ML20235T560
| ML20235T560 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 09/28/1987 |
| From: | Hollingshaus H BECHTEL POWER CORP. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8710130128 | |
| Download: ML20235T560 (2) | |
Text
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Bechtel Western Power Company Engineers - Constructors Fifty Beale Street San Francisco, Cahfornia MaII Address; n0 box 3965. San Francrsca CA 94119 September 28, 1987 Mr. Thomas Murley Director, Office of Nuclear Reactor Regulation i
United States Nuclear Regulatory Commission
(
Washington, DC 20555
Reference:
Letter, M.
R.
Wisenbury (HL&P) to USNRC Resolution of Concerns Relative to the ME101 Stress Analysis
- Program, File No.
ST-HL-AE-2306: G12.396, dated July 16, 1987
Dear Sir:
The reference letter notified the Nuclear Regulatory Commission of the actions taken by Houston Lighting and Power with regard to a specific ME101 error.
The letter indicated that the generic implications of this issue would be addressed by Bechtel Western Power Company.
The letter stated that the error affected four stress analysis problems, and that reevaluations of these problems demonstrated that the error did not affect the validity of the previous stress analysis.
We have evaluated the effect of the error on all Bechtel projects where ME101 was used.
The use of the specific combination of ME101 features necessary to invoke the error was not used on any project, other than the South Texas Proj ect.
The attachment provides a description of the error, the chronology of events related to the error, and a summary of the procedures utilized in the course of our investigative activities.
In summary, the error had no effect on any other Bechtel projects; the only facility to have piping system analysis with the error was the South Texas
)
Project.
If you have any additional questions on this matter, please contact
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me at (415) 768-0788.
Very truly yours, i
BECHTEL WESTERN POWER COMPANY i
spoq8oM$$8ge
(
H. Hollingshaus Manager of Engineering HH:LM:TEB:epk Attachment ygo h
1111n-1 A Unit of Bechtel Power Corporation
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I.
DESCRIPTION OF ERROR Bechtel standard computer program ME101 (Linear Elastic Analysis Program) is used to perform ASME Section III, Class 1, 2 and 3 piping stress j
analyses.
A Bechtel ctress analyst at South Texas Project noticed a discrepancy between the ME101 calculated values in the project stress
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analyses and a subsequent ME101 analysis using a different processing-l option and notified Bechtel Western Power Company (BWPC) ME101 technical l
specialist, who evaluated the discrepancy.
The evaluation showed the concern to be confined to the use of a specific processing option (EAL Solver) when performing Class 1 piping stress analyses in accordance with
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the ASME Code Section III Winter 1975 addenda,
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The discrepancy involves the modeling of the stiffness of Class 1 piping I
tees in accordance with the ASME Section III Winter 1975 addenda Section i
NB-3687.4.
Section NB-3687.4 requires that the branch connection be treated as extending to the center line of the run with the imaginary juncture and the imaginary length of branch piping to 'be assumed as I
rigi d.
However, the ME101 program update in 1984 that included this requirement results in low stiffnesses for the imaginary elements for specific sizes of tees (branch to run diameter ratio > 0.7) in Class 1 piping systems.
The forces, moments and stresses calculated by the previous version of ME101 for a piping system containing one or more Class 1 tees of the affected size, may not be accurate at all data points.
When the imaginary elements of the tee (s) are treated as rigid, redistribution of the forces and stresses can result in higher values for some data points.
The recalculated values from the ME101 analyses could impact the following:
o Pipe support design load input o
Calculated pipe stress versus ASME Coda requirements l
o Calculated equipment nozzle loads (including Reactor Coolant System loop nozzles) o Input loads for Leak Before Break (LBB) analyses l
II. CHRON0 LOGY OF EVENTS RELATED TO ERROR l
Error Identified: 5-18-1987 Error Confimed: 5-20-1987 Error Notice Issued: 6-2-1987 PIR (Problem Investigation Request) Issued: 6-22-1987 III. QA PROCEDURES APPLICABLE l
1.
EDP 4.36 - Standard Computer Programs 2.
EDP 4.38 - Computer Program Error Reporting and Corrective Action 3.
EDP 4.74 - Problem Investigation Request i
1111n-2 L
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