NUREG-1537, Part 2 - NRC

18 HIGH1LY ENRICHED TO LOW-ENRICHED
URANIUM CONVERSIONS
The conversion of a non-power reactor from the use of highly enriched uranium
(OEU) to the use of low-enriched uranium (LEU) as a fuel was mandated by
10 CFR 50.64, which was published in the Federal Register (51 FR 6514) on
February 25, 1986. The general basis for the regulation was that BEU posed a
nuclear weapon proliferation risk through theft or diversion, and that limiting the
availability of BEU would also limit this risk, promote the common defense and
security, and protect the health and safety of the public.
The regulation stipulates that NRC will effect necessary amendments to the
operating licenses of non-power reactors through an enforcement order. The use
of an enforcement order places the responsibility to defend the order on NRC and
not on the licensee. Therefore, NRC requires information'and analyses from the
licensee that support the conclusions that the health and safety of the public will
continue to be protected during operation with LEU. Such'a conclusion should be
reached if no applicable acceptance criteria are -exceeded by the conversion of the
fuel from BEU to LEU. The following considerations may also influence the
safety-related operating characteristics of the LEU-fueled reactor:
* -A principal premise of 10 CFR 50.64 is that the use-relited performance
characteristics of the reactor are not to be degraded significantly by the fuel
conversion. (See NRC Statement of Policy, No. 82-127, August 24, 1982;
and NRC Proposed Rule, Federal Register, Vol. 49, No. 131, July 6,
1984, p. 27769.)
* Some design limitations may be caused by physical principles or other
factors ofthe LEU-fueled reactor that are not subject to the licensee's
control. For example, a generic LEU fuel plate design was adopted by
joint concurrence of the U.S. Department of Energy (DOE), NRC, and
licensees. Conversion to this fuel could require significant changes in the
core geometry, core physics, and safety analyses of a particular reactor.
Modifications to the reactor systems, procedures, or technical
specifications required by the fuel conversion usually will be acceptable;
however, the licensee should co'mpare the safety-related characteristics of
the BEU- and LEU-fueled reactors and should analyze all changes.
* Added features may be needed to ensure that the applicable acceptance
'criteria continue to be met. -
Modifications to the reactor not required by the conversion, but made to
improve reactor capability beyond that of the HEU-fueled reactor, or done
for reasons other than safety, will generally not be acceptable under the
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