ML20209H020
| ML20209H020 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 04/24/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20209H006 | List: |
| References | |
| NUDOCS 8705010121 | |
| Download: ML20209H020 (1) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATIVE TO TOPUS ATTACHED PIPING MODIFICATIONS - MARK I PROGRAM PHILADELPHIA ELECTRIC COMPANY PEACH BOTTOM UNIT 3 DOCKET NO. 50-278 1.0 DISCUSSION AND EVALUATION By letter dated February 20, 1987, the licensee Philadelphia Electric Company, sought the staff approval of the intended use of actual material 1
properties from Certified Material Test Reports (CMTRs) for determining i
allowable piping stress in the resolution of Mark I containment hydro-dynamic loads at the Peach Bottom Atomic Power Station Unit 3.
Actual i
material properties will be utilized in a single instance to qualify a piping system which has a stress combination level that slightly exceeds the code allowable. This situation involves the Unit 3 RHR system outside containment in the vicinity of a torus nozzle. This one location is a tapered transition to a valve. The stress combination level that exceeds the code allowable is the upset (Level B) combination. All other loading combinations and associated stress levels meet code allowables. The load case involved is Pressure + Weight +SRV which is to produce stresses less than nr equal to 1.2 S, where SR ggbpresentsmultipleactuationof t
i six adjacent valves fo IBA/SBA L kt The calculated stress under the i
combined loading is 18,104 psi, based upon a stress intensification factor l
(SIF) of 1.77, whereas code allowable is 18,000 psi.
1 An allowable stress of 21,896 psi was then calculated by the licensee using the CMTR values of yield strength, Sy, and ultimate strength, Su.
i This allowable stress was taken as the minimum of 1/4 Su (Su=72,990 psi) or 5/8 Sy (Sy=47,530 psi) which is consistent with the 1977 ASME BAPV Code,Section III, Division 1 through the Summer 1977 Addenda, used to l
qualify this piping for Mark I hydrodynamic loading. Note that, for the same load case, if NC-3650 from the 1980 ASME B&PV Code,Section III j
through the Winter 1981 Addenda were used, the resulting stress level would i
be well below the code allowable, without use of the actual material l
properties. This situation is attributed to the use of stress indices, i
as well as the change of code allowable from 1.2 Sh to 1.8 Sh, in the l
1980 ASME Code, for the same load case.
1 j
2.0 CONCLUSION
f The staff has reviewed the licensee's analysis and has determined that there would be an acceptable margin of safety under postulated abnormal i
i conditions. The staff concludes that the use of actual material properties as proposed by the licensee for the one specific instance is acceptable for resolution of Mark I containment hydrodynamic loads at Peach Bottom Unit 3.
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Principal Contributor:
A. Lee j
8705010121 870424 PDR ADOCK 05000278
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