ML20234D077
| ML20234D077 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 06/30/1987 |
| From: | Cockfield D PORTLAND GENERAL ELECTRIC CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TAC-65472, NUDOCS 8707070092 | |
| Download: ML20234D077 (3) | |
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e Portland GeneralElectricCompany David W. Cockfield Vice President, Nuclear Junc 30, 1987 l
Trojan Nuclear Plant Docket 50-344 5
License NPF-1 l
U.S. Nuc1 car Regulatory Commisslun i
ATTN: Document Control Desk Washington DC 20555
Dear Sir:
Main Steam Line Wal1 Thickness During the 1987 refueling outage, wall thickness measuromonts were obtained for the main steam lino piping inside containment. These measurements revealed an area at the outlet of the steam flow venturi i
on each line as being below the minimum allowable thickness. Analyses woro performed to demonstrate the acceptability of the as-found condi-tions. A report summarizing theco analyses was submitted for Nuclear Regulatory Commission (NRC) review on June 11, 1987.
In accordance with the Final Safety Analysis Report, the original construction code for the main steam piping is American National Standards Institute (ANSI) B31.7-1969 Edition with Addenda through 1971. This Code provides allowabic stress values for piping materials and refers the user to ANSI B31.1.0 to determino minimum wall thickness requirements for Class II piping. Utilizing ANSI B31.1.0, the original design calculations determined the minimum allowable wall thickness to be 0.858 inches.
During the wall thickness examination, areas as low as 0.807 inches were discovered with a very localized area of 0.780-0.790 inches identified on the "B" main steam line.
The Introduction to ANSI B31.7-1969 indicates "the specific design requirements of the Codo usually revolvo around a simplified engineer-ing approach to a subject.
It is intended that a designer capable of l
applying more complete and rigorous analysis to special or unusual problems shall havo latitudo in the development of such designs and the evaluation of complex or combined stresses".
Since the regions of the main steam line which are below the minimum wall thickness requirements do not satisfy the simplified approach of Subsection 2 of ANSI B31.7, a more complete and rigorous analysis was used.
8707070092 B70630 PDR ADOCK 0500 4
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Pbrtland General Electdc CoriT) arty i
Document Control Desk June 30, 1987 Page 2 The more complete and rigorous analysis was performed utilizing " Design by Analysis" procedures like those of American Society of Mechanical Engineers (ASME)Section VIII, Division 2, the Class 1 design rules of ASME Section III, Division 1, and Appendix F of ANSI B31.7.
These
" Design by Analysis" procedures are given in the_" Criteria of the ASME Boller and Pressure Vessel Code for Design by Analysis in Sections III and VIII, Division 2".
The analysis is based on the maxi-mum shear theory for combining stresses. This methodology calculates stress intensities (ie, primary general membrane and primary local membrane) and compares these values to multiples of the allowable stress intensity.(S ) for the given material. Since the allowable m
stress intensity is based only on the physical properties (Sy and S ) of the material being utilized, this analytical methodology is u
independent of piping code classifications. These more rigorous analyses demonstrated the as-found wall thickness was acceptable.
Recognizing that ANSI B31.7-1969 is a relatively old code and has since been superseded, the analysis performed was verified using the more current methodology of the 1983 Edition of Section III of the ASME-Boiler and Pressure Vessel Code. This analysis was performed in accor-dance with Paragraph NC 3200 for Class II components. The results of i
this analysis were presented in the report provided to the NRC on l
June 11, 1987.
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t In discussing these analyses with members of the NRC staff, several questions arose regarding the application of the Code by PGE.. The NRC
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Staff has questioned if the more rigorous analysis methodology provided j
in Appendix F of ANSI B31.7 is limited to use only on piping designated I
as Class I.
While Portland General Electric Company.(PGE) and the'NRC continue to discuss this issue, the NRC has concluded the analyses performed by PGE are acceptable to justify two cycles of operation before permanent corrective actions must be completed.
On this basis, PGE has agreed to complete one of the following three actions before the startup from the 1989 refueling outage:
1.
Demonstrate to the NRC's satisfaction the acceptability of the Code applications used for the main cteam line analyses.
2.
Upgrade the main steam lines inside Containment from Class II to Class I per ANSI B31.7.
3Property "ANSI code" (as page type) with input value "ANSI B31.7.</br></br>3" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process..
Repair or replace the main steam piping sections where the original minimum wall thickness requirements are not satisfied.
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Podland GeneralBechicCompany Document Control Desk June 30, 1987 Page 3 I
We trust this approach is acceptable to the NRC for resolution of the startup issue. We will be in contact with the NRC Staff in the near future to cone to a final resolution on the Code application questions.
Sincerely, I
c:
Mr. John B. Martin Regional Administrator, Region V U.S. Nuclear Regulatory Commission Mr. R. C. Barc NRC Resident Inspector Trojan Nuclear Plant J
i Mr. David Kish, Director State of Oregon Department of Energy l
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