Determination of low-level tritium concentrations in surface water and precipitation in the Czech Republic

Past tests of nuclear weapons in the atmosphere, nuclear energy facilities and tritium of natural origin are main sources of tritium in the environment. Thanks to its presence in environment and its favourable properties, tritium is used as a radiotracer. Since stopping of atmospheric nuclear tests, tritium in precipitation has been decreasing towards natural levels below 1 Bq l^?1 and precise analyses of low level tritium activities are necessary. This paper focuses on tritium development at sites not influenced by any technogenic release of tritium in Elbe River basin (Bohemia) in the Czech Republic using liquid scintillation measurement with electrolytic enrichment.     

Dopamine receptor stimulants N-0923 and (+/-)-<Emphasis Type="Italic">threo-</Emphasis>methylphenidate: Labeling with tritium

Summary Dopamine receptor ligands N-0923 (1) and (+/-)-threo-methylphenidate (4) have been labeled with tritium at high specific activity, for becoming useful tools to study the dopamine receptor family.     

Ultraviolet photolysis of urine for suppression of color quenching prior to liquid scintillation counting of tritium

In order to reduce the color quenching in the measurement of tritium in urine by liquid scintillation counting , UV irradiation was applied to decompose the organic substances in the sample. Urine was decolorized under UV irradiation in the presence of hydrogen peroxide. As a result, color quenching was considerably suppressed and higher counting efficiency of tritium was obtained. This UV treatment made it possible to increase the urine content in the sample from 2 to 40% (v/v) without significant decrease of counting efficiency. Either higher sensitivity or shorter analysis time was achieved in the tritium measurement by the augmentation of urine content. When the measurement time was 30 min, the detection limit of tritium defined as 3s was 0.03 Bq/ml. At the expense of some sensitivity (set at a detection limit of 0.3 Bq/ml), the measurement time was shortened to 0.5 min. These results will make a great improvement to routine tritium monitoring as well as to emergency monitoring in mass tritium exposure.      

Trace tritium recovery from the residue of liquid Li17Pb83 alloy

The liquid Li₁₇Pb₈₃ alloy is a prominent breeder material for use in a fusion reactor. In the design of an effective tritium extraction system for the liquid lithium lead bubbler of the test blanket module of such a reactor, finding ways to strictly limit the losses of tritium and to minimize radioactive risks is very important. For this purpose, the isotope exchange process has been investigated as a means of trace tritium recovery from a model of the residue from Li₁₇Pb₈₃ alloy. The results indicate that the isotope exchange process is an effective means of tritium recovery from the residue of Li₁₇Pb₈₃ alloy, and the optimum composition of the exchange carrier gas is He + 0.1% D₂. The exchange temperature and number of exchange steps are the main factors influencing the efficiency of tritium recovery from the residue. Trace tritium recovery efficiency increases with increasing exchange temperature and number of times of exchange. Tritium recovery efficiency can approach 80% when the residue is treated six times at 823 K. A gas-liquid two-phase contact model to describe the proceeding of tritium release from the liquid Li₁₇Pb₈₃ alloy has been derived on the basis of this experiment.     

Chemical shifts for tritons in the ortho,meta and para positions of toluene as determined by tritium NMR spectroscopy

Chemical shifts for tritons in ortho, meta and para positions in toluene have been determined using a 64 MHz tritium NMR spectrometer. The order of shift is meta>para>ortho, whereas the calculated shift order for protons is meta>ortho>para.     

Tritium in surface waters, tap water and in precipitation in Poland during the 1994–1999 period

Concentrations of tritium in environmental waters (precipitation, rivers, lakes, tap water) have been determined using electrolytic enrichment and liquid scintillation counting. In waters of big rivers (the Vistula and the Odra rivers), lakes and tap water the annual average concentrations were similar to each other being from 1.4 to 1.9 Bq·dm^-3. These concentrations were similar to those in the precipitation in which they ranged from 1.7 to 2.2 Bq·dm^-3. The lowest tritium concentrations were found in waters of the Seashore Region rivers (average for 1994–1999 was 1.1 Bq·dm^-3). The tritium concentrations in surface waters and in precipitation are still higher than that of natural level. The data obtained show that tritium concentration in the water of rivers might depend on the size of drainage area. The observed seasonal variations of tritium concentration in the precipitation collected in Warsaw and at the Mount Sniezka indicate the stratospheric source of tritium. It was found that about 30% of tritium deposited with precipitation is removed to the Baltic Sea with river waters.     

Relation between tritium concentration and chemical composition in rain at Fukuoka

Tritium concentrations in rain collected at Fukuoka, Japan from 1982 have been measured. From May 1996 tritium concentrations and chemical species have been analyzed for each rain to examine their relationship. Recent rain was concluded not to be affected by tritium from atmospheric nuclear tests. Tritium concentrations showed a seasonal pattern, high during winter and spring and low during summer and fall and had positive correlations with non-sea-salt SO₄ ⁻², indicating a long distance transport of acidic materials as tritium from continental China.     

