R. V. Carlson

Experience of TSTA Milestone Runs with 100 Grams-Level of Tritium

The first loop operation tests of the Tritium Systems Test Assembly (TSTA) with 100 grams-level of tritium were performed at the Los Alamos National Laboratory (LANL) in June and July, 1987. The July run was resumption of the June run, which was halted because of a loss of cryogenic refrigerant in the hydrogen isotope separation system.

Behavior of tritium in the TSTA test cell combined with operation of the Experimental Tritium Cleanup (ETC) system

Abstract Tritium and deuterium are expected to be the fuel for the first fusion power reactors. Being radioactive, tritium is a health, safety and environment concern. Room air tritium clean systems can be used to handle tritium that has been lost to the room from primary or secondary containment. Such a system called the Experimental Tritium Cleanup (ETC) systems is installed at the Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory. The ETC consists of (1) two compressors which draw air from the room, (2) a catalyst bed for conversion of tritium to tritiated water, and (3) molecular sieve beds for collection of the water. The exhaust from this system can be returned to the room or vented to the stack. As part of the US–Japan fusion collaboration, on two separate occasions, tritium was released into the 3000 m3 TSTA test cell, and the ETC was used to handle these releases. Each release consisted of about one Curie of tritium. Tritium concentrations in the room were monitored at numerous locations. Also recorded were the HT and HTO concentrations at the inlet and outlet of the catalyst bed. Tritium surface concentrations in the test cell were measured before and at a series of times after the releases. Surfaces included normal test cell equipment as well as idealized test specimens. The results showed that the tritium became well-mixed in the test cell after about 45 min. When the ETC was turned on, the tritium in the TSTA test cell decreased exponentially as was expected. The test cell air tritium concentration was reduced to below one DAC (derived air concentration) in about 260 min. For the catalyst bed, at startup when the bed was at ambient temperature, there was little conversion of tritium to HTO. However, once the bed warmed to about 420 K, all of the tritium that entered the bed was converted to HTO. Immediately after the experiment, surfaces in the room initially showed moderately elevated tritium concentrations. However, with normal ventilation, these concentrations soon returned to routine levels. The data collected and reported here should be useful for planning for the operation of existing and future tritium facilities.

Operation of a simulated non-steady tokamak fuel loop using the tritium systems test assembly

Abstract In order to develop a fuel system for a realistic fusion device in near future, a number of experimental campaigns of a simulated fusion fuel loop were performed under practical non-steady conditions at the Tritium Systems Test Assembly (TSTA). Some technical issues specific for non-steady fuel loop were identified and are being investigated further. The overall process loop was operated with non-steady inputs to better interface with pulsed tokamak operation, which requires a rather different and improved processing capability specific to each subsystem. The cryogenic distillation columns in the isotope separation are modified to provide side-stream recycle paths with isotopic equilibration function. This change improved separation characteristics with various feed compositions, and reduces the required number of columns for processing and resulted in a reduced tritium inventory in the isotope separation system (ISS). Another major technical development on the ISS is addition of a number of feed-back control loops that automatically operate the distillation columns stably under changing feed conditions. The plasma exhaust processing system composed of palladium diffuser, catalytic reactor, electrolysis cell and cold trap was operated mainly in the batch mode to handle a broader range of input flow rate and composition in various configurations to minimize tritium loss and inventory. The results demonstrated the overall capability and flexibility of the TSTA loop to serve as a fuel processing system under non-steady conditions; however, they imply that many technical issues arise in operating a practical fuel processing system. These may not be foreseen in the design stage and can only be determined during integrated tests under realistic operating conditions.

Dispersion and removal of tritium released into the main cell of TSTA

Approximately 145 mCi (about 0.06 cm/sup 3/) of tritium in DT form was released into the main cell of the Tritium Systems Test Assembly at Los Alamos National Laboratory. At equilibrium with the cell isolated, this amount resulted in concentrations of about 50 mu Ci/m/sup 3/ throughout the 2900 m/sup 3/ of the cell volume. Tritium was held in the cell for 29 min before normal ventilation was restored and was released through the facilitys 30-m stack. The dispersion, confinement, removal, and decontamination times associated with the release are discussed. The broad results of the test are as follows: (1) tritium became distributed uniformly in the cell within 10 min. (2) no tritium was detected leaking from around the inner doors to the cell, (3) with ventilation, tritium was removed from the cell faster than predicted by idealized calculations assuming perfect mixing in the cell, and (4) no residual air contamination remained three days after the release, with no residual removable contamination of surfaces remaining one month after the release.<<ETX>>

Transportation of tritiated waste from fusion facilities

This paper examines methods of handling tritiated waste from a fusion facility. Gaseous effluent from a fusion reactor can currently be transported from a fusion facility in two forms - as a gas or solidified on uranium beds. Tritiated water can be transported if it is solidified by adsorption onto molecular sieve beds or on clay or cement. Solid waste being shipped for disposal can be transported in low specific activity (LSA, less than 0.3 mCi/g (1.1x10/sup 7/ Bq/g)), type A (less than or equal to 1000 Ci (3.7x10/sup 13/ Bq)) or type B (greater than 1000 Ci (3.7x10/sup 13/ Bq)) standard containers. The method chosen for transport depends on the amount and level of activity of the tritiated material and whether or not it will be reprocessed at another facility.

