John Stempien

A key component of the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) effort is to expand instrumentation available to users conducting irradiation tests in this unique facility. In particular, development of sensors capable of providing real-time measurements of key irradiation parameters is emphasized because of their potential to increase data fidelity and reduce posttest examination costs. This paper describes the strategy for identifying new instrumentation needed for ATR irradiations and the program underway to develop and evaluate new sensors to address these needs. Accomplishments from this program are illustrated by describing new sensors now available to users of the ATR NSUF In addition, progress is reported on current research efforts to provide improved in-pile instrumentation to users.

Three advanced 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 the same graphite-matrix coated-particle fuel as high-temperature gas-cooled reactors and clean fluoride salt coolants. Molten salt reactors (MSRs) dissolve the fuel in a fluoride or chloride salt with release of fission product tritium into the salt. In both systems, the base-line salts contain isotopically separated 7Li to minimize tritium production. The Chinese Academy of Science plans to start operation of a 10-MWt FHR and a 2-MWt MSR by 2020. For high-magnetic-field fusion machines it is proposed to use lithium enriched in 6Li to maximize tritium generation—the fuel for a fusion machine. Advances in superconductors that enable higher power densities may require the use of lithium salts as coolants. Recent technical advances in these three reactor classes has resulted in increased government and private interest—and the beginning of a coordinated effort to address the tritium control challenges in 700°C molten 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 is the primary constraint for designing efficient cost-effective methods of tritium control. This paper includes the results of two workshops on tritium control in 700°C salt.