Abstract
The spent fuel from a PWR still contains some amount of fissile materials depending on their initial enrichment and the burnup. Thus, spent fuel from PWRs containing about 1.5% of fissile material could be used as fuel for CANDU reactors after some fission products are removed from it. Thus, an important proposal is the DUPIC cycle, where spent fuels from a PWR are packaged into a CANDU fuel bundle using mechanical reprocessing but without the need of chemical reprocessing. When it is refueled with reprocessed fuel, the reactivity of the system increases, and this behavior may affect the safety parameters of the reactor. Therefore, this work studies the neutronic parameters of two reprocessing fuel techniques: AIROX and OREOX, which are evaluated for two different cores configuration. The first one considers heavy water as a moderator and coolant. The second one considers heavy water and light water as moderator and coolant respectively. These studies evaluate the core behavior based on the different number of reprocessed fuels channels and compare them with the reference core. To perform the simulation the MCNPX was used to calculate the effective multiplication factor, fuel temperature coefficient of reactivity, void reactivity coefficient, and neutron flux, which were evaluated at steady state condition for the different cases. The results show that the presence of parasitic absorbers in the reprocessed fuels hardens the neutron spectrum. This behavior provokes an increase in the core reactivity, in the fuel temperature coefficient and in the void reactivity coefficient. Among these parameters, the use of light water reduces the core reactivity but do not improve the fuel temperature coefficient and the void reactivity coefficient.
Highlights
Nowadays, LWRs (Light Water Reactors) and HWRs (Heavy Water Reactors) represent a great share of the total nuclear power plants in the world, about 65% and 11%, respectively [1]
The simulations were performed in MCNPX code using 50,000 particles with 200 active cycles which results in low standard deviation of the keff around 2 10–4
These fuels have a higher percentage of fissile isotopes and absorber isotopes
Summary
LWRs (Light Water Reactors) and HWRs (Heavy Water Reactors) represent a great share of the total nuclear power plants in the world, about 65% and 11%, respectively [1]. The development of the fuel cycle technology for recycling the SF (Spent Fuel) of nuclear reactors has particular importance to improve the uranium utilization, to reduce the high-level nuclear waste. The most important process is the DUPIC (Direct Use of spent PWR fuel In CANDU), which reuses SF from a LWR into an HWR core, using a direct re-fabrication method without separating fissile materials. The AIROX is a precursor of the DUPIC concept, developed by Atomic International, by recycling LWR spent fuels retaining most of the fissionproduct inventory in reconstituted fuel assemblies. This method avoids the generation of high-level liquid waste streams, recycling the fertile 238U and unburned fissile transuranics. The main purpose of the DUPIC fuel cycle is improving the utilization of uranium fuels while at the same time reducing the volume of radioactive waste
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