ML19211C818
| ML19211C818 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 12/31/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 8001150033 | |
| Download: ML19211C818 (1) | |
Text
C UNITED STATES
/ " %,#'c,
- b*
NUCLEAR REGULATORY COMMISSION
/
f
.t
- / 1 REGION IV
'i 0
611 RY AN PLAZA oRIVE, SUITE 1000 2
e'.k).'$1S' f
'd 3
ARLINGTON, TEX AS 76012 5
2, s%.,,.. 4 December 31, 1979 In Reply Refer To:
RIV Docket Nos. 50-498/IE Information Notice No. 79-36 50-499/IE Information Notice No. 79-36 Houston Lighting & Power Company ATTN:
Mr. E. A. Turner, Vice President Power Plant Construction and Technical Services Post Office Box 1700 Houston, Texas 77001 Gentlemen:
The enclosed IE Information Notice No. 79-36 provides information on a computer code defect which can result in incorrect stress values for piping elbows.
Sincerely,
/
^
a_,
f.f; (i lU
~ Karl" V. Seyfrit, Director
Enclosures:
1.
IE Information Notice No. 79-36 2.
List of Recently Issued Information Notices 1744 300 R0"1150033
UNITED STATES SSINS No.:
6870 NUCLEAR REGULATORY COMMISSION Accession No:
OFFICE OF INSPECTION AND ENFORCEMENT 7910250519 WASHINGTON, D.C.
20555 IE Information Notice No. 79-36 Date: December 31, 1979 Page 1 of 1 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 piping systems contained a defect which could result in incorrect stress values at one end of piping 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-ELAST0JT connection in NUPIPE terminology).
This defect in the NUPIPE code is in the transformation of the loads in the ELAST0JT 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 piping elbow.
This can result in the incorrect assignment of the stress intensification factor for the individual moments.
The correct stress may be higher 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-ELAST0JT connection exists, and 3.
an absolute sum of two load cases is being calculated, and 4.
the ELBOW torsional moment axis does not align with the ELAST0JT local x-axis.
Possible users of the NUPIPE code include the code developer, Stone and Webster, EG6G (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 signif-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 Regional Office.
}
No written response to this IE Information Notice is required.
IE Information Notice No. 79-36 December 31, 1979 LISTING OF AECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To Notice No.
Issued 79-31 Use of Incorrect Amplified 12/13/79 All power reactor Response Spectra (ARS) facilities holding Operating Licenses (OLs) and Construction Permits (cps) 79-32 Separation of Electrical 12/21/79 All power reactor Cables for HPCI and ADS facilities holding Operating Licenses (OL) and Construction Permits (cps) 79-33 Improper Closure of 12/21/79 All power reactor Primary Containment facilities holding Access Hatches Operating Licenses (OL) and Construction Permits (cps) 79-34 Inadequate Design of 12/27/79 All holders of of Safety-Related Heat power reactor Exchangers Operating Licenses (OLs) and Con-struction Permits (cps) 79-35 Control of Maintenance 12/31/79 All power reactor facilities and Essential Equipment with an Operating Licenses (OLs) and Construction Permits (cps) 79-36 Computer Code Defect 12/31/79 All holders of power reactor Stress Analysis of Piping Operating Licenses (OLs)
Elbow and Construction Permits (cps)
Enclosure 1744 302)