ML20207F039

Informs That NRC Planning to Issue Info Notice Discussing Problem Reported by Holtec Intl Re Erroneous Results from Ansys Computer Code.Review of Encl Draft of Info Notice to Ensure Accuracy of Technical Info Requested

ML20207F039
Person / Time
Issue date:	06/02/1999
From:	Marsh L NRC (Affiliation Not Assigned)
To:	Bryan W External (Affiliation Not Assigned)
References
NUDOCS 9906080013
Download: ML20207F039 (5)

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June 2, 1999-Mr. Willi:m Bry:n< Quality Assur:nce Ming:r

Ansys incorporation 275 Technology Drive 1 Canonsburg, Pennsylvania 15317-9565

SUBJECT:

REQUEST FOR A TECHNICAL REVIEW OF A DRAFT INFORMATION' NOTICE REGARDING ERRONEOUS RESULTS FROM AN ANSYS COMPUTER CODE Mr.' Bryan:

The U.S. Nuclear Regulatory Commission (NP.C) is planning to issue an information notice discussing a problem reported by Holtec Intemational regarding er oneous results from an Ansys computer code. We ask that you review the enclosed draft of that information notice to ensure the technical information is accurate.' Your cooperation in this matter is appreciated.

Please return any comments you may have as soon as possible. A copy of this request and your response will be placed in the Public Document Room for review by the public. Your response should be mailed to:

U.S. Nuclear Raulatory Commission ATTN: Thomas Greene, NRR/REXB

. MAIL STOP: 0-12D1

" Washington, DC 20555-0001

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Please address any questions you may have on this matter to Tom Greene of my staff.

Mr. Greene may be reached by phone 301-415-1175. If no comments are received by close of business on June 10,1999, we will assume the technical information in the notice is correct.

Orig. /s/'d by Ledyard B. Marsh, Chief Events Assessment, Generic Communications and Non-Power Reactors Branch Division of Regulatory improvement Programs Office of Nuclear Reactor Regulation

Enclosure:

Draft Information Notice -

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To receive a copy of this document, indicate in the box C= Copy w/o attachment / enclosure E= Copy with attachment / enclosure N = No copy OFFICE PECB: DRIP

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d UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION 1 WASHINGTON, D.C. 20555 June XX,1999 l

NRC INFORMATION NOTICE 99-XX:

ERRONEOUS RESUL'iS FROM A COMMERCIALLY AVAILABLE COMPUTER CODE l

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r All holders of operating licenses or conttruction permits for nuclear r reacto'rs.

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The U.S. Nuclear Regulatory Commission (NRC) is issuing this infi atiori notice to alert \\,

addressees of the use of a commercially available computer code t

,if used in modeling i

sensitive nonlinear phenomena, could yield erroneous results it is that recipients will review the information for applicability to their facilities and consi actioq,as appropriate, to avoid similar problems. However, suggestions contained in this information

'ce are not NRC requirements; therefore, no specific action or written respon isIroquired.

Descriotion of Circumstances

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HOLTEC Intemational (HI), in accordance with 10 CFR Part 21, submtted a notification to the NRC in November 1995 identifying comptdational problemsnith the c0mputer code, ANSYS.

i ANSYS is a commercially available three-dimensional finite element computer program for J

enginearing analysis and design (e.g., linear and nonlinear static and dynamic analysis for civil structures and mechanical components under differentloading conditions such as dead weight, pressure, thermal, displacement, wind,1mpact, and esqrthquake loads). The notification performing a nonlin&st transient anal'putational problems that arose during the proc

.nvolved the following two distinct catn

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using ANSYS 5.0A and ANSYS 5.1: (1) disparate results for calculated di cements are ined depending on the type and version of personal computer empi and (2) dispa results for forces and displacements are obtained depending u

. ' techniques emp to launch the analysis runs. Enmples of the computer platform d the chirg techne ues used in the analysis art shown in.

g With regard to h first problem, thehrilinear analysis has been tried on five different computers usjng ANSYS 5.0A under a disk operating system (DOS) and resulted in two distinct sets of answers on the five compulem. In addition, the same analysis has been run using ANSYS 5.1 1 m one of the five puters and this gave a third set of results.

