NUREG-1537, Part 2 - NRC

CHAPTER I8
NRC order. These changes should be requested by license amendment 1
under 10 CFR 50.90, 10 CFR 50.91, 10 CFR 50.92, or 10 CFR 50.59.
Background material follows for the different reactor fuels used to date:
For rraing reactor, isotope production, general Atomics (TRIGA)
reactors, the fuel was developed and marketed by a sole source, General
Atomics (GA), and since about 1962, the neutronics characteristics have
been reasonably constant The earlier 8.5 weight percent (wlo) uranium
loading of 20-percent enmiched uranium can be replaced by the modern 20
or 30 wlo, (20 % enriched) fuel, if changes in neutron flux and power
peaking are adequately anlyed and considered. In NUREG-1282, NRC
has reviewed and accepted LEU fuel for TRIGA reactors.
* For plate-type fuel [materials testing reactor (AMR) type], the designs of
the original and replacement fuels were not standardized among the various
facilities and various reactor designers. The variations were primarily
related to the physical dimensions of the plates and water spaces, as well as
to the uranium density of the fuel. As a result of these variations, core
sizes iLe., number of fuel elements) vary by a fiactor of almost 2.
After some discussion, DOE, NRC, and licensees selected a single generic
LEU fuel plate made of U3Si2 -7A NRC generically evaluated and accepted J
an MTR fuel plate design in NUREG-1313.
This plate design could lead to extensive changes in the core design of
some reactors. Therefore, the licensee should explain the fiactors involved
in modifying the facility or its operating characteristics and provide
applicable safety analyses. The characteristics of the approved fuel plate
could be sufficientlk different from the existing HEU fuel plate for a
particular reactor that changes to the reactor would be required. The
licensee should provide the technical reasons for the required changes and
an analysis of the effect of the changes.
NRC has determined that the conversion to LEU should not result in a significant
reduction in the nuclear capability of the reactor, nor should it increase the nuclear
capabilities of the reactor with a significant decrease in safety margin. Therefore,
conversion to LEU fuel should allow licensees of non-power reactors to maintain
the current nuclear capabilities if no applicable acceptance criterion is exceeded
and to state that the change is needed to accommodate the design differences for
the LEU core and fuel.
NUREG-1537,PART2 18-2 REv. 0.2196
NUlREG-1537,PART2, 18-2 REV. O. 2/96
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