Radioactive Tritium Research Articles

Hydrogen Traps in Tungsten: A Review

Tungsten is currently the most promising material for plasma-facing in FRs. The accumulation of radioactive tritium in tungsten is caused by presence of hydrogen traps in this metal. This paper analyzes literature data on the parameters of hydrogen traps in tungsten. The review results can predict the accumulation of tritium in tungsten cladding of fusion reactors, ensuring their radiation safety.

Pressure control of tritiated hydrogen isotopologues in hermetically sealed vessels by non-evaporable getters for sub-Doppler-resolution spectroscopy

Small molecules serve as valuable benchmarks for testing quantum chemical theories. Ultra-high-resolution spectroscopy currently offers the capability of measuring molecular hydrogen energy levels with a relative accuracy on the order of 10-10. Expanding such investigations to encompass different isotopologues of molecular hydrogen has emerged as a promising avenue for examining mass-dependent contributions to the full description of molecular structure in the framework of relativistic quantum electrodynamics. However, the delicate nature of handling radioactive tritium in a high-resolution spectroscopy environment poses significant technological challenges, thereby limiting the extension of these studies to include T2, DT and HT isotopologues. In this work, we present the experimental setup of the very sensitive, Doppler-free technique of Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS), used to measure rovibrational transitions in the HT molecule. The NICE-OHMS measurements were performed in a closed cavity system without connection to an actively pumped vacuum system. For this reason, a new method for tritium storage and pressure regulation within 0.05–1Pa based on a temperature-controlled mini-getter system is employed using less activity than the tritium exemption limit (1GBq). Non-Evaporable Getters of the type SAES St171 were used for this purpose exploiting their property that hydrogen is released upon heating, while other gases remain being pumped. Prior to the NICE-OHMS experiment, the reversible sorption properties of the getter for hydrogen isotopes were investigated. We show measurements of the equilibrium (hydrogen) pressure for all three pure isotopes and for a H2:HT:T2 mixture (with H:T = 1:1) as a function of temperature for a system of defined volume and amount of gas. For the read-out of the temperature, a method using the resistance of the getter in combination with a pyrometric calibration has been implemented. We discuss the experiences from practical use of the tritium getter and show results obtained with the NICE-OHMS setup leading to frequency calibration of near-infrared transitions in HT at an accuracy, surpassing previous studies by nearly three orders of magnitude.

Dimensional effects in analysis of laser-induced-desorption diagnostics data

The accurate assessment of the local tritium concentration in the tokamak first wall by means of the laser-induced desorption (LID) diagnostics is sought as one the key solutions to monitoring the local radioactive tritium content in the first wall of the fusion reactor ITER. Numerical models of gas desorption from solids used for LID simulation are usually closed with the one-dimensional transport models. In this study, the temperature and particle dynamics in the target irradiated by a short laser pulse during LID are analyzed by means of the two-dimensional model to assess the validity of using one-dimensional approximation for recovering the diagnostics signal. The quantitative estimates for the parameters governing the heat and particle transfer are presented. The analytical expressions for the sample spatiotemporal temperature profiles driven by the target irradiation with a Gaussian laser beam with the trapezoid temporal shape are derived. The obtained relations are used to simulate tritium desorption from a tungsten sample driven by pulsed heating. It is shown that depending on the ratio between the laser spot radius and the heat diffusion length, the one-dimensional approach can noticeably overestimate the sample temperature in the limit of small laser spot radius (estimated for tungsten as ∼0.5–1.0 mm), resulting in more than 100% larger amounts of tritium desorbed from the target, compared to the two-dimensional approximation. In the limit of large laser spot radius (≥1.5 mm), both approaches yield comparable amounts of tritium desorbed from the sample.

Roadmap of Graphite Moderator and Graphite-Matrix TRISO Fuel Management Options

Most high-temperature reactors use graphite as a moderator and structural material. This includes high-temperature gas-cooled reactors with helium cooling and TRi-structural ISOtropic (TRISO) fuel particles embedded in graphite, as well as fluoride salt–cooled high-temperature reactors with clean salt coolant and TRISO fuel particles embedded in graphite and thermal spectrum molten salt reactors with a graphite moderator and fuel dissolved in the salt. The largest volume radioactive waste stream from these reactors is the irradiated graphite. We describe herein a roadmap for management of these graphite wastes that contain radioactive 14C, tritium, and other radionuclides. There may be some graphite wastes with sufficiently low radioactivity levels that can be treated as nonradioactive waste and managed like other graphite waste. Management options for the graphite include (1) direct disposal, (2) recycled back to the reactor or other nuclear applications, and (3) oxidizing the graphite with release as an effluent or underground sequestration of the carbon dioxide. Cosequestration of this carbon dioxide with carbon dioxide from industrial, biological, and cement production processes can isotopically dilute the 14C before sequestration to eliminate the possibility of exceeding individual radiation exposure limits. We also describe options for processing graphite-matrix TRISO fuel, including separating the bulk graphite to reduce the volumes of used fuel for disposal or processing to recover fissile materials. The inventories of radioactive isotopes in different carbon wastes vary by many orders of magnitude; thus, there is no single economic option for the management of all graphite waste.

