NUREG-1537, Part 2 - NRC

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design bases and functional characteristics, construction materials, thermal
capabilities, effects of radiation, design life, and replacement capability.
4.2.4 Neutron Source and Holder
Any modifications to the startup neutron source or holder required to
accommodate the HEU to LEU conversion should be reviewed. These should
include mechanical and functional designs, construction materials, thermal and
radiation capabilities, and the ability to be retracted or replaced.
4.2.5 In-Core Experimental Facilities
Any proposed changes to in-core experimental facilities to accommodate the BEU
to LEU conversion should be reviewed. The design bases, design parameters, and
functional characteristics should be compared for the HEU- and LEU-fueled
reactors. The review should include the thermal-hydraulic characteristics, effects
on core reactivity, and effects on nearby fuel elements and control rods. Potential
accidents involving in-core experimental facilities should be addressed in the
accident analyses in Section 13. Limitations on the use of experimental facilities
should be addressed in Section 10 on experimental programs.
4.2.6 Reactor Materials
In the conversion from HEU toLEU, the fuel will be replaced and other core
components niay be modified or replaced. The reviewer should verify that the
materials from which these components are made have been chosen for the LEUfueled
reactor core environment. Resistance to radiation damage, corrosion,
erosion, or vibration should be reviewed. The licensee's safety-related comparison
of the capabilities of the proposed materials between the HEU- and LEU-fueled
reactors should be reviewed and evaluated.
Acceptance Criteria (Sections 4.2.1-4.2.6)
Acceptance criteria should be based on the following considerations: All proposed
changes from the HEU-fueled reactor should be analyzed sufficiently to show that
changes in design and operating characteristics would caue no significant decrease
in safety margins and would not compromise safe shutdown of the reactor. Any
proposed changes in core components other than the fuel must be made only to
accommodate conversion to an available LEU fuel that is acceptable to NRC. The
following criteria are specific to core components:
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