Synthesis of the AChE inhibitor [phenyl-7-3H] (−)-phenserine tartrate at high specific activity

The AChE inhibitor (−)-phenserine tartrate is a promising candidate as a treatment for Alzheimer’s disease and tritium labeling of it was required for biological testing. This was accomplished by a halogenation, catalytic tritium dehalogenation strategy resulting in a highly efficient incorporation of tritium. The position of tritium labeling was elucidated by a consideration of both proton and tritium NMR spectra.     

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.     

Recovery of tritium obtained as a by-product in the production of fluorine-18

For samples of irradiated natural and enriched (95%) Li₂CO₃, normal distillation to dryness of the alumina column eluates permits recuperation of approximately 80% of the tritium. The distilled samples were concentrated by electrolysis and a subsequent vacuum distillation resulted in a tritium enrichment of the order of 30%. The enriched samples were used to prepare sealed, calibrated sources, with different levels of tritium radioactivity, to be used as standards for the determination of tritium in unknown samples using liquid scintillation.     

Trace amine receptor ligands: tritiation at high specific activity

d-amphetamine and tyramine are both amines which are active at the recently discovered trace amine-associated receptor 1 (TAAR1) and analogues of these compounds labelled with tritium would be useful reagents for neurochemistry investigators. This paper describes the tritiation and characterization of these substances. d-amphetamine was radiolabelled by a direct tritium catalytic method and characterized by proton decoupled tritium NMR. For tyramine, a bromination??catalytic tritium debromination approach worked best to afford a tritiated analogue at high specific activity.     

Autoradiographical detection of tritium and14C-ethylene on nickel sheet

The detection of tritium and¹⁴C-ethylene on the surface of nickel sheet was carried out by means of autoradiography. Two autoradiographical methods were used, the ordinary stripping-film method and the electron-microscope autoradiographical method. The ordinary autoradiographs indicated that¹⁴C-ethylene accumulates at scratches on the surface of the sheet; however, tritium accumulates at grain boundaries and scratches. Electron-microscope autoradiographs indicated that tritium accumulates on the step-edges of slip band of nickel.     

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.     

Tritium monitoring with a scintillation chamber

A tritium monitor based on plastic scintillation sheets is described. The sensitive volume of the scintillation chamber is 0.95 l. The chamber with coincidence electronics has a discrimination capability and permits to detect tritium in the presence of other radionuclides and external gamma-radiation. The monitor characteristics obtained with tritiated air are presented. The monitor sensitivity for tritium in air is 5.6 cpm for each kBq·m⁻³. The monitoring of tritium in air and water is possible using the instrument described.     

Precise assay of weight per cent sodium in high-level processed nuclear tank waste using a <Superscript>252</Superscript>Cf neutron source

An infrared furnace (ULVAC RHL-410P) was newly applied to the extraction of tritium from concrete samples. After studying the tritium recovery yield regarding temperature and time, the best extraction conditions were set to 800 °C (setting temperature) for 30 minutes under Ar-gas flow of 200 ml/min. Tritium was collected in two cold traps and transferred to a vial for liquid scintillation counting. It took about one hour for the extraction of tritium. Reproducibility and recovery yield of tritium were about 100% compared to the values obtained by the ordinary heating method using an electric furnace. Gamma-ray emitters and tritium of concrete samples collected from several accelerator facilities have been determined. The specific activity of tritium strongly correlated with that of ¹⁵²Eu and ⁶⁰Co, so it was found that tritium was produced by thermal neutron reaction by the ⁶Li(n,)³H reaction. The results indicate that the tritium specific activity in concrete can be estimated from the ⁶⁰Co specific activity obtained easily by -ray measurement.On leave from IHEP, Beijing.This work was supported by Japan Society for the Promotion of Science. The authors also are grateful to Dr. S. Watanabe, Center for Nuclear Study, University of Tokyo, Dr. T. Ohtsuki, Laboratory of Nuclear Science, Tohoku University, and Dr. T. Saito, Research Center for Nuclear Physics, Osaka University, and their colleagues for concrete sampling.     

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.     

