to secondary system leakage. The discharge of the condenser air removal system is routed to the plant vent. The 1R15 detector is located in a shielded sample chamber that is located directly in the discharge header from the air removal system. The 1R15 monitor is expected to perform its function when condenser vacuum is established and there is process flow. The 1R15 channel has a history of problems which are documented back to the mid 1980's. As the system was out of service during the Unit 1 extended shutdown, experience -between mid 1995 to early 1998 was not available.

Recent experience has shown increased problems with the channel. The problems appear to be warm weather associated.

On August 16, 1998 the channel failed in high alarm. The 1R15 channel has failed on four separate occasions in the last 2 months. Based on these failures, the channel will remain inoperable until the corrective actions discussed below are incorporated.

Technical Specification 3.3.3.1, Table 3.3-6 item 2.b.4) requires that 1R15 be operable in Modes 1-4. With 1R15 inoperable, Table 3.3-6, Action 23 was taken. This action requires that a preplanned alternate method of monitoring be initiated, and the channel be restored to operable status within 7 days or a special report submitted.

The preplanned alternate method of monitoring was initiated within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in accordance with Technical Specifications.

However, since 1R15 has been inoperable for greater than 7 days, this special report is also being submitted.

The cause of this occurrence is under investigation.

At this point in the investigation, condensation, moisture intrusion and high temperature effects on the detector are believed to be the most probable contributors to the monitor failure. Failure symptoms have been duplicated during bench testing via high .heat and humidity. (Unit 2 radiation monitor, 2R15, is a different original design in a similar application.

2R15 does not exhibit the same problem as 1R15.) Corrective actions include replacement of the detector assembly with a higher temperature rated detector in an effort to mitigate the effects of the high temperature environment.

The replacement will be completed by October 19, 1998. Procurement of the replacement detector is expected October 5, 1998. It is expected that the replacement will return the channel to a technical specification operable status. Methods to mitigate the effects of condensation on the detector are being evaluated.

Other Industry experience is being AUG*s 11998 ATTACHMENT TO LR-N980422 . considered with regard to mitigation of condensation and temperature.

The failed detectors are being sent to the vendor for failure analysis to help confirm the cause and define the effective corrective actions. Upon conclusion of the investigation, and evaluation of the success of the replacement detector, additional corrective actions may be implemented as required.

The investigation is expected to be completed by October 31, 1998. Evaluation of the effects of the replacement detector will require sufficient warm weather operating experience and may involve operation through the summer of 1999. An additional concern exists with the condenser air ejector radiation monitors' associated alarm setpoints.

These setpoints are used as part of Salem's primary to secondary system leakage detection program. Use of the radiation monitors for primary to secondary leakage decision making requires knowledge of two factors to convert the monitor response to gallons per day (GPO) value. The factors are Reactor Coolant system (RCS) radioactivity concentrations and vacuum pump exhaust process flowrate at the radiation monitor. The current alarm setpoints were developed using 1987 empirical data. Current RCS activity is improved over the levels which existed in 1987 due to improved fuel performance.

As a result a greater GPO is required to reach the alarm setpoints.

It should be* noted that the setpoints are conservative with respect to the technical specification limit for primary to secondary leakage and the alarm setpoint specified in Table 3.3-6. A calculation is being developed to provide setpoints based on the current RCS radioactivity concentrations and vacuum pump exhaust process flowrate consistent with EPRI guidelines.

This calculation and associated procedure changes for Salem Unit 1 and 2 are expected to be complete by October 15, 1998. As described above, corrective actions will be completed in three phases. The first phase will return the channel to a technical specification operable status (operable and available status). We expect this will be accomplished by replacement of the detector as described above. The second phase will involve completion/implementation of setpoint calculations to allow enhanced detection of primary to secondary leakage detection at the EPRI guideline levels in accordance with the leakage detection program. The third phase would involve any further corrective actions, including possible design changes, indicated by the results of the ongoing investigation and the success of the replacement detector.

This will likely require operating experience in the summer of 1999. 2