ML20002C982
| ML20002C982 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 02/27/1969 |
| From: | Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20002C981 | List: |
| References | |
| NUDOCS 8101150529 | |
| Download: ML20002C982 (3) | |
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Consumers Power Company Docket No. 50-155 Proposed Change No. 16 SAFETY EVALUATION BY THE DIVISION OF REACTOR LICENSING RELOAD "E-G" FUEL BUNDLES By letter dated January 22, 1969, Consumers Power Company has proposed Change No. 16 to the Technical Specifications of License No. DPR-6 i
for the Big Rock Point Nuclear Plant.
This change would permit refueling with Reload "E-G" fuel bundles beginning with the insertion of about 16 fuel bundles into the Big Rock Point core during the refueling outage scheduled for May 1969. According to the proposal, four fuel rods in each of the Reload "E-G" fuel bundles would contain gadolinium oxide burnable poison to provide reactivity control supplemental to the reactor control rods. According to the applicant, modification of the previously approved Reload "E" fuel bundle by increasing and redistributing the U-235 enrichment within the bundle and adding gadolinium oxide to 4 of the 77 fuel rods will result in higher fuel burnup and longer periods between core refueling.
1 We have examined the changes in core performance brought about by in-creasing the U-235 content of the Reload "E" fuel bundle by 21% and shifting the distribution of the U-235 toward the bundle center so that 41% of the U-235 is contained in the high enrichment fuel rods at the center of the bundle compared with 32% in the Reload "E" fuel bundles. Calculations show that there is less power peaking within the more highly enriched Reload "E-G" fuel bundles and that the gadolinia is burned to near zero neutron absorption prior to the end of the first operating cycle of the "E-G" fuel.
It is shown by calculations that core reactivity decreases slowly until the gadolinia is depleted and then continues at the normal rate. At no time, however, does the core reactivity increase during the burnup of gadolinia.
Our comparison of the principal nuclear characteristics as calculated for Reload "E" and "E-G" fuel bundles reveals no changes which could in-crease the severity of postulated accidents beyond those previously reviewed for Reload "E" fuel bundles.
The gadolinia poison added to selected fuel rods more than compensates for the reactivity increase resulting from greater fuel enrichment thereby providing a slightly larger core reactivity shutdown margin.
Similarly, small reductions in control rod reactivity worths and the temperature coefficient of
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-reactivity and the slightly more negative void coefficient of reactivity
-will reduce the severity of power excursions resulting from accidental reactivity insertions.
"The calculational methods are unchanged from those used in the Reload "E" fuel analysis and the applicant.has noted that addition of gadolinia to fuel does not add any new uncertainties to the results. We have concluded therefore that the use of Reload "E-U' fuel bundles in the Big Rock Point core does not significantly alter the conclusions of our evaluation of Reload "E" fuel, Change No. 14 dated July 2, 1968.
The design basis accident which assumes that all fission _ product gases are released from the fuel matrix without time dependence is not altered by use of Reload "E-G" fuel bundles in the ' Big Rock Point core nor is the probability of an accident which could release fission products
.from the primary system or impair.the effectiveness of the installed engineered safety features increased.
Since the mechanical design of the "E-G" fuel and bundle is essentially e considerations identical to the "E" fuel and bundle, there are no ne in-this area which could affect _ operational reliability or plant safety.
Satisfactory performance of similar bundles containing gadolinia in the Big Rock and Dresden I cores provides added assurance of the mechanical design _ adequacy and burnup calculations of the "E-G" fuel bundles.-
However, as was noted in the evaluation of Reload "E" fuel bundles, it is evident that use of an increasing variety of fuel rod compositions increases the possibility of errors in assembling the rods into fuel bundles. We have been advised that strict identification and accountability procedures are followed and that each rod inserted into a fuel bundle h g an. identifying number which is checked a number of times against a maPoer loading sheet. Therefore, as we have previously concluded in the Reload "E" evaluation, the probability of loading an improperly assembled fuel bundle into the core continues to be acceptablyElow.
The proposed changes to the Technical Specifications involve sections which identify the fuel and poison rod arrangement within the bundle.
The present reactor operating limits are not changed.
Our previous safety evaluation for use of Reload "E" fuel bundles, for reasons already stated, is equally applicable to the "E-G" fuel bundles.
We conclude that' Proposed Change No. 16 does not represent significant l
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- hazards' considerations not described or implicit in the safety analysis report and tiiere is reasonable assurance that the health and safety of the public will'not be endangered.
Therefore, the Technical. Specifications of License No. DPR-6 may.be revised as indicated in Attachment A.
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.fi, Yf Donald J./Skovholt Assistant Director for Reactor Operations Division of Reactor Licensing
- Date: February 27, 1969
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