Information Notice 1979-36, Computer Code Defect in Stress Analysis of Piping Elbow
| ML031180207 | |
| Person / Time | |
|---|---|
| Site: | 05000000 |
| Issue date: | 12/31/1979 |
| From: | NRC/OI |
| To: | |
| References | |
| IN-79-036, NUDOCS 7910250519 | |
| Download: ML031180207 (2) | |
UNITED STATES
SSINS No.: 6870
NUCLEAR REGULATORY COMMISSION
Accession No:
OFFICE OF INSPECTION AND ENFORCEMENT
7910250519 WASHINGTON, D.C.
20555
December 31, 1979
IE Information Notice No. 79-36 COMPUTER CODE DEFECT IN STRESS ANALYSIS OF PIPING ELBOW
Description of Circumstances
The NRC was informed on December 17, 1979 that a computer code, NUPIPE, used
in the stress analysis of pipinq systems contained a defect which could result
in incorrect stress values at one end of pipinq elbows. This defect was iden- tified from discussions with a user of NUPIPE and the NUPIPE code developers.
The stress calculation error can occur when a flexible joint is modeled at the
end of an elbow (ELBOW-ELASTOJT connection in NUPIPE terminology). This defect
in the N1IPIPE code is in the transformation of the loads in the ELASTOJT coordin- ate axis to the piping ELBOW coordinate axis. The incorrect coordinate axis
transformation may incorrectly interchange the torsion and bending moment loads
on the pipinq elbow. This can result in the incorrect assignment of the stress
intensification factor for the individual moments. The correct stress may be
hiaher or lower than calculated by NUPIPE, depending on the loading condition.
Four conditions must exist for the possibility of the calculation of an incorrect
stress in the NUPIPE code:
1. an USAS B31.1.0 - 1967 Code analysis is being done, and
2. an ELBOW-ELASTOJT connection exists, and
3. an absolute sum of two load cases is beinq calculated, and
4. the ELBOW torsional moment axis does not align with the ELASTOJT local
x-axis.
Possible users of the NUPIPE code include the code developer, Stone and Webster, EG&G (Idaho Falls), and those using the Cybernet system. The NRC is currently
reviewing the extent of usage of the NUPIPE code and the generic implications
for other facilities. There is a potential for a similar defect to occur in
other piping analysis computer codes.
This Information Notice is provided as early notification of a possible siqnif- icant matter. It is expected that recipients will review the information for
possible applicability to their facilities. No specific action is requested in
response to this Information Notice. If NRC evaluations so indicate, further
licensee actions may be requested or required. If you have any questions
regarding this matter, please contact the Director of the appropriate NRC
Reaional Office.
No written response to this IE Information Notice is required.
-7 IE Information Notice No. 79-36
December 31, 1979
Enclosure
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