ML17146A981
| ML17146A981 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 09/28/1987 |
| From: | Thadani M Office of Nuclear Reactor Regulation |
| To: | Keiser H PENNSYLVANIA POWER & LIGHT CO. |
| References | |
| NUDOCS 8710010377 | |
| Download: ML17146A981 (6) | |
Text
k-September 28I 1987 Docket Nos. 50-387/388 Mr. Harold W. Keiser Vice President Nuclear Operations Pennsylvania Power and Light Company 2 North Ninth Street Al 1 entown, Pennsylvania 18101
Dear Mr. Keiser:
SUBJECT:
DYNAMIC EFFECTS OF POSTULATED PIPE RUPTURES RE:
SUS(UEHANNA STEAM ELECTRIC STATION, UNITS I AND 2 In a [[letter::05000388/LER-1986-013-01, :on 860919,full Reactor Protection Sys Scram Occurred When Intermediate Range Monitors C & G Spiked Upscale.Caused by Noise Due to Faulty Primary Containment Penetration Connectors.Cables Rebuilt|letter dated October 17, 1986]], you requested an exemption from the requirements of the General Design Criterion 4 (GDC-4) of Appendix A to 10 CFR 50, related to the dynamic effects of postulated pipe ruptures in the reactor recirculation piping.
The requested exemption would permit you to apply the fracture mechanics "leak-before-break" technology as an alternative to providing physical protection against dynamic loads due to jet impingement following postulated pipe ruptures.
The staff has reviewed your supporting analysis provided in MPR Associated report MPR-949, "Susquehanna Steam Electric Station, Leak Before Break Evaluation of Postulated Recirculation System Pipe Cracks", Revision I, dated
- October, 1986.
As a result of our review, we have prepared the enclosed request for additional information which is needed to assure that the underlying pur pose of GDC-4 is satisfied by the alternative analysis provided in your request.
Please provide your response to the enclosed questions within 60 days from the receipt of this letter.
Sincerely, pe7~~
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Enclosures:
As stated cc w/enclosures:
See next page
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Mohan Thadani, Project Manager Project Directorate I-2 Division of Reactor Projects I/II DISTRIBUTION
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Docket Nos.
50-387/388 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 September 28> l987 Mr. Harold W. Keiser Vice President Nuclear Operations Pennsylvania Power and Light Company 2 North Ninth Street Al 1 entown, Pennsyl vani a 18101
Dear Mr. Keiser:
SUBJECT:
DYNAMIC EFFECTS OF POSTULATED PIPE RUPTURES RE:
SUSQUEHANNA STEAM ELECTRIC STATION, UNITS 1 AND 2 In a [[letter::05000388/LER-1986-013-01, :on 860919,full Reactor Protection Sys Scram Occurred When Intermediate Range Monitors C & G Spiked Upscale.Caused by Noise Due to Faulty Primary Containment Penetration Connectors.Cables Rebuilt|letter dated October 17, 1986]], you requested an exemption from the requirements of the General Design Criterion 4 (GDC-4) of Appendix A to 10 CFR 50, related to the dynamic effects of postulated pipe ruptures in the reactor recirculation piping.
The requested exemption would permit you to apply the fracture mechanics "leak-before-break" technology as an alternative to providing physical protection against dynamic loads due to jet impingement following postulated pipe ruptures.
The staff has reviewed your supporting analysis provided in MPR Associated report MPR-949, "Susquehanna Steam Electric Station, Leak Before Break Evaluation of Postulated Recirculation System Pipe Cracks", Revision 1, dated
- October, 1986.
As a result of our review, we have prepared the enclosed request for additional information which is needed to assure that the underlying purpose of GDC-4 is satisfied by the alternative analysis provided in your request.
Please provide your response to the enclosed questions within 60.days from the receipt of this letter.
Sincerely,
Enclosures:
As stated ohan Thadani, Project Manager Project Directorate I-2 Division of Reactor Projects I/II cc w/enclosures:
See next page
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 Allentown, Pennsylvania 18101 Mr. E. A. Heckman Licensing Group Supervisor Pennsylvania Power
& Light Company 2 North Ninth Street Allentown, Pennsylvania 18101 Mr. Loren Plisco Resident Inspector P.O.
Box 52 Shickshinny, Pennsylvania 18655 Mr. R. J.
Benich Services Project Manager General Electric Company 1000 First Avenue King of Prussia, Pennsylvania 19406 Mr. Thomas M. Gerusky, Director Bureau of Radiation Protection Resources Commonwealth of Pennsylvania P. 0.
