ML20198J875
| ML20198J875 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 05/28/1986 |
| From: | Allen C COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 1710K, NUDOCS 8606030237 | |
| Download: ML20198J875 (5) | |
Text
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\\ Commonwe:lth Edison
) One First National Plaza, Chicago. Hhnois
^D ' Address Arply to: Post Office Box 767 Chicago, Illinois 60690 May 28, 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 Snubber Reduction Program Topical Report NRC Docket Nos. 50-373 and 50-374 Reference (a): Letter transmitting Snubber Reduction Program Topical Report dated April 18, 1986 from C. M. Allen to H. R. Denton
Dear Mr. Denton:
On April 18, 1985, the Commonwealth Edison Company submitted a topical-report (reference (a)) for NRC review and approval. Subsequently, Commonwealth Edison representatives met with the NRC Staff in Bethesda, on May 13, 1986, to discuss which items in that report are acceptable for universal application at LaSalle. The purpose of this letter is to document the consensus reached during the May 13th meeting and specifically request approval for peak Shifting (ASME Code Case N-397) and High Energy Line Breaks (no arbritrary intermediate break locations).
Attachment I displays a comparison between FSAR criteria and the criteria proposed in reference (a). Please note that some of the criteria in Attachment 1 are the same criteria contained in the FSAR. These criteria are included for the sake of completeness. Attachment 2 further describes and clarifies other matters discussed during the meeting.
The Commonwealth Edison Company understands that on a case-by-case basis, the NRC Staff will consider allowing the use of advanced analysis techniques and relaxed design criteria in a limited number of cases.
Examples of when a deviation request might be appropriate include a situation where FSAR techniques and criteria do not allow the removal of a difficult-to-access snubber in a high radiation area or a snubber which is highly prone to failure.
In these cases, a deviation request will be discussed with the NRR Staff describing the extenuating circumstances and the specific methodology to be used to justify removal.
PDR ADOCK 05000373
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8606030237 860528 P
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F-Mr. H. R. Denton May 28, 1986 Commonwealth Edison requests a written response from the NRC on the items identified as soon as possible to allow the selection of a vendor to use these techniques in the first refueling outage of LaSalle county Station Unit 2.
When the NRC response is received, these changes along with the use of the previously approved ASME Code Case N-411 will be incorporated into the updated FSAR.
For other items in the original topical report (reference (a)),
we request your review and approval in a manner consistent with your implementation schedule for recommendations in NUREG-1061.
If there are any further questions regarding this matter, please contact this office.
Very truly yours, C. M. Allen Nuclear Licensing Administrator 1m Attachment cc:
Dr. A. Bournia - NRR Resident Inspector - LSCS 1710K
i ATTACHMENT 1 LASALLE COUNTY STATION SNUBBER REDUCTION PROGRAM COMPARISION FSAR CRITERIA AND PROPOSED CRITERIA AND METHODOLOGIES PROPOSED CRITERIA FOR SNUBBER REDUCTION ITEM PSAR PROGRAM
- 1. Damping Reg. Guide 1.61 ASME Code Case N-411*
- 2. Modal Combination Reg. Guide 1.92 Existing FSAR
- 3. Direction Combination Reg. Guide 1.92 Existing PSAR
- 4. peak Shifting Not considered ASME Code Case N-397
- 5. Input Spectra Envelope Response Spectra Existing FSAR
- 6. OBE/SSE Stress ASME,Section III 1974 Existing FSAR Criteria (piping and supports)
- 7. High Energy Line Breaks Terminal ends and two No arbitrary interme-arbitrary intermediate diate break locations, locations
- 8. Auxiliary Steel for Same as that for structural Existing FSAR pipe supports steel (see Att. 2 for detail)
- 9. Seismic Anchor Not specifically addressed.
SAM plus inertial Motions (SAM) loads combined by SRSS
- 10. Load Combination Hydraulic transients, where Hydraulic transients applicable, will be combined will be decoupled from with inertial loads by SRSS SRV (inertial) loads, method.
if time phasing can be justified. Hydraulic transients will conti-nue to be combined with seismic loads by SRSS.
- CECO has received authorization to use ASME Code Case N-411 in a letter from E. G. Adensam to D. L. Farrar dated April 1, 1986.
1710K
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e 2.
Load combinations for BOP Piping Systems Another item which was discussed during the meeting dealt with load combinations to be used for BOP piping systems. Ceco stated that some hydraulic transient loads such as turbine trip loads were not combined with building inertial loads resulting from SRV discharge for NSSS systems. Decoupling of these loads was justified on the basis of time phasing of the events. The same approach will be considered for the BOP systems. Ceco will use a 10 CPR 50.59 Safety Evaluation to document changes made to load combinations used in the original design.
1~110K t_
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ATTACHMENT 2 1.
Auxiliary Steel for Pipe Supports The design of pipe support hardware follows the requirements of ASME Code Section III or ANSI B31.1, as applicable. The design of auxiliary steel is not specifically addressed in the FSAR but generally follows the FSAR criteria for building steel in Sections 3.8.3.5.2 and 3.8.4.5.2.
3.8.3.5.2 Structural Steel For the working stress load combinations specified in Subsection 3.8.3.3, the stresses in structural steel are limited to those specified in Part I of the 1969 AISC specification with no overstress allowed for earthquake loads.
For the yield stress load combinations, steel stresses are limited to 1.6 times the AISC working stress allowables but no more than 0.95fy ensuring a safety factor of 1.05 against yield.
Under working stress conditions, deflections are limited to L/200 for floor beams.
In all loading cases, steel deformations are limited by the steel stresses to the elastic range.
3.8.4.5.2 Structural Steel The stresses and strains in structural steel are limited to those specified in the 1969 AISC Specifications, Part I, for the service load combinations of Subsection 3.8.4.3.
The related margins of safety are as described in the commentary, Section 1.5, of the specifications. No overstresses are allowed for severe environmental loading combinations.
For the design-basis load combinations the allowable stresses are increased to 1.6 times the AISC allowable but not more then 0.95 times the steel yield strength, ensuring a margin of safety of 1.05 against steel yielding.
In both loading cases, steel deformations are limited since stresses are held within the elastic range. Thus, an additional margin of safety against failure is provided since no plastic deformation allowed.
In addition, deflections are checked and kept within the limits prescribed in the AISC specification.
In instances where the weak axis bending governs the design, the basic AISC allowable is 0.75 times the material yield strength. Therefore, only a 1.33 increase factor for SSE load conditions was used.
In addition to maintaining stresses in the elastic range, the maximum deflection of steel members is generally limited to i 1/4 inch. Dynamic displacement of auxiliary steel may exceed i 1/4 inch if the effect of the larger displacement on the piping is evaluated. The above stress and deflection criteria are consistent with the functionality and operability requirements of piping systems.
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