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TitleDesign summary of the Mark-I pebble-bed, fluoride salt-cooled, high-temperature reactor commercial power plant Abstract -The University of California, Berkeley (UCB), has developed a preconceptual design for a commercial pebble-bed (PB), fluoride salt-cooled, high-temperature reactor (FHR) (PB-FHR). The baseline design for this Mark-I PB-FHR (Mk1) plant is a 236-MW(thermal) reactor. The Mk1 uses a fluoride salt coolant with solid, coated-particle pebble fuel. The Mk1 design differs from earlier FHR designs because it uses a nuclear air-Brayton combined cycle designed to produce 100 MW(electric) of base-load electricity using a modified General

Three advanced nuclear power systems use liquid salt coolants that generate tritium and thus face the common challenges of containing and capturing tritium to prevent its release to the environment. The fluoride salt-cooled high-temperature reactor (FHR) uses clean fluoride salt coolants and the same graphite-matrix coated-particle fuel as high-temperature gas-cooled reactors. Molten salt reactors (MSRs) dissolve the fuel in a fluoride or chloride salt with release of fission product tritium into the salt. In most FHR and MSR systems, the baseline salts contain lithium where isotopically separated 7 Li is proposed to minimize tritium production from neutron interactions with the salt. The Chinese Academy of Sciences plans to start operation of a 2-MW(thermal) molten salt test reactor by 2020. For high-magnetic-field fusion machines, the use of lithium enriched in 6 Li is proposed to maximize tritium generation-the fuel for a fusion machine. Advances in superconductors that enable higher power densities may require the use of molten lithium salts for fusion blankets and as coolants. Recent technical advances in these three reactor classes have resulted in increased government and private interest and the beginning of a coordinated effort to address the tritium control challenges in 700°C liquid salt systems. We describe characteristics of salt-cooled fission and fusion machines, the basis for growing interest in these technologies, tritium generation in molten salts, the environment for tritium capture, models for high-temperature tritium transport in salt systems, alternative strategies for tritium control, and ongoing experimental work. Several methods to control tritium appear viable. Limited experimental data are the primary constraint for designing efficient cost-effective methods of tritium control.

The co‐assembly between a polyisoprene‐block‐poly(dimethylaminoethyl methacrylate) block copolymer and poly(ureamethylvinyl)silazane is investigated. The hybrid morphology can be controlled by systematically increasing the inorganic‐to‐organic ratio or by changing the molecular weight of the block copolymer. Temperature treatment up to 1 500 °C of the hybrids resulted in mesoporous, ordered non‐oxide‐type ceramics. The results suggest that careful control of co‐assembly processes enables access to nanostructured high‐temperature ceramics that may have novel mechanical, thermal, and chemical properties.magnified image

2LiF-BeF2 (FLiBe) is proposed as coolant for advanced nuclear fission and fusion reactors designs. Electrochemical techniques can be used to answer important research questions about the chemistry, mass transport, and corrosion behavior of FLiBe. The use of electrochemical techniques is predicated upon a thermodynamic reference electrode (RE) for FLiBe. This paper reports the design and characterization of a RE for FLiBe based on the Ni/Ni(II) redox couple, a boron nitride body, and a LaF3 ionic membrane. This electrode, tested in the range of 500°C–600°C shows stability of +/−1 mV for ten hours, good polarizability behavior, and Nernstian behavior. This data is comparable to other RE data reported for other fluoride salt mixtures. This paper also shows that beyond ten hours the RE potential drifts and there is evidence of Ni(II) depletion from the RE. We discuss some of the mechanisms that may cause this drift.