ML20246N161

Special Rept:On 890407,discovered That Channel a Indication for Reactor Vessel Level Monitoring Sys Level 6 Not Operating Properly.Caused by Malfunctioning Reactor Vessel Probe.Probe Will Be Replaced w/in-kind Spares

ML20246N161
Person / Time
Site:	San Onofre
Issue date:	05/08/1989
From:	Nandy F SOUTHERN CALIFORNIA EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 8905190357
Download: ML20246N161 (2)

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W Southern California Edison Company P. O DOx 800 2244 WALNUT GPOVE AVENUE HOSE ME AD. CAliFOf'tNIA 91770 TELEPHONE F ft NANDy (818)302 1896 MANAGEH OF NUCLE. AH LICENSING U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C. 20555

Subject:

Docket No. 50-361 Special Report San Onofre Nuclear Generating Station, Unit 2 Pursuant to Technical Specification 3.3.3.6, Table 3.210, Action Statement 22, of Facility Operating License NPF-10 for San Onofre Nuclear Generating Station, Unit 2, this submittal provides the required Special Report involving channel "A" of the Reactor Vessel Level Monitoring System (RVLMS) being out of service for greater than 7 days.

The RVLMS consists of the "A" and the "B" channels. Each channel consists of a probe which contains eight heated junction thermocouple (HJTCs) providing indication for eight different levels in the reactor vessel (RV). Three of the HJTCs (1, 2, and 3) are located in the RV head region and the remaining five (4, 5, 6, 7, and 8) are located in the RV outlet plenum. The TS requires that one or more of the three HJTCs in the RV head region and three or more of the five HJTCs in the RV outlet plenum be operable for the respective RVLMS channel to be considered operable.

On 04/07/80 _with_1 nu e at lout. power, roiftine c'omputer dper'ator surveillance on the Qualified Safety Parameter Display System (QSPDS) discovered that channel "A" indication for RVLMS level 6 was not operating properly. RVLMS channel "A" was conservatively removed from service on 04/11/89 to allow troubleshooting the HJCTs. Results of the troubleshooting effort determined that a malfunctioning RV probe for the eight HJTCs caused the improper operation. As corrective action, each of the existing probes for Unit 2 RVLMS channel "A" and channel "B" will be replaced with in-kind spares. Since the probes can not be replaced with the plant in operation and RVLMS channel "B" remains operable, replacement of the Unit 2 probes is planned for the Cycle 5 refueling outage currently scheduled for September 1989.

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.. 1 Document Control Desk' May 8, 1989 Plans to replace the existing RVLMS HJTC probes at SONGS 2 and 3 with a new

,. design are under evaluation. The existing probes were the first generation 1' probes designed and built by Combustion Engineering (CE).. CE has modified the design and the newer probes are expected to be more suitable for long term-service. The new modified design is planned to be implemented at Unit 3 during

~the Unit 3 Cycle 5 refueling outage.

Please contact us if we can be of further assistance.

Sincerely, cc: J. B. Martin (Regional Administrator, USNRC Region V)

F. R. Huey (USNRC Senior Resident Inspector, Units 1, 2, and 3)

Institute of Nuclear Power Operations (INPO)

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