Tritium Production and Permeation in High-Temperature Reactor Systems

Abstract

Tritium (H13) is a radioactive isotope of hydrogen formed by ternary fission events (rare emissions of three nuclides rather than two during a fission) and neutron absorption (and subsequent decay) of predecessor radionuclides, particularly 6Li and 7Li. Also in fusion, the concept of breeding tritium during the fusion reaction is of significance for the future needs of a large-scale fusion power plant. Tritium is of special interest among the fission products created in next-generation nuclear reactors such as gas cooled reactors and molten salt reactors, because of the large quantities produced when compared with conventional light-water reactors (LWR) and the higher temperatures of operation for these systems enhances permeation. To prevent the tritium contamination of proposed reactor buildings and surrounding sites, this paper examines the root causes and potential solutions for mitigation of permeation of this radionuclide, including materials selection and inert gas sparging. A model is presented that can be used to predict permeation rates of hydrogen through metallic alloys at temperatures from 450–750°C. Results of the diffusion model are presented along with mitigation strategies for tritium permeation.

Study of tritium transport characteristics in a transportable fluoride-salt-cooled high-temperature reactor

“…After passing through the metal, atomic tritium can recombine into molecular form on the free surface of the metal. The physical process is shown in Figure …”

A Comparative Evaluation and Selection of High-Temperature Heat Exchangers for Application to Integrated Energy Systems

“…It is important to highlight that the reactor type connected to the HE determines how significantly the end users should consider the risk of tritium permeation. For example, the tritium production in gas-cooled reactors is much less than in molten-salt reactors [54].…”

Assessment of thermodynamic stability of sapphire in eutectic molten chloride environment

“…Some of the newest MSR and CSP designs use molten chloride salts due to their desirable properties, such as relatively low melting points, low viscosities, and lesser effect on structural materials (corrosion) compared to fluoride melts. [1][2][3][4] In this aspect, molten chloride salts have been an excellent choice for thermal energy storage material in CSP plants and heat transfer media in nuclear reactors. Regarding raw materials cost, chloride salts, particularly those containing MgCl 2 , are by far the least expensive.…”

“…Energy production using molten salt reactors (MSRs) and concentrated solar power (CSP) plants offers several advantages, including lower cost and higher operational safety. Some of the newest MSR and CSP designs use molten chloride salts due to their desirable properties, such as relatively low melting points, low viscosities, and lesser effect on structural materials (corrosion) compared to fluoride melts 1–4 . In this aspect, molten chloride salts have been an excellent choice for thermal energy storage material in CSP plants and heat transfer media in nuclear reactors.…”