ML20127A321

Topical Rept Evaluation of NEDE-22290,Suppl 1, Safety Evaluation of GE Hybrid 1 Control Rod Assembly for BWR4/5 C Lattice. Rept Acceptable for Referencing in Licensing Applications

ML20127A321
Person / Time
Issue date:	06/12/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20127A301	List: ML20127A297 ML20127A321
References
TAC-56929, NUDOCS 8506210102
Download: ML20127A321 (4)

Text

- . _ . _ _ -_

__;_, _ , 7 7 i .

1 i

Enclosure

. Evaluation of NEDE-22290, Supplement 1 (TACS56929) ,

i j

i

! By letter dated February 20,1985(MFN023-85)GeneralElectricCompany

} submitted Reference 1 for staff review. The Core Performance Branch has re-l viewed the report and prepared the following evaluation.

l; 1. Description of Report Reference 1 describes proposed replacement control rod assemblies to be used in BWR/4 and 5 reactors as substitutes for current standard assemblies. The  ;

new assembly design, designated HICR-C, is a variation on the previously  ;

! approvedHICRassembifes(Reference 2). Section 2 of Reference 1 consists l 1  :

j of a description of the design, Section 3 presents design bases, and Section  ;

4 describes the physical, chemical, irradiation and mechanical properties of

the HICR-C materials. Sections 5 and 6 present the design evaluations and  !

j transient and accident effects. ,

l The emphasis in the report is on comparison of the proposed assembly with the

{

j currently used control rods. The most significant differences between the two ,

! are:

i i

l 1. Improved 4B C absorbers rod tube material to eliminate

cracking during the residence time of the assembly, and  !

i l 2. Replacement of some 4B C rods with solid hafnium absorber l rods to increase blade life. ,

? I j Since the hafnium has a higher density than B C 4 the HICR-C asst,@,1y is heavier  !

than the current all B C assembly. In other respects the proposed design is  !

l 4 identical in outline to the current B C 4 C-lettice design. Materials changes  !

l in the B C absorber rods and the pins and rollers do not impact the safety l 4

performance of the new assemblies. l MIQ  ;

.w . .- -...... .. ._  : . . . . - . . . . . ~ . . . . . . . .

i The design bas'es and materials evaluations are the same as those for the HICR I

~

) production assemblies described in Reference 2, as is the thermal expansion l and irradiation growth of the hafnium rods. It is concluded that the increase

, in weight of the assembly will have an insignificant effect on the mechanical adequacy of the control rod. Likewise the results of the nuclear evaluation

! show that the reactivity worth of the HICR-C control rod is the same as that of the all B C rod to within the uncertainty in the calculations.

4 The effect of the increased weight of the HICR-C on the scram speed was calculated

) by a computer code that models the scram performance of the control rod drives.

The model has been verified against actual full stroke scram data. The results of the calculation show an insignificant increase in scram times for the HICR-C assembly as compared to the all B4 C assembly. An extension to the surveillance program presented in Reference 2 is given which provides additional monitoring i

of the performance of the HICR rods. The results of this extended program will be applicable to the HICR-C rods.

2. Sununary of Evaluation The design bases for the HICR-C asstably are the same as those of the HICR l

assembly described in Reference 2. Those bases were approved for the HICR assembly and continue to be acceptable for the HICR-C assembly. For the l

j same reason the materials evaluation, including the thermal expansion and j irradiation growth of the hafnium, is acceptable. Since the increase in weight is a small fraction of the total weight and large margins to stress 1 limits are present in the design we concur with the conclusion that the effect of the weight increase on the mechanical adequacy of the HICR-C assembly

! is negligible.

)

The comparison of reactivity worth for the two rod designs was performed with

aMonteCarlocalculationwhichhasbeenverifiedagainstexperiment(see Reference 2). We conclude that suitable comparisons of reactivity worth have l been made. The analysis of the scram time for the heavier HICR-C rods has I

i 2

been performed by a method which has been verified by comparison with experiment.

The results show that the scram times for the HICR-C rods are significantly less than those assumed in safety analyses and are therefore acceptable.

3. Conclusions Based on our review, which is described above, we conclude that HICR-C assemblies may be substituted for the current all B C4 control rods in BWR/4-5 reactors having C lattice fuel designs. No additional analysis beyond those presented in supplemental reload licensing submittals will be required. The staff encourages the continued monitoring of the performance of the Hybrid I control rods and wishes to be informed of any significant findings.

3

s.

~- ^ ^^'

. . . . . . . . . . T. .. . .. -. ..

l 1

l i

References

1. NEDE-22290, Supplement 1, " Safety Evaluation of the General Electric Hybrid I Control Rod Assembly for the BWR4/5 C Lattice", October 1984.

2. NEDE-22290-A, " Safety Evaluation of the General Electric Hybrid I Control

Rod Assembly", September 1983, (Approval letter follows immediately after the Proprietary Information Notice in this report).

I 1

4

. _ -