ML20079K717
| ML20079K717 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 10/18/1991 |
| From: | Lyster M CLEVELAND ELECTRIC ILLUMINATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.084 GL-88-01, PY-CEI-NRR-1374, NUDOCS 9110240140 | |
| Download: ML20079K717 (2) | |
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C.8-un PERRY NUCLEAR POWER PLANT und Ad*ess:
PO. DOx n Micha91 D. Lyster i
to NNTER ROAD nW. OHIO 4M VICE P9ESIDENT NUCLEAR NRW. OHIO 44081 lam em October 18, 1991 PY-CEI/NRR-1374 L b
I U.S. Nuclear Regulatory Commission Document Control Desk l
Vashington, D. C.
20555 Perry Nuclear Power Plant Docket No. 50-440 Snubber Optimization Prograim, R.G. 1.84 and ASHE Code Case N-411-1 Application and Clarification Gentlement 1
The purpose of this letter is to inform you of the planned snubber optimization program at the rerry Nuclear Power Plant (PNPP) and to identify our applien ion of ASHF ;
guidance which vill require performence of a case-wpecific evahmtion e NRC reviev of that evaluation.
Historically, snubbers vele extensively uced in piping analysis to mitigate the effects of earthquake and other dynamic loads.
Perry, as well as much of the industry, has found that snubbers are complex and require extensive maintenance and functions 1 testing programs to assure reliable snubber and piping system performancos. These programs have resulted in increased. levels i
of occupational radicioa exposure and increased,,lant operating and maintenance costs. As a result of these concerns, Technical and Steering Committees on piping vet e organized by the Pressure Vessel Research Cominittee (PVRC) with active indu*try and USNRC participation.
These groups have 1
developed more realisti: methods for dynamic analysis.
At the next refueling rutage, which commences in March 1992 PNPP vill start implementing the snubbar optimization program. Tr.e four major goals of our program are to improve safety, reduce occupational radiation exposure, decrease maintuance costs, and to improve system reliability.
The refuel outage efforts vill-bo concentrated on systems within the Unit 1 dryvell, specifically.reactar ecircul.atiot., feedvater, reactor water cleanup, and all i ing within the dryvell.
Once these initial systems are associated branch f
complete, our int' it! op. is to continue the program for oth'er systems and other areas of the plar. viere similar -benefits can be realized.
One of-our analyt. ta ; techniques used for snubber optimization is the l
L application of ASH. Oode Case N-411-1.
This Code case is currently recognized in Regulatory Guide
'.04, " Design and Fabrication Code case Acceptability, ASME Section III Divi ion 1", Revision 27 dated November 1990. There exist 9110240140 911018 PDR ADOCK.05000440 -
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USNRC October 18, 1991 PY-CEl/NRR-1374 h five conditions within Reg. Guide 1.84 which must be met to implement the Codt Cace.
PNPP intends to comply with all five conditions, however, the fifth condition requires a case-specific evaluation to be performed (with subsequent teview by the NRC) for application of the Code Cast; on piping in which intergranular stress corrosion cracking (IGSCC) has occurted.
PNPP has feedvater system piping which through previous inservice Examination tin tefuel outage #2) has shown " indications" of pottsntial IGSCC and for which snubber reduction is also planned utiliring Code case N-411-1.
Specifically, our letter dated Hatch 25, 1991 (PY-CE1/NRR-1337b), which is attached for fnformation, identified ultrasonic testing indl. cations on two velds asseelated with the feedvater RPV nozzle'to safe end velds. The indications vere conservatively assumed, for analysis purposes, to be the result of stress corrosion cracking. That letter and technical analysis has been reviewed by your staff. The NRC letter dated September L2, 1991 noted that folleving inspection and evaluation of the identified indications during the third refueling outage, NRC approval vill be requited prior to startup.
Concurrent with the plans for snubber optimLzation implementation on the feedvater systr;m during our third refuel outage, ve are also scheduling a mechanical stress improvement process (HSIP) at the two feedvator system velds containing the indications. The HSIP is expected to successfully arrest any crack growth.
It is recognized that the NRC has estsblished critella in Generic Letter 88-01 for shon applications of stress improvement vill be consider (d to affectively mitigate cracks (from a regulatoty standpoint);
1.e., the ernck does not exceed 30% through vall or 10% of the circumference. Assuming cracking has not progressed past these criteria, the case-specific evaluations for this situation vill recognize the ef fectivene' i of HSIP in mitigating further growth. Assuming cracking has grown beyond these criteria, the evaluations vill take into account post-MSIP crack size inspection results.
All evaluations vill consider any revised nozzle veld loadinFs (and resultant-stresses) following implementation of snubber optimization, and the evaluation vill keep applicable stresses within pertinent ASME Code allovables. The evaluation results vill also be provided for NRC review prior te restart from the third refueling outage.
All of the feedvater HSir and.feedvater snubber reduction work is planned to be implemented during our third refuel outage which is presently scheduled to start in March 1902. If the NRC staff has any questions or concerns related to snubber optimization on the fewister system prior to receipt of the case-specific evaluates 1, please feel free to call, and any necessaty di.
sions vill be supported. It vould be appreciated if any such o.wstions could be discussed prior to December 1, 1991, in consideration of the tefuel i
outage scheduling process.
Sinperely, p/
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, v 4wLL Mt c) ff 4 Michael D.
y ter HDLtHJHisc Attachment cet NRC Project Manager NRC Resident Inspector Office NRC Region 111
.