ML17054B905
| ML17054B905 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 09/26/1985 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Hooten B NIAGARA MOHAWK POWER CORP. |
| References | |
| NUDOCS 8509300439 | |
| Download: ML17054B905 (2) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SEP 2 6 1985 Docket No. 50-410 Mr. B. G. Hooten, Executive Director Nuclear Operations Niagara Mohawk Power Corporation 300 Erie Boulevard West
- Syracuse, New York 13202
Dear Mr. Hooten:
SUBJECT:
USE OF ASME CODE CASE N-392 FOR NINE'h1ILE POINT 2 This is in response to your July 25, 1985 application (submitted through your
- attorney, Mark J. Wetterhahn) to utilize an alternative to the requirements of 10 CFR 50.55a.
Specifically, you requested approval of the use of ASME Code Case N-392 for Nine Mile Point Unit 2.
Code Case N-392 is not listed in any revision of Regulatory Guide 1.84 or 1.85; Code Case N-392 entitled Procedure for Evaluation of the Design of Hollow Circular Cross Section Welded Attachments on Class 2 and 3 Piping Section III, Division 1, was developed because the. Code does not specifically address this type of attachment to a pipe.
Attachment A to your application stated the following:
1)
The current analysis technique employs qualified computer programs PITRUST and PITRIFE to determine the stresses in the joint for the design and service loading conditions.
2)
The PITRUST program is based on the Welding Research Council Bulletin WRC-107 method of analysis.
PITRIFE, which was developed later, uses a
finite element method of analysis and is applicable to large trunnion-to-run pipe diameter ratios not covered by PITRUST.
Both programs are in compliance with the ASME III'equirements for evaluating the pressure boundary integrity.
3)
The design approach in the Code Case utilizes the criteria of Subarticle NC-3650 with the addition,of a term which contains the stress due to the discontinuity at the junction of the trunnion and the pipe.
The Code Case permits higher allowable stresses for primary loads with the condition that additional criteria be met, and the method of analysis is more conservative than PITRUST. and PITRIFE.
In surInIary, this Code Case provides an alternate method for qualifying a trunnion joint which may otherwise be physically modified in order to pass code allowables.
The Code Case is based on a more realistic calculation of stress and represents a more up-to-date approach to the design of a trunnion joint.
It is an alternate method which does not affect plant safety.
It helps to 850'P3DO439 8
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