Feasibility study for the recycling of reprocessed uranium in a heavy water reactor

Pressurised Heavy Water Reactors (PHWR) can use natural uranium fuel ("Unat", whose U-235 concentration is 0.7114%) without enrichment, whereas Light Water Reactors (LWR) need a more than 3.5% enriched uranium fuel. This specificity enables "synergy" between LWR and PHWR, giving that irradiate fuel from LWR still contents enough fissile materials to be reused in PHWR, in a second fuel cycle. This study, part of an internship with AREVA (France), focuses on the feasibility of recycling Reprocessed Uranium (URT), which is a product from backend LWR cycle, in PHWR. The type of PHWR considered in this work is the CANDU 6. The objective is to perform a sensitivity analysis to compare several types of URT about their efficiency in PHWR, according to the main neutronic parameters. First, a bibliography on PHWR physics is done so as to determine pertinent parameters to study in order to conclude about the feasibility of recycling URT in PHWR. Then, a complete calculation scheme of PHWR is computed with lattice and full-core codes DRAGON and DONJON Version 4. The sensitivity analysis consists, on the one hand, in determining an energetic equivalence law for URT in PHWR, which associates a URT fuel (knowing its isotopy) with an equivalent (enriched) Unat fuel. This law is established by comparing core calculation for different fuels, with the Time Average method. On the other hand, safety parameters are computed for various fuels (URT or Unat) in order to quantify the impact of URT isotopes on PHWR's safety. The calculation of the safety parameters uses both lattice and core calculation scheme. (author)