ML20084D450
| ML20084D450 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 04/24/1984 |
| From: | Root R WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| GO1-84-0124, GO1-84-124, NUDOCS 8405010354 | |
| Download: ML20084D450 (3) | |
Text
Washington Public Power Supply System P.O. Box 968 3000 George Washington Way Richland, Washington 99352 (509)372-5000 April 24, 1984 Responds to:
G01-84-0124 Response required by:
Mr. J.B. Martin Regional Administrator 4
Nuclear Regulatory Commission Region V a ut eek A 94596
- g
Subject:
NUCLEAR PROJECTS NOS. 1 AND 4 DOCKET NOS. 50-460 and 50-513 POTENTIALLY REPORTABLE CONDITION 10CFR50.55(e)
OPERATING CHARACTERISTICS OF MAIN STEAM AND FEEDWATER ISOLATION VALVES
Reference:
Telecon, C.R. Edwards, Supply System, to R.T. Dodds, NRC, same subject, dated March 26, 1984.
In the reference, the Supply System informed your office of a potentially reportable deficiency under 10CFR50.55(e).
Attachment A provides a statement of the identified condition and a brief description of our planned actions to correct the identified deficiency. Based on the current construction status at WNP-1/4, the Supply System will not be able to issue a final report at this time.
An update will be provided at construction restart.
If you have any questions or desire further information, please advise.
R.W. Root, r.
WNP-1 Program Director (821)
RWR/LC0/cmh Attachment cc:
TA Mangelsdorf, BPC (862)
V Mani, UE&C (899)
EC Haren, UE&C (895)
NRC Document Control Desk FDCC (899)
ORM (847)
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ATTACHMENT A DOCKET NOS. 50-460 513 POTENTIALLY REPORTABLE CONDITION PER 10CFR50.55(e)
OPERATING CHARACTERISTICS OF MAIN STEAM AND FEEDWATER ISOLATION VALVES Description of Deficiency The WNP-1/4 design has two steam generators per plant.
Each steam generator is isolated from the Feedwater System by two Feedwater Isolation Valves (FWIV's) in series for a total of four FWIV's per plant (FWS-V-16B, 17A, 28B, and 29A).
Each steam generator has two outlet lines containing one Main Steam Isolation Valve (MSI'.) per line for a total of four MSIV's per plant (MSS-V-lC, 2C, 3C, and 4C).
These eight valves per plant are all located just outside containment in the Main Steam and Feedwater Isolation Area (MSFIA) which is an enclosed structure.
All eight valves were supplied by Anchor Darling Valve Company.
The emergency closure design requirements of these valves include a fast closure b
mode at the abnormal minimum postulated environment temperature of 55 F.
The environmental conditions for the MSFIA structure were defined in the technical specification as:
Normal Maximum 90 F Normal Minimum 55 F Abnormal Maximum 420 F Abngrmal Minimum temperature was not specifically given.
Anchor Note that an Darling used 60 F as the abnormal minimum temperature when designing and calibrating the valves for the fast closure mode.
As these valves use hydraulic fluid (Fryquel 220), the fast closure time of tge valves may not be met due to the increased viscosity of the hydraulic fluid at 55 F.
Specifically, the MSIV and FWIV's are required to close in 4.5 to 5.0 and 11.5 to 12.5 seconds respectively in the fast closure mode at abnormal conditions.
Preliminary calculations by Anchor Darling indicate that closure times may be closer to 7 and 17 seconds respectively.
Analysis of Safety Implication The eight valves in question isolate the secondary side of the steam generators (OTSG's) during normal and off normal conditions.
Although the immediate effects of a slow valve closure depend on the event and specific circumstances, several generalizations can be made.
Effects of slow closure of MSIV's include the following:
e Increase in Main Steam dump to atmosphere e Potential for increased depressurization of OTSG's Effects of slow closure of FWIV's include the following; e Increase in mass and energy release to containment e Increase in feedwater inventory in 0TSG e Reduction in transient pipe loadings.
i Due to the complexity of the analyses required to analyze the cooling transients and radiological effects caused by slow valve closure, the Supply System is currently unable to determine the exact safety implications.
Cause of Deficiency Anchor Darling improperly interpreted the technical specification when determining the abnormal minimum environmental temperature.
Although the MSFI A structure is normally heated, the heaters are not safety class.
In summary, Anchor Darling should have used 55 F as both the normal and abnormal minimum environmental temperature.
Corrective Action The valve closure times are based on needle valve settings in the hydraulic operator of the valve.
The Supply System is shipping one Main Steam and one Feedwater valve actuator back to Anchor Darling for recalibration at 55 F.
As all four MSIV's are indentical and the four FWIV's are identical it is only necessary to
- ilibrate one of each type.
Anchor Darling will determine correct needle vrd sittings and forward the data to the Project. The valves will then have to be properly adjusted in order to close out the nonconformance reports that have been issued (1-BNCR-87-03 and 4-BNCR-87-04).
Action to Prevent Recurrence As these eight valves are the only hydraulic operated safety related valves of this type with critical closure times, this is an isolated case and no further actions are necessary.