Tritium Injection Research Articles

Operational and engineering experiences of gas injection to JET for TT and DT operational campaigns

Following the first deuterium–tritium experiment (DTE1) at UKAEA, modifications were investigated to the Joint European Torus’ (JET) gas introduction (GI) systems to increase the gas feed capabilities of the JET facility to better support future campaigns. The GI systems comprise the GI and gas distribution system in the Active Gas Handling System (AGHS), and neutral beam injection and the tritium injection modules on the torus. During DTE1 about 100 g of tritium was supplied from AGHS to JET users. During the second deuterium–tritium experiment (DTE2) and the tritium–tritium experiment (TT) just over 373 g and 630 g of tritium respectively was supplied to JET users for the campaigns. The tritium and deuterium gas supply systems of the fuel cycle can be underestimated as having fewer technical or scientific challenges based on the mechanical simplicity of equipment that they consist of. However, operational experience has shown these systems have the potential to bottleneck a campaign programme. This publication outlines the upgrade requirements foreseen, following DTE1, for operations in the DTE2 and TT campaigns, how these changes impacted the gas supply operations, and where limitations were encountered. The areas discussed include—challenges of upgrading and maintaining equipment designed for a short operating life; the impact of having differences between user requirements and gas supply capabilities; the logistics of gas supply involving multiple control room locations; communication routes between gas supply systems and teams; and safely controlling and tracking tritium gas movements. The latest JET tritium campaigns highlighted a number of challenges for future facilities looking to operate in both batch and continuous gas injection operational modes. The recommendations from this publication intend to provide a starting point for how to address these challenges and optimise gas supply in support of future fusion programmes. This work has been carried out within the framework of the contract for the operation of the JET Facilities and has received funding from the European Union’s Horizon 2020 research and innovation programme. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

Tritium Processing Systems and First Tritium Operation of the KATRIN Experiment

The KArlsruhe TRItium Neutrino (KATRIN) Experiment aims for the determination of the effective mass of the electron-antineutrino. KATRIN uses a strong, gaseous, windowless tritium source for precision spectroscopy of the β-electrons. The 70-m-long experiment has been set up at the Tritium Laboratory Karlsruhe (TLK) and was commissioned with traces of tritium during two measurement campaigns in 2018. In spring 2019, the first campaign with full source luminosity started. KATRIN uses a complex gas-handling system called Loops for stabilized injection of tritium into the source and tritium gas handling. It also makes use of the unique facilities and possibilities found at the TLK for gas handling, cleanup, and purification. This paper describes the integration of KATRIN into TLK’s existing infrastructure and the current status of the experiment and concludes with a summary of the tritium measurements.

On a fusion born triton effect in JET deuterium discharges with H-minority ion cyclotron range of frequencies heating

An effect due to fusion born triton production has been observed in JET high-performance deuterium plasma discharges with neutral beam injection (NBI) and H-minority ion cyclotron range of frequencies (ICRF) heating, using DD and deuterium tritium (DT) neutron spectrometry as well as fusion product loss measurements. The observations show that a decrease of the second harmonic ω = 2ωcD enhancement of the DD neutron rate correlates with an increase of the triton burnup rate. An acceleration of tritons due to absorbing ICRH power at the third harmonic ω = 3ωcT has been observed. This effect could indicate a redistribution of ICRH power absorption at ω ≈ ωcH = 2ωcD = 3ωcT with increasing triton concentration at the ion cyclotron resonance layer. Also, the reduction of the second harmonic enhancement of the DD neutron rate can be caused by burning of the accelerated deuterium as the tritium concentration grows. This is an extremely non-linear process as both mechanisms intensify with triton concentration. It determines the necessity to consider the ICRH power absorption ω = 3ωcT in modelling of high-performance deuterium discharges with simultaneous NBI and H-minority ICRF heating as well as the assessment of enhanced burnup of ICRF accelerated deuterium for the development of high-performance plasma scenarios and DT fusion rate predictions.

