Tritium Gas Research Articles

Influence of Microstructure on the Absorption of Tritium into Gold-Plated 316 Stainless Steel

The interaction of tritium with metal surfaces is the initial step in the overall absorption of tritium by the substrate metal. As a result, limiting the adsorption of tritium to the surface may effectively reduce the quantity of tritium absorbed by a metal when it is in contact with tritium gas. To limit tritium adsorption, many tritium users electroplate gold onto the substrate metal. The gold layer is expected to reduce tritium adsorption, and subsequently absorption, by reducing water adsorption. The present work shows a comparison between tritium inventories in nonplated 316 stainless steel to the inventories in 316 stainless steel samples electroplated with gold by various commercial vendors and laboratories. Of the various gold-plated samples, only one type of plating shows ~25% reduction in tritium inventory, relative to nonplated steel samples. The degree of tritium absorption appears to be significantly influenced by the porosity, texture, and completeness of the gold layer. Incomplete and/or porous layers lead to increased absorption, while gold layers with smaller surface features lead to similar tritium inventories as nonplated samples. Reduced tritium absorption was observed only for complete gold layers with small surface features.

SYNCA: A Synthetic Cyclotron Antenna for the Project 8 Collaboration

Cyclotron Radiation Emission Spectroscopy (CRES) is a technique for measuring the kinetic energy of charged particles through a precision measurement of the frequency of the cyclotron radiation generated by the particle's motion in a magnetic field. The Project 8 collaboration is developing a next-generation neutrino mass measurement experiment based on CRES. One approach is to use a phased antenna array, which surrounds a volume of tritium gas, to detect and measure the cyclotron radiation of the resulting β-decay electrons. To validate the feasibility of this method, Project 8 has designed a test stand to benchmark the performance of an antenna array at reconstructing signals that mimic those of genuine CRES events. To generate synthetic CRES events, a novel probe antenna has been developed, which emits radiation with characteristics similar to the cyclotron radiation produced by charged particles in magnetic fields. This paper outlines the design, construction, and characterization of this Synthetic Cyclotron Antenna (SYNCA). Furthermore, we perform a series of measurements that use the SYNCA to test the position reconstruction capabilities of the digital beamforming reconstruction technique. We find that the SYNCA produces radiation with characteristics closely matching those expected for cyclotron radiation and reproduces experimentally the phenomenology of digital beamforming simulations of true CRES signals.

Operation modes of the KATRIN experiment Tritium Loop System using 83mKr

The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to search for the effective electron antineutrino mass with a sensitivity of 0.2 eV (90 % C.L.).In order to achieve this goal, KATRIN measurement phases focusing on the neutrino mass search are alternated with phases of investigations of systematic effects.During these phases, metastable 83mKr is used as a calibration source.The monoenergetic conversion electrons emitted accompanying the decay of 83mKr allow a direct access to the starting conditions of β-electrons produced inside the windowless gaseous tritium source (WGTS) of KATRIN.To make use of 83mKr in the WGTS, the Tritium Loop System, which provides a stable flow of tritium to the WGTS, needs to be operated in special modes.This paper focuses on the technical implementation of these modes and their performance with regard to the achievable 83mKr-rates, gas densities, and gas compositions inside the WGTS.

Characterization of the KATRIN cryogenic pumping section

The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to determine the effective anti-electron neutrino mass with a sensitivity of 0.2eV/c2 by using the kinematics of tritium β-decay. It is crucial to have a high signal rate which is achieved by a windowless gaseous tritium source producing 1011β-electrons per second. These are guided adiabatically to the spectrometer section where their energy is analyzed. In order to maintain a low background rate below 0.01cps, one essential criteria is to permanently reduce the flow of neutral tritium molecules between the source and the spectrometer section by at least 14 orders of magnitude. A differential pumping section downstream from the source reduces the tritium flow by seven orders of magnitude, while at least another factor of 107 is achieved by the cryogenic pumping section where tritium molecules are adsorbed on an approximately 3K cold argon frost layer. In this paper, the results of the cryogenic pumping section commissioning measurements using deuterium are discussed. The cryogenic pumping section surpasses the requirement for the flow reduction of 107 by more than one order of magnitude. These results verify the predictions of previously published simulations.

