Transition Core Analysis for HEU to LEU Fuel Conversion at the University of Missouri Research Reactor

Startup, transition core, and molybdenum-99 production upgrade analyses for low-enriched uranium fuel conversion at the University of Missouri research reactor

“…After the burnup of the fuel elements in the transition cycles were calculated with REBUS-DIF3D, the accuracy of this assumption was evaluated by comparing the calculated element burnup at BOC from the neutronics analysis with that obtained from the equal power sharing assumption. While the Python program and element loading and cycle information for the REBUS-DIF3D input were written and executed at MURR as part of this work, the evaluation of this assumption was performed at ANL [32]. Figure 24 summarizes this difference in element burnup for each element utilized during the first 49 weeks of LEU operation (identified as MO-001 to MO-032).…”

“…As stated above, 454 key experimental locations and flux and reaction rate metrics were identified by experts at MURR to evaluate the performance of the proposed transition and equilibrium LEU cores relative to HEU. The MCNP5 output files were postprocessed at ANL to arrive at the final calculated values for the metrics [32]. These metrics were calculated for the LEU cores operating at 12 MW and compared with values calculated for a typical HEU core operating at 10 MW.…”

“…In order to assess the magnitude of the experimental performance penalty during the transition cycles relative to current operations with HEU, 454 key experimental locations and flux and reaction rate metrics were identified by experts at MURR. While the MCNP5 model preparation and execution was done at MURR as part of the current work, the postprocessing of the tally results was done at ANL [32]. These metrics were calculated for the all fresh LEU core in the first transition cycle operating at 12 MW and compared with values calculated for a typical HEU core operating at 10 MW.…”