Tritium Experiment Research Articles

A new symmetry model for hohlraum-driven capsule implosion experiments on the NIF

We have developed a new model for predicting the time-dependent radiation drive asymmetry in laser-heated hohlraums. The model consists of integrated Hydra capsule-hohlraum calculations coupled to a separate model for calculating the crossbeam energy transfer between the inner and outer cones of the National Ignition Facility (NIF) indirect drive configuration. The time- dependent crossbeam transfer model parameters were adjusted in order to best match the P2 component of the shape of the inflight shell inferred from backlit radiographs of the capsule taken when the shell was at a radius of 150-250 μm. The adjusted model correctly predicts the observed inflight P2 and P4 components of the shape of the inflight shell, and also the P2 component of the shape of the hotspot inferred from x-ray self-emission images at the time of peak emission. It also correctly captures the scaling of the inflight P4 as the hohlraum length is varied. We then applied the newly benchmarked model to quantify the improved symmetry of the N130331 layered deuterium- tritium (DT) experiment in a re-optimized longer hohlraum.

A