ML20154R665
| ML20154R665 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 03/27/1986 |
| From: | Farrar D COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 1480K, NUDOCS 8603310127 | |
| Download: ML20154R665 (2) | |
Text
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'D Commonwrith Edison
'] ) One F rst National Plaza. Chicago. lltinois Address Reply to: Post Office Box 767 Chicago. Illinois 60690 March 27, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
LaSalle County Station Units 1 and 2 Use of ASME Code Case N-411 NRC Docket Nos-. 50-373 and 50-374 References (a): Letter from M. S. Turbak to H. R. Denton dated February 11, 1986.
(b): Letter from D. L. Farrar to H. R. Denton dated March 21, 1986.
Dear Mr. Denton:
In the reference (a) letter, Commonwealth Edison Company (CECO) requested approval to use the Pressure Vessel Research Council (PVRC) damping values contained in ASME Code Case N-411 for LaSalle Units 1 and 2.
The reference (b) letter supplemented this request and described the manner in which piping systems are modeled. In these letters, CECO-requested an expedited review of the' Code Case N-411 application so that PVRC damping values could be used in analyses of inaccessibile snubbers on Unit 1.
Two of the inaccessible snubbers are located on a Standby Liquid Control Subsystem which must be declared operable prior to fuel loading. The results of this analysis were discussed with R. Lagrange and other members of your staff on March 26, 1986 and are documented in this-letter. In order to prevent any delays in fuel loading, we request your prompt approval of the use of PVRC damping at LaSalle Units 1 and 2 as described herein and in the referenced transmittals.
Sargent & Lundy (S&L) has completed an evaluation for LaSalle Unit 1 which demonstrates that leaving three (3) _ inaccessible snubbers installed uninspected poses no safety concern. The snubbers are identified below:
System Snubber Standby Liquid Control (SLC)
SC02-1047S SCO2-1055S Reactor Water Clean-Up (RWCU)
RR28-1007S The S&L evaluation assumed the worst case failure mode for the snubbers. This failure mode assumes the snubbers are locked-up during piping thermal expansica and that they are unrestraining during a dynamic event.' This failure mode is conservative since the condition can never occur h
DR P
b
o' H. R. Denton March 27, 1986 at the same point in time. It is possibile that for some of the plant life, the snubbers could be locked rigid and for the remaining plant life the snubbers could be free moving dynamically.
To more accurately model the piping system during a dynamic event, Code Case N-411 (PVRC Damping) was used. The piping system raodel did not include any large equipment.
'In order.to satisfy all design allowables,.one minor modification is required. A U-Bolt on the 1 1/2" SLC system is to be tightened such that
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it will perform as an axial restraint. With this modification in place, the following conclusions are applicable:
(1) All ASME B&PV Code, Subsection NB-3650 stress criteria, are satisfied.
(2) All USNRC-MEB 3-1 stress criteria are satisfied. There are no additional locations requiring high energy line break postulation.
(3) The changes in support loads, auxiliary and mainframe steel loadings are accepta* ale with no modifications.
(4) Vendor allowables for equipment are satisfied.
(5) Vendor allowables for valve accelerations are satisfied.
During the March 26, 1986 telecon, your staff indicated that use of the PVRC damping for the above described application as well as other applications as described in the references (a) and (b) transmittals was acceptable. As such, we request your prompt approval of the use of PVRC damping recommendations as described in these transmittals for LaSalle Units 1 and 2.
As we previously indicated, use of ASME Code Case N-411 will be documented in a subsequent update to the LaSalle FSAR.
I If you have any further questions concerning this matter, please contact this office.
Sincere D. L. Farrar Director of Nuclear Licensing im cc:
Dr. A. Bournia - NRR Region III Inspector.- LSCS 1480K
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