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Concept: Tritium


Nuclear fusion is regularly created in spherical plasma compressions driven by multi-kilojoule pulses from the world’s largest lasers. Here we demonstrate a dense fusion environment created by irradiating arrays of deuterated nanostructures with joule-level pulses from a compact ultrafast laser. The irradiation of ordered deuterated polyethylene nanowires arrays with femtosecond pulses of relativistic intensity creates ultra-high energy density plasmas in which deuterons (D) are accelerated up to MeV energies, efficiently driving D-D fusion reactions and ultrafast neutron bursts. We measure up to 2 × 106fusion neutrons per joule, an increase of about 500 times with respect to flat solid targets, a record yield for joule-level lasers. Moreover, in accordance with simulation predictions, we observe a rapid increase in neutron yield with laser pulse energy. The results will impact nuclear science and high energy density research and can lead to bright ultrafast quasi-monoenergetic neutron point sources for imaging and materials studies.

Concepts: Helium-3, Energy, Tritium, Plasma, Neutron, Laser, Nuclear fission, Nuclear fusion


Tritium concentrations in Japanese precipitation samples collected after the March 2011 accident at the Fukushima Dai-ichi Nuclear Power Plant (FNPP1) were measured. Values exceeding the pre-accident background were detected at three out of seven localities (Tsukuba, Kashiwa and Hongo) southwest of the FNPP1 at distances varying between 170 and 220km from the source. The highest tritium content was found in the first rainfall in Tsukuba after the accident; however concentrations were 500 times less than the regulatory limit for tritium in drinking water. Tritium concentrations decreased steadily and rapidly with time, becoming indistinguishable from the pre-accident values within five weeks. The atmospheric tritium activities in the vicinity of the FNPP1 during the earliest stage of the accident was estimated to be 1.5×10(3)Bq/m(3), which is potentially capable of producing rainwater exceeding the regulatory limit, but only in the immediate vicinity of the source.

Concepts: Sustainable energy, Precipitation, Tritium, Nuclear fission, Desalination, Nuclear power, Water


The objective of this study is to quantify the relative amounts of exchangeable organically bound tritium (OBT) and non-exchangeable OBT in various vegetables. A garden plot at Perch Lake, where tritium levels are slightly elevated due to releases of tritium from a nearby nuclear waste management area and Chalk River Laboratories (CRL) operations, was used to cultivate a variety of vegetables. Five different kinds of vegetables (lettuce, cabbage, tomato, radish and beet) were studied. Exchangeable OBT behaves like tritium in tissue free water in living organisms and, based on past measurements, accounts for about 20% of the total tritium in dehydrated organic materials. In this study, the percentage of the exchangeable OBT was determined to range from 20% to 57% and was found to depend on the type of vegetables as well as the sequence of the plants exposure to HTO.

Concepts: Nuclear medicine, Annual plant, Root vegetable, Organism, Tritium, Plant, Waste, Fruit


Concentrations of organically bound tritium (OBT) and tissue-free water tritium (TFWT, also referred to as HTO) in fruits and tubers were measured at a garden plot in the vicinity of the source of chronic airborne tritium emissions during the 2008, 2010, and 2011 growing seasons. A continuous record of HTO concentration in the air moisture was reconstructed from the continuous record of Ar-41 ambient gamma radiation, as well as from frequent measurements of air HTO by active samplers at the garden plot and Ar-41 and air HTO monitoring data from the same sector. Performed measurements were used for testing the modified Specific Activity (SA) model based on the assumption that the average air HTO during the pod-filling period provides an appropriate basis for estimating the levels of OBT present in pods, fruits and tubers. It is established that the relationship between the OBT of fruits and tubers and the average air HTO from a 15-20 day wide window centred at the peak of the pod-filling period is consistent throughout the three analysed years, and could be expressed by the fruit or tuber’s OBT to air-HTO ratio of 0.93 ± 0.21. For all three years, the concentration of HTO in fruits and tubers was found to be related to levels of HTO in the air, as averaged within a 3-day pre-harvest window. The variability in the ratio of plant HTO to air HTO appears to be three times greater than that for the OBT of the fruits and tubers. It is concluded that the OBT of fruits and tubers adequately follows an empirical relationship based on the average level of air HTO from the pod-filling window, and therefore is clearly in line with the modified SA approach.

Concepts: Tritium, Plant morphology, Assumption of Mary, Measurement, Concentration, Tuber, Plant, Ratio


One-atom-thick crystals are impermeable to atoms and molecules, but hydrogen ions (thermal protons) penetrate through them. We show that monolayers of graphene and boron nitride can be used to separate hydrogen ion isotopes. Using electrical measurements and mass spectrometry, we found that deuterons permeate through these crystals much slower than protons, resulting in a separation factor of ≈10 at room temperature. The isotope effect is attributed to a difference of ≈60 milli-electron volts between zero-point energies of incident protons and deuterons, which translates into the equivalent difference in the activation barriers posed by two-dimensional crystals. In addition to providing insight into the proton transport mechanism, the demonstrated approach offers a competitive and scalable way for hydrogen isotope enrichment.

Concepts: Isotope, Tritium, Chemistry, Electric charge, Proton, Deuterium, Atom, Hydrogen


A thorough understanding of the pharmacokinetic and pharmacodynamic properties of a drug in animal models is a critical component of drug discovery and development. Such studies are performed in vivo and in vitro at various stages of the development process–ranging from preclinical absorption, distribution, metabolism and excretion (ADME) studies to late-stage human clinical trials–to elucidate a drug molecule’s metabolic profile and to assess its toxicity. Radiolabelled compounds, typically those that contain (14)C or (3)H isotopes, are one of the most powerful and widely deployed diagnostics for these studies. The introduction of radiolabels using synthetic chemistry enables the direct tracing of the drug molecule without substantially altering its structure or function. The ubiquity of C-H bonds in drugs and the relative ease and low cost associated with tritium ((3)H) make it an ideal radioisotope with which to conduct ADME studies early in the drug development process. Here we describe an iron-catalysed method for the direct (3)H labelling of pharmaceuticals by hydrogen isotope exchange, using tritium gas as the source of the radioisotope. The site selectivity of the iron catalyst is orthogonal to currently used iridium catalysts and allows isotopic labelling of complementary positions in drug molecules, providing a new diagnostic tool in drug development.

Concepts: Chemistry, Atom, Tritium, Metabolism, Pharmacokinetics, Hydrogen, Pharmacology, Isotope


Deuterium- and tritium-labeled pharmaceutical compounds are pivotal diagnostic tools in pharmaceutical drug discovery research, providing vital information about the biological fate of drugs and drug metabolites. Herein, we demonstrate that a photoredox-mediated hydrogen atom transfer (HAT) protocol can efficiently and selectively install deuterium and tritium at α-amino sp(3) C-H bonds in a single step, using isotopically labeled water (D2O or T2O) as the source of hydrogen isotope. In this context, we also report a convenient synthesis of T2O from T2, providing access to high specific activity T2O. This protocol has been successfully applied to the high incorporation of deuterium and tritium in 18 drug molecules, which meet the requirements for use in ligand binding assays and absorption, distribution, metabolism and excretion (ADME) studies.

Concepts: Drug, Hydrogen atom, Pharmacology, Isotopes of hydrogen, Atom, Hydrogen, Deuterium, Tritium


Thousands of tons of isotopic mixtures are processed annually for heavy-water production and tritium decontamination. The existing technologies remain extremely energy intensive and require large capital investments. New approaches are needed to reduce the industry’s footprint. Recently, micrometre-size crystals of graphene are shown to act as efficient sieves for hydrogen isotopes pumped through graphene electrochemically. Here we report a fully-scalable approach, using graphene obtained by chemical vapour deposition, which allows a proton-deuteron separation factor of around 8, despite cracks and imperfections. The energy consumption is projected to be orders of magnitude smaller with respect to existing technologies. A membrane based on 30 m(2) of graphene, a readily accessible amount, could provide a heavy-water output comparable to that of modern plants. Even higher efficiency is expected for tritium separation. With no fundamental obstacles for scaling up, the technology’s simplicity, efficiency and green credentials call for consideration by the nuclear and related industries.

Concepts: Neutron, Capital, Heavy water, Nuclear fusion, Isotopes of hydrogen, Deuterium, Tritium, Hydrogen


The production of pure deuterium and the removal of tritium from nuclear waste are the key challenges in separation of light isotopes. Presently, the technological methods are extremely energy- and cost-intensive. Here we report the capture of heavy hydrogen isotopes from hydrogen gas by selective adsorption at Cu(I) sites in a metal-organic framework. At the strongly binding Cu(I) sites (32 kJ mol(-1)) nuclear quantum effects result in higher adsorption enthalpies of heavier isotopes. The capture mechanism takes place most efficiently at temperatures above 80 K, when an isotope exchange allows the preferential adsorption of heavy isotopologues from the gas phase. Large difference in adsorption enthalpy of 2.5 kJ mol(-1) between D2 and H2 results in D2-over-H2 selectivity of 11 at 100 K, to the best of our knowledge the largest value known to date. Combination of thermal desorption spectroscopy, Raman measurements, inelastic neutron scattering and first principles calculations for H2/D2 mixtures allows the prediction of selectivities for tritium-containing isotopologues.

Concepts: Spectroscopy, Isotopes of hydrogen, Atom, Tritium, Deuterium, Hydrogen, Nuclear fusion, Neutron


The compound [Cp2Ti(Me)(CD2Cl2)][B(C6F5)4] reacts with trimethylvinylsilane (TMVS) to form the 1,2-insertion product [Cp2TiCH2CHMe(SiMe3)]+ (III), which exists in solution as equilibrating - and -agostic isomers. In addition, while free rotation of the -methyl group results in a single, averaged -H atom resonance at higher temperatures, decoalescence occurs below ~200 K and the resonance of the -agostic hydrogen atom at  ~7.4 is observed. Reaction of [Cp2Ti(CD3)(CD2Cl2)]+ with TMVS results in the formation of [Cp2TiCH2CH(CD3)(SiMe3)]+ which converts, via reversible -elimination, to an equilibrium mixture of specifically [Cp2TiCH2CH(CD3)(SiMe3)]+ and [Cp2TiCD2CD(CH3)(SiMe3)]+. Complementing this conventional process, EXSY experiments show that the -H atom of [Cp2TiCH2CHMe(SiMe3)]+ undergoes exchange with the three hydrogen atoms of the -methyl group (-H/-H exchange) but not with the two α-H atoms. This exchange process is completely shut down when [Cp2TiCH2CH(CD3)(SiMe3)]+ is used, suggesting an H/D kinetic isotope effect much larger (apparently >16000) than the maximum possible for an over-the-barrier process. It is proposed that -H/-H exchange is facilitated by quantum mechanical proton tunnelling in which a hydrogen atom of the 2-methyl group of the alkene-hydride deinsertion product [Cp2TiH{CH2=CMe(SiMe3)}]+ undergoes reversible exchange with the hydride ligand via the allyl dihydrogen species [Cp2TiH2{(3-CH2C(SiMe3)CH2}]+. Complementing these findings, DFT calculations were carried out to obtain energies and NMR parameters for all relevant species and thence to obtain better insight into the agostic preference(s) of complex III and the observed exchange processes. In all cases where comparisons between experimental and calculated data were possible, agreement was excellent.

Concepts: Tritium, Proton, Isotope, Hydrogen atom, Quantum mechanics, Atom, Hydrogen, Deuterium