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IN 99-XX June XX,1999 Page 2 of 3 With regard to the second problem, the nonlinear analysis has been run on one of the five computers using ANSYS 5.1 with different techniques to launch the analysis runs, and different

tenswers were obtained depending on the launching techniques used.

HI reviewed the procedures and results of the analysis, and concluded that the magnitude of the discrepancies in both cases is considered significant and should not occur. Hi advised ANSYS, Inc., the developer of the ANSYS code, of these disparities.

The NRC staff reviewed the displacement results of the analysis, and found that t

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magnitudes of the results are small; however, one result is 2.5 times a anuch a smaller 1

result. Although the analysis involves small magnitudes, in a nonline analysis much difference in result fror i the same computer code is a concem. It well be ible that some users with an inedequate computer platform may have obtair results mai by

..e as much as 250 percent or more without realizing the significance if the enf u,thse pf the -

erroneous results.

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Part 21 to Title 10 of the Code of Federa/ Regulations (10 CFR Part 21)

' s that suppliers of basic components or services associated with basic components, evaluateiloviations.

i Deviations must be evaluated for potential safety significance to detenr.ine whehwr the deviation could create a substantial safety hazard, and alius be glassified as a defect.

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In this case, HI notified the NRC in accordance with 10 CFR Part 21Mt the deviation was considered significant, but its evaluation concluded that the deviation joes not affect any safety-related equipment or ser; ices previoulp li dj6licenseesty Hl.

The ANSYS code has been used for engine / ysupp e s by ma/

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ering ana ny architect-engineering firms, consultants, and licensees of nuclearpower plants fo any years. Consequev.ly, there is a potential for the usepf erroneoud re(ults in scfety-rel applications. The ANSYS user's Manualdoes providb ions regard ng the use of the nonlinear option of the computer code, and an experienced a ualified analystymuld be able to determine the sensitivity of the end results to initial conditions the choice oN c values of input parameters. However, the NRC staff has no way t triine the actua ty significance of the problems because there is insufficient i longarding which uclear licensees actually performed a nonlinear analysis usling the ANSYS code, the types of computer platforms used, or to what extent licensees'#:tual use of the chde would have contributed to inaccurate results that could potentially cause an unsafe conditiori. Therefore, it is expected that recipients will review the information forapplicability to their $cilities and corrective acticas, as appropriate to address potential problems.

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4 IN 99-XX June XX,1999 Page 3 of 3 Related Generic Communications Information Notice 96-29

• Requirements in 10 CFR Part 21 for Reporting and Evaluating Software Errors," May 20,1996 (Accession number 9605150209).

This information notice requires no specific action or written response. If you have any questions about the information in this notice, please contact the technical contact listed belo j i

or the appropriate Office of Nuciear Reactor Regulation project manager.

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4, Ledyard B. Marsh, C 4

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Events Assessment, ommunications and Non-Power Rea Division of Regulatory nt Programs Office of Nuclear Re 1

Attachment:

Examples of The Computer Platforms and Lau chniqu

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June XX,1999 Page 1 of 1 i

EXAMPLES OF THE COMPUTER PLATFORMS AND LAUNCHING TECHNIQUES A.

Comouter Platforms: IBM-compatible PCs 1.

Pentium-1 90 MHZ,64MB ram,2GB SCSI Hard Drive, no disk compression, DOS 6.22 or Windows NT 3.5 (workstation) 2.

Pentium-2

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90 MHZ,32MB ram,1GB IDE Hard Drive, no disk co

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Pentium-3 90 MHZ,16MB ram,540 MB IDE Hard Drive, StackI d,

compression, *W' DOS 6.22 t7 4.

Pentium-100

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100 MHZ,64MB ram

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Launchina Technioues:

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Run RAxxUSE.INP via input fil

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