ML17157A789
| ML17157A789 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 08/08/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17157A788 | List: |
| References | |
| GL-88-01, GL-88-1, NUDOCS 9108150278 | |
| Download: ML17157A789 (6) | |
Text
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~g REMI UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 "e
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PENNSYLVANIA POWER 5 LIGHT COMPANY ALLEGHENY ELECTRIC COOPERATIVE INC.
SUSQUEHANNA STEAM ELECTRIC STATION UNITS 1
AND 2 DOCKET NOS.
50-387 AND 388
1.0 INTRODUCTION
In Reference (1), Pennsylvania Power and Light Company (PPSL),
the licensee, transmitted a request for an exemption to 10 CFR 50 Appendix A, General Design Criterion 4.
The request was made due to the discovery of jet impingement scenarios that,potentially threatened certain containment isolation valves, including the Main Steam Isolation Valves (MSIVs).
The exemption request was
'ased on leak-before-break (LBB) analyses of the weld locations in question.
The NRC staff raised several questions regarding the scope and base assumptions of the LBB analyses as presented in Reference (1).
Because of these
- concerns, PPKL decided to resolve the issue without relying on LBB approach.
An action plan for such a resolution was proposed in Reference (2) for staff review.
A proposed completion schedule for this action plan is also provided in Reference (3).
In addition, a justification for continued operation until the action plan is completed was also provided in Reference (2) for staff review.
The action plan consists of the following:
2.0 EVALUATION The staff conducted a review of the proposed action plan and the associated completion schedule.
The action plan consists of the following:
1.
Review target areas for jet loads from the Recirculation System nozzle breaks and other nozzles where configurations of piping and bioshield doors are similar.
A.
Perform walkdowns as necessary during the upcoming Unit 1 fifth and Unit 2 fourth refueling and inspection outages to identify potential safety-related targets.
9l08l50278 9i0808 PDR ADOCK 05000387
'DR
2.
gualify the NSIVs to the Recirculation System jet impingement loads and temperatures (includes the NSIVs and associated components).
A.
Finalize jet impingement analyses for the most limiting Nl and N2 nozzle break locations.
These analyses will provide jet pressure
~
and temperature envelopes as a function of distance from the break locations and will form a basis for llSIV load definition.
B.
Determine by analysis an enveloping jet impingement load to which the NSIVs can be qualified.
gualify the HSIVs by comparison of qualification load to calculated load.
3.
Analyze the effect of jet impingment on other equipment.
A.
Using the jet impingment pressure and temperature envelopes for the worst case Recirculation System nozzle breaks, evaluate the effects of jet impingement on other equipment within the jet zone of influence.
B.
Analyze equipment targets for jet loads from other nozzle breaks where configurations of piping and bioshield doors are similar to the Recirculation System.
C.
Where safety-related equipment analyzed for jet loads cannot be qualified, design and install hardware to mitigate the effects of the jet loadings.
The staff has found the above action plan and the associated completion schedule to be acceptable.
The licensee should submit the final documented results of their efforts for staff review following the implementation of the action plan.
The staff has also reviewed the licensee's justification for continued operation of the station unti 1 complete implementation of the above action plan.
Such justification is found acceptable based on the following:
l.
At the suggestion of the NRC staff in the November 5, 1987, meeting, PP&L has pursued defining a more realistic jet model with GE.
The preliminary results indicated that the jet pressures which could impact the NSIVs (the closest safety-related component to the postulated break location) are less than half of that originally estimated.
This information provides reasonable assurance that the tlSIVs can be qualified, i.e., they are structurally capable of withstanding the postulated loads.
2.
Weld inspections have been and continue to be performed by the licensee to verify weld integrity.
Radiograph and dye penetrant inspections of welds were performed during the construction phase of Susquehanna.
Ultrasonic inspection of welds was performed for the Preservice Inspection Program.
Ultrasonic inspection of welds continues to be performed under the Inservice Inspection Program.
