IR 05000309/1985027
| ML20205B751 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 09/04/1985 |
| From: | Elsasser T, Holden C, Robertson J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20205B742 | List: |
| References | |
| 50-309-85-27, NUDOCS 8509120217 | |
| Download: ML20205B751 (3) | |
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I U.S. NUCLEAR REGULATORY COMMISSION
REGION I
Docket / Report: 50-309/85-27 License:
DRP-36 Licensee:
Maine Yankee Atomic Power Company Inspection at: Wiscasset, Maine
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Dates:
September 3-4, 1985 Inspectors:
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- 4//pr C. Holden, Senior Resident Inspector
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Summary:
Inspection on September 3-4, 1985 (Report No. 50-309/85-27)
Areas Inspected:
This special inspection (15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />) was conducted to determine the circumstances surrounding the discovery of the inoperable Channel A low Steam Generator Pressure trip for the Reactor Protective System.
The inspection involved a review of plant systems involved, documentation reviews, and interviews with i
plant personnel.
Results: One violation was found.
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DETAILS 1.
Description of the Event On September 3, 1985, plant Instrument and Control (I&C) technicians were conducting a routine refueling surveillance of the Reactor Protective System (RPS).
The objective of this procedure, 3-6.2.1.2, Prot :ctive and Safeguard Channel Calibration for Steam Generator Pressure, is to calibrate the Steam Generator Pressure Protective channels and conduct a logic verification of the Feedwater Valve Trip and Feedwater Train Trip.
During the course of the procedure, Channel A for the Low Steam Generator Pressure Trip was found in-operable. An investigation revealed that Channel A had been inoperable for all of Cycle 8 operations.
2.
Cause of the Event The licensee performs two types of surveillances on the RPS.
A monthly check is performed during plant operations to check the trip bistable to ensure that it trips at the proper setpoint.
The other surveillance is performed on a refueling interval and inputs a signal into the process loop and sets the trip setpoint.
Procedure 3-6.2.1.2 controls the refueling interval calibration of Steam Generator Pressure.
During this procedure, an electrical signal is generated on each of the three Channel A Steam Generator (S/G) instrument loops. One of the S/G pressure signals is reduced to the trip setpoint of 485 psig while the other two pressure signals remain at 850 psig.
When Chan-nel A did not trip the RPS as anticipated, an investigation was initiated.
The cause of the failure of Channel A to trip was determined to be a common ground which placed the RPS dropping resistors in parallel. With two S/G pressure transmitters generating a current reflective of 850 psig, the voltage drop across the RPS resistor for the third S/G was not sufficient to cause the RPS bistable to trip.
During the last refueling outage the plant installed subcooling margin moni-tors (SMM).
This modification, performed under an Engineering Design Change Request (EDCR 83-32), installed a resistor and a common ground for each of the three Channel A instruments. At the conclusion of the outage a functional test of the SMM was performed satisfactorily.
No functional test of the Reactor Protective System was performed.
A review of the surveillance data for the last outage revealed that the re-fueling interval calibration of the Low S/G Pressure Instrument was performed on April 22, 1984.
A review of EDCR 83-32 revealed that the EDCR 83-32 for the SMM was installed on or about May 21, 1984.
Therefore, the calibration which had the ability to detect the effect of the modification on the RPS was not performed until this (August 1985) outage. As a result, Channel A Low Steam Generator Pressure was inoperable for the entire Cycle 8 operations.
Technical Specifications (TS) Section 3.9 requires that three channels of low S/G pressure be operable when the reactor is in power operations.
Two chan-nels are permissible providing one channel is placed in the trip conditio r
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During monthly calibrations of the RPS, one channel is removed from service in the bypass mode. With Channel A inoperable, each time Channels B, C, and D were removed from service for monthly surveillance, the minimum number of channels were not available for the Reactor Protective System.
This is a violation of Technical Specifications (VIO 309/85-27-01).
We note that as reported in Inspection Report 85-19, Channels B, C, and D were not available to perform their intended safety function since June 22, 1984.
Hence, with Channel A also inoperable, all steam generator pressure safety channels were inoperable for all of Cycle 8.
3.
Exit Interview Meetings were periodically held with senior facility management to discuss the inspection scope and findings.
A summary of the findings was presented to the licensee at the end of the inspection.
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