NUREG-1537, Part 2 - NRC

APPEDix 18 1
derivtions is contained in Chapter 14, "Technical Specifications, of the format
and content guide, which revises the ANSI/ANS 15.1 definition.
4.5.3 Other Core Physics Parameters
The various core physics parameters that affect reactor behavior should be
compared for the HEU- and LEU-fueled reactors. Areas of review should include
quantitative discussions and analyses of reactivity feedback coefficients (fuel
temperature, moderator temperature, void, and the power defect); the magnitude
and effect of prompt temperature coefficients on stability and safety of reactor
operation, including pulsing if applicable; and changes in the delayed neutron
fraction and the prompt neutron lifetime. The reviewer should compare the
neutron flux densities, flux spatial distributions, neutron spectra, and power
densities in fuel plates or rods for the HEU- and LEU-fueled reactors.
Because of the relatively low enrichment of uranium-235 in the LEU fuel, a new
area for review is the buildup of plutonium-239 and its effect oni reactor operating
characteristics. Factors to be considered include the fractions of delayed neutrons
from uranium-235 and plutonium-239 and the spatial distribution of the plutonium-
239 in the core. Comparisons ofthe plutonium-239 effects on the reactor physics
parameters between the BEU and proposed LEU-fueled reactor should be
reviewed.
The information provided should compare the physics parameters for the existing
HEU core, the initial LEU core, and subsequent LEU cores to the end of life.
4.5.4 Operating Conditions
The dynamic operating conditions for the LEU fuel designs should be compared to
those for the BEU fuel. Core thermal power and neutron flux spatial distributions,
both radial and axial, power peaking within individual fuel plates or rods, and
related temperature distributions for the range of allowable operating conditions
should be analyzed. This analysis should include calculations of both the BEU and
LEU cores, giving a quantitative description of the main changes in operating
characteristics. The values and characteristics calculated as operating conditions
(e.g., maximum temperatures, power peaking factors) will be used or referenced in
other areas, such as under accident analyses.
The dynamic response of the reactor to anticipated and postulated disturbances in
the process variables and to changes in reactivity, including inherent feedback
mechanisms and protective actions of the reactivity control elements, should be
provided. For example, analyses for maximum allowable power, temperature and
reactivity addition conditions should not result in exceeding LEU fuel design
temperature limits. Further, any relevant changes in the technical specifications
NUREG-1537, PART 2 16 REV 0.2/96
NUREG 1537,PART2 16 REV 0, 2196