ML20210E559
| ML20210E559 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Diablo Canyon |
| Issue date: | 03/24/1986 |
| From: | Rossi C Office of Nuclear Reactor Regulation |
| To: | Schierling H Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML082840462 | List:
|
| References | |
| FOIA-86-197 NUDOCS 8603270412 | |
| Download: ML20210E559 (4) | |
Text
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UNITED STATES 8"
NUCLEAR REGULATORY COMMISSION o
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WASHINGTON, D. C. 20555
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MAR 2 41996 MEMORANDUM FOR: Hans Schierling, Senior Project Manager PWR Project Directorate #3 Division of PWR Licensing-A FROM:
Charles E. Rossi, Assistant Director for PWR-A Division of PWR Licensing-A SURJECT:
ACCEPTANCE OF USE OF ASME CODE CASE N-411 FOR i
DIABLO CANYON UNITS 1 AND ?
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The staff has reviewed and evaluated the licensee's request for the approval of the use of ASME Code Case N-411. The attached evaluation apnroves the use of Code Case #N-411 with snme restrictions and provides the basis for approval.
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b c /b hw Charles E. Rossi, Assistant director for PWR-A Division of PWP Licensing-A
Attachment:
As stated cc:
R. L. Ballard B. J. Youngblood J. Brammer G. Ragchi l
Contact:
G. Bagchi X-27070
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o Diablo Canyon Units 1 and ?
Engineering Branch, PWR-A Evaluation of Request ror Use of ASME Code Case N-411
Background:
The licensee proposed in a letter #DCL-84-183 dated 5/16/84 to eliminate snubbers and presented criteria to be used in the proposed program.
In a letter #DCL-86-009 dated 1/21/86 the licensee indicated that the use of ASME Code Case N-411 should facilitate elimination of unnecessary snubbers, since the use of damping values allowed by N-411 should reduce the seismic loading on the remaining supports. The licensee has requested general approval for the use of N-411. The purpose of this evaluation is to review the acceptability of the licensee's proposal.
Evaluation: The NRC Piping Review Committee in its report (NUREG 1061 Vol 5) recommended acceptance of N-411 and ranked this item'as A2 for regulatory change. The basis for acceptance is a staff sponsored study which showed that a new design with fewer seismic restraints (using N-411 damping values) had equal or even hiaher reliability than the original stiff system when seismic and thermal loads were considered simultaneously (see NUREG 1061 Vol 2 page 2-4).
In Volume 5 of NUREG 1061 the Committee recommends immediate implementation of N-411 criteria.
The Piping Review Committee recommendation is generic and applicable for use in all power reactor piping design.
Based on this discussion, the use of ASME Code Case N-411 is acceptable for the piping reanalysis of Diablo Canyon Units 1 and 2 with certain restrictions detailed below:
(1) Use of N-411 is limited to only those cases where response spectrum i
method of seismic analysis is performed along with the modal superposition technique.
(2) The FSAR and other applicable documents must be anended to identify all pipe stress packages reanalyzed using N-411.
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-2 (3) All revised piping stress analyses packages must he identified as calculations of record, and must, therefore, be subject to applicable requirements of 10 CFR Part 50 Appendix B.
(4) Where predicted maximum piping displacement using N-411 criteria exceed the current design calculations, a physical verification of the availability of adequate clearance with adjacent structures, equipment and components must be performed.
For equipment mounted on piping, such as valves with extended structures, proper account must be taken for both rotation and translation in arriving at the predicted maximum displacement at the extreme ends of the pipe mounted equipment.
(5) Verify that the operability qualification level of pipe mounted equipment is not exceeded by the predicted response using N-411.
(6) Verify that the existing design loads of piping supports are not exceeded by new loads predicted by the use of N-411.
(7) Verify that the cumulative effect of the changes of loads on piping supports that are in turn supported by a structural element of building, such as walls, slabs, beams and columns, does not exceed the load carrying capacity of the affected structural element.
(8) The use of N-411 damping values is restricted to piping sections only.
N-411 damping values must not be mixed in with the Regulatory Guide (R.G.) 1.61 values. This is specially important to note since the R.G.
1.61~ damping values could be higher for some modes (higher frequency modes) compared to the values permitted by N-411.
Also, fi-411 damping values are not applicable to equipment and components either
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. attached to or mounted on the pipe.
For a piping run with equipment and component the composite damping approach is acceptable.
In the composite ' damping approach energy dissipation in piping sections should be consistent with the N-411 damping values and energy dissipation in eaufpment should be consistent with R.G. 1.61 damping values.
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Conclusion:==
The staff finds the licensee's request for the use of ASME Code Case N-411 acceptable with certain restrictions indicated above.
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