Carlos E. Velasquez

Neutron Irradiation of Thorium-Based Fuels: Comparison Between Accelerator-Driven Systems and Fusion–Fission Systems

Accelerator-driven systems (ADS) and fusion–fission systems are investigated for long-lived fission product (LLFP) transmutation and fuel regeneration. The aim is to investigate nuclear fuel evolution and the neutronic parameters under neutron irradiation. Each system was loaded with thorium-based fuel; both systems were designed to have an initial criticality around k eff ≈ 0.99 due to safety terms. The criticality and depletion of both systems were analysed for a simulated period of 10 years. The simulations were performed in the MONTEBURNS code that links Monte Carlo N-Particle Transport Code (MCNP) to the radioactive decay burnup code ORIGEN2. The results indicate which of system produces higher fissile isotopes rate, as well as the most suitable system for achieving transmutation. The mass production from the nuclides that influence the differences in criticality are presented.

Thorium and Transuranic (TRU) Advanced Fuel Cycle: An Option for Brazilian Nuclear Plants

A typical pressurised water reactor (PWR) fuel element containing TRU–Th fuel cycle was simulated. The study analysed the behaviour of thorium insertion spiked with reprocessed fuel by considering different enrichments that varied from 5.5 to 7.0 %. The reprocessed fuels were obtained by using the ORIGEN 2.1 code from a burnt PWR standard fuel (33,000 MWd/tHM burned), with 3.1 % of initial enrichment, which has remained in the cooling pool for five years. The k eff, hardening spectrum, and the fuel evolution during burnup were evaluated. This study was performed by using the SCALE 6.0 code.

First Wall Materials Effects on Nuclear Criticality Evaluation of Fusion-Fission Systems

Abstract Different first wall material proposals based on tungsten alloy WNiFe, WLa2O3, W1.1TiC, W26Re, beryllium alloy S-B65, stainless steel SS316 and graphite have been studied in the last years. These materials must be capable of withstanding high temperature and neutron flux. Nevertheless, using hybrid systems, the first wall material choice could influence the criticality system due to the different properties of each material. To analyze this influence, two hybrid reactors were evaluated. The first one is a Tokamak based on magnetic confinement and the second one based on inertial confinement. Both systems contain a transmutation layer with reprocessed fuel spiked with thorium. The results showed the principal nuclides affected in the transmutation layer and the differences in the criticality due to neutron flux variations produced by the changes in the first wall material.