ML20077K250
| ML20077K250 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 07/31/1991 |
| From: | J. J. Barton GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C321-91-2203, GL-89-10, NUDOCS 9108070151 | |
| Download: ML20077K250 (4) | |
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OPU Nuclear Corporation G > Nuclear
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Forked River New Jersey 087310380 009 971 4000 Wnter s D< rect D,al Number.
C321-91-2203 July 31,1991 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Subjects Oyster Creek Nuclear Generating Station Docket No. 50-219 Response to Generic Letter 09-10, supplement 3 Dear Sirs on October 25, 1990, the USNRC issued Supplement 3 to Generic Letter 89-10,
' Consideration of the Results of NRC Sponsored Tests of Motor Operated Valves.
This Generic Letter contained a 120-day reporting requirement to - submit information relating to identified motor operated valves.
By letter dated February 27, 1991, GPU Nuclear requested an extension of this requirement to 120 days following the restart from the 13R refueling outage.
During subsequent telephone conferences, GPU Nuclear agreed to submit the letter by the end of July 1991. This letter is being submitted to meet that commitment.
Please note that the Oyster Creek Nuclear generating Station has neither a High Pressure coolant Injection system nor a Reactor Core Isolation Cooling system.
Therefore, these portions of Supplement 3 are not applicable to Oyster Creek.
Attachment I to this letter discuses four valves in each of the Isolation Condenser systems at Oyster Creek.
Attachment II discusses two valves in the Reactor Water Cleanup system at Oyster Creek. These ten valveu were determined to define the ocope of supplement 3 to the Generic Letter at the Oyster Creek Nuclear Generating Station.
If any further information is required, please contact Mr. John Rogers at 609-971-4093.
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ATTACHMEl{L1 As requestod in Supplement 3 to Generic Letter (GL) 89-10, the Isolation Condenser system motor operated valves (HOV) were assessed for the applicability of data f rom the NRC-sponsored testing to evaluato tho *as-is" capability of each valve. Oyster Croek has two 10 systems. Each system han ono AC and one DC steam isolation valvo, and one AC and one DC condensate isolation valve. On tho steam header, both isolation valves are welded together in series into an integral unit, and the pair is directly welded to the outer opening of the drywoll penotration.
Thorofore, thoro is no IC piping betwoon the containment and the outer isolation valve.
On the condannate header, the AC isolation valve is located inside the containment, and the DC valve is directly wolded to the drywell penetration. Again, there is no IC piping between the containment and the outer isolation valve.
During the recent 13R refueling outage, the HOVs outside the drywell (six total) were replaced with 10 inch 900 lb. parallel disc st ainless steel gato valves.
The motor operators for these valvos were sized using a valve factor of 0.4 (which is consistent with NRC information Notico 90-72), based on manufacturer test results for a similar valve.
The vendor values assumed a dif ferential pressure of 1250 peid.
The Oyster Crook operating dif f erential pressure is 1020 paid.
The vendor sizing calculation indicated a required clouing thrust of 39,707 lbs.
based on a dif f arential pressure of 1250 paid. This number was revised for the Oyster Creek operating differential pressure and resulted in a value of 32,769 lbs. Therefore, the specified thrust. range f or the HOVs outside the drywoll was 32,769 lbs to 39,707 lbs.
The now valves were set and testod using dynamic test equipment and yieldod the following values:
Valve Thrust at Torquo 11Lg No..
.. Switch Trio Total Thrgel, V-14-30 39,453 53,092 V-14-31 46,105 50,912 V-14-32 36,217 54,715 V-14-33 53,932 59,373 V-14-34 50,599 54,448 V-14-35 42,711 51,785 The two MOVs inside the drywell were also set and tested during 13R. Utilizing a valvo f actor of 0.49 based on similarity to Valvo 4 in EPRI Roport NP-7065, the calculated required thrust would be 39,267 lbs.
The as-left test results were as followet Valve Thrust at Torque Tao no.
Switch Trip Total Thtagi V-14-36 26,915 33,207 V-14-37 32,081 37,782 The original design of those valves utilized a valve f actor of 0.3.
Calculating the required thrust with a valve factor of 0.3 yields a value of 26,102 lbs.