Long-term groundwater recharge rates across India by in situ measurements

Abstract. Groundwater recharge sustains groundwater discharge, including natural discharge through springs and the base flow to surface water as well as anthropogenic discharge through pumping wells. Here, for the first time, we compute long-term (1996–2015) groundwater recharge rates using data retrieved from several groundwater-level monitoring locations across India (3.3 million km2 area), the most groundwater-stressed region globally. Spatial variations in groundwater recharge rates (basin-wide mean: 17 to 960 mm yr−1) were estimated in the 22 major river basins across India. The extensive plains of the Indus–Ganges–Brahmaputra (IGB) river basins are subjected to prevalence of comparatively higher recharge. This is mainly attributed to occurrence of coarse sediments, higher rainfall, and intensive irrigation-linked groundwater-abstraction inducing recharge by increasing available groundwater storage and return flows. Lower recharge rates (<200 mm yr−1) in most of the central and southern study areas occur in cratonic, crystalline fractured aquifers. Estimated recharge rates have been compared favorably with field-scale recharge estimates (n=52) based on tracer (tritium) injection tests. Results show that precipitation rates do not significantly influence groundwater recharge in most of the river basins across India, indicating human influence in prevailing recharge rates. The spatial variability in recharge rates could provide critical input for policymakers to develop more sustainable groundwater management in India.

Modeling of localized impulsive injection of neutrals and plasma response

Neutral particles of hydrogen isotopes, released locally and impulsively into the plasma of fusion devices, can significantly affect local plasma properties. A model, allowing to describe self-consistently the spreading of neutrals from the source and their effect on the local and global plasma conditions is developed. It is based on the separation on each flux surface of two zones, the ‘cold’ cloud, comprising neutral molecules injected and atoms generated in collisions of molecules with electrons and ions, and the ‘hot’ environment affected by flows along the magnetic field of newly produced charged particles outward and heat conduction toward the cloud. Computations are done for the conditions of laser induced desorption spectroscopy applied in Ohmically heated plasmas in the TEXTOR tokamak and foreseen for the ITER fusion reactor. In both cases the local plasma state is strongly changed by the desorption pulse, and this effect is increasing with the growing isotope mass. As a result the total number of photons emitted is reduced noticeably, up to 4 times in the case of tritium injection in ITER, and the necessity to take into account the plasma response by interpreting measurements is demonstrated.

Overview of the tritium system of Ignitor

Among the recent design activities of the Ignitor program, the analysis of the tritium system has been carried out with the aim to describe the main equipments and the operations needed for supplying the deuterium–tritium mixtures and recovering the plasma exhaust. In fact, the tritium system of Ignitor provides for injecting deuterium–tritium mixtures into the vacuum chamber in order to sustain the fusion reaction: furthermore, it generally manages and controls the tritium and the tritiated materials of the machine fuel cycle. Main functions consist of tritium storage and delivery, tritium injection, tritium recovery from plasma exhaust, treatment of the tritiated wastes, detritiation of the contaminated atmospheres, tritium analysis and accountability. In this work an analysis of the designed tritium system of Ignitor is summarized.

The closed tritium cycle of KATRIN

The objective of the KArlsruhe TRItium Neutrino experiment (KATRIN) is a direct measurement of the absolute mass of the electron (anti)neutrino by means of a precise spectroscopy of the tritium β -spectrum near its endpoint. KATRIN combines an ultra-luminous molecular windowless tritium source (WGTS) with a high resolution electrostatic retarding spectrometer. It is planned to inject ultra-cold molecular tritium gas of high isotopic purity (>95%) through a set of capillaries at the middle of the 10 m long WGTS tube. For a gas injection pressure of 3.4×10 −3 mbar and a source temperature of 27 K, the column density of the WGTS is fixed to the reference value of 5×10 17 molecules/cm 2. Since the main systematic uncertainty of the WGTS is associated with the column density, it has to be known to a precision of 0.1%. This stability is the most challenging requirement for the KATRIN WGTS and has essentially influenced its design and the design of the connected tritium cycles. Technical solutions to meet these demands are the proposed WGTS tube cooling system by means of two-phase neon to a stability of ±30 mK and the setup of a so-called Inner Loop to achieve a tritium injection rate of 4.7 Ci/s=1.7×10 11 Bq/s (=40 g tritium throughput per day) with a stability on the level of 0.1%. The Tritium Laboratory Karlsruhe is worldwide the only scientific laboratory which can provide the infrastructure necessary to accomplish such a challenging task.

