ML20141E321

Topical Rept Evaluation of XN-NF-81-51(P) LOCA Seismic Structural Response of Exxon Nuclear Co BWR Jet Pump Fuel Assembly. Rept Acceptable for Referencing in Applications

ML20141E321
Person / Time
Issue date:	12/26/1985
From:	NRC
To:
Shared Package
ML20141E245	List: ML20141E240 ML20141E321
References
NUDOCS 8601070660
Download: ML20141E321 (3)

Text

, .

l l

Enclosure Safety Evaluation of ENC's LOCA-Seismic Structural Response of An Exxon Nuclear Company BWR Jet PumpFuelAssembly(XN-NF-8I-51P)

1. INTRODUCTION ENC has developed a finite-element computer model to analyze BWR jet-pump fuel assemblies under seismic and LOCA loading events. The approach used in the development of this technique and interpretation of test results was based on linear-elastic response of the fuel-structural system. The fuel rod motion, fuel rod-grid spacer interaction, fuel assembly-channel box interaction, and e

the channel box motion were analyzed in the model. The LOCA and seismic-loads were applied to the model to obtain stresses. The allowable stresses of different components were defined according to the ASME code,Section III. This review was performed primarily by our consultant Idaho National Engineering Laboratory (INEL) under a technical assistance contract (FIN-A6494).

2. SUPPLIED LOADS Two distinct loadings were considered: LOCA and seismic loads. The LOCA load is primarily the vertical pressure loading on the channel box. For the combined seismic and LOCA loadings, the seismic spacer loads are added to the LOCA channel box pressure loads. The seismic load is mainly the lateral displacement loading on the grid. spacers and fuel rods.

3. STRUCTURAL ANALYSIS AND MODELING A finite element stress analysis model was developed by Exxon. Stiffness and damping values to be used in the model were not known because of nonlinearities in the fuel assembly, primarily, the fuel rods sliding through the spacer grids.

$[0h C

? --

The stiffness and damping values for the finite element model were found by running random vibration, pull-release, and load deflection tests on an actual fuel' assembly and then adjusting the values in the model to simulate the results of the tests. Then the LOCA and seismic loads were applied to the model to'obtain stresses. The allowable _ stresses used for this analysis were defined by the ASME Code,Section III.

4. ANALYTIC RESULTS ENC has preformed calculations to determine the fuel system responses under seismic-and-LOCA loading conditions. Our consultant, INEL, concluded that the results showed that all the fuel component stresses were below the allow-able limits and were thus acceptable except for the channel box. Because the channel boxes are GE-manufactured, ENC does not have the proprietary GE allow-able stress value and therefore cannot determine the channel box adequacy.

5. CHANNEL BOX ALLOWABLE STRESS EVALUATION

' For GE-manufactured channel boxes, neither INEL nor Exxon can determine the adequacy of the allowable stress. However, the GE approved topical report NEDE-21175-3 has the proprietary value of allowable stress for GE designed channel boxes. The GE approved topical report NEDE-21175-3 describes the response of BWR fuel assemblies under seismic and LOCA combined forces. The l fuel assembly includes fuel rods, grid spacers, channel boxes, etc. with a  !

specified allowable stress for each component. We have reviewed Exxon's j channel box stress value based on additional infonnation from Exxon (J. C.

Chandler, June 11,1984) and compared it to the GE proprietary data. We conclude that the Exxon value of stress for GE-made channel box is conser-vatively within the GE value.

We, therefore, conclude that the Exxon allowable stress value can be used in XN-NF-81-51P and the analytic results are adequate. However. for other non-GE-manufactured channel boxes, those. licensees referencing XN-NF-81-51P will be required to provide the allowable value to be compared with the Exxon value in

/

order to show that the Exxon value is still bounding.

2

• ~" '

D

6. CONCLUSION Because (1) the ENC channel box allowable stress is bounding, and (2) the component stresses are all below the allowable stresses, we conclude that the report XN-NF-81-51P can be referenced for licensing applications for BWR jet-pump fuel assembifes under seismic and LOCA lording conditions.

S e

t t

4 l

l 1

3