ОБОСНОВАНИЕ НОВОЙ ПРИЧИННО-СЛЕДСТВЕННОЙ ТРАКТОВКИ РАЗВИТИЯ И ТРАНСФОРМАЦИИ ЧРЕЗВЫЧАЙНЫХ СИТУАЦИЙ НА ПРИМЕРЕ АВАРИИ НА АТОМНОЙ ЭЛЕКТРОСТАНЦИИ «ФУКУСИМА-1»

Using the example of the radiation accident at the Fukushima-1 nuclear power plant and subsequent measures to discharge tritium-containing aqueous coolant into the ocean, the adequacy of a new causal interpretation – the «triangle of emergencies», justifying and explaining scenarios of mutual transition of one type of emergency into another, as well as its graphical interpretation is considered. The issues of existing and possible consequences related both directly to the accident and to the discharge of the coolant are investigated. The results of calculating the change in the radioactivity of tritium in the volume of water planned for discharge for a period equal to ten of its half-life are presented. The prospects of applying the concept of an «emergency triangle» are considered, which are seen in the construction of an «emergency space», which is an array of emergency data collected for the purpose of analyzing, interpreting information, establishing cause-effect relationships and forecasting, as well as the principles of its formation.

PTOLEMY's test of generalized neutrino interactions: unveiling challenges and constraints

Unanswered questions surrounding neutrinos have motivated investigations into physics beyond the standard model (SM) of particle physics. In particular, generalized neutrino interactions (GNI) provide a broader framework for studying these effects compared to the commonly studied non-standard neutrino interactions. These interactions are described by higher dimensional operators while maintaining the gauge symmetries of the SM. Furthermore, the cosmic neutrino background, a predicted component of the SM and standard cosmology, has yet to be directly detected. To shed light on this elusive phenomenon, we conduct a comprehensive analysis of the relevant GNI, specifically focusing on their implications for the proposed cosmic neutrino detector PTOLEMY. We make an attempt to see the capabilities and the limitations of PTOLEMY in sensing GNI while remaining optimistic regarding PTOLEMY's experimental resolution. These interactions play a significant role in modifying the electron spectrum resulting from the capture of cosmic neutrinos on radioactive tritium. This work also explores how the presence of these interactions influences the differential electron spectrum, taking into account factors such as finite experimental resolution, the mass of the lightest neutrino eigenstate, the strength of the interactions, and the ordering of neutrino mass.

Thermal simulations on a spinning rotor gauge to improve systematic uncertainties for viscosity measurements

Experimental values for the viscosity of the radioactive hydrogen isotope tritium (T2) are currently unavailable in literature. The value of this material property over a wide temperature range is of interest for applications in the field of fusion, neutrino physics, as well as to test ab initio calculations. To measure the viscosity of tritium, a measurement setup has been built utilizing a spinning rotor gauge inside a Dewar. Temperature control is of high importance to produce accurate and precise values. To ensure high quality measurement results, prior to the tritium measurements, thermal simulations are done on measurements with protium and deuterium inside the sample gas volume of the spinning rotor gauge.

Precision Measurement of Vibrational Quanta in Tritium Hydride.

Saturated absorption measurements of transitions in the (2-0) band of radioactive tritium hydride are performed with the ultrasensitive noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy intracavity absorption technique in the range 1460-1510nm. The hyperfine structure of rovibrational transitions of tritium hydride, in contrast to that of hydrogen deuteride, exhibits a single isolated hyperfine component, allowing for the accurate determination of hyperfineless rovibrational transition frequencies, resulting in R(0)=203 396 426 692(22) kHz and R(1)=205 380 033 644(21) kHz. This corresponds to an accuracy 3 orders of magnitude better than previous measurements in tritiated hydrogen molecules. Observation of an isolated component in P(1) with reversed signal amplitude contradicts models for line shapes in hydrogen deuteride based on crossover resonances.

