NUREG-1537, Part 2 - NRC

Acceptance Criteria
_HEU TOLEU CoNvERsioN
Acceptance criteria should be based on the following considerations. If no
modification is proposed, the LEU core operating conditions (e.g., neutron
spectrum and flux levels) or components should not cause loads, stresses, or
changes in material response that significantly change the core support function
from those currently acceptable for the HEU core components. If there are
proposed changes in the core support structures to accommodate the conversion,
they should be specified and analyzed to ensure that LEU geometry will be
maintained and loads will not be beyond design limits. Proposed changes in the
design specifications and tolerances should not be significantly different from those
for the current HEU core system. If major modifications or replacement of the
core support structure are proposed, in addition to the above structural designs,
the design should not decrease resistance to corrosion and erosion or cause a
significant increase in long-term induced radioactivity above that for the existing
HEU core support system. (This latter issue generally relates to'maintenance and
ultimate decommissioning and should not be'an operational safety issue.)
Review Procedures
The reviewer should compare the design specifications for the proposed
modifications to the core support systems with those systems used with the BEU
core. The reviewer should compare changes in functional stresses between the
two systems and the capabilities to withstand the stresses for the projected
duration of the license with LEU core conditions (e.g., neutron spectrum and flux
levels). The reviewer should compare construction materials or structure, reactor
operating characteristics, and mechanisms of degradation. If the core support
structures will not be changed, the reviewer should determine the change in weight'
between the HEU and LEU fuels and cores and its'effect -on the support structures
and any changes in reactor operating characteristics that could affect the core
support systems.
Evaluation Findings
This section of the SAR should contain sufficient information to support the
following type 6f conclusions, which will be included in'the staff's safety
evaluation report: - -
The proposed core support structure for the LEU-fueled reactor will not
provide significantly less reliable support, rigidity, and spacings of core
components thin the existing system for BEU fuel.
REv. 0,2196 13. Smiauu, REVIEW PLA1
REV. O. 2/96 13. STANDARD REvmw PLAN