ML20128G366
| ML20128G366 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 07/03/1985 |
| From: | Mittl R Public Service Enterprise Group |
| To: | Butler W Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8507090168 | |
| Download: ML20128G366 (2) | |
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O I)#S G Cornoany Pubkc Serwce Electnc and Gas 80 Park Plaza, Newark, NJ 07101/ 201430-8217 MAILING ADDRESS / P.O. Box 570, Newark, NJ 07101 Robert L. Mitti General Manager Nuclear Assurance and Regulation July 3, 1985 Director of Nuclear Reactor Regulation U.S.
Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, MD 20814 Attention:
Mr. Walter Butler, Chief Licensing Branch 2 Division of Licensing Gentlemen:
ELIMINATION OF ARBITRARY INTERMEDIATE PIPE BREAKS HOPE CREEK GENERATING STATION DOCKET NO. 50-354 Pursuant to D. Wagner's request for additional information to support Public Service Electric and Gas Company's request for approval to eliminate the postulation of intermediate pipe breaks as specified by SRP 3.6.2 Sections II.1 and II.2, the following justification is provided as to why the systems for which arbitrary breaks are to be eliminated are not susceptible to thermal fatigue and mixing:
For the Hope Creek Generating Station ASME B&PV Class 2 and 3 piping, the Code design allowables are intended to prevent fatigue failure.
For Class 2 and 3 piping components, fatigue failure protection is provided for by the allowable stress range checks and a stress range reduction factor for thermal expansion stress.
This stress is included in the break stress ratio for all non-class 1 breaks.
Even after elimination of the arbitrary intermediate breaks, the cut-off for postu-lating mandatory breaks
(" threshold") is still 80 percent of the Code allowables.
As required by ASME B&PV Code Section III, a detailed fatigue analysis is performed in all class 1 piping systems.
For ASME B&PV Class :L lines, the conservatism allowed for fatigue failure is even more obvious.
The ASME Code limit for -the Cumulative Usage Factor (CUF) is 1.0 to assure that pipe fatigue failure will not occur.
The pipe break postulation limit is 10 percent of this number, and all of the Class 1 arbitrary ggg(
intermediate break locations involve CUFs below this p
I limit.
g !
The Energy People 8507090168 850703 PDR ADO' K 05000354 A
PDR 9sa m u m sa i
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.Dir. of Nuc. Reac. Reg.'
2 7/3/85 By limiting.the mixing offlow velocity, low temperature
- water with high - temperature. water, cyclic thermal stresses and the resultant thermal fatigue in the Hope Creek piping systems are minimized.
Thermal fatigue due.to pipe temperature gradients as a result of stra-tified flow results from the combining of. hot and cold flows at low flow velocity (laminar or transition flow) in combination with a horizontal' pipe run-with few
-valves and fittings which would promote mixing and limit stratification..
The piping. systems for which arbitrary intermediate breaks are to be eliminated will not exhibit tempera-ture gradients due to flow stratification based on a review which showed that the pipes have no flow during normal plant operation and therefore are not subject to hot / cold mixing, the piping layout consists of' vertical
. runs or: sloped horizontal runs with valves and fittings
~
'to promote mixing, and/or the piping is preheated,
_(e.g.,-HPCI/RCIC steam supply lines) to minimize ther-mal stresses during system initiation.
Based on the system design and-layout which minimizes thermal stratification and cyclical. stresses, and the analyses performed to verify the piping will experience no fatigue failure, the systems for which arbitrary breaks are to be eliminated are not susceptible to-thermal fatigue and mixing.
Should you have any questions in this regard, please contact
.b.
M f;. AI Very truly yours, i
l C
D.'H. Wagner USNRC-Licensing Project-Manager
-:- A. R..Blough USNRC Senior' Resident-Inspector
.-