Systematic spectral features in the neutron emission from NB heated JET DT plasmas

Neutron emission spectroscopy (NES) has been used at JET to study deuterium–tritium discharges heated with neutral beam (NB) injection of tritium and deuterium at energies of 150 keV and 75 keV, respectively. The measurements were performed using the magnetic proton recoil neutron spectrometer and the data analysed with several contributing spectral components. The analysis model considers neutrons from reactions involving high-energy NB ions in (co and counter) passing and trapped orbits and NB ions slowed down to epithermal energies besides ion reactions within the thermal bulk. This study was undertaken to explore the level of fuel ion kinetic information that can be obtained for different NB heating scenarios. Time dependent information was extracted to study how the plasma response to NB injection is manifested in the neutron emission for apparent quiescent periods, during spontaneous plasma instabilities (such as sawteeth) and as a result of intentional changes of the plasma conditions such as the NB injection. The discharges for this study were selected to explore the systematic features that neutron emission spectra display for NB heated discharges and the possibility to interpret them in terms of the underlying kinetic state of the fuel ions. The results obtained on the ion temperature, the toroidal rotation and the supra-thermal fraction of the total neutron yield are compared with those of charge exchange recombination spectroscopy and, in some cases, with plasma equilibrium model calculations. A phenomenological analysis of the results is performed from studies of systematics with the object of exploring the uses of the NES diagnostic and their dependence on data quality.

Redemarcation of recharge area of stressed confined aquifers of Neyveli groundwater basin, India, through tritium tracer studies

Natural recharge due to rainfall (annual average 1,200 mm) over an area of 1,500 km2 of the Neyveli groundwater basin was carried out for two consecutive hydrological years, using the tritium injection technique. The lignite seams, occurring within the Upper Miocene formation in the basin have been mined for the last 40 years. The confined aquifer underlying the lignite seams has been pumped continuously since 1961, for depressurization and safety around the mine. The recharge zone is identified as an elongated zone, oriented in a NE–SW direction within the basin. Natural recharge measurements were made at several sites (single and duplicate injections), covering the entire basin. They indicate a recharge rate of 333–556 mm/year (24–40% of rainfall) in the north and northeastern parts, covering the previously defined recharge areas as well as some adjoining areas. Soil moisture movement at several duplicate sites in these areas showed significant downward migration of tracer during the non-monsoon period, probably caused by pumping in the mine area. Isotopic data of ground water samples in the northern and northeastern part of the basin indicates modern ages. Concurrent field observations like deep water table with high annual fluctuations and exposure of pebble beds, enabled the redemarcation of the aggregate recharge area as 650 km2. The redefined recharge area includes the areas identified by earlier workers as well as the new area on the northeastern side of the lignite mine.

Tritium Application: Self-Luminous Glass Tube (SLGT)

To manufacture SLGTs (Self-Luminous Glass Tubes), 4 core technologies are needed: coating technology, tritium injection technology, laser sealing/cutting technology and tritium handling technology. The inside of the glass tubes is coated with greenish ZnS phosphor particles with sizes varying from 4~5 [µm], and Cu, and Al as an activator and a co-dopant, respectively. We also found that it would be possible to produce a phosphor coated glass tube for the SLGT using the well established cold cathode fluorescent lamp (CCFL) bulb manufacturing technology. The conceptual design of the main process loop (PL) is almost done. A delicate technique will be needed for the sealing/cutting of the glass tubes. Instead of the existing torch technology, a new technology using a pulse-type laser is under investigation. The design basis of the tritium handling facilities is to minimize the operator's exposure to tritium uptake and the emission of tritium to the environment. To fulfill the requirements, major tritium handling components are located in the secondary containment such as the glove boxes (GBs) and/or the fume hoods. The tritium recovery system (TRS) is connected to a GB and PL to minimize the release of tritium as well as to remove the moisture and oxygen in the GB.

