ML20207C188
| ML20207C188 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 07/27/1988 |
| From: | Wilson R GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| RTR-NUREG-0313, TASK-03-05.B, TASK-RR 5000-88-1604, GL-88-01, NUDOCS 8808050106 | |
| Download: ML20207C188 (3) | |
Text
GPU Nuclear Corporation
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g g gs One Upper Pond Road t
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M wMB Parsippany, New Jersey o7054 2o1 316 7000 TELEX 136 482 Writer's Direct Dial Nurnber:
July 27, 1988 5000-88-1604 U.S. Nuclear Regulatory Commission Attention:
Document Control Desk fiail Station Pl-137 Washington, D.C.
20555
Dear Sir:
Subject:
Oyster Creek Nuclear Generating Station (0CNGS)
Docket No. 50-219 License No. DPR-16 Isolation Condenser Piping / Penetrations Our letter to the NRC Staff, dated November 25, 1986, indicated our intent to resolve three issues concerning isolation condenser piping and containment pipe penetrations.
These issues are 1) a postulated high energy line break (HELB) within an isolation condenser penetration, 2) HUREG 0313 Revision 2, "Technical Report on Material Selection and Process Guidelines for BWR Coolant Pressure Boundary Piping", and 3) Systematic Evaluation Progran (SEP) Topic III-5.B. "Pipe Break Outside Containment".
The HELB issue concerns one isolation condenser condensate return line penetration (X-SA).
At normal reactor pressure and only during isolation condenser operation, the drywell shell at this penetration would be overstressed should a guillotine rupture of the isolation condenser piping occur within the penetration.
Originally, it was thought that each of the four isolation condenser piping penetrations would be overstressed during a postulated HELB.
However, reanalysis showed only one penetration would be overstressed.
This revised information was communicated verbally to the Staff at a meeting on February 11, 1987 and documented in meeting minutes dated March 9, 1987.
NUREG 0313, Revision 2, requires weldments in boiling water reactor (BWR) piping susceptible to intergranular stress corrosion cracking (IGSCC) be replaced, inspected on an augmented schedele or leak detection provided.
Present isolation condenser piping is ICSCC susceptible and the weldments within each penetration are uninspectible, g805oj06800727 p
ADOCK 03000p39 PNU 0
GPU Nuclear Corporat on is a subsdary of General Pubbc Ut1;t.es Corporat,on
U.S. Nuclear Regulatory Commission Page 2
-SEP Topic III-5.B concerns the two isolation condenser steam line isolation valves located outside containment for each of the two isolation condensers.
Should an isolation condenser pipe break occur in the vicinity of these valves, the valve operators may be affected and fail to close the valves.
All four isolation condenser steam and condensate lines are routed near each other and penetrate containment near the-75 foot elevation in the reactor building.
-GPU Nuclear submitted fracture mechanics studies of isolation condenser piping F
by letters dated October 16, 1984 and May 18, 1982.
Since the Staff has not accepted the results of these studies due to the revised acceptance criteria l
(no IGSCC or water hammer susceptibility) associated with the revision to GDC 4 regarding the application of leak-before-breek, this issue still remains open.
In our November 25, 1986 letter, we expressed our intent to implement a modification during the next (Cycle 12R) refueling outage which would affect an integrated resolution of all three issues.
This modification schedule was contingent upon the timely publication of NUREG 0313, Revision 2, so that all issues were clearly understood prior to the start of engineering.
Due to the delay in issuance, GPU Nuclear, early in 1987, decided to proceed with the design of a modification to resolve the HELB issue during the Cycle 12R i
outage. A flow restrictor baffle, mounted on the penetration X-SA guard pipe, was planned to be installed to alleviate the HELB overstress condition.
In addition, our plans included the installation of a leek detection system at 1
j penetration X-SA so that its performance could be evsluated during the next operating cycle (Cycle 12).
This was planned in anticipation of potential j
NUREG 0313. Revision 2, alternatives.
This course of action was initiated due to the uncertainty of the NUREG publication and was discussed at the February 11, 1987 meeting.
l 1
As a result of the issuance of Generic Letter 88-01 on January 25, 1988 and i
our subsequent evaluation of its requirements, we have decided to replace all four isolation condenser penetrations to eliminate the process piping
.i weldments within.
In addition, all isolation condenser piping outside 1
containment on the 75 foot elevation will be replaced.
The replacement piping and penetration material will be Nuclear Grade 316 stainless steel.
The i
penetration to isolation valve, valve to valve and valve to piping weldments
[
will be treated with corrosion resistant cladding.
The above measures are believed to be a significant step in our effort to effectively res11ve all I
three issues.
This work is scheduled for the Cycle 13R refueling outage.
]
Further correspondence will be necessary to fully describe and justify our j
application of leak-before-break technology to the resolution of both the SEP
)
Topic III-5.B and HELB issues. We believe that the above modifications, scheduled for the 13R outage, will permit the application of Leak-before-break.
i i
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U.S. Nuclear Regulatory Commission Page 3 In consideration of the above, we are cancelling the flow restrictor baffle and leak detection modification for penetration X-SA planned for the Cycle 12R outage.
It is the most cost effective solution and efficient utilization of available resources to perform all work at the same time during the Cycle 13R outage. Occupational exposure will also be minimized.
The precautionary measures described in our November 25, 1986 letter regarding increases in unidentified leak rate, visual inspection of the affected penetration and the employment of diagnostic techniques to reasonably assure the absence of a leak in the affected penetration will be continued, to address the HELB issue, during Cycle 12 operation.
In accordance with paragraph 2.C.(10) of the Oyster Creek license regarding our Integrated Schedule, the next schedule update will reflect the deletion of the penetration upgrade (Item No. 22) from the 12R work scope and the addition of pipe / penetration replacement to the 13R work scope.
ery truly yours, 5 N}w
. F. W son Vice President Technical Functions RFW/PC/pa(7083f) cc: fir. William T. Russell, Administrator Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA.
19406 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, N.J.
08731 fir. Alex Dromerick U.S. Nuclear Regulatory Commission flail Station Pl-137 Washington, D.C.
20555