High Temperature Nuclear System Research Articles

Core neutronic characterization of a large molten‐salt cooled thorium‐based solid fuel fast reactor

Thorium is three to four times as abundant as uranium, providing a potentially large, reliable long-term supply of clean energy, if it is exploited. In high temperature nuclear systems, molten salts have many attractive advantages as a coolant. Prior work of homogenous core model indicated that the liquid-salt-cooled solid-fuel fast reactor (LSFR) could achieve a self-sustained core based on thorium fuel with exciting neutronic performance. To further explore this concept, a fuel assembly design and a heterogeneous LSFR reference reactor core model were put forward in this study. The aim of this study was to inspect more closely the LSFR self-sustaining core and deeply investigate the neutronic characteristics with fine burnup computational model. One of the benefits of using fine burnup computation model for heterogeneous core was that the detailed physical information in each assembly could be obtained. The leakage rate at End of Equilibrium Cycle (EOEC) comprised 4.93% of 3100 MWth LSFR heterogeneous active core model and 3.00% of prior homogenous active core model. Besides this, the LSFR core neutronic characteristics were in good consistency with that of homogenous model. The characteristics of thorium-based LSFR reference core are (a) a high discharge burnup ~20% FIMA; (b) small reactivity swing during the reactor lifespan; and (c) the negative reactivity temperature coefficients for all cases.

Computational model of a sulfur-iodine thermochemical water splitting system coupled to a VHTR for nuclear hydrogen production

Sulfur-Iodine thermochemical water splitting cycle coupled is one of the most promising methods for hydrogen production using a nuclear reactor as the primary energy source. However, there are not references in the scientific publications of a test facility that allow to evaluate the efficiency of the overall process. A computational model for the evaluation and optimization of the sulfur-iodine cycle coupled to a very high temperature reactor for nuclear hydrogen production was developed using a chemical process simulator Aspen HYSYS®. Some operational and design parameters of the cycle sections can be optimized in order to obtain the maximum hydrogen production and higher efficiency. The optimized sections of the flowsheet are coupled to a very high temperature nuclear system (TADSEA) through a Brayton gas cycle for power cogeneration. It is proposed a closed flowsheet for the sulfur-iodine thermochemical water splitting cycle coupled to an accelerator driven system, considering a Brayton cycle for the energy production. It is obtained an acceptable value of global efficiency for the initial operating condition. Several parametric studies are conducted using the flowsheet proposed to evaluate important operating parameters in the overall process efficiency.

Neutronics physics analysis of a large fluoride-salt-cooled solid-fuel fast reactor with Th-based fuel

Fast reactors based on thorium fuel have enhanced inherent safety. Fluoride salt performs well as a coolant in high-temperature nuclear systems. In this paper, we present a reference core for a large fluoride-salt-cooled solid-fuel fast reactor (LSFR) using thorium–uranium fuel cycle. Neutronics physics of the LSFR reference core is investigated with 2D and 3D in-core fuel management strategy. The design parameters analyzed include the fuel volume fraction, power density level and continuous removal of fission products with 3D fuel shuffling that obtains better equilibrium core performance than 2D shuffling. A self-sustained core is achieved for all cases, and the core of 60% fuel volume fraction at 50 MW/m3 power density is of the best breeding performance (average breeding ratio 1.134). The LSFR core based on thorium fuel is advantageous in its high discharge burn-up of 20–30% fissions per initial heavy metal atom, small reactivity swing over the whole lifetime (to simplify the reactivity control system), the negative reactivity temperature coefficient (intrinsically safe for all cases) and accepted cladding peak radiation damage. The LSFR reactor is a good alternative option for the deployment of a self-sustained thorium-based nuclear system.

The feasibility research of thorium breeding using fluoride salt as a fast reactor coolant

Breeder reactors are considered as a unique tool for fully exploiting natural resources. Fast breeder reactors based on thorium fuel can enhance inherent safety. Fluoride salt has good performance as a coolant in high-temperature nuclear systems. However, there is some doubt about the fuel breeding ability using fluoride salt coolant for fast spectrum due to its moderating ability. The aim of this study was to choose a proper fluoride salt mixture for Liquid-salt-cooled Solid-fuel Fast Reactor (LSFR) based on thorium-uranium fuel and give parametric studies to provide a design window for flexible self-sustaining core design. Infinite assembly model was used to analyze the salt selection from five candidate fluorides for fast spectrum as coolant. Combining neutron balance analysis with linear least squares fitting method based on 0D model, parametric studies at the neutron balance equation unique solution with burn-up for several parameters such as fuel volume fraction, removing fission gases process, total neutron losses and power density were presented in this paper. It was found that BeF2-NaF was a promising coolant in the five candidate fluoride salt mixture. This study proved that the design of a self-sustaining core for fluoride-salt-cooled fast breeder based on thorium fuel is achievable. A design window was found in the definition of a self-sustaining core for various fuel volume fractions and neutron loss fractions. Core design and fuel management strategy will be given in future.

Eurocorr 2009: 'Corrosion from the nanoscale to the plant' – part 5

Last year’s Eurocorr conference took place at the Acropolis Convention Centre in Nice from 6 to 10 September. The focus of the meeting was ‘Corrosion from the Nanoscale to the Plant’. The meeting attracted 800 delegates and over 360 papers and 200 posters were presented during the 25 sessions and workshops. Part 1 of the report, published in the December issue, covered the opening session and plenary lectures. Part 2, published in the February issue, reviewed technical sessions on automotive corrosion, corrosion of archaeological and heritage artefacts, organic coatings and cathodic protection and marine corrosion. Part 3, published in the April issue, reviewed technical sessions on inhibitors, oil and gas, polymeric materials, metallic and inorganic coatings and pretreatments. Part 4 published in the June issue reviewed corrosion and corrosion protection in drinking water systems, recent advances in surface analytical techniques and applications to corrosion research, simulation, modelling and life prediction, environmental sensitive fracture and corrosion mechanisms and methods. The fi nal part of the report reviews technical sessions on nuclear corrosion, including corrosion issues in future high temperature nuclear systems, microbial corrosion: biomolecules and biofi lms on surfaces – impact on the corrosion resistance and biotribocorrosion, corrosion by hot gases and combustion products, and corrosion of steel in concrete.