Tritium Ions Research Articles

Proton driven fast ignition of low-radioactivity DT–3He fuel

With the advent of proton fast driven ignition and more efficient energy transport of the ignitor beam, we might be interested to try successful ignition of the targets mixed with advanced fuels where DT main fuel acts simply as a seed. Here, we have examined the ignition and burn conditions of a DT–3He pre-compressed fuel pellet driven by proton ignitor beam generated separately by the well-known laser-accelerated ion mechanism. We have, first, derived the zero-dimensional model of the energy balance equations of one fluid, three temperatures (i.e. electron, ion and radiation temperatures) including the most important gain and loss processes. Then, in order to evaluate the feasibility of the system and its energy gain, these coupled equations are solved numerically. It has been shown that the system energy gain quickly responses and is sensitive to the initial concentration of He-3, proton beam power and total areal density of fuel. A saturation in energy gain for ρR > 8 g/cm2 has been demonstrated which is equivalent to burn fraction of higher than 0.4. Enhancement in energy gain exceeds 33 percent. Moreover, in a complete catalytic regime of both tritium and He-3 ions, as much as an order of magnitude reduction in neutron flux is observed.

Core plasma ion cyclotron emission driven by fusion-born ions

Ion cyclotron emission (ICE) signals whose spectral peaks match the fundamental cyclotron frequencies of hydrogen and tritium in the plasma core, near the magnetic axis, are observed in ASDEX Upgrade deuterium plasmas. In these cases the only source of energetic (⩾1 MeV) hydrogen and tritium ions is D–D fusion reactions between neutral beam injected deuterium ions and bulk deuterium ions. Hydrogen-matched core ICE is observed in a wide variety of ASDEX Upgrade plasmas, while tritium-matched core ICE is (so far) only observed in so-called H-mode density limit plasmas. In all cases ICE signals are detected directly using B-dot probes, which provide information on the emission frequency, the amplitude, and, in principle, the parallel wavenumber values. These observations support the idea of using an ICE-based diagnostic to monitor the presence of fusion-born alpha particles in tritium-burning fusion plasmas on devices such as JET, ITER, CFETR, or DEMO.

Thermal Release Behavior of Tritium from Tungsten After Implantation by Glow Discharge

Tritium release behavior in a tungsten sample after exposing to tritium ions with energy about 200 eV created by glow discharge has been studied by both β-ray–induced X-ray spectrometry (BIXS) and imaging plate (IP). The tungsten sample was heated stepwise in a vacuum vessel at temperatures from 400 to 1000 K in experiments, and results obtained from both BIXS and IP measurements showed that the amount of tritium absorbed on the sample surface decreased more than 97% after heating at 800 K. Both intensity and shape of the measured X-ray spectrum have been specified to estimate the change of the tritium depth profile after each heat treatment. Besides, the Monte Carlo Stopping and Range of Ions in Matter (SRIM) code has been introduced to calculate the initial tritium depth profile just after being irradiated by glow discharge. Analysis shows that tritium atoms locate around 3 nm in depth before annealing, and tritium distribution becomes uniform in the near-surface layers (around several nanometers) gradually after heat treatment. At about 800 K, the relative tritium concentration in the near-surface layers reaches its maximum value compared with tritium in the deeper part of the tungsten sample. Then more and more tritium diffuses deeper into the sample as the temperature increases.

Microbial Community and in situ Bioremediation of Groundwater by Nitrate Removal in the Zone of a Radioactive Waste Surface Repository.