Box 2063 Harrisburg, Pennsylvania 17120 Robert W. Alder, Esquire Office of Attorney General P.O.
Box 2357 Harrisburg, Pennsylvania 17120 Mr. Jesse C. Tilton, III Allegheny Elec. Coorperative, Inc.
212 Locust Street P.O.
Box 1266 Har risburg, Pennsyl vania 17108-1266 Mr. W. H. Hirst, Manager Joint Generation Projects Department Atlantic Electric P.O.
Box 1500 1199 Black Horse Pike Pleasantville, New Jersey 08232 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406
ENCLOSURE REQUEST FOR ADDITIONAL INFORMATION ON ELIMINATION OF POSTULATED REACTOR RECIRCULATION SYSTEM PIPE RUPTURES AS A DESIGN BASIS PENNSYLVANIA POWER
& LIGHT COMPANY SUSQUEHANNA STEAM ELECTRIC STATION UNITS I AND 2 DOCKET NOS. 50-387
& 50-388 (I) The leak-before-break (LBB) analysis must be performed for the functional piping system from anchor point to anchor point.
A through-wall flaw should be postulated in each size of pipe comprising the functional system in the LBB analysis.
However, the licensee indicated that LBB analyses were performed on the pipe-to-safe end welds for the 28-inch recirculation discharge nozzles and the 12-inch recirculation inlet nozzles.
Although the licensee may only intend to eliminate the postulated pipe ruptures at these discrete locations for operational
- reasons, the LBB analysis must be performed for the entire pipina system.
For each pipe size, the limiting location for LBB analyses is the location having the least favorable combination of stress and material properties.
(2) For application of LBB to piping that has a history of intergranular stress corrosion cracking (IGSCC), the piping must qualify for the standard Section XI of the ASME Code inspection schedule (i.e.,
no augmented inspection).
The staff requires that (I) the piping be fabricated with IGSCC resistant material, or (2) the piping be treated with remedial stress improvement (within two years of operation) and an acceptable hydrogen water chemistry be implemented.
Also, the application of LBB is not permitted in piping with any cracking or weld overlay.
The licensee must discuss the compliance of the staff's requirements for the Susquehanna recirculation system pipino.
(3) Susquehanna, being a boiling water reactor (BWR), has a
5 gallon per minute (gpm) Technical Specification allowable unidentified leakage rate.
Because Susquehanna can continue to operate without containment entry to identify the source of less than 5 gpm unidentified leakage, the staff considers it appropriate to use 5 gpm as the basis for the detectable leakage rate in LBB analyses.
To account for uncertainties inherent in the analyses and leak detection capability, a margin of 10 on leakage is required.
Furthermore, there are margins of 2 on the flaw size and 1.4 on the loads.
The LBB margins are discussed in detail in NUREG-1061, Volume 3.
Thus, in order to demonstrate LBB based on a
5 gpm leakage
- rate, the stability of a 50 gpm leakage-size through-wall flaw has to be demonstrated.
The licensee would have to perform a fracture mechanics analysis to show that a through-wall flaw at least twice the size of the 50 gpm leakage-size flaw will be stable under combined normal (pressure, deadweight, and thermal expansion) and safe shutdown earthquake (SSE) loads.
Also, the licensee's fracture mechanics analysis would have to demonstrate that the 50 gpm leakage-size flaw will be stable if the loads are increased to at least 1.4 times the combination of normal and SSE loads.
(4) The licensee indicated that the Susquehanna recirculation system pipino and nozzle safe ends were fabricated from forged austenitic stainless steel and not from cast stainless steel.
The weld properties were not discussed in the submitted report.
However, the submitted report referenced toughness properties for cast stainless steel from the literature as representative of those for welds without providing justification.
The licensee should identify the welding process of the recirculation system piping.
The fracture toughness of the welds should be considered in the flaw stability analyses.
The licensee should consider lower-bound weld toughness properties in LBB analyses.
- However, the fracture toughness of welds depends on the weld wire type, weld wire heat number, flux type, flux lot number, post-weld heat treatment, and welding procedures.
- Thus, when literature data are used, the number of material and we1d procedures tested must be adequate to cover the range of properties at Susquehanna.
(5) The licensee used both linear elastic fracture mechanics (LEFN) and e1astic-plastic fracture mechanics (EPFN) procedures in the flaw stability analysis.
However, the staff considers ft inappropriate to use LEFN when the associated Irwin p1ane-stress plastic zone sizes are not small compared with the half-crack lenath.
The licensee should clarify that the staff's requirement is satisfied when LEFN was used.