NUREG-1537, Part 2 - NRC

HEU To LEU CoNvRiow
acceptable assumptions were used. The transport of fission products and
other radioactive material from the core to the unrestricted area was'
analyzeA,'and potential dose rates and accumulative doses to the staff
members of the public, and the environment were calculated. All changes
in the reactor parameters'and ESFs were included in the analyses.
(2) The radiological consequences to members of the public in the unrestricted
area and to the environment resulting from the postulated MHA for the
proposed LEU-fueled reactor would not significantly exceed the
consequences previously calculated and found acceptable for the HEUfueled
reactor. Furthermore, the maximu projected dose rates and
accumulative doses for the MHA exceed and envelope the radiological
consequences of all other accidents postulated for this LEU-fueled reactor
and are within the guidelines of that acceptable for the BEU MIA.
13.2 Rapid Addition of Reactivity Accident
At non-power reactors there may be the potential for the inadvertent or accidental
addition of significant amounts of excess reactivity in an uncontrolled way.
Among the reasons for this excess reactivity are the need for frequent power
changes (including startups and shutdowns), experimental programs, and the need
for versatility to accomplish these readily. The design and operation of a nonpower
reactor requires systems, administrative controls, and procedures to limit
the likelihood and magnitude of accidental reactivity additions.
Areas ofReview
The reviewer should consider the initiating events and scenarios postulated for
accidental reactivity addition for the existing HEU-fueled reactor and the bases and
criteria for selecting the ones with the most serious consequences for detailed
analysis. The reviewer should evaluate comparisons of these considerations with
similar ones for the proposed LEU-fueled reactor. The comparisons should show
the parameters of the reactor fuel, core, operating characteristics, and procedures
that affect the type and magnitude of consequences for postulated reactivity
accidents in both HEU- and LEU-fueled reactors. Accidents can be grouped as
either rapid addition of reactivity or slow (ramp) addition. The rapid reactivity
addition includes rapid control or safety rod withdrawal or ejection, dropping a
fuel element into a core vacancy, failure or dislodging of a component in the core,
including an unsecured experiment, or a sudden change in coolant temperature or
flow. A ramp reactivity addition could include any of the above on a slow time
scale, such as continuous withdrawal of a control or safety rod by malfunction of
its normal drive system, melting or flowing of an experiment from its intended
location and configuration, or a slower change in coolant conditions that allows
REV. 0,2196 45 STANDARD REVIEW PLAN
RVv. 0, 2/96 45 -STANDARD REviEwPLAN