NUREG-1537, Part 2 - NRC

Evluation Findings
HEU TOLEU CONVERSION
This section of the SAR should contain sufficient information to support one of the
following type of conclusions, which will be included in the staffs safety
evaluation report:
* The licensee's analyses of the thermal-hydraulic characteristics for the
proposed conversion from BEU to LEU fuel have been reviewed. Any
changes in these characteristics are small and within calculational
uncertainties and the changes have been accounted for in the safety analysis
and in the technical specifications. These changes have been verified
through measurements (on the HEU core), calculations, and comparisons.
The safety significance of the changes has been accounted for with no
significant decrease in safety margins from the BEU core during normal or
transient operating conditions Qi.e., design and safety limits are not
exceeded). This conclusion is based on the methods and assumptions used
to analyze the core thermal-hydraulic performance. The licensee has
committed to an initial startup test program to measure and confirm the -
change in the thermal-hydraulic design characteristics.
or
The licensee's analyses of the theimal-hydraulic characteristics for the
conversion from HEU to LEU fuel have been reviewed. The methods and
assumptions in the analyses were verified by comparisons with
measurements on the HEU-fleled reactor.' The same methods and
assumptions were used to analyze the proposed LEU-fueled reactor. Some
of the thermal-hydraulic parameters, namely power density in the fuel,
reactor coolant system flow around the fuel, and fuel-plate temperatures,
would be changed significantly in the converted core for normal operation,
sand some postulated accident scenarios. These chaniges resulted from
factors required to accommodate the conversion, as stated in 10 CFR
50.64. The use of the standardized fuel plates (rods) approved by NRC led
to a higher uranium conceniration than in the BEU core and, consequently,
to a smaller reactor core with higher pdwer density. These'changes in core
parameters were selected to avoid significantly degrading reactor
performance characteristics to maintain the neutronic characteristics of
experimental facilities. Even with the changed thermal-hydraulic
parameters, the predicted DNBR for the LEU-fueled reactor should have a
minimum value of 2.0 for licensed operations, which is conservative and
acceptable to the NRC for non-power reactors.
REV 0,2/96 23 STANDARD REVIEW PLAN
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