Novel Non-Evaporable Getter Materials and Their Possible Use in Fusion Application for Tritium Recovery.

Non-evaporable getters (NEGs) are metallic compounds of the IV group, particularly titanium and/or zirconium-based alloys and are usually used as pumps in vacuum technologies since they are able to sorb, by chemical reactions, most of the active gas molecules, with particular efficacy towards hydrogen isotopes. This work suggests an alternative application of these materials to fusion nuclear reactors, where there is the need to recover small amount of tritium from the large helium flow rate composing the primary coolant loop. Starting from the tritium mass balance inside the primary coolant loop, the amount of coolant to be routed inside the coolant purification system (CPS) is identified. Then a feasibility study, based on the bulk getter theory, is presented by considering three different commercial alloys, named ST707, ST101 and ZAO. The results provide the mass, the area and the regeneration parameters of the three different alloys necessary to fulfill the requirements of the CPS unit. By comparing the features of the three alloys, the ZAO material appears the most promising for the proposed application because it requires the lower amount of material and a lower number of regeneration cycles.

Spatial variations of tritium concentrations in groundwater collected in the southern coastal region of Fukushima, Japan, after the nuclear accident.

Spatial variations in tritium concentrations in groundwater were identified in the southern part of the coastal region in Fukushima Prefecture, Japan. Higher tritium concentrations were measured at wells near the Fukushima Daiichi Nuclear Power Station (F1NPS). Mean tritium concentrations in precipitation in the 5 weeks after the F1NPS accident were estimated to be 433 and 139 TU at a distance of 25 and 50 km, respectively, from the F1NPS. The elevations of tritium concentrations in groundwater were calculated using a simple mixing model of the precipitation and groundwater. By assuming that these precipitation was mixed into groundwater with a background tritium concentration in a hypothetical well, concentrations of 13 and 7 TU at distances of 25 and 50 km from the F1NPS, respectively, were obtained. The calculated concentrations are consistent with those measured at the studied wells. Therefore, the spatial variation in tritium concentrations in groundwater was probably caused by precipitation with high tritium concentrations as a result of the F1NPS accident. However, the highest estimated tritium concentrations in precipitation for the study site were much lower than the WHO limits for drinking water, and the concentrations decreased to almost background level at the wells by mixing with groundwater.

Experimental investigation on feasible bioreactor using mechanism of hydrogen oxidation of natural soil for detritiation system.

A passive reactor for tritium oxidation at room temperature has been widely studied in nuclear engineering especially for a detritiation system (DS) of a tritium process facility taking possible extraordinary situation severely into consideration. We have focused on bacterial oxidation of tritium by hydrogen-oxidizing bacteria in natural soil to realize the passive oxidation reactor. The purpose of this study was to examine the feasibility of a bioreactor with hydrogen-oxidizing bacteria in soil from a point of view of engineering. The efficiency of the bioreactor was evaluated by kinetics. The bioreactor packed with natural soil shows a relative high conversion rate of tritium under the saturated moisture condition at room temperature, which is obviously superior to that of a Pt/Al2O3 catalyst generally used for tritium oxidation in the existing tritium handling facilities. The order of reaction for tritium oxidation with soil was the pseudo-first order as assessed with Michaelis-Menten kinetics model. Our engineering suggestion to increase the reaction rate is the intentional addition of hydrogen at a small concentration in the feed gas on condition that the oxidation of tritium with soil is expressed by the Michaelis-Menten kinetics model.

An innovative distillation device for tritiated water analysis with high decontamination factor.

Institute of Nuclear Energy Research (INER) has designed an air-cooling distillation device and got a US patent. The decontamination factor (60)Co and (137)Cs is above 23,000. Tritium loss rate is one of testing items in ASTM D4107 Standard Test Method for Tritium in Drinking Water. In this study, the 3 levels (high, middle and low level) of tritium concentration of testing samples for the loss rate test were prepared similar to the concentrations reported in ASTM D4107. The loss rate of the high level is -2.37%, the middle is -2.31% and the low level is -2.47%. These results show that the air-cooling distillation device has good performance in the environmental water tritium analysis work.

Quick management of accidental tritium exposure cases.