Synthesis of tritium-labeled nucleoside 5′-triphosphates and nucleoside 5′-diphosphates

Tritium-labeled nucleoside 5′-triphosphates (NTPs) nucleoside 5′-diphosphates (NDPs) containing the tritium label in positions 8 (in the purine nucleus) and 5 (in the pyrimidine nucleus) have been obtained by the dehalogenation of the corresponding bromine derivatives with gaseous tritium. The dehalogenation of the Br-NTPs and Br-NDPs was carried out at atmospheric pressure in an aqueous alkaline medium using palladium catalysts (5% Pd/BaSO₄ or α-Pd). The possibility of introducing a tritium label into nucleotides of the adenine series by the heterogenecus isotope exchange reaction with gaseous tritium in the presence of 5% Pd/BaSO₄ has been investigated. For the compounds synthesized, the compositions of the eluents used for the chromatographic isolation of the desired products are given. The molar activities of the compounds synthesized were between 370 and 740 TB_q/mole (10–20 kCi/mole).     

Tritium measurement in the Western Caucasus

Measurement of tritium in water of rains, springs, wells, mud volcanoes and rivers, lakes of the Western Caucasus (Krasnodar region) has been carried out since 1997 for hydrogeology, engineering geology, ecology and seismology. Electrolytic cells with spiral electrodes and the big multiwire proportional chamber were used for low tritium concentration measurements on expeditions. With the new design of the cell the enrichment factor of 64.0 ± 1.5 % was obtained during the electrolytic process. Correlation of tritium concentration is observed in mud volcanoes and spring water with regional seismicity. The long-term tritium data are shown in natural waters in South Russia.     

Radiochemical characteristics of tritium to be considered in fusion reactor facility design

The results of research and development related to radiochemical characteristics of tritium to be considered in a fusion reactor facility design are summarized. Reactions induced by tritium beta-decay under presence of high purity tritium, which might give an impact to tritium inventory control and safety, have been identified and investigated. Results of researches of radiolysis of tritiated water implied necessity of some measures to prevent hydrogen explosion and avoid a corrosive condition. A calorimetric method to measure tritium decay heat has been applied successfully to accountancy of the ITER fuel storage system with satisfaction of the required specification.     

Determination of tritium enrichment parameters of a commercially available PEM electrolyzer: a comparison with conventional enrichment electrolysis

The combination of an Ir/Pt PEM electrolyzer with a 1 L flow-through gas proportional counter was characterized for the quantification of tritium in water. The goal of the detection system is to quantify at concentrations below the Environmental Protection Agency (EPA) primary drinking water standard (740 Bq/L) with minimal expendables. The detector operating voltage, efficiency, background count rate of the passively shielded counter were measured in order to calculate the minimum detectable concentration of the detection system. The electrolyzer fractionation factor β _e value deduced from the measurement of gas phase activity concentrations generated from tritium aqueous standards was found in good agreement with literature values.     

Tritium content as indicator of environmental character on Taiwan Island

Environmental characters have been established by tritium contents in well water, coastal seawater and reservoir water collected from various places around Taiwan island. Tritium concentrations of samples were detected by a liquid scintillation analyzer TRI-CARB-LSC 2550 TR mode, with a low level standard quench curve. After samples were concentrated by electrolysis, tritium concentration was detected in optimum conditions of LLLSA. An electrolytic enrichment technique was also developed with a eurrent density of 100 mA/cm² and 0.4–0.6% (Na₂O₂) electrolyte in concentrated samples. Data observed show a lower tritium concentration for coastal seawater than for wells in the same area. The tritium concentration ratio of well and coastal seawater on the western side of Taiwan is 4.000 and on the eastern side 5.801. Tritium content of reservoir water is related to the logarithm of effective volume capacity.     

锂铅合金中氚扩散行为的理论研究

锂铅合金是非常有前途的聚变堆、聚变-裂变混合堆包层产氚材料,研究氚在其中的扩散行为是很有意义的工作.从氢在金属中扩散的宏观规律出发,依据平板模型初步建立了氚-锂铅体系的扩散模型,利用相关文献数据,探讨了不同研究方式、氚浓度、温度对扩散行为的影响,分析了这种扩散的微观机制.计算结果表明:造成研究结论之间巨大差异的原因在于锂铅表面物理和化学状态的不同考虑;在一定温度范围内,氚浓度的升高引起扩散系数的下降,温度的升高引起扩散系数的增加.     

Distribution and movement of tritium in an ion exchanger-water system

The study of the behavior of hydrogen in ion exchange columns is of theoretical and practical interest. This problem can be solved by using tritium as radioactive hydrogen tracer. The present paper describes the first results obtained in an experimental study of the statics and dynamics of the distribution and movement of tritium in an ion exchanger-water system.The materials studied were Ku-2 cation exchange resin in the H- and Sr-forms, and AN-2F and AV-17 anion exchange resins in the Cl-form. The isotopic effects in the distribution of tritium have been estimated. It has been shown that tritium is concentrated to a greater extent in the water than in the resin. Study of the filtration of water labeled with tritium in ion exchange columns has established that, as a result of isotopic exchange sorption, the rate of movement of the water front labeled with tritium is less than the rate of flow of water. The effluent curves have been interpreted theoretically on the basis of the general theory of the dynamics of sorption, and values for the constants of the dynamics of sorption have been estimated.     

