A Preliminary Study of the Effect of Shifts in Packing Fraction on k-effective in Pebble-Bed Reactors
- Idaho National Engineering and Environmental Laboratory (INEEL), Idaho Falls, ID (United States)
A preliminary examination of the effect of pebble packing changes on the reactivity of a pebble-bed reactor (PBR) is performed. As a first step, using the MCNP code, the modeling of a PBR core as a continuous and homogenous region is compared to the modeling as a collection of discrete pebbles of equal average fuel density. It is shown that the two modeling approaches give the same trends inasmuch as changes in keff are concerned. It is thus shown that for the purpose of identifying trends in keff changes, the use of a homogeneous model is sufficient. A homogenous model is then used to assess the effect of pebble packing arrangement changes on the reactivity of a PBR core. It is shown that the changes can be large enough to result in prompt criticality. It is shown that for uranium fueled PBRs, thermal feedback could have the potential to offset the increase in activity, whereas for plutonium fueled systems, thermal feedback may not be sufficient for totally offsetting the packing-increase reactivity insertion and could even exacerbate the initial response. It is thus shown that a full study, including reactor kinetics, thermal feedback, and the dynamics of energy deposition and removal is warranted to fully characterize the potential consequences of packing shifts.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); USDOE Idaho Operations Office (IO)
- DOE Contract Number:
- AC07-99ID-13727
- OSTI ID:
- 910942
- Report Number(s):
- INEEL/CON-01-00342; TRN: US0704300
- Resource Relation:
- Conference: M & C 2001: ANS International Meeting on Mathematical Methods for Nuclear Applications, Salt Lake City, UT (United States), 1 Sep 2001
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
CRITICALITY
FEEDBACK
PEBBLE BED REACTORS
PLUTONIUM
REACTIVITY INSERTIONS
REACTOR KINETICS
REMOVAL
SIMULATION
URANIUM
Nuclear Criticality Safety Program (NCSP)
packing
pebble-bed
prompt criticality
reactor
temperature feedback