The Impact of Tides and Monsoons on Tritium Migration and Diffusion in Coastal Harbours: A Simulation Study in Lianyungang Haizhou Bay, China

Many nuclear power plants have been built along China’s coasts, and the migration and diffusion of radioactive nuclides in coastal harbours is very concerning. In this study, considering the decay and free diffusion of radioactive nuclides, a local hydrodynamic model based on the FVCOM was built to investigate the migration and diffusion of the radioactive nuclide tritium in Haizhou Bay, China. This model was calibrated according to the observed tidal level and flow velocity and direction, which provide an accurate background. This study aimed to evaluate the impact of tides and monsoons on the migration path and concentration variations in tritium over time. The results demonstrated that the simulated flow field can reflect real-life receiving waters. The distribution of the tritium concentration is affected by the flow field, which is related to the tides. Moreover, more severe radioactive contamination was exhibited in winter than in summer because monsoons may have hindered the migration and diffusion of tritium within the harbour. Given the poor hydrodynamic conditions and slow water exchange in the open ocean in Haizhou Bay, the diffusion rate of radioactive nuclides outside the bay area was higher than that within it.

Tritiated stainless steel (nano)particle release following a nuclear dismantling incident scenario: Significant exposure of freshwater ecosystem benthic zone

Nuclear facilities continue to be developed to help meet global energy demands while reducing fossil fuel use. However, an incident during the dismantling of these facilities could accidentally release tritiated particles (e.g. stainless steel) into the environment. Herein, we investigated the environmental dosimetry, fate, and impact of tritiated stainless steel (nano)particles (1 mg.L−1 particles and 1 MBq.L−1 tritium) using indoor freshwater aquatic mesocosms to mimic a pond ecosystem. The tritium (bio)distribution and particle fate and (bio)transformation were monitored in the different environmental compartments over 4 weeks using beta counting and chemical analysis. Impacts on picoplanktonic and picobenthic communities, and the benthic freshwater snail, Anisus vortex, were assessed as indicators of environmental health. Following contamination, some tritium (∼16%) desorbed into the water column while the particles rapidly settled onto the sediment. After 4 weeks, the particles and the majority of the tritium (>80%) had accumulated in the sediment, indicating a high exposure of the benthic ecological niche. Indeed, the benthic grazers presented significant behavioral changes despite low steel uptake (<0.01%). These results provide knowledge on the potential environmental impacts of incidental tritiated (nano)particles, which will allow for improved hazard and risk management.

Gas composition change during operation of a compact discharge fusion neutron source with a closed deuterium supply system

A compact cylindrical fusion neutron source has been developed for various applications, such as a D–T fusion neutron source for blanket neutron transport experiments for blanket development. Currently, the operation of a discharged fusion device is mostly deuterium–deuterium (D–D) fusion, in which D2 fuel is continuously fed to the vacuum chamber and pumped out to keep its pressure constant. Deuterium–tritium (D–T) fusion operation requires a closed supply system for radioactive tritium. So, the fuel supply system has been developed using ZrCo. In this system, however, fuel D2 gas is diluted due to light hydrogen released from the inner wall of the vacuum chamber and the surface of the electrodes, which results in a decrease of neutron production rate (NPR). Therefore, the external gas supply mode was performed to remove light hydrogen from the electrode surface before the operation of the closing system. The results of the gas analysis show that H2 was not increased and the D2 ratio was maintained. As a result, the neutron production rate achieved (NPR) > 105 n/s, and the dependency of the NPR on the voltage was similar to that of the external supply mode. These results indicate that removing light hydrogen from the electrode surface is effective to suppress fuel gas dilution.

Preliminary engineering design of vacuum thermal shielded Pb-Li loop section for potential nuclear fusion application

Nuclear fusion reactor design and engineering has reached into an advanced phase where the issues pertaining to radioactive tritium handling & accountability, divertor heat load mitigation, reactor size reduction & cost minimization are some of the core problems being addressed globally. Tritium breeding blanket is an important sub system of the reactor, which demands the most efficient design from many perspectives including that of tritium handling and accountability. Especially, Liquid Metal Breeder Blanket (LMBB) design consists of a complex network of heated pipes carrying Lead-Lithium (Pb-Li) Eutectic Alloy liquid metal. There are a few major issues with such pipes, namely (1) Large Space required due to substantial increase in diametric size of such pipes covered with heating elements and silica fibre based thermal insulation, (2) Loss of the bred tritium from liquid metal through permeation across the pipe wall and associated radioactive safety issues, and (3) Tritium retention in silica fibre based insulation resulting in tritium accountability problem and health hazard during maintenance duration. One possible solution to these problems could be putting a vacuum envelope over the loop pipe. The vacuum isolation will take care of thermal insulation for convection loss and at the same time, the pumping port of the envelope will collect all the lost tritium. In order to demonstrate the feasibility of the concept from thermal shielding point of view, we have prepared a conceptual and preliminary engineering design of such a vacuum envelope on a segment of the Pb-Li loop of 1 inch diameter. The loop segment includes a straight part as well as one 180° U bend too. The design is to maintain the envelop temperature less than 50 °C while the loop pipe is maintained at 350 °C. Basic calculation of thermal conductivity of low pressure air (vacuum) is done and compared with that of conventional insulation material silica based fibre felt. The fabrication, integration and maintenance schemes are also discussed in this report.