The goal of the present work was to investigate the physicochemical and radiochemical conditions and the composition of the microbial community in the groundwater of a suspended surface repository for radioactive waste (Russia) and to determine the possibility of in situ groundwater bioremediation by removal of nitrate ions. Groundwater in the repository area (10-m depth) had elevated concentrations of strontium, tritium, nitrate, sulfate, and bicarbonate ions. High-throughput sequencing of the V3–V4/V4 region of the 16S rRNA gene revealed the presence of members of the phyla Proteobacteria (genera Acidovorax, Simplicispira, Thermomonas, Thiobacillus, Pseudomonas, Brevundimonas, and uncultured Oxalobacteraceae), Firmicutes (genera Bacillus and Paenibacillus), and Actinobacteria (Candidatus Planktophila, Gaiella). Canonical correspondence analysis suggested that major contaminant – nitrate, uranium, and sulfate shaped the composition of groundwater microbial community. Groundwater samples contained culturable aerobic organotrophic, as well as anaerobic fermenting, iron-reducing, and denitrifying bacteria. Pure cultures of 33 bacterial strains belonging to 15 genera were isolated. Members of the genera Pseudomonas, Rhizobium, Cupriavidus, Shewanella, Ensifer, and Thermomonas reduced nitrate to nitrite and/or dinitrogen. Application of specific primers revealed the nirS and nirK genes encoding nitrite reductases in bacteria of the genera Pseudomonas, Rhizobium, and Ensifer. Nitrate reduction by pure bacterial cultures resulted in decreased ambient Eh. Among the organic substrates tested, sodium acetate and milk whey were the best for stimulation of denitrification by the microcosms with groundwater microorganisms. Injection of these substrates into the subterranean horizon (single-well push-pull test) resulted in temporary removal of nitrate ions in the area of the suspended radioactive waste repository and confirmed the possibility for in situ application of this method for bioremediation.

Activation material selection for multiple foil activation detectors in JET TT campaign

In the preparation for the Deuterium-Tritium campaign, JET will operate with a tritium plasma. The T + T reaction consists of two notable channels: (1) T + T → 4He + 2n, (2) T + T → 5He + n → 4He + 2n. The reaction channel (1) is the reaction with the highest branching ratio and a continuum of neutron energies being produced. Reaction channel (2) produces a spectrum with a peak at 8.8 MeV. A particular problem is the ratio between the individual TT reaction channels, which is highly dependent on the energy of the reacting tritium ions. There are very few measurements on the TT spectrum and the study at JET would be interesting.The work is focused on the determination of the spectral characteristics in the TT plasma discharges, especially on the presence of the 8.8 MeV peak, a consequence of channel (2) of the TT reaction. The possibility to use an optimized set of activation materials in order to target the measurement of the 8.8 MeV peak is studied. The lower limit of detection for the channel (2) ratio within the TT reaction is estimated and the influence of DT source neutrons, which are a consequence of deuterium traces in the plasma, is investigated.

Estimation of the tritium retention in ITER tungsten divertor target using macroscopic rate equations simulations

Based on macroscopic rate equation simulations of tritium migration in an actively cooled tungsten (W) plasma facing component (PFC) using the code MHIMS (migration of hydrogen isotopes in metals), an estimation has been made of the tritium retention in ITER W divertor target during a non-uniform exponential distribution of particle fluxes. Two grades of materials are considered to be exposed to tritium ions: an undamaged W and a damaged W exposed to fast fusion neutrons. Due to strong temperature gradient in the PFC, Soret effect’s impacts on tritium retention is also evaluated for both cases. Thanks to the simulation, the evolutions of the tritium retention and the tritium migration depth are obtained as a function of the implanted flux and the number of cycles. From these evolutions, extrapolation laws are built to estimate the number of cycles needed for tritium to permeate from the implantation zone to the cooled surface and to quantify the corresponding retention of tritium throughout the W PFC.

Tritium ion blocking and detection in the KATRIN experiment

The aim of the KATRIN experiment is to determine the absolute neutrino mass scale in a model independent way by measuring the electron energy spectrum shape near the endpoint of molecular tritium beta decay. The beta electrons are guided from the source to the spectrometers by a high magnetic field. The beta decays and ionisations of the beta electrons in the source produce a variety of positive tritium ions that are not allowed to reach the spectrometers. Therefore they will be blocked by a positive potential and removed by dipole electrodes in the beam transport system. Various ion detection methods (Faraday cup, FT-ICR and ionisation of the residual gas in the spectrometers) will be used to test the ion blocking and removal efficiency.