Tritium activity induced in the accelerator building and its correlation to radioactivity of gamma-nuclides

An infrared furnace (ULVAC RHL-410P) was newly applied to the extraction of tritium from concrete samples. After studying the tritium recovery yield regarding temperature and time, the best extraction conditions were set to 800 °C (setting temperature) for 30 minutes under Ar-gas flow of 200 ml/min. Tritium was collected in two cold traps and transferred to a vial for liquid scintillation counting. It took about one hour for the extraction of tritium. Reproducibility and recovery yield of tritium were about 100% compared to the values obtained by the ordinary heating method using an electric furnace. Gamma-ray emitters and tritium of concrete samples collected from several accelerator facilities have been determined. The specific activity of tritium strongly correlated with that of ¹⁵²Eu and ⁶⁰Co, so it was found that tritium was produced by thermal neutron reaction by the ⁶Li(n,)³H reaction. The results indicate that the tritium specific activity in concrete can be estimated from the ⁶⁰Co specific activity obtained easily by -ray measurement.On leave from IHEP, Beijing.This work was supported by Japan Society for the Promotion of Science. The authors also are grateful to Dr. S. Watanabe, Center for Nuclear Study, University of Tokyo, Dr. T. Ohtsuki, Laboratory of Nuclear Science, Tohoku University, and Dr. T. Saito, Research Center for Nuclear Physics, Osaka University, and their colleagues for concrete sampling.     

A new technique for tritium labeling of complex technical mixture of PCB congeners

The method of labeling by thermally activated tritium of technical mixture of PCB congeners (Sovol) has been developed. Influence of labeling procedure on mixture of PCB congeners was investigated and optimum conditions of producing of tritium labeled complex mixture of PCB congeners were determined. The system purification of tritium labeled Sovol by thin layer chromatography was developed. Purified tritium labeled Sovol was analyzed by gas chromatography. The developed technique can be used for producing of tritium labeled similar complex mixtures of congeners of other organic compounds.     

Study of kinetics,equilibrium and isotope exchange in ion exchanger systems

An automatic, rapid combustion method has been developed for the determination of tritium and¹⁴C in singly or doubly labelled organic materials by liquid scintillation counting. The sample is burned in a stream of oxygen. The water formed and its tritium content are retained from the gas stream in an absorber containing a small amount of diethyleneglycol monoethyl ether. Radioactive carbon dioxide, if included in the combustion products, is transferred into 3-methoxypropylamine. The final solutions ready for counting are obtained in less than three minutes. Quantitative collection recoveries for both tritium and¹⁴C are achieved and no cross-contamination occurs.     

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.     

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).     

Acoustic emission induced by tritium decay

An observation of signals of acoustic emission induced by tritium decay is reported. The equipment consisting of PZT detectors, preamplifiers, low-cut filters and computer evaluation was used in this study as a differential system. The result shows that the two types of clear signals of acoustic emission are induced by tritium decay. They seem to be related to some radiation effects due to tritium irradiation, and not to acoustic waves during tritium decay events.     

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.     

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.      

Tritium analysis with an ethane-filled proportional counter

An apparatus for natural tritium concentration measurement using an ethane-filled proportional counter with anticoincidence shielding is described. The counter characteristics and the counter calibration with internal tritium and external¹³⁷Cs standards are discussed. Results of tritium analysis of Bratislava rains are presented.     

Development and validation of Ni–Ni electrolytic enrichment method for tritium determination in samples of underground waters of Jeju Island

A method of tritium electrolytic enrichment was developed, optimized and validated. The enrichment parameters were compared with different current and total current charge variation and tritium separation factor was from 8 to 36 with a current density variation. The detection limit of tritium measurement is about 0.5 TU using 1,000 mL sample and 600 min counting time. Several samples of groundwaters were processed in our and another laboratory with good agreement of results within 15% deviation. Developed and validated method of tritium determination was applied groundwaters in Jeju Island with a liquid scintillation counter (LSC) and electrolytic enrichment method using Ni–Ni electrodes. The tritium concentrations in fifty eight groundwaters in Jeju Island were ranged <0.5 TU-3.9 TU and averaged value was 2.12 TU.     

Chemical forms and specific activity of tritium extracted from neutron-irradiated Li−Al alloys

When neutron-irradiated Li(1 wt%)-Al alloys were heated under vacuum at temperatures above 770 K, more than 95% of tritium was extracted in the gas phase within 1 h. The predominant species of extracted tritium were HT and HTO, although the distribution of both species varied depending upon the extraction temperature. The specific activity of the HT fraction was found to change within wide limits also depending upon the extraction temperature. The phenomenon was attributed to the difference in the release behaviour between tritium produced by the⁶Li(n, α) T reaction and protium contained as impurity in the alloy.