Gas dynamic trap as high power 14 MeV neutron source

It is now widely recognized that further progress toward a commercial fusion reactor critically depends on the availability of low activated materials to be operated for many years in the fusion neutron environment without degradation of their properties. Therefore, high power neutron source (NS) for extensive material tests is in great demand. The realistic NS can be built on the basis of the gas dynamic trap (GDT) which is one of the simplest system for magnetic plasma confinement. GDT is an axisymmetric mirror machine of the Budker–Post type, but with a high mirror ratio ( R>10), and operated with warm and relatively dense plasma. Thus, due to frequent collisions, the plasma confined in a trap is very close to isotropic Maxwellian, and hence many instabilities are not excited and plasma behavior is similar to a classical one. It is proposed to use the oblique injection of neutral tritium and deuterium beams with an energy of the order of 100 keV into the GDT “warm” target plasma (electron temperature T e≥750 eV) to produce high intensity neutron flux. In this case, due to the ionization and charge-exchange collisions with plasma particles the energetic atoms will turn into ions confined in the trap. The axial density profile of these anisotropic energetic ions will be strongly inhomogeneous. Namely, the maximum of the fast ion density will be located in the vicinities of mirrors and the minimum—at the middle plane of the device. Thus, a strongly inhomogeneous fusion neutron flux, mostly generated in the fast deuterium–tritium (D–T) ion collisions will appear. GDT NS looks to be rather flexible system. It enables to construct the source stepwise, starting from rather moderate parameters. Increasing the testing zone length and neutral beam power one can increase both neutron flux and the flux density. Calculations show that even in the modest version of the NS with T e∼250 eV quite appreciable neutron flux density in the range of 0.2–0.3 MW/m 2 can be produced. At present, the maximum temperature about 130 eV is obtained in the experiments at the model GDT device at Budker INP. Further increase of the electron temperature in the device requires higher neutral beam power and now is considered to be straightforward.

Characterization of Carbon Tritide Particles in a Tokamak Fusion Reactor

ABSTRACTAmorphous tritiated carbon films are formed through co-deposition of the radioactive isotope tritium (3H or T) with carbon onto plasma facing surfaces in fusion plasmas. The Tokamak Fusion Test Reactor (TFTR), operated by the Princeton Plasma Physics Laboratory, was fueled by tritium and deuterium neutral beam injection and gas puffing. Tritium was co-deposited as amorphous hydrogenated carbon onto graphite tiles and stainless steel surfaces inside the reactor. Since termination of plasma operations, carbon tritide particles have remained in the air in the vessel. Dosimetric limits for occupational exposure to carbon tritide particles need to be established. The purpose of this study was to characterize carbon tritide particle samples inside the TFTR in terms of size, self-absorption of tritium beta, and dissolution rate in simulated lung fluid. Dose estimates of the inhaled carbon tritide particles can be calculated based on the dissolution rate, particle size, and self-absorption factor. The count median diameter and geometric standard deviation were 1.23 µm and 1.72, respectively, indicating that they are respirable particles and can stay suspended in the air for a longer time. The dissolution rate in the lung-simulated fluid was determined in a static system. The dissolution rate ranged from 10−1–10−3 per day in the first few hours, then it decreased to between 10−3 and 10−4. The retention curve of tritium in carbon indicated that >90% of the tritium remained in the particles after 110 d in the simulated lung fluid. This information is being used to support the establishment of respiratory protection requirements.