Measurement of the Bi209(n,4n)Bi206 and Tm169(n,3n)Tm167 cross sections between 23.5 and 30.5 MeV relevant to reaction-in-flight neutron studies at the National Ignition Facility

At the National Ignition Facility, experiments are being performed to measure charged-particle stopping powers in the previously unexplored warm dense plasma regime. These measurements are done using reaction-in-flight (RIF) neutrons from an inertial confinement fusion system. RIF neutrons are produced with a continuum of energies up to 30 MeV. By making activation measurements utilizing threshold reactions for neutrons in the energy range of $15l\phantom{\rule{4pt}{0ex}}{E}_{n}\phantom{\rule{4pt}{0ex}}l30\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$, the number of RIF neutrons can be determined and from this the stopping power of the deuterium and tritium ions that produced the RIF neutrons can be inferred. Currently, the $^{169}\mathrm{Tm}(n,3n)^{167}\mathrm{Tm}$ reaction has been used. However, in an effort to provide a secondary complimentary measurement, efforts are underway to make use of the $^{209}\mathrm{Bi}(n,4n)^{206}\mathrm{Bi}$ reaction, with a threshold of 22.5 MeV. The cross sections were measured at the 10 MV tandem Van De Graaff accelerator at the Triangle Universities Nuclear Laboratory with quasimonoenergetic neutrons between 23.5 and 30.5 MeV, where few previous measurements have been made. Cross-section data are compared to calculations and other available measurements.

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculated when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.

Tritium decay helium-3 effects in tungsten

Tritium (T) implanted by plasmas diffuses into bulk material, especially rapidly at elevated temperatures, and becomes trapped in neutron radiation-induced defects in materials that act as trapping sites for the tritium. The trapped tritium atoms will decay to produce helium-3 (3He) atoms at a half-life of 12.3 years. 3He has a large cross section for absorbing thermal neutrons, which after absorbing a neutron produces hydrogen (H) and tritium ions with a combined kinetic energy of 0.76 MeV through the 3He(n,H)T nuclear reaction. The purpose of this paper is to quantify the 3He produced in tungsten by tritium decay compared to the neutron-induced helium-4 (4He) produced in tungsten. This is important given the fact that helium in materials not only creates microstructural damage in the bulk of the material but alters surface morphology of the material effecting plasma-surface interaction process (e.g. material evolution, erosion and tritium behavior) of plasma-facing component materials. Effects of tritium decay 3He in tungsten are investigated here with a simple model that predicts quantity of 3He produced in a fusion DEMO FW based on a neutron energy spectrum found in literature. This study reveals that: (1) helium-3 concentration was equilibrated to ∼6% of initial/trapped tritium concentration, (2) tritium concentration remained approximately constant (94% of initial tritium concentration), and (3) displacement damage from 3He(n,H)T nuclear reaction became >1 dpa/year in DEMO FW.

Tracking of tritium charged into stainless steel by BIXS

Retention and release behavior of tritium charged into stainless steel type 316 by two different methods were tracked by β-ray-induced X-ray spectrometry (BIXS). Exposure to tritium gas and irradiation of tritium ions were employed. Effects of pre-irradiation of helium ions on tritium retention were also investigated. After charging tritium by these methods and tracking by BIXS, thermal release behavior of tritium was examined by BIXS. The observed X-ray spectrum showed clearly that thermally charged tritium at a high temperature diffused into the bulk of SS316, but tritium ions irradiated at room temperature were trapped in surface layers of the sample irrespective of tritium ion energy. Thermally charged tritium was not able to remove completely even heating at high temperature of 973K. On the contrary, it was seen that the ion-irradiated tritium decreased almost linearly with temperature irrespective of ion energy. Furthermore, rapid decrease of tritium appeared in the helium pre-irradiated samples.