Removal half-life (RHL) of tritium is one of the best means for optimising medical treatment, reduction of committed effective dose (CED) and quick/easy handling of a large group of workers for medical treatment reference. The removal of tritium from the body depends on age, temperature, relative humidity and daily rainfall; so tritium removal rate, its follow-up and proper data analysis and recording are the best techniques for management of accidental acute tritium exposed cases. The decision of referring for medical treatment or medical intervention (MI) would be based on workers' tritium RHL history taken from their bodies at the facilities. The workers with tritium intake up to 1 ALI shall not be considered for medical treatment as it is a derived limit of annual total effective dose. The short-term MI may be considered for tritium intake of 1-10 ALI; however, if the results show intake ≥100 ALI, extended strong medical/therapeutic intervention may be recommended based on the severity of exposure for maximum CED reduction requirements and annual total effective dose limit. The methodology is very useful for pressurized heavy water reactors (PHWRs) which are mainly operated by Canada and India and future fusion reactor technologies. Proper management will optimise the cases for medical treatment and enhance public acceptance of nuclear fission and fusion reactor technologies.

Development of tritiated vapor absorbent applicable to the atmospheric detritiation system in a nuclear facility.

The combination of hydrogen oxidation reactor packed noble metal catalysts and water vapor absorber has been applied to the atmospheric detritiation system of the tritium handling facility. Commercial synthetic zeolite such as molecular sieve 5A has been used as an adsorbent of ADS absorber. In the case of application of molecular sieve 5A to the ADS absorber of a large-scale tritium handling facility such as a future fusion plant, an absorber becomes huge due mainly to the difficulty in dehydration from molecular sieve 5A. Hence, application of CaY Faujasite-type zeolite with a high framework silica-to-alumina ratio to the adsorbent for atmospheric detritiation system was investigated. It was clear that the dehydration behavior at room temperature was significantly improved using CaY zeolite. In contrast, detritiation factor for CaY zeolite with a high framework silica-to-alumina ratio depended strongly on the space velocity through the absorber. To apply CaY zeolite with a high framework SiO(2)/Al(2)O(3) ratio to the ADS absorbent, the space velocity less than 250h(-1) was recommended to maintain the detritiation factor more than 1000. The steep increase in water adsorption at the relative pressure lower than 0.05 is a feature of synthetic zeolite with calcium cation. However, such an increase was not observed in water adsorption on CaY zeolite with a framework SiO(2)/Al(2)O(3) ratio more than 7.0. Consequently, the CaY zeolite with the framework SiO(2)/Al(2)O(3) ratio of 5.0 is a promising candidate as absorbent of ADS absorber.

Tritium production, recovery and application in Korea.

Four CANDU reactors have been operating at the site of Wolsong Nuclear Power Generation in Korea. The Wolsong tritium removal facility was constructed to reduce the tritium levels in heavy water systems. This facility was designed to process 100kg/h of tritiated heavy water feed and to produce 99% pure T(2). This recovered tritium will be made available for commercial applications. The initial phases on the tritium applications are made to establish the infrastructure and the tritium controls.

Experience acquired on environmental sample combustion for organically bound tritium measurement.

In order to determine organically bound tritium (OBT) concentrations, environmental samples are generally first freeze-dried. This first step is to remove tritiated water. Then, the dry residue is burnt in a special furnace with oxygen. Finally, the tritiated water fraction obtained is measured using a liquid scintillation counter. Our laboratory has developed a "pyroxydiser" tubular furnace for a computer controlled combustion. This paper presents the different improvements of the equipment. For three years, the analysis of each sample has been replicated. The experience acquired on the environmental matrices analysed using this setup is shown.

Release limits and decontamination efficacy for tritium: lessons learned outside nuclear power operations.

Various pieces of equipment in use by the Canadian Department of National Defence (DND) contain radiation-emitting components. One such piece is a sight knob used on light artillery. At the request of the DND's Director General Nuclear Safety (DGNS-DND's internal nuclear regulatory agency), the authors were contacted to remove the luminous tritium-impregnated paint strip from over 300 sight knobs. This paper discusses the physical description of the sight knobs, the protocol developed for decontaminating the sight knobs, the rationale for the release limits used, and experience gained in using and modifying the decontamination protocol.

Colforsin analogues: tritiation and characterization.

Methods are presented to tritiate and characterize colforsin analogues 2 and 3.

LCAT facilitates transacylation of 17 beta-estradiol in the presence of HDL3 subfraction.

