NUREG-1537, Part 2 - NRC

APPENDIX 18.1 :. -
temperature evolution may be different in the LEU core from the HEU core during
LOFA situations.
The objecties of this review are to (I) compare the consequences for fuel integrity
resulting from a LOFA scenario in the LEU core if the HEU and LEU LOFA
scenarios are similar or (2) evaluate the licensee's demnonstration of compliance
with acceptance criteria used in the HEU safety analysis if a more severe LOFA
scenario results from the conversion. The required analyses should include
independent calculations of the lIEU and LEU fuel temperature evolutions as a
function of time in a LOFA, along with qualitative and quantitative comparisons of
any differences in these temperature evolutions between the cores.
To accomplish these objectives, the reviewer should examine the postulated core
and reactor conditions that are pertinent to the LOFA comparison, the thermalhydraulic
methods and assumptions used, the analyzed sequence of events, and the
comparison with the HEU accident calculations for its scenario.
Acceptance Criteria
Acceptance criteria should be based on the following considerations: The
information should demonstrate that the consequences to fuel integrity resulting
from a LOFA scenario in the proposed LEU-fueled reactor are not significantly
greater than those projected in the licensed HEU-fueled reactor for the same
accident scenario during the transient until conditions are stabilized. However, if
the licensee can demonstrate that some changes in characteristics of the core
therma-hydraulics were required, some decrease in.safety margin may b
acceptable. In any case', the results of the safety analysis should show that fuel
cladding integrity would not be lost as a result of the LEU core LOFA.
Review Procedures
The reviewer should compare the information submitted to determine if there are
significant differences in the postulated LOFA events for the HEU- and LEUfueled
reactors. The 'review should reveal any differences and should trace the
scenarios and analyses from initiation of the event until conditions are stabilized.
The information ihould justify changes in reactor systems or operating,'
characteristics designed to mitigate consequences to fuel, the reactor, and the
public.
The reviewer'should compare the analyzed consequences for the HEU- and LEUfueled
reactors and should also compare the consequences from the LEU LOFA
with the acceptance criteria for the HEU LOFA.
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