Hydrological and environment tritium investigation to evaluate groundwater in capital territory of Pakistan

The capital territory of Pakistan constitutes twin cities, Islamabad and Rawalpindi. Islamabad is the capital city, located at the foot of the Margallah Hills, whereas Rawalpindi lies in the Potohar Plateau. Both cities are located in the semi-arid region of Pakistan, where the residents meet their basic need of water through groundwater resources. For the last many years, the quantity and quality of groundwater in these cities has been deteriorating very rapidly. In this study, the foremost recharge source for these cities was identified using tritium and major ion chemistry, and different physiochemical parameters were studied to find out the facts behind the quality deterioration of the groundwater. Tritium values and chemical data suggested that aquifers located in the territory of Islamabad were mainly recharged by upland areas (the Margalla Hills), which accounts for their low electrical conductivity and total dissolved solids contents. A higher sodium adsorption ratio (SAR) suggested an alteration in recharge patterns through soil compaction and cementation (from increased construction activity) that reduced the recharge inputs. The high SAR also disturbs the recharge pattern and had disturbed the natural equilibrium of the groundwater system, deteriorating the quality of the water.

Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.

Effects of Multi‐Species Ions on Sheath and Presheath in a Magnetic Field Decreasing toward a Wall

AbstractIn the divertor region, the plasma contains deuterium (D) ion and tritium (T) ion in an open magnetic field. The effect of D ion and T ion on the electric potential near the wall in plasma with magnetic field decreasing toward a wall is investigated analytically. The distribution of the electric potential is obtained by plasma‐sheath equation, where D ion and T ion are considered. The potential distribution depends on the parameters such as the profile of the magnetic field, the temperatures of D ion and T ion, and the amount rate of T ion to D ion. The particle distribution also is shown. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Simulation aided design of a low cost ion mobility spectrometer based on printed circuit boards

Miniaturized low-cost drift tubes with high analytical performance are a key component for the design of powerful and mass-deployable hand-held ion mobility spectrometers. Thus, a simple model that estimates the influence of the geometrical dimensions on the analytical performance is highly desirable for an effective design process. In this work, we present a simple procedure to predict peak distortion based on only the electrical field distribution inside the drift tube, which can be rapidly simulated using the finite element method. A simulation of the ion motion is not required. Based on these results, we developed an ion mobility spectrometer manufactured entirely from standard printed circuit boards (PCB). Since no additional components were used apart from electrical and gas connectors, ion source and metal grids, the presented ion mobility spectrometer is very simple and inexpensive. Nevertheless, the design provides a resolving power of 82 at a drift length of 50 mm and a drift voltage of 3 kV using a tritium ion source and a field switching shutter. The limits of detection for one second of averaging are 80 pptv for acetone, 35 pptv for dimethyl methylphosphonate and 180 pptv for methyl salicylate.