MELCOR-TMAP: The integration of MELCOR for fusion and TMAP4 for fusion reactor systems safety analysis and tritium inventory tracking

The design of fusion reactors requires the prediction of radioactive tritium migration during normal operating conditions and accident scenarios. Safety standards such as those from the U.S. Department of Energy (DOE) require that fusion reactor designs limit the release of hazardous material to the environment. In addition to safety requirements, the rarity of tritium supplies for burning D-T fusion plasma requires tritium breeding blankets. Computational modeling of migration of tritium and various reaction products throughout the fusion reactor serves to create designs that fulfill these requirements. MELCOR-TMAP, owned and developed at Idaho National Laboratory (INL), is an integrated system-level engineering code adapted for the analysis of fusion reactor systems. The history of the conception and evolution of the MELCOR-TMAP code, as well as its current capabilities, recent updates including a corrected composite material wall nodalization scheme, and plans for future development, are discussed.

Development and Basic Qualification Steps towards an Electrochemically Based H-Sensor for Lithium System Applications

IFMIF-DONES, or the InternationalFusionMaterialsIrradiationFacility-DEMOOrientedNeutronSource, is a facility for investigations into foreseen fusion power plant materials using the relevant neutron irradiation of 14 MeV. This special n-irradiation is generated by the interaction of deuteron beams with liquid lithium. A critical issue during the operation of IFMIF-DONES is the enrichment of dissolved impurities in the Li-melt loops. The danger occurs as a result of hydrogen-induced corrosivity and embrittlement of the loop components, as well as the security hazards associated with the radioactive tritium. Hence, the application of liquid lithium in IFMIF-DONES requires a suitable impurity control system for reliable and low-level maintenance under the operating conditions of DONES. Regarding those requirements, an electrochemical sensor for hydrogen monitoring was developed in the frame of an international EUROFusion–WPENS task, to determine H-concentrations via the electro-motive force (EMF) of Li-melts and a suitable online-monitoring system. Long-term tests demonstrated that the sensor fulfills the requirements of chemical and mechanical stability and functionality under the harsh Li environment under the planned DONES conditions. Obtained results and operational experiences will be discussed in regard to application windows, reproducibility and calibration needs. Additionally, recommendations will be outlined for upgraded systems and future qualification needs.

Analysis on the influencing factors of radioactive tritium leakage and diffusion from an indoor high-pressure storage vessel

Analysis on the influencing factors of radioactive tritium leakage and diffusion from an indoor high-pressure storage vessel

PERFORMANCE EVALUATION OF COMMERCIAL SCINTILLATION COCKTAILS FOR LOW-LEVEL TRITIUM COUNTING BY HIGH-CAPACITY LIQUID SCINTILLATION COUNTER.

Low-background liquid scintillation counter is one of the popular measuring instruments used to investigate tritium radioactivity in environmental media. These instruments require the liquid sample and organic solvent to be mixed for tritium measurement. In the European Union, the registration, evaluation, authorization and restriction of chemicals regulation was established to control the use of chemical substances of very high concern. It is important to find continuously available alternative reagents. In this paper, a performance evaluation was conducted using four scintillation cocktails according to Japanese conventional procedure; although one of them, Gold Star LT2, contains nonylphenol ethoxylate, it will continue to be available for research and development. From the evaluation results it was confirmed that Gold Star LT2 would be a satisfactory alternative scintillator, which is similar performance of Ultima Gold LLT.

Analyzing Tritium Radioactivity in Nihon-shu Specialized by Fukushima Using MAgnetically Levitated Electrode Ionization Chamber

Analyzing Tritium Radioactivity in Nihon-shu Specialized by Fukushima Using MAgnetically Levitated Electrode Ionization Chamber

A Step Closer to Detecting Ancient Neutrinos

Using radioactive tritium, scientists improve laboratory constraints on the overdensity signal of cosmic relic neutrinos by a factor of 100, an advance that should improve the chances of spotting this elusive particle.

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%.

Study on the growth and redistribution of deuterium–deuterium layer driven by temperature gradient

We report results of crystal growth, layering of the deuterium–deuterium (D2) layers in cylindrical cryogenic targets. For the first time, we realized the global coverage of the D2 layer on the inner surface of the capsule through the crystal growth of D2 ice, and the control of the temperature field without the infrared radiation, foam lining, and magnetic field. Analysis of the image of x-ray phase contrast imaging shows that the thickness of the D2 layer is about 36.53 μm, and the inner surface roughness is 3.23 μm. The finite element method is applied to simulate the temperature field of the target, and the phase transition process of D2, revealing the mechanism of D2 covering the inner surface of the capsule. These initial experiments provide a new vision and method for exploring and achieving the pure crystal growth as well as layering of D2 without operation of radioactive tritium.