Annual replenishable ground water potential of India—an estimate based on injected tritium studies

Natural recharge is a vital parameter to be known for ground water budgeting, management and modelling. Percolation of a portion of the rainfall, through the vadose zone, is the principal source of natural recharge to the aquifer systems in India. The tritium injection method, based on piston flow model, is particularly suitable for quantifying the downward flux of moisture in the vadose zone and for measuring natural recharge in Indian climatic condition, where about 80% of the annual rainfall is received as pulses and occurs during the four monsoon months from June to September. Natural recharge measurements, using the tritium injection method, have been carried out in India during the last 25 years, in several basins and watersheds, located in varying climatic and hydrogeological situations. The mean natural recharge values for 35 study areas, well distributed over 17 major river basins are presented. The recharge rates range from 24 to 198 mm yr −1 or 4.1 to 19.7% of the local average seasonal rainfall. The natural recharge data are grouped into four main hydrogeological provinces, namely granitic, basaltic, sedimentary and alluvial and the regression equations between rainfall and natural recharge are derived for each province. These equations enable one to determine the approximate value of natural recharge in any watershed/basin from the rainfall data for any year. The regression equations are used to compute the total annual replenishment of ground water reserves of the country, for an average rainfall year. The calculated annual input is about 476×10 9 m 3 yr −1. This can be considered as a minimal quantity, as it represents the natural recharge due to precipitation alone and does not account for seepage from ponds, lakes, stream bed, canals and return flow from surface water irrigation.

Broadening of the particle resonance drift trajectory and tritium injection into a fusion reactor with an I=3 helical winding

Two fusion reactor problems, removal of helium ash and fuel (tritium) injection, can be solved using the concept of “drift island motion.” The motion of a drift island is an indicator of the broadening of the resonant trajectory of a charged particle guiding center. This trajectory broadening occurs if two conditions are satisfied. First, the drift pitch angle of the particle is equal to the resonance values i*=n/m, where n and m are the “wave numbers” of the perturbing magnetic field. Second, the drift pitch angle i*=n/m “moves” over the plasma cross section as the particle moves. This displacement is caused by a slow change in the helical magnetic field with time as the particle moves. It is shown that this effect may occur in a fusion reactor with an l=3 helical winding and may be used for tritium ion injection.

JET results in D-T divertor plasmas

Recent results obtained during the first part of the JET D-T phase arepresented. Emphasis is placed on conditions carefully set to be similar to thoserequired in ITER. Wall loading changeover from 100% deuterium to 90% tritium wasachieved in about twenty discharges with 100% tritium injection. H mode thresholdpower was found to have inverse isotopic mass dependence whereas there was little massdependence of global energy confinement time in the ELM free or ELMy H mode discharges.Preliminary results are consistent with the gyro-Bohm physics form of global energyconfinement time. This form has a weak negative mass dependence but a stronger densitydependence than the ITERH93-P form. The second harmonic ICRH ITER reference scenario(2ωCT with and without the addition of a small amount of 3He) wasassessed in JET D-T plasmas. High performance combined heating (neutral beam + ICRH)hot ion and optimized shear regime experiments were carried out with only half theinstalled neutral beam power. Nevertheless, internal confinement barriers in theoptimized shear regime were also demonstrated in D-T plasmas.

Blood tritium level as a conservative estimate of soft tissue dose after tritium injection in mice.

The usefulness of the determination of the tritium concentration in blood for estimating the average soft tissue dose after tritium intake was tested. Tritiated water and a mixture of tritiated amino acids dissolved in saline solution were separately administered to adult male mice by intraperitoneal injection. The tritium levels in the blood, urine, whole body, spleen, liver, testis, and brain were then determined at various periods. With both types of tritium administration, the results suggested that the accumulated dose in the blood pool gave a conservative estimate of the accumulated dose to the soft tissue.