Fast ion motion in the plasma part of a stellarator-mirror fission–fusion hybrid

Recent developments of a stellarator-mirror (SM) fission–fusion hybrid concept are reviewed. The hybrid consists of a fusion neutron source and a powerful sub-critical fast fission reactor core. The aim is transmutation of spent nuclear fuel and safe fission energy production. In its fusion part, a stellarator-type system with an embedded magnetic mirror is used. The stellarator confines deuterium plasma with moderate temperature, 1–2 keV. In the magnetic mirror, a hot component of sloshing tritium ions is trapped. There, the fusion neutrons are generated.A candidate for a combined SM system is a DRACON magnetic trap. A basic idea behind an SM device is to maintain local neutron production in a mirror part, but at the same time eliminate the end losses by using a toroidal device. A possible drawback is that the stellarator part can introduce collision-free radial drift losses, which is the main topic for this study. For high energy ions of tritium with an energy of 70 keV, comparative computations of collisionless losses in the rectilinear part of a specific design of the DRACON type trap are carried out. Two versions of the trap are considered with different lengths of the rectilinear sections. Also the total number of current-carrying rings in the magnetic system is varied. The results predict that high energy ions from neutral beam injection can be satisfactorily confined in the mirror part during 0.1–1 s.The Uragan-2M experimental device is used to check key points of the SM concept. The magnetic configuration of a stellarator with an embedded magnetic mirror is arranged in this device by switching off one toroidal coil. The motion of particles magnetically trapped in the embedded mirror is analyzed numerically with use of motional invariants. It is found that without radial electric field particles quickly drift out of the SM, even if the particles initially are located on a nested magnetic surface. We will show that a weak radial electric field, which would be spontaneously created by the ambipolar radial particle losses, can make drift trajectories closed, which substantially improves particle confinement. It is remarkable that the improvement acts both for positive and negative charges.

Theory of turbulent heating of current DT plasma

The theory of turbulent heating in the mode of hot deuterium ions and cold tritium ions is developed for plasma with equal deuterium and tritium ion concentrations. The possibility of heating electrons and deuterium ions by thousands of times is shown.

Investigation of parameters of interaction of hydrogen isotopes with liquid lithium and lithium capillary-porous system under reactor irradiation

In this study, the effect of reactor irradiation on the processes of interaction of hydrogen with liquid lithium and a lithium capillary-porous system (CPS) is considered. The experiments are carried out by the gas-absorption method with use of a specially designed ampoule device. The results of investigation of the interaction of hydrogen with liquid lithium and a lithium CPS under conditions of reactor irradiation are described; namely, these are the temperature dependences of the rate constant for the interaction of hydrogen with liquid lithium at different reactor powers, the activation energies of the processes, and the pre-exponential factor in the Arrhenius dependence. The effect of increasing absorption of hydrogen by the samples under investigation as a result of the reactor irradiation is fixed. The effect can be explained by increasing mobility of hydrogen in liquid lithium due to hot spots in lithium bulk and the interaction of helium and tritium ions (formed as a result of the nuclear reaction of 6Li with neutron) with a surface hydride film.

Mechanisms of helium accommodation in lithium metatitanate

Helium is generated as a by-product of the transmutation of lithium in the breeder blanket region of a fusion reactor. The presence of helium in ceramic breeder materials, such as lithium metatitanate (Li2TiO3), can lead to pressure in the pebble and degradation of mechanical properties as well as influencing tritium retention in the matrix. Here, density functional theory is used to examine the mechanisms of helium accommodation in Li2TiO3 across a range of conditions relevant to a fusion reactor. The results show that the mechanism of helium accommodation depends on the availability of defect trap sites, which itself depends on the stoichiometry of the crystal. It is also shown that helium may displace tritium from lithium vacancy defects and may therefore increase the tritium extraction rate by increasing the fraction of mobile tritium ions.

Effect of Atomic-Molecular and Isotopic Composition of an Ion Beam on the Neutron Yield from Tamped Targets in Sealed Tubes

A neutron generator with a sealed tube is a controlled electrophysical source of fast neutrons which is safe in the off state. A tritium- and deuterium-saturated target is bombarded by a beam of deuterium and tritium ions in order to obtain neutrons. The neutrons are formed in the reactions 3H(d, n)4He and 2H(d, n)3He. Generators are used in nuclear geophysics, inspection systems for detecting dangerous substances, thermonuclear research, and other fields of industry and science. A method is presented for calculating the neutron yield from the targets in sealed tubes in generators, taking account of the accelerating voltage, the atomic-molecular and isotopic composition of the ion beam, and the properties of the target. The computational method presented makes it possible to obtain the dependences of the neutron yield on the operating parameters of gas-filled sealed tubes. The expressions obtained can be used for almost all solid-state targets currently used in generators.