Therefore, these valves exceed the design basis requirements for operability as defined for Oyster Creek.
including inertia offects
A Page 2 C321-91-2203 The IC systems at Oyster Creek are normally configured with both steam isolation valves and the AC (inside containment) condensate isolation valve opon. The DC condensate isolation valve is closed and is used for system initiation and termination.
The only time the design differential preneure of 1020 paid can occur across a valve is during an IC line break. As both steam isolation valves and the DC condonsate isolation valve are physically weldod to the drywell penetrations, all IC line breaks outside of containment are isolable by valvoo which were recently installed and exceed the GPUN thrust requirements.
Additionally, all the IC piping outside of the drywell was replacod during the 13R outage, and 100% of the wolds were inspected using radiographic testing, ultrasonic testing, and dye ponotrant testing. Therefore, the probability of a leak in a pipe or a wold outside of containment in the IC system is exceedingly remote.
An IC line break inside containment could potentially result in a momentary differential pressure across the AC condensato isolation valve of 1020 paid, by design. However, Oyster Creek utilizes a low pressure coolant injection system.
Corrective actions for a largo line break inside containment direct the operators to ensure reactor pressure is lowered (in preparation for water injection). The minimum thrust values for the two AC condensato isolation valves result in acceptable differential pressures of 677 paid and 052 paid. Thereforo, if the AC condensate isolation valve f ails to close on first attempt, subsequent ef forts at reduced pressures would in all probability prove successful. The increase in probability cf valve closure atter depressurization has been docketed by the NRC in its " Safety Assessment Relative to BWR Containment Isolation Valves for HPCI, RCIC, and RWCU" (Enclosure 1 to supplement 3 of GL 89-10).
Based on the above discussion, no correctivo actions would be warranted with respect to the Imolation Condenser systems.
AIIACIMIT_11 As requested in Supplen,ent 3 to GL 89-10, the Reactor Water cleanup (RWCU) system HOVs were assessed for the applicability of data f rom the NRC sponsored testing to evaluate the "as-is" capability of each valve. The RWCU system has two valves within the scope of Supplement 3.
An AC HOV (V-16-1) is located inside the containment, and a DC HOV (V-16-14) is located outsido containment.
It has been determined that both of these valves are similar to Valve A in EPRI Report NP-7065. Actual measurements taken during the recent 13R refueling outage revealed that V-16-1 has a tighter clearance between the body guide and disc guide slot than Valve A.
Therefore, V-16-1 will have losa of a disc tilt angle and will have a reduced probability of the anomalous behavior noted during the NRC sponsored tooting.
Utilizing a valve f actor of 0.45, based on the aimilarity to Valve A in the EPRI Report, the required thrust is 15,851 lbs.
These two valves were set and tested during 13R and yielded the following as-lef t test results:
Valve Thrust at Torque Taa.No.
_fwit ch Trio 121ALThrgal, V-16-1 17,033 17,103 V-16-14 15,277 15,427 Tthe original design of these valves utilized a valve f actor of 0.3.
Calculating the required thrust using the 0.3 value results in a required thrust of 11,669 lbs.
Therefort, these valves exceed the design basis requirements for operability as defined for Oyeter Creek.
The operating dif ferential pressure for oyster Creek is 1020 poid. As the inside containment HOV provides suf ficient thrust to close, all line breaks outside the inner valve are isolable.
When a valve f actor of 0.45 is used, calculations indicate that V-16-14 will clase against a differential pressure of 965 paid.
If the inner valve did not fully close on an isolation attempt, it would only have to travel suf ficiently to reduce the dif ferential pressure by 55 paid before the outer motor operator would provide suf ficient thrust to close the valvo.
Alternatively, the blowdown resulting from a leak would only have to decrease l
reactor pressure by 55 lbs. for the outer motor operator to have sufficient thrust to close the valve.
The increase in probability of valve closure af ter depressurization, or partial travel by a series valvo, has been docketed by the NRC in its " Safety Assessment Rela'. ve to DWR Containment Isolation Valves for HPCI, RCIC, and RWCU" (Enclosure 1 t t.
Npplement 3 of GL 89-10).
Based on the above, no corrective actions would be warranted with respect to the Reactor Water Cleanup system.
including inertia etfects
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