One hundred percent of the Recirculation System nozzle welds are inspected every two refueling and inspection outages.
This is consistent with the staff position as stated in Generic Letter 88-01.
r h
3.
Induction Heat Stress Improvement (IHSI) has been performed by the licensee on both units on welds where breaks are assumed to occur.
This treatment lessens the susceptibility of the material to intergranular stress corrosion cracking (IGSCC) and significantly reduces the probability of failure.
PPSL's water chemistry control program also reduces the probability of failure.
In addition, safe ends at the N2 nozzles have been replaced with corrosion-resistant material and the piping has been clad with corrosion-resistant material.
4.
The probability of occurrence of Recirculation System nozzle breaks is small.
For recirculation line breaks which impact the inboard NSIVs, the outboard t1SIVs would still be expected to close and provide containment isolation.
The probability of a double-ended guillotine break at the N1A
- nozzle, in addition to the failure of impacted inboard A and D NSIVs and a corresponding outboard tlSIV random failure is exceedingly small.
Other potential jet impingement effects on the Reactor Water Cleanup and Reactor Building Chilled Water systems would be contained within the Secondary Containment where the leakage would be processed by the Standby Gas Treatment System.
5.
Susquehanna has a Technical Specification Limiting Condition for Operation of 5 gpm unidentified leakage.
Existing leak detection systems of Susquehanna Station are capable of identifying the leakage.
3.0 CONCLUSION
Based on a review of the information provided by the licensee, the staff finds that the proposed Jet Impingement action plan and the associated completion schedule to be acceptable.
The staff also reviewed the licensee's justification for continued operation of the Susquehanna Steam Electric Station until full implementation of the action plan is completed, and finds such justification to be acceptable.
The staff will review the licensee's documented results on the above jet impingement issue when the action plan is completely implemented, and report its review findings in a supplemental safety evaluation.
Principal Contributors:
A. Lee J. Raleigh Dated:
August 8, 1991
Mr. Harold W. Keiser Pennsylvania Power
& Light Company Susquehanna Steam Electric Station Units 1
& 2 CC:
Jay Silberg, Esq..
'Shaw, Pittman, Potts
& Trowbridge 2300 N Street N.W.
Washington, D.C.
20037 Bryan A. Snapp, Esq.
Assistant Corporate Counsel Pennsylvania Power
& Light Company 2 North Ninth Street Al 1 entown, Penn sy 1 vani a 18101 the. J.
M. Kenny Licensing Group Supervisor Pennsylvania Power
& Light Company 2 North Ninth Street Allentown, Pennsylvania 18101 Mr. Scott Barber Senior Resident Inspector U. S. Nuclear Regulatory Commission P.O.
Box 35 Berwick, Pennsylvania 18603-0035 Mr. Thomas M. Gerusky, Director Bureau of Radiation Protection Resources Commonwealth of Pennsylvania P. 0.
Box 2063 Harrisburg, Pennsylvania 17120 Mr. Jesse C. Tilton, III Allegheny Elec. Cooperative, Inc.
212 Locust Street P.O.
Box 1266 Harrisburg, Pennsylvania 17108-1266 Mr. S.
B. Ungerer Joint Generation Projects Department Atlanti c E1ectri c P.O.
Box 1500 1199 Black Horse Pike Pleasantville, New Jersey 08232 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, Pennsylvania 19406 Mr. Harold G. Stanley Superintendent of Plant Susquehanna Steam Electric Station Pennsylvania Power and Light Company 2 North Ninth Street Allentown, Pennsy1vani a 18101 Mr. Herbert D. Woodeshick Special Office of the President Pennsylvania Power and Light Company 1009 Fowles Avenue Berwick, Pennsylvania 18603 Mr. Robert G.
Byram Vice President-Nuclear Operations Pennsylvania Power and Light Company 2 North Ninth Street Allentown, Pennsy1 vani a 18101