Identification of ion cyclotron emission from fusion alpha particles during jet deuterium-tritium experiments

Summary form only given, as follows. In the course of the preliminary tritium experiment (PTE) in JET, where combined D and T neutral beam injection generated a DT fusion power of 1.7 MW, ion cyclotron emission (ICE) in the frequency range up to 180 MHz was measured using an ICRF heating antenna as probe. The ICE spectrum showed a number of superthermal narrow, equally spaced emission lines which correspond to deuteron or alpha -particle ion cyclotron harmonics at the outer mid-plane edge (major radius R approximately 4 m). DD and DT power spectra are similar in form, and show split lines which, above approximately 100 MHz, merge into a continuum. With tritium injection, the ICE power increased by a factor comparable to the increase of neutron flux, indicating that 3.5 MeV fusion alpha -particles provide the free energy for generating ICE. The ICE power increases almost linearly with neutron flux over a range of six decades. The evolution of the ICE follows the rise of the neutron flux, but is delayed by a time comparable with the slowing-down time of the alpha -particles. The ICE intensity is anti-correlated with large amplitude edge-localized modes.

Identification of ion cyclotron emission from fusion alpha particles during JET deuterium-tritium experiments

Summary form only given, as follows. In the course of the preliminary tritium experiment (PTE) in JET, where combined D and T neutral beam injection generated a DT fusion power of 1.7 MW, ion cyclotron emission (ICE) in the frequency range up to 180 MHz was measured using an ICRF heating antenna as probe. The ICE spectrum showed a number of superthermal narrow, equally spaced emission lines which correspond to deuteron or alpha -particle ion cyclotron harmonics at the outer mid-plane edge (major radius R approximately 4 m). DD and DT power spectra are similar in form, and show split lines which, above approximately 100 MHz, merge into a continuum. With tritium injection, the ICE power increased by a factor comparable to the increase of neutron flux, indicating that 3.5 MeV fusion alpha -particles provide the free energy for generating ICE. The ICE power increases almost linearly with neutron flux over a range of six decades. The evolution of the ICE follows the rise of the neutron flux, but is delayed by a time comparable with the slowing-down time of the alpha -particles. The ICE intensity is anti-correlated with large amplitude edge-localized modes.

Tritium Gas Injection System for TFTR D-T Operations

PPPL is presently preparing TFTR for D-T operation beginning the summer of 1993. Included in this preparation is the design and installation of a Tritium Gas Delivery and Injection System which will supply tritium to the TFTR vacuum vessel. The Gas Delivery System will be required to deliver the tritium gas from the Tritium Vault which is located in the TFTR basement to various components located on the TFTR device located in the Test Cell. These components include three Tritium Gas Injection Assemblies (TGIA); twelve Tritium Neutral Beam Injectors (TNB); and the Tritium Pellet Injector (TPI). The Tritium Gas Delivery System which will be described in this paper will include a double walled supply manifold plus the TGIA’s.

Neutral beam heating and current drive systems

Several Neutral Beam Injection (NBI) systems are now capable of injection of powers greater than 20 MW, some for pulse lengths in excess of 5 s. These high power NBI systems have demonstrated the flexibility and utility of neutral beam heating; coupling easily to many plasma configurations; providing heating, fuelling and current drive capability and allowing access to new, improved plasma confinement regimes. All the high power NBI systems have now achieved routinely high reliability and system availability (≳80–90%). The current status of NBI systems is reviewed and successful solutions to the technological problems encountered in design of high power beams, ranging from high heat transfer elements to large area cryopumps, are discussed. The interface to tokamak operations such as the drift duct, stray field cancellation and fast interlock mechanisms are presented, emphasising the considerable progress in these areas. The upgrading of NBI systems for tritium injection on JET and TFTR is reviewed. The possible parameters for a ‘Next Step’ injector are presented, showing the choice of negative ion beams as an attractive option. With reference to the existing conceptual designs for ITER/NET it is shown that the main areas of uncertainty exist in the source and accelerator stack designs. The beamlines themselves should be able to take advantage of the properties of negative ions to lead to some marked simplifications.