ML20134B792

Discusses Results of Audit Review of Changes to Siemens Large Break ECCS Evaluation Model

ML20134B792
Person / Time
Site:	Millstone, Palisades, Kewaunee, Harris, Saint Lucie, Robinson
Issue date:	06/24/1996
From:	Collins T NRC (Affiliation Not Assigned)
To:	Mckee P NRC (Affiliation Not Assigned)
Shared Package
ML20134B794	List: ML20134B792 ML20134C761 ML20134Q098
References
FOIA-96-485 NUDOCS 9606260213
Download: ML20134B792 (3)

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Juno 24, 1996 felDRAIER81 T0: Phillip F. McKee, Director i Project Directorate I-3 (N111 stone-2)

Division of Reactor Projects I/II l Eugene V. Imbro, Director

Project Directorate 11-1 (Shearon Harris-1, H.8 Robinson-2)

! Division of Reactor Projects I/II John N. Hannon, Director l Project Director 111-1 (Pa111sades)

! Division of Reactor Pro;jects III/IV Frederick J. Hebdon, Director i Project Director II-3 (St. Lucie-1) l Division of Reactor Projects I/II i

! Gail H. Marcus, Director l Project Director III-3 (Kewaunee) l Division of Reactor Pro;iects III/IV FROM: Timothy E. Collins, Acting Chief Reactor Systems Branch i Division of Systems and Analysis 1

SU8 JECT: POTENTIAL VIOLATION OF 10 CFR 50.46 l We have recently completed an audit review of changes to the Siemens large

! break ECCS evaluation model which is used at one or more plants under your

purview (Kawuanee, M111 stone-2 Pa111sades, N.B. Robinson-2, Shearon Harris 1, St.Lucte-1). We have determined that Siemens made significant changes to the code without staff approval and may have incorporated these model clianges into

plant specific licensing calculations for the noted plants. The not impact of 1

the unapproved model changes for some plants where tte Siemens 1991

methodology was used exceeded 50 degrees in the calculation of PCT used in the 4 LOCA analyses. We are concerned that these plants may be operating in violation of 10 CFR 50.46. Specifically, Appendix K requires that, when 4 l

! significant change is made to the evaluation model ( > 50 degrees F PCT impact) the evaluation model must, at the same time be modifned to delete the use of the Dougall-Rohsenow film boiling correlation (see Appendix K. j i I. C. 5. c). "he Dougall-Rohsenow correlation was not deleted when the above i noted changes were made to the code. In addition, the impact of the changes

! were not reported to the staff as required by 10 CFR 50.46. We recommend that ;s I you send the attached letter to the individual licensees to notify them of the 1 I potential violation.

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Contact:

G. Thomas, SRK8/DSSA, 415-1814 i *see previous concurrence page j SRx8:DSSA* SASG:DSSA* SRX8:DSSA* SASG:DSSAY SR18:

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j N nuclear Regulatory Commission (NRC) staff approved the siemens large break

] ECC5 evaluatten model en July 8,1986. N evaluation model approved by the

! staff included the T000EE2 code. We have recently completed an audit review l of changes to W Siemens large break ECCS evaluation model which is uwJ

! at--- . We have determined that Siemens made significant changes to the code I

without staff approval and may have incorporated these model changes into plant specific Itcensing calculations. The not impact of the unapproved model j changes for same plants where the Siemens 1991 methodology was used exceeded 50 degrees in the calculation of KT used in the LOCA analyses. We are

concerned that--- plant may be operating in violation of 10 CFR 50.46.

l Specifically, Appendix K tres that, when a significant change is made to the evaluation model (> 50 rees F K T impact) the evaluation model must, at l l N same time be modified to delete the use of the Dougall-Rohsenow fils

boiling correlation (see Appendix K. I. C. 5. c). N Dougall-Robsenow j

correlation was not replaced when the aforementioned model changes were made.

hrefore, the model does not meet h requirement of Appendix K. In addition l the impact of the changes were not reported to the staff as required by 10 CFR i 50.46.

Since ------- uses the Siemens ECCS evaluation model for the LOCA analyses, we st that you ascertain whether ----used the unapproved 1991 version of the

1. A plant for which the unapproved methodolony was used may be in violation of 10 CFR 50.46. If the unapproved vers'on of the model was used, we request that you evaluate the not tapact of the code changes in the calculation of KT.10 CFR 50.46 requires that the licensee estimate the effect of any change in a acceptable evaluation model to determine if the change is significant. 10 CFR 50.46 also states that a significant change is one which results in a calculated KT different by more than 50 degrees F from i the temperature calculated for the limitN transient using the last acceptable model. 10 CFR 50.46 also states that if the change is significant, the licensee shall provide the report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking owr action as may be needed to show compilance with 10 CFR 50.46. h staff expects that

---

will promptly report back to the staff if the change in calculated KT is greater than 50 degrees F.

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