United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9607100167



ANSYS               ANSYS, Inc.

                    201 Johnson Road              Telephone 412-746-3304

                    Houston, PA 15342-1200        Facsimille 412-746-3434



                              July 2, 1996



Thomas Greene, NRC/PECB

U.S. Nuclear Regulatory Commission

Mail Stop: 0-11E4

Washington, DC 20555-0001



Ref:      1. Accession 9601190322

          2. ANSYS, Inc. letter dated June 24, 1996

          3. Holtec Fax dated June 19, 1996



Subj:     Request for a Technical Review of a Draft Information Notice

          Regarding Erroneous Results from ANSYS 5.0A and ANSYS 5.1

          Computer Codes



Dear Mr. Greene:



     Per our telephone conversation and the two referenced letters,

ANSYS, Inc. and Holtec International believe that Item 1 of Holtec's 10

CFR 21 Notification has been explained and is therefore not an error. We

recommend that an information notice not be sent out on item 1.



     To investigate the second item (i.e. disparate results for forces

and displacements are obtained depending upon the techniques employed to

launch the analysis runs), ANSYS, Inc. has performed various analyses

using the Holtec input and has observed minor changes in the results for

cases run on Personal Computers, but identical results if run on

workstations.



     These changes between personal computer results are observed when

models requiring extreme numerical accuracy are solved. We are presently

investigating why this phenomenon occurs. However, we can only reproduce

these differences using ANSYS Revision 5.1.



     To correctly identify the cause and scope of this phenomenon, we are

requesting an additional week to investigate.



                                   Sincerely,

                                   ANSYS, Inc.



                                   William J. Bryan

                                   Quality Assurance Manager



cc:  Holtec              ANSYS, Inc.

       A. Soler               D. Looman

                              M. Imgrund

                              J. Bittner

                              D. Conover





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