ML19317F800
| ML19317F800 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/04/1975 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19317F799 | List: |
| References | |
| NUDOCS 8002210561 | |
| Download: ML19317F800 (2) | |
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7 SACRAMEtsTO MU:ltCIPAL UTILITY DISTRICT C 6201 S Street. Box 15830. Sacramento. California 95813:.(016) 452-3211 April 4, 1975 Director Division of Reactor Licensing f
U.S.- Nuclear Regulatory Commission Washington, D.C.
20545-Re: Operating License DPR-54 Docket No. 50-312 Rancho ~ Seco Nuclear Generating Station Unit No. One Abnormal' Occurrence No. 75-4
Dear Sir:
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o As defined by Proposed Amendment No. 30 to Technical Specifications.
-for the Rancho Seco Nuclear' Power Station, Section 6.9.1 and Regulatory Cuide 1.16, Rev. _3, Section C.2.a(1), we are reporting the following Abnormal Occurrence as A0 75-4.
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' s, On. March 11, 1975, Abnormal occurrence 75-3 was submitted to NRC concerning a pressure transmitter drift in the Reactor Protection' System.
The pressure transmitter was replaced and a commitment was made to verify the calibration of the remaining RPS pressure transmitters within 60 days.
The transmitters w te checked on March 25 and three of the four units.T were found outside the "Re ctor Protection System Trip Setting Limits" o'f Technical Specifications Table 2.3-1.
The transmitters had drif ted greater ;
than the original prediction of +4 psig.
Bistable trips were set to 1904 psig for the low pressure trip and 2351 psig for the high pressure trip.
Set;at these values and using the maximum setpoint drift of 4 psi, the trips should not have been below 1900 psig or above 2355 psi, as required by the Technical Specifications. One unit was indicating eight (8) psi low and one unit was' indicating' twelve (12) psi high. The third unit was slightly above~the maximum 4 psi tolerance.
All four units, plus.a spare unit which was removed February 12, 1975 due to the initial detection of drif t on these units, were returned to the manufacturer to determine the cause of the excessive drift. The units were p:
-checked at the factory and were reported to be within the purchase specifica-
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tions. Drift was stated to be 0.1% of span per nonth. The units have.an 800 psi span which indicates that the drift could be 0.8 psi per month.
A check of the original purchase-specifications revealed no requirement or d'
niinit.of drif t -to which the pressure transmitters were purchased. The units were returned and reinstalled.in the RPS on April 4, 1975.
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d-Director Division of Reactor Licensing April 4, 1975 To' resolve this problem and stay within the Technical Specification Limits, a progrr.m is being developed to assure the correct calibration.and limit the drift of the RPS pressure transmitters. A reference gauge will be.
set up to measure the reactor coolant pressure. The gauge will have a dead--
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-weightftester calibration capability which will be used each time the gauge is read. The-reference setup will be compensated for " height above tap" and be capable of reading the system pressure within 2 psi..At two week intervals the gauge will be. calibrated and the output of the pressure. transmitters will be monitored and recorded on a digital' voltmeter. The reference value will-be' compared with'each of the' pressure transmitter values and the drift will be followed. If'the drift indicates that the Technical Specification limit may be exceeded on any unit, n. recalibration will be performed on the trans-mitter..This procedure will be followed until a final resolution is determined concerning the transmitter drift rate and the applicable calibration intervalg r,
If. the above procedure does not prove feasible, then each pressure -
transmitter will be recalibrated at three-month intervals until a final resolution is determined.
f This is the second Abnormal Occurrence of this type. A similar report' was submitted March 11, 1975 as A0 75-3.
The pressure transmitters are manufactured by:
Westinghouse Electric Corporation
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Veritrak Products Phoeni.x, Arizona Model No. 59 PH.443-7050 There was no reactor transient associated with this occurrence.
R'spectfully, e
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J. J. Mattimoe Assistant General Manager and Chief Engineer-Enclosure cc: 1R.H.-Engelken, Region'V
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