ML20141E965

Topical Rept Evaluation of XN-NF-696, Exxon Nuclear Co Solution to Sample Problems-PWR Fuel Assemblies Mechanical Response to Seismic & LOCA Events. Rept Acceptable for Referencing in License Applications

ML20141E965
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Issue date:	12/26/1985
From:	NRC
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ML20141E957	List: ML20141E953 ML20141E965
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NUDOCS 8601080445
Download: ML20141E965 (3)

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Enclosure Safety Evaluation of ENC's Solutions to the NRC Sample Problem - PWR Fuel Assemblies Mechanical l

Response to Seismic and LOCA Events (XN-NF-696)

1. INTRODUCTION Previously, we have app oved the uxon Nuclear Company (ENG) PWR fuel assembly mechanical response model under combined seismic and LOCA loads (XN-NF-76-47(P)(A)).

The model calculations were based on the nonlinear transient dynamic analysis option of the ANSYS code. Subsequently, ENC changed the model calculations from ANSYS to the NASTRAN code. In order to demonstrate thtt the resuD, of NASTRAN

< analysis still complied with the SRP criteria, u requested ENC to provide a new calculation of the NRC standard problems. ENC provided a new solution described in the report XN-NF-696 for review. Our contractor, Idaho National EngineeringLaboratory(INEL),hasperformedanindependentcalculationusing the FAMREC computer code (Ref.1) as a check of the ENC results.

2. > ANALYSIS

SUMMARY

Three cases were considered depending on the core plate displacement functions.

The core plate displacement determined the response of impact forces on the fuel assemblies, in particular, the grid spacers under seismic and LOCA loading conditions. INEL ran these three cases using the auditing code FAMREC and then

, compared the results with the ENC's results as described in the INEL technical report (Ref.2). The comparisons showed that the ENC spacer grid maximum forces were either equal to or greater than the maximum forces criculated by INEL for the first and third cases, and the INEL maximum forces were larger than the ENC forces for second case. However, the second case had smaller core plate motions and thus smaller spacer grid forces.

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Both INEL and ENC predicted that the maximum forces occurred at approximately

. the same times. The locations of the maximum forces appeared different for different calculations. INEL attributed the cause of these discrepancies to the different assumed shapes of the baffle plate. However, since the more important parameter, maximum impact force, was not sensitive to the shape ~of the baffle plate, we conclude that ENC analysis is acceptable.

3. CONCLUSIONS Because (1) ENC's new analysis is consistent with our audit calculation, and (2) the NASTRAN and ANSYS codes are widely acceptable computer codes for structural analysis, we conclude that the report XN-NF-696 can be referenced for licensing applications for PWR seismic and LOCA loading analysis.

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References

1. R. L. Grubb, " Pressurized Water Reactor Lateral Core Response Routine, FAMREC (Fuel Assembly Mechanical Response Code)", USNRC NUREG/CR-1019 September 1979.

2. B. L. Harris, " Review of Exxon Nuclear Company's Fuel Assembly LOCA-Seismic Response Reports XN-NF-81-51P and XN-NF-696", EG&G EGG-EA-6618, May 1984.

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