ML19317G105
| ML19317G105 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/16/1976 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML19317G103 | List: |
| References | |
| NUDOCS 8002210794 | |
| Download: ML19317G105 (2) | |
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SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street Box 15830. Sacramento. California 95813; (916) 452-3211 g
April 16, 1976 G
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Mr. R. H. Engelken
' I'i $IS Director of Regulatory Operations
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Region V, NRC Operations Office 1990 N. California Boulevard Walnut Creek Plaza, Suite 202 Walnut Creek, California 94596 Re: Operating License DPR-54 Docket No. 50-312 Reportable Occurrence 76-4
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Dear Mr. Engelken:
As defined by Technical Specifications for Rancho Seco Nuclear Generating Station, Section 6.9.1, and Regulatory Guide 1.16, Revision 4, n
Section C.2.a.5, the Sacramento Municipal Utility District hereby submits j
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a written follow-up report on Reportable Occurrence 76-4, reported to NRC s
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on April 6, 1976.
As described in the April 6 transmittal, a calibration check of tne Reactor Protection System pressure transmitters on April 5,1976, revealed that all four transmitters had drif ted beyond the 4 psi accuracy t'
allowed in the safety analysis. Three of the transmitters had drifted
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high (1 psi,1.2 psi and 4.9 psi beyond the 4 psi tolerance) which would have prevented a reactor trip on low pressure at the Technical Specifica-tion limit of 1900 psi. The fourth transmitter had drifted low (2.2 psi beyond the 4 psi tolerance) which by itself would not have prevented a trip on high pressure; tha three other channels would have tripped prior to the system reaching the Technical Specification limit of 2355 psi.
On two previous occasions the District has reported excessive drift in these pressure transmitters. Abnormal Occurrence Report 75-3 dated March 11, 1975, reported one transmitter out of calibration and stated that the calibration of the remaining transmitters would be checked within sixty days. On April 4, 1975, Abnormal Occurrence Report
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75-4 described the drif t of three transmitters beyond the tolerance limits. As a corrective action for the problem, a biweekly check was instituted by which drif t could be determined, providing an alert prior to exceeding of specification limits. On March 18, 1976, during one of these biweekly checks, ic was observed that the drift on the transmitters 2,
had increased, possibly beyond the permissible 4 psi limit. During the
.j scheduled shutdown two weeks later, a calibration check was made and the
[~N excessive drif t was discovered.
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i Mr. R. H. Engelken April 16, 1976 Based on the drift of 0.8 psi / month allowed by the manufacturers' specifications, the high and low RPS pressure trip setpo!.nts will be set 10 psi more conservative.. This action should prevent drif t ootside the gj limits during the period between refueling calibrations. An equivalent L
correction'will be applied to the variable low RCS pressure / temperature trip. Also,' the biweekly check for drif t, which was successful in iden-
- tifying the instance of excessive drift, will be continued. A new reference point will be established with each startup. The refueling interval calibration, setting a null point with a deadweight gauge, will be continued as described in A0 75-4. -
l The NRC is currently conferring with Florida Power Corporation about.the RPS pressure trip setpoints for chef.r Crystal River Plant.
The reactor vendor, Babcock & Wilcox, maintains that the pressure related d
trip setpoints required for their plants include 30 psi of consefvatism for instrument string error. The setpoints actually used in the Final Safety Analysis Report used the~30 psi margin and the Technical Specifi-cation trip settings can be relaxed accordingly. Babcock & Wilcox considers this a. generic issue for its plants, including Rancho Seco, 3
T and if their position is upheld, the drift experienced by our-four J
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transmitters would be acceptable. The final determination of action on this problem will be delayed pending resolution of this issue.
The pressure transmitsers are Veritrak Model No. 59 PH 443-7050, manufactured by Westinghouse Electric Corporation, Veritrak Products, j
Phoenix, Arizona.
There was no transient' associated with this occurrence.
Respectfully - Submitted,
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J'J.7. Mattimoe J
Assistant General Manager and Chief Engineer 7.-
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