DNA EXCISION REPAIR IN LYMPHOCYTES FOLLOWING PHOTOAFFINITY LABELING WITH ETHIDIUM MONOAZIDE

Irradiation of ethidium monoazide by fluorescent light promotes a chemical decomposition of the azide into a highly reactive nitrene intermediate. Covalent bonding of this electrophile to the DNA in the cell provokes repair of damage which can be monitored by incorporation of [³H]-thymidine. Human lymphocytes were labeled with [¹⁴C]-ethidium azide and then allowed to undergo DNA repair. Repair incorporation of [³H]-thymidine showed saturation at 5 µM ethidium azide, but excision of the labeled drug failed to saturate at 20 µM, suggesting that excision and resynthesis are two separate events. Cells were also labeled with the photosensitive drug and/or exposed to UV radiation, and then allowed to undergo a period of DNA repair. The tritium incorporation for the combined insults was less than the sum of the two insults. Quinacrine, progesterone and chloroquine inhibited repair incorporation of [³H]-thymidine, but had no effect on the excision of the drug from the DNA. After damage by ethidium azide, chromatin was isolated from lymphocytes which had been allowed to repair label with [³H]-thymidine. Partial digestion of the chromatin with micrococcal nuclease released 80% of the tritium when approximately 40% of the DNA had been hydrolyzed by the enzyme.     

锂锡合金中氚扩散行为的计算

锂锡合金是非常有前景的聚变能源堆液态包层产氚材料,研究氚在其中的扩散行为是很有意义的工作.本文从氢在金属中扩散的宏观规律出发,依据平板模型初步建立了氚-锂锡体系的扩散模型,利用相关文献数据,探讨了不同研究方式、氚浓度、温度对扩散行为的影响,分析了这种扩散的微观机制.计算结果表明:造成研究结论之间巨大差异的原因在于锂锡表...     

Studies in Pheromone Biosynthesis: Preparation of 3H Labelled Precursors of Drosophila Pheromones

Two synthetic schemes were designed giving access to tritium labelled potential precursors of Drosophila pheromones. An intermediate in the first scheme allowed the preparation of [³H]-labelled vaccenyl acetate.     

Reproducible tritium generation in electrochemical cells employing palladium cathodes with high deuterium loading

Reproducible tritium generation well above background has been observed in tightly closed D₂SO₄-containing cells in four out of four Pd wire cathodes of one type. Tritium analysis was performed before and after each experiment on the Pd, the electrolyte and the gas in the head space. No tritium generation was observed in four identical Pd cathodes in H₂SO₄ cells operated at the same time under the same conditions. A cyclic loading-unloading regime with low current densities, rather than the usual continuous constant current regime, was employed to attain D/Pd and H/Pd loadings of 1±0.05 reproducibly. D/Pd loadings greater than 0.8±0.05 appear to be necessary to generate tritium. The largest amount of tritium, generated in 7 days of continuous electrolysis, was 2.1 × 10¹¹ tritium atoms, compared with a background of 4 × 10⁹ tritium atoms. The concentration of tritium and its axial distribution in the Pd were determined and concentrations of up to 9 × 10¹⁰ atoms/g Pd were found compared with a maximum background of 5 × 10⁸ atoms g⁻¹. The T/D ratio in the Pd is about 100 times larger than in the electrolyte or gas and indicates that tritium generation occurs in the Pd interior rather than at its surface. No tritium generation was observed in two other types of Pd electrodes in D₂SO₄, despite the attainment of D/Pd ratios near 1:1. Thus high D/Pd ratios appear to be a necessary but not sufficient condition for tritium generation in D₂SO₄ electrolysis.     

Radioactivity in deuterated compounds

Commercially available D₂O and deuterated toluene have been measured with a liquid scintillation spectrometer and were found to contain 2.71–6.15 Bq of tritium in 1 ml of D₂O, and 1.10 Bq of tritium in 1 ml of deuterated toluene.     

Preparation of tritium-labelled oleic acid and prostaglandins E2 and F1α. A study of the process of including tritium in molecules of unsaturated fatty acids and prostaglandins

[³H]Prostaglandin E₂ and [³H]prostaglandin F_1a have been obtained with the aid of heterogeneous catalytic isotope exchange with gaseous tritium in solution. The distribution of the tritium in the labelled unsaturated fatty acids and prostaglandins has been studied.Institute of Molecular Genetics, Academy of Sciences of the USSR, Moscow. M. M. Shemyakin Institute of Bioorganic Chemistry, Khimiya Prirodnykh Soedinenii, No. 2, pp. 148–157, March–April, 1980.