Residual tritiated water in molecular sieves

This paper discusses results of experiments that measured the residual tritiated water remaining on the sieve after regeneration and experiments to determine if the tritium inventory can be reduced after regeneration. Three types of experiments were performed. First, molecular sieve was placed in a standard calorimeter, which measures the heat resulting from the decay of the residual tritium in the sieve. These measurements indicated an average residual tritium concentration of 0.3 Ci/g of molecular sieve. However, there were substantial variations in the calorimeter readings from run to run. Second, small samples of sieve were soaked in water to leach out the tritiated water. Samples of the water were then measured in a liquid scintillation counter to determine the quantity of tritium in the liquid. These experiments indicated a residual tritium concentration of 0.08 Ci/g of molecular sieve. Third, an additional sample of the molecular sieve was heated and dissolved in Na/sub 2/CO/sub 3/ in a glove box. The tritium that evolved was then measured by noting the increase in the tritium concentration in the glove box. This experiment indicated a minimum tritium concentration of 0.03 Ci/g of molecular sieve.

Tritium behavior intentionally released in the room

Abstract To construct a fusion reactor with high safety and acceptability, it is necessary to establish and to ensure tritium safe handling technology. Tritium should be well-controlled not to be released to the environment excessively and to prevent workers from excess exposure. It is especially important to grasp tritium behavior in the final confinement area, such as the room and/or building. In order to obtain data for actual tritium behavior in a room and/or building, a series of intentional Tritium Release Experiments (TREs) were planned and carried out within a radiologically controlled area (main cell) at Tritium System Test Assembly (TSTA) in Los Alamos National Laboratory (LANL) under US-JAPAN collaboration program. These experiments were carried out three times. In these experiments, influence of a difference in the tritium release point and the amount of hydrogen isotope for the initial tritium behavior in the room were suggested. Tritium was released into the main cell at TSTA/LANL. The released tritium reached a uniform concentration about 30 ~ 40 minutes in all the experiments. The influence of the release point and the amount of hydrogen isotope were not found to be important in these experiments. The experimental results for the initial tritium behavior in the room were also simulated well by the modified three-dimensional eddy flow analysis code FLOW-3D.

Experiences with a Japanese-American fusion fuel processing hardware project

This paper reports that the United States Department of Energy (USDOE) and the Japan Atomic Energy Research Institute (JAERI) have installed a full-sale fuel cleanup system (JFCU) for testing at Los Alamos. The JFCU was designed by JAERI and built by Mitsubishi Heavy Industries (MHI) in Kobe, Japan. Experience gained by Japanese working at Los Alamos facilitated development of a system consistent with Los Alamos operations and standards. US or equivalent Japanese standards were generally used for design resulting in minor problems at electrical interfaces. Frequent written interchanges were essential to project success, as spoken communications can be misunderstood. Differing work styles required detailed pre-planning, separation of responsibilities, and daily scheduling meetings. Safety and operational documentation drafted by JAERI personnel was revised at Los Alamos to assure conformance with USDOE and Los Alamos standards. The project was successful because both Japanese and American participants worked hard to overcome potential problems. These experiences will be valuable in conducting future international fusion projects.

Tritium handling safety and operating experience at the Tritium Systems Test Assembly

The Tritium Systems Test Assembly (TSTA) is designed to develop and demonstrate, in full scale, technologies necessary for safe and efficient operation of tokamak fusion reactors. The TSTA currently consists of systems for pumping DT gas mixtures for removing impurities; for separating the isotopes of hydrogen; for storage of hydrogen isotopes; for gas analysis; and for assuring safety by the necessary control, monitoring, and detritiation of effluent gaseous streams. TSTA also has several small-scale experiments to develop and test new equipment and processes necessary for fusion reactors. Data on component reliability, failure types and rates, and waste quantities are presented. Operational experience under normal, abnormal, and emergency conditions is presented. The DOE (US Department of Energy) requirements for the operation of a tritium facility like TSTA include specifications on personnel training, emergency preparedness radiation protection, safety analysis, and preoperational appraisals.<<ETX>>