05000285/LER-1982-020-03, /03L-0:on 821207,during Main Steam Safety Valve Test,Four Main Steam Safety Valves Had Lift Setpoints Out of Tolerance.Caused by Normal Drift of Valves Over Operating Cycle.Valves Readjusted

/03L-0:on 821207,during Main Steam Safety Valve Test,Four Main Steam Safety Valves Had Lift Setpoints Out of Tolerance.Caused by Normal Drift of Valves Over Operating Cycle.Valves Readjusted

ML20028C771
Person / Time
Site:	Fort Calhoun
Issue date:	01/06/1983
From:	Core M OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20028C767	List: 05000285/LER-1982-020, Forwards LER 82-020/03L-0 05000285/LER-1982-020-03, /03L-0:on 821207,during Main Steam Safety Valve Test,Four Main Steam Safety Valves Had Lift Setpoints Out of Tolerance.Caused by Normal Drift of Valves Over Operating Cycle.Valves Readjusted
References
LER-82-020-03L, LER-82-20-3L, NUDOCS 8301140085
Download: ML20028C771 (4)

LER-1982-020, /03L-0:on 821207,during Main Steam Safety Valve Test,Four Main Steam Safety Valves Had Lift Setpoints Out of Tolerance.Caused by Normal Drift of Valves Over Operating Cycle.Valves Readjusted

Event date:
Report date:
2851982020R03 - NRC Website

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NRC FORM 364 U. S. NUCLEAR CCULATORY COMAS 4SSION (7 77)

LICENSEE EVENT REPORT 1

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discovered that 4 out of 10 main steam safety valves had lift setpoints that were l

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LER No.82-020 Omaha Public Power District -

- Fort Calhoun Station Unit No. 1 Docket No. 05000285

. ATTACHMENT NO. 1

Safety Analysis

Overpressure protection at the Fort Calhoun Station is ensured by means of primary safety valves, secondary safety valves, and the reactor protective system. The worst case pressure transient, loss-of-load, in conjunction with a delayed reactor trip, is the design basis for deter-mining the adequacy of the Fort Calhoun Station safety valves.

The primary safety valves, secondary safety valves, and reactor protective system mainta1n reactor coolant system and steam generator pressures below 110% of their respective design pressures during worst case-transients.

An analysis of the loss-of-load (LOL) event demonstrates that there is additional-secondary system safety valve and primary system safety valve capacity above that which is required to provide overpressure protection. The analysis shows that the two sets of secondary system.

safety valves with the highest setpoint pressure never achieve a full open position and that the higher setpoint primary system safety valves never open during the design basis transient.

The expected effect of this safety valve setpoint out-of-tolerance condition would be as follows. The safety valves which had opening pressures lower than required would have achieved a full open position sooner and would have released more steam than was calculated in the original LOL analysis. This effect would be to lower the secondary pressures. The valve which had an opening pressure 10 psig greater than required would have achieved a full open position later than was assumed in the LOL analysis. However, this slower opening would have been more than compensated for by the earlier opening of the previously discussed valves. The valve which was discovered with an opening pressure which was higher than 1042 psig must be considered inoperable.

It is judged that an overpressurization of the secondary system would not have occurred because two of the subject safety valves would have opened earlier due to their lower opening pressures and four of the other safety valves which did not achieve a full open position in the original LOL analysis would have achieved a more fully open position and released more steam. The original LOL analysis showed a peak pressure of at least 40 psia less than the secondary system design pressure, and the District's analysis for this postulated event is still bounded by this conservative value.

It is judged that an overpressurization of the primary system would not have occurred because only one of the two primary system safety valves is shown to open in the LOL analysis.

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a LER No.82-020 Omaha Public Power District Fort Calhoun Station Unit No. 1 Docket No. 05000285 ATTACHMENT NO. 2

Corrective Action

The main steam safety valves are required to have lift settings between 1000 psia and 1050 psia, with a tolerance of +1% of the nominal nameplate setpoint values. The four valves in question had test data as follows:

1)

MS-275 - set pressure = 1035 psig; as found = 1015_psig.

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Th~erefore, the lift setpoint was 9.65 psi below the required lift pressure. Recalibrated setpoint = 1040 psig.

2)

MS-278 - set pressure = 1000 psig; as found = 1020 psig.

Therefore, the lift pressure was 10 psi high.

Recalibrated setpoint = 993 psig.

3)

MS-280 - set pressure = 1025 psig; as found = 995 psig.

Therefore, the lift pressure was 19.75 psi low.

Recalibrated setpoint = 1022 psig.

4)

MS-282 - set pressure = 1000 psig; as found was greater than 1042 psig which was the measurement limit of available test equipment. Valve was calibrated and retested several times at 995 psig.

The corrective action, already completed, consisted of recali-brating the lift set pressure on the four valves in question.

All four valves were then subsequently retested and found to be within +1% of their nameplate rating as specified in Technical Specification 2.1.6(3).

Additionally, the District intends to completely overhaul and retest MS-282.

This overhaul will be completed during the present refueling outage and will provide additional assurance that MS-282 will function as required. No further corrective action is deemed necessary or contemplated for the other three safety valves.

The District will continue to test the main steam safety valves during refueling shutdowns to ensure proper operability of the system.

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LER No.82-020

- Omaha Public Power District ~

Fort Calhoun Station Unit No. 1 Docket No. 05000285 ATTACHMENT NO. 3 Failure' Data

. This is the third reportable occurrence of the Fort Calhoun Station main steam safety valve system exceeding the minimum operability re-quirements of Technical Specification 2.1.6(3) (See LER's 76-19, 76-19 Supplement 1, and 77-24).

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