ML19317F871
| ML19317F871 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/17/1977 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML19317F872 | List: |
| References | |
| NUDOCS 8002210605 | |
| Download: ML19317F871 (2) | |
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[f~) SACRAMENTO MUNICIPAL UTILITY DISTRICT C SMUD
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95813; (916) 452-3211 j~
May 17, 1977 EFILE COPY Mr. R. H. Engelken Director of Regulatory Operations
- 5 NRC Operations Office, Region V 9
1990 N. California Boulevard Walnut Creek Plaza, Suite 202 Walnut Creek, California 94596 Re: Operating License DPR-54 Docket No. 50-312 Reportable Occurrence 77-5
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Dear Mr. Engelken:
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,0 In accordance with Regulatory Guide 1.16, Revision 4, Section C.2.b.1, and Technical Specifications for Rancho Seco Nuclear Generating Station, Section 6.9.1, the. Sacramento Municipal Utility District is hereby reporting the following Reportable Occurrence as RO 77-5.
,y On April "
'"77, a channel surveillance test was being performed ot)
V, Reactor Proter
. em (RPS) Channel A.
Evaluation of the surveillance data revealed.
.c t e actual Flux / Imbalance / Flow trip setpoints for Channel A' h
fell outside the maximum allowable trip envelope for the RPS as defined by Teclutical Specifications Figure 2.3-2. The power level setting for Break Point 4 (maximum positive imbalance) was greater than the maximum allowable powei' icvel at the actual imbalance setting of the Break Point (se.e attached Figur'es 1 and 2).
The drift experienced by this point created the small, triangular shaped area shown on Figure 2 where Channel A would have permitted operation beyond Technical Specification limits.
The drift was found in two parameters of the envelope. The slope had drifted to 1.967, outside the 2.03 i.02 tolerance established in the calibration. Combined with this was an unusual drift of 0.5% on the positive imbalance limit, which remained within tolerance but was sufficient with the abnormal slope to place Break Point 4 beyond the Technical Specification limit.
Similar surveillance tests had been performed monthly on all channels prior to April 19 with acceptable results and in the three weeks following discovery of the drift on Channel A, the remaining three channels have been
-tested again. This testing verified that for the period of time that Channel A could have been outside the limits (one month), the remaining channels would have provided adequate protection in the 2-out-of-4 logic of the RPS.
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Mr. R. H. Engelken May 17, 1977 After the drift was discovered, no failed components could be located, so Channel A was recalibrated and returned to service. The channel has been checked. weekly for_ indications of abnormal drif t and this checking will
,g continue until the next regularly scheduled monthly surveillance. Testing
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will return to normal if results are acceptable at that time.
As Figure 2 indicates, the actual power level setting of Break Point 4 exceeded the allowable level by only 0.0656% full power. Data from Babcock and Wilcox indicates that the safety analysis imbalance limit curve which the envelope is designed to approximate would allow power to be 3% higher than the Technical Specification limit at Break Point 4 (see Figure 1).
This leads f
to the conclusion that although the allowable trip envelope was exceeded on one channel, the actual limits that the envelope is intended to represent
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were not exceeded, even on that channel.
/f; The component in which the drift occurred was a Bailey Meter Company Function Generator, Model 6625027A1.
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f There was no plant transient associated with this occi rrence.
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a Respectfully submitte..i, 5c.
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J. J. Mattimoe
!I Assistant General Matager and Chief Engineer
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JJM:RWC: sal Enclosures es: Director, MIPC (3)
Director, IE (30) il 4
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