It has been shown that estrogens need to be metabolized to their hydrophobic estrogen ester derivatives to act as antioxidants in lipoproteins. Data suggest that 17beta-estradiol (E(2)) becomes esterified in LCAT-induced reactions and the esters are transported from HDL particles to LDL and VLDL particles by a CETP-dependent mechanism. In the present study we have further investigated the regulation of E(2) esterification by LCAT and focused on the importance of HDL structure and composition in the esterification process. Isolated LDL, HDL(2), HDL(3), and reconstituted discoidal HDL (rHDL) were incubated with labeled E(2), with and without purified LCAT, at 37 degrees C for 24 h. After purification of the lipoprotein fractions, there was a significant peak of radioactivity representing esterified estradiol attached to HDL(3) and rHDL, but HDL(2) and LDL contained only trace amounts of labeled estradiol ester. TLC analysis confirmed that the radioactivity migrated in a position corresponding to that of 17beta-E(2) 17-monoester standard. The amount of radioactivity associated with HDL(3) and rHDL representing esterified E(2) was significantly increased by addition of purified LCAT. However, only limited increases of radioactivity were observed in HDL(2) and LDL. In conclusion, HDL subfractions differ in their potential to regulate estradiol esterification by LCAT.

Tritium in [15O]water, its identification and removal.

The present investigation was undertaken to identify the long-lived radionuclide and its chemical forms existing in [15O]water which was synthesized from 15O produced by the nuclear reaction 14N(d,n)15O, and to develop a method for its removal to facilitate radioactive waste disposal. The long-lived nuclide was identified as tritium based on a comparison of its physical half-life and the energy spectrum of beta-rays with those of tritium. The major chemical form of tritium in the target gas was estimated to be molecular hydrogen. The tritium radioactivity was completely removed without a serious loss occurring to the yield of [15O]water by passing the irradiated target gas over a heated palladium catalyst followed by a calcium chloride column before the final synthesis of the [15O]water. This provided a practical way of removing tritium from the [15O]water.

Simple separation of tritiated water and [3H]deoxyuridine from [5-3H]deoxyuridine 5'-monophosphate in the thymidylate synthase assay.

A simple micromethod was developed for the accurate measurement of the activity of dTMP synthase in rat liver crude extracts. The reaction product of dTMP synthase activity assay, i.e., tritiated water, generated by the release of tritium from carbon-5 of [5-3H]deoxyuridine 5'-monophosphate (dUMP), was separated simply by 100% KOH absorption from [5-3H]deoxyuridine (dUrd), which is the side-product by dephosphorylation of [5-3H]deoxyuridine (dUrd), which is the side-product by dephosphorylation of [5-3H]dUMP during the enzyme reaction. Tritiated water was trapped in three droplets of 100% KOH deposited on the underside of the vessels' lids, while [3H]dUrd remained in the bottom of vessels after absorption of the substrate, [5-3H]dUMP, from the reaction mixture by charcoal treatment. Under standard assay conditions in the crude extract of rat liver, the specific activities of dTMP synthase and dUMP phosphatase were 0.092 +/- 0.002 and 0.351 +/- 0.013 nmol/h/mg protein, respectively. This method was also adapted for dTMP synthase assay in crude extracts of rat hepatoma 3924A. The major advantages of this procedure are the elimination of the phosphatase activity which interferes with the estimation of dTMP synthase activity in crude extracts, one-step separation of 3H2O, high sensitivity (with a limit of detection of 10 pmol of 3H2O production), high reproducibility (less than +/- 4.3%), and capability to measure activity in small amounts of sample (30-45 micrograms protein).

[Separation of HT and HTO in the atmosphere with porous Vycor glass tube].

The continuous selective monitoring of tritium gas (HT) in the air containing HT and tritiated water vapor (HTO) was investigated by using the separation cell made of porous Vycor glass tube. On admitting the air containing HT or HTO into the separation cell, HT permeated immediately through the Vycor tube depending on the partial pressure, however, HTO permeated very slowly through the Vycor tube after initial induction period. The initial induction period was elongated with a rise of the temperature of separation cell and then the permeability of HTO decreased remarkably. In the air containing HT and water vapor, the permeation of HT through the Vycor tube was considerably restricted by the water vapor adsorbed on the Vycor tube at lower temperature (at 25 degrees C) but it was hardly affected by water vapor at higher temperature (greater than 50 degrees C) since water vapor was difficult to adsorb on the Vycor tube. These results indicated that HT in the air containing HT and water vapor can be continuously monitored by using the separation cell made of the porous Vycor glass tube.