Low-Enriched Uranium Fuel Design with Two-Dimensional Grading for the High Flux Isotope Reactor

Impact of the High Flux Isotope Reactor HEU to LEU Fuel Conversion on Cold Source Nuclear Heat Generation Rates

“…The enhanced HEU models [1] based on the cycle 400 HEU model of the HFIR fresh core [6] and the 2011 models for the LEU core [1] were used for this set of comparison studies. Previous HEU to LEU comparison studies documented in [7] and [8] also made use of these models.…”

“…Calculations were performed with beginning-of-cycle (BOC) and end-of-cycle (EOC) conditions to bound typical HFIR operating conditions. The EOC inputs were obtained from previous depletion studies [1] performed with VESTA [10], a Monte Carlo-based depletion tool developed and maintained at Institut de Radioprotection et de Sûreté Nucléaire (French Institute for Radiological Protection and Nuclear Safety), which was validated against HFIR post-irradiation, spatially dependent uranium isotopic measurements [11] and compared to calculations performed with the Standardized Computer Analysis for Licensing Evaluations code package (SCALE) [12] in [13]. The fuel, CEs, and curium targets (applicable only to the LEU inputs) were depleted, and CE withdrawal was simulated during the VESTA calculations.…”

“…No photons are produced from any other isotopes in the problem. It is valid to only use the 235 U isotope for the HEU core pikmt inputs because 235 U dominates the fission process in the HEU core, the 238 U content is very small, and the plutonium build-in is very low (see Table 18 in [1]).…”

“…To maintain the neutron flux at the experiment facilities, FP will need to be increased from 85 MW(t) to 100 MW(t). A more thorough description of the reference LEU design is provided in [1].…”

“…Cold source nuclear heat generation rates were calculated previously for the 85 MW HEU core and reported in [2][3][4]. The purpose of this report is to compare the nuclear heat generation rates in the cold source for the HEU-loaded HFIR core and the reference LEU-loaded HFIR core operating at 100 MW [1]. Heat deposition due to photons, neutrons, and beta particles (only in aluminum) and the sum of these constituents were calculated in watts per gram for the cold source LH 2 moderator, the cold source moderator vessel, the HB-4 aluminum structure, and other regions of interest including stainless steel screws and titanium wires.…”