Insights into near-surface distribution characteristics of multi-form tritium with consideration of atmospheric buoyancy and gravitational deposition

Tritium contributes majority to the total airborne radioactive effluents from the nuclear facility because of its considerable production and difficulty in separation. Tritium inventory in the fusion reactor would reach an unprecedented magnitude which brings new safety concern. After being released into the atmosphere, inconsistent atmospheric dispersion behaviors might appear regarding different physicochemical forms such as gaseous state HT, gaseous-aerosol-droplet state HTO. In this study, atmospheric dispersion characteristics of multi-form tritium were investigated based on the computational fluid dynamics method validated by multi-fan type wind tunnel experiments. Species transport model and discrete phase model were used to describe atmospheric dispersion of gaseous and aerosol-droplet state tritium, respectively. Deposition velocity was predicted for gaseous and aerosol-droplet state tritium with different particle sizes. Conditions for describing the changes of particle diameter and its influencing on near-surface tritium distribution due to condensation were provided. The results show that buoyancy effect would strengthen along with the increasing gaseous tritium mass fraction in the airborne effluents. We also indicated that obvious gravitational deposition would appear once gaseous HTO was transformed into droplet state HTO with the particle diameter larger than 20 μm. Both the atmospheric buoyancy and deposition phenomenon would result in a quite different near-surface tritium distribution.

A 2-4keV multilayer mirrored channel for the NIF Dante system.

During inertial confinement fusion experiments at the National Ignition Facility (NIF), a capsule filled with deuterium and tritium (DT) gas, surrounded by a DT ice layer and a high-density carbon ablator, is driven to the temperature and densities required to initiate fusion. In the indirect method, 2 MJ of NIF laser light heats the inside of a gold hohlraum to a radiation temperature of 300eV; thermal x rays from the hohlraum interior couple to the capsule and create a central hotspot at tens of millions degrees Kelvin and a density of 100-200 g/cm3. During the laser interaction with the gold wall, m-band x rays are produced at ∼2.5keV; these can penetrate into the capsule and preheat the ablator and DT fuel. Preheat can impact instability growth rates in the ablation front and at the fuel-ablator interface. Monitoring the hohlraum x-ray spectrum throughout the implosion is, therefore, critical; for this purpose, a Multilayer Mirror (MLM) with flat response in the 2-4keV range has been installed in the NIF 37° Dante calorimeter. Precision engineering and x-ray calibration of components mean the channel will report 2-4keV spectral power with an uncertainty of ±8.7%.

Tritium Operation of the JET Neutral Beam Systems and Tritium NBI Power Calculations

Neutral beam injection (NBI) is a very flexible auxiliary heating method for tokamak plasmas, capable of being efficiently coupled to various plasma configurations required in the tritium and deuterium–tritium experimental campaign (DTE2) to be undertaken in the Joint European Torus (JET) device. In particular, experiments for high fusion yield and alpha particle studies require high-power NBI heating, and for maximum performance and optimum fuel mixture control in deuterium–tritium (D–T) plasmas, it is necessary to operate the JET NBI systems in both deuterium and tritium. The technical aspects of the JET NBI systems for compatibility with T operation are discussed, and the associated commissioning is described. The characterization of the JET NBI system in the tritium gas mode will be presented, with particular focus on the power and species mix measurements; this will be the first time that such data have been collected and analyzed for tritium neutral beams. Deuterium operation in the tritium gas mode was successfully carried out in 2019 with no loss in reliability. In this period of operation, the NBI power has been measured using beamline diagnostics and corroborated with plasma measurements. The species mix of the beam has been measured on the neutral beam test bed (NBTB) and also corroborated by plasma diagnostics on JET. These results will be presented alongside tritium NBI results allowing comparison of possible JET NBI performance between deuterium and tritium. Measurements of the NBI power in tritium show that there will be a higher neutralized fraction than in deuterium and a higher full energy fraction. When the effect of particle mass is also accounted for, this will lead overall to reduced beam penetration and lower particle flux per MW.

On the definition of the deuterium-tritium ion beam parameters for the SORGENTINA-RF fusion neutron source

The SORGENTINA-RF project aims to develop a 14 MeV fusion neutron source to produce medical radioisotopes with special focus on ^{99}Mo. The facility is based on a positive ion source with an acceleration stage to produce a deuterium (D^{+}) and tritium (T^{+}) ion beam that, impacting on a titanium-coated rotating target, allows fusion reactions to take place. Maximizing the neutron production rate is one of the main issues to be addressed in the project and the optimization of some key parameters of the ion beam is of paramount importance in this regard. In this study, a methodology is discussed to reach a definition of the beam characteristics for an effective and sustainable operation of the plant. The most convenient layout that has been found out is based on a single ion source fed by a deuterium and tritium gas mixture. Eventually, a series of considerations about the operation of the ion source and fuel cycle have been drawn.

Theoretical investigation of tritium concentration quantification method for DT fuel system using β-ray induced X-rays

Tritium measurement is one of the most important issues in DT fuel system of a fusion reactor. Beta-ray Induced X-ray Spectrometry (BIXS) method is a promising way to obtain tritium concentration in-line, especially for fuel processing system. However, till now there is no theory to establish the quantification relationship between tritium concentration and gas information including gas composition and pressure. Theoretical relationship between tritium concentration and X-ray spectrum in BIXS measurement is derived, and a quantitative method was proposed to determine tritium concentration directly by using the counts of X-ray spectrum. Non-linear Response Coefficients (NRCs) are introduced in the method to indicate the response of X-ray detector at different gas pressures for different gas compositions. Effects of both gas compositions (hydrogen/deuterium/tritium) and gas pressure (over five orders of magnitude, 1 Pa to 100 kPa) have been investigated quantitatively by Monte-Carlo simulations to determine the key parameters in the proposed method. Results show that for gas composed of hydrogen, deuterium, and tritium, NRCs are independent of gas composition within gas pressure from 1 Pa to 100 kPa. And NRCs can be obtained from the counts calculated within any energy region of X-ray spectrum detected in BIXS measurements. With the calculated NRCs, the tritium concentration can be obtained using only one reference experiment performed at any gas pressure (1 Pa to 100 kPa) for gas composed of any hydrogen isotopes. For gas composition including hydrogen, deuterium and tritium with different concentration, the error of NRCs in the proposed method is estimated to be 1.4%.

Measurement and sampling techniques verification for an online gaseous tritium monitoring method

During the development and envisaging of an online monitor method, a selection of measurement techniques, counting processes, instrument and sampling methods were performed. Firstly, Liquid scintillation counting was found to be the suitable technique, mass to volume ratio between pretreated water and liquid scintillation cocktail, the MDCs for 3 different liquid scintillation counter (LSCs) were tested individually. The results show that the minimum available MDC of Aloka LB7 is 0.39 Bq L-1 at the condition of 50 g pretreated water, being the one chosen to be the measurement LSC. Secondly, vapor condensation method, which could collect at least 201 g of water each day, was chosen among 3 tested sampling methods. Finally, automatic machinery measures were implemented to integrate the online monitoring method. A stable running status was proved by 15 days of duration test, which indicated that the chosen measurement and sampling technique are suitable for online monitoring.

Simulation calculation of the influence of interstitial atoms on the desorption behavior of tritium in nuclear graphite

In order to explore the effect of interstitial atoms on tritium desorption behavior of nuclear graphite, the adsorption and desorption behaviors of hydrogen atoms on interstitial atoms were simulated by first-principles. The results indicated that the interstitial atoms can gradually adsorb 3 hydrogen atoms until the sp3 hybrid structure is formed. The CH3 structure with dangling bonds tends to desorb as ionic CH3, which will combine with free H or other CH3 to form CH4 or C2H6. The CH (or CH2) structure tends to polymerize with other CH (or CH2) structures to form C2H2 (or C2H4), which reaction energy barrier is slightly lower than that of the CH3 structure; Although the migration energy of the interstitial atoms with H adsorbed on the graphite flakes is not much different from that of the interstitial atoms without H, the energy barrier of their recombination with single vacancies is significantly greater than that of the interstitial atoms without H. Therefore, it can predict that the large number of interstitial atoms in decommissioned nuclear graphite will become important sites for chemisorption of tritium. In addition, the reaction energy barrier of the interstitial atoms possessed large adsorption energy with tritium gas desorption is significantly higher than that with carbon containing tritium products (including C2T2, C2T4, CT4 or C2T6). This work will provide technical guidance and support for the heat treatment of the adsorbed tritium in decommissioned nuclear graphite.

New Constraint on the Local Relic Neutrino Background Overdensity with the First KATRIN Data Runs.

We report on the direct search for cosmic relic neutrinos using data acquired during the first two science campaigns of the KATRIN experiment in 2019. Beta-decay electrons from a high-purity molecular tritium gas source are analyzed by a high-resolution MAC-E filter around the end point at 18.57keV. The analysis is sensitive to a local relic neutrino overdensity ratio of η<9.7×10^{10}/α (1.1×10^{11}/α) at a 90% (95%) confidence level with α=1 (0.5) for Majorana (Dirac) neutrinos. A fit of the integrated electron spectrum over a narrow interval around the end point accounting for relic neutrino captures in the tritium source reveals no significant overdensity. This work improves the results obtained by the previous neutrino mass experiments at Los Alamos and Troitsk. We furthermore update the projected final sensitivity of the KATRIN experiment to η<1×10^{10}/α at 90% confidence level, by relying on updated operational conditions.

Novel Nuclear Batteries Based on Radioluminescence

A new type of nuclear battery, based on the sandwich structure of solar cells and tritium gas‐filled radioluminescent glass tubes (RLGTs), is developed and used successfully as a low‐power source. The radioluminescence (RL) is produced by bombarding beta particles, emitted by tritium gas, on ZnS: Cu is coated on the inner cylindrical surface of a glass tube. The response of solar cells to the optical spectrum of RL is studied and corelated with the current–voltage characteristics of the nuclear battery. The results show that the short‐circuit current, maximum output power, and energy conversion efficiency are enhanced but nonlinearly, with the increase in the number of RLGTs and by mounting the sandwich structure on an aluminum or plastic holder which acts as light reflector. Three such nuclear batteries are developed using different types of solar cells and their electrical performance is studied. Use of the developed nuclear battery as a low direct current power source is demonstrated by operating a digital watch and a light‐emitting diode for long periods.

Towards the first direct measurement of the dynamic viscosity of gaseous tritium at cryogenic temperatures

Accurate values for the viscosity of the radioactive hydrogen isotope tritium (T2) at cryogenic temperatures are unavailable. Values for tritium found in literature are based on extrapolation by mass ratios as well as an empirical factor derived from hydrogen (H2) and deuterium (D2) viscosity measurements, or classical kinetic theory which does not handle quantum effects. Accurate data of the tritium viscosity will help to improve the modelling of the viscosity of diatomic molecules and can be used as a test of their interaction potentials.With this contribution we report a major step towards a fully tritium and cryogenic temperature compatible setup for the accurate measurement of the viscosity of gases, using a spinning rotor gauge (SRG) at the Tritium Laboratory Karlsruhe. After calibration with helium, measurements with hydrogen and deuterium conducted at room temperature agree with literature values within 2%. The performance at liquid nitrogen (LN2) temperature has been successfully demonstrated with a second setup in a liquid nitrogen bath. Again after calibration with helium at LN2 temperature, the viscosities of H2 and D2 were determined and are in agreement with literature to about 2%.

Permeation behavior of gaseous tritium through the assembly composed of Zr and Al2O3 simulating Li rod

• An assembly simulating the Li rod structure for T production in HTGR was used. • The assembly was composed of inner Zr tube - outer Zr tube - Al 2 O 3 tube. • T permeation rate through the assembly from HT was much faster than that from HTO. • The rate-determining step was T permeation through the Al 2 O 3 tube. For starting up a fusion reactor stably, the tritium production by the nuclear reaction of neutrons and lithium in a high-temperature gas-cooled reactor has been studied. In order to suppress the migration of tritium to the whole reactor, it is important to design a Li rod with tritium confinement function and understand tritium behavior. A Li rod structure consisting of Zr - LiAlO 2 - Zr - Al 2 O 3 was proposed, and an assembly simulating proposed Li rod was fabricated. In the previous work using tritium gas containing mainly HTO rather than HT, the present authors succeeded in confining tritium in the assembly at 700 ℃ for 87 h. In this work, tritium gas containing mainly HT rather than HTO was supplied to the assembly, tritium permeation behavior was observed. Unlike the case of HTO, tritium permeated immediately after the introduction of HT. This result indicates that the chemical form of tritium significantly affects tritium confinement performance of the Li rod.

Study on emergency ventilation optimization method for tritium leakage accident of high-pressure storage vessel

In the process of tritium storage, the high-pressure storage vessel may be damaged due to accidental conditions, such as impact or drop, which results in tritium leakage. The tritium gas will be released and diffused into the space immediately, which inevitably causes radioactive hazards to personnel and the environment. Ventilation is considered to be the best emergency treatment method for a tritium leakage accident. According to the characteristics of fixed tritium amount and rapid release of tritium in the tritium leakage accident of the high-pressure storage vessel, the numerical simulation of high-pressure released tritium behavior in a confined space is carried out based on Fluent and compared with CATS test data. The error is no more than 5%. The ventilation conditions are optimized according to different ventilation positions and different ventilation rates. It is founded that the tritium removal efficiency when the vent is set on the roof is 30% higher than that on the side wall. The tritium concentration in a confined space can be reduced to the background level after ventilation for 30 min at a rate of 0.5 m3 s−1. The optimal recovery time of the environment is given, which provides technical support for the emergency treatment of the tritium leakage accident of the high-pressure storage vessel.

Monte Carlo simulations of the electron — gas interactions in the KATRIN experiment

At the KATRIN experiment, the electron antineutrino mass is inferred from the shape of the β-decay spectrum of tritium. Important systematic effects in the Windowless Gaseous Tritium Source (WGTS) of the experiment include the energy loss by electron scattering, and the extended starting potential. In the WGTS, primary high-energy electrons from β-decay produce an extended secondary spectrum of electrons through various atomic and molecular processes including ionization, recombination, cluster formation and scattering. In addition to providing data essential to the simulation of energy loss processes, the electron spectrum also provides information important in the simulation of plasma processes. These simulations will then provide an insight on the starting potential. Here, a Monte Carlo approach is used to model the electron spectrum in the source for a given magnetic and electric field configuration. The spectrum is evaluated at different positions within the WGTS, which allows for a direct analysis of the spectrum close to the rear wall and detector end of the experiment. Alongside electrons, also ions are tracked by the simulation, resulting in a full description of the currents in the source.

Characteristics of uranium hydride bed for fusion fuel cycle: Hydrogen and deuterium absorption

Metal hydride beds will become essential components in the tritium plant for the safe handling and processing of tritium gases in nuclear fusion machines. Korea has been developing metal hydride beds focusing on robustness, reliability, and longevity. In this study, the authors designed an improved uranium hydride bed and fabricated an experimental bed with a storage capacity equivalent to 70 g of tritium based on our previous research efforts. We investigated the hydrogen and deuterium absorption characteristics of the experimental bed. After uranium was successfully activated by hydrogen, absorption performance experiments based on various operational conditions in the tritium plant were conducted. Full capacity absorption was performed with a different initial temperature of uranium and the time and rate for absorption were analyzed. We found that the different absorption rates between hydrogen and deuterium are related to the difference in equilibrium pressure between uranium hydride and uranium deuteride. These experimental results will be the basis of the operation mode development and performance reference for the uranium hydride bed in the fusion fuel cycle.

Tritium permeation from tritiated water to water through Inconel

From a safety standpoint, it is important to understand the behavior of tritium in the coolant of DT fusion reactors. The high-temperature and high-pressure water is expected to be used as a coolant in JA DEMO. Therefore, it is necessary to deepen the understanding of the tritium transfer from the primary cooling water to the secondary cooling water in a heat exchanger. In this study, a double-tube permeation device consisting of Inconel 600 tube, which is a heat exchanger material, and SS316 tube, was assembled and the tritium permeation from tritiated water to water at 300 °C and 17 MPa was observed. Remarkable tritium permeation was observed after around 17 days as the cumulative heating time. Gaseous tritium (HT and T2) was detected in the gas phase of the tritiated water side after the permeation experiments. This suggests that a part of tritium generated in the metal oxidation reaction dissolved in the Inconel and diffused and permeated. With assuming that the diffusion process of tritium through the Inconel was the rate controlling step of permeation, the permeability of tritium through the Inconel tube from the tritiated water derived from the experimental data was 3 orders of magnitude smaller than that obtained from the hydrogen isotope permeation experiments from gas phase to gas phase.

Easy-to-Implement Hydrogen Isotope Exchange for the Labeling of N-Heterocycles, Alkylkamines, Benzylic Scaffolds, and Pharmaceuticals.

Facilitating access to deuterated and tritiated complex molecules is of paramount importance due to the fundamental role of isotopically labeled compounds in drug discovery and development. Deuterated analogues of drugs are extensively used as internal standards for quantification purposes or as active pharmaceutical ingredients, whereas tritiated drugs are essential for preclinical ADME studies. In this report, we describe the labeling of prevalent substructures in FDA-approved drugs such as azines, indoles, alkylamine moieties, or benzylic carbons by the in situ generation of Rh nanoparticles able to catalyze both C(sp2)–H and C(sp3)–H activation processes. In this easy-to-implement labeling process, Rh nanocatalysts are formed by decomposition of a commercially available rhodium dimer under a deuterium or tritium gas atmosphere (1 bar or less), using the substrate itself as a surface ligand to control the aggregation state of the resulting metallic clusters. It is noteworthy that the size of the nanoparticles observed is surprisingly independent of the substrate used and is homogeneous, as evidenced by transmission electron microscopy experiments. This method has been successfully applied to the one-step synthesis of (1) deuterated pharmaceuticals usable as internal standards for MS quantification and (2) tritiated drug analogues with very high molar activities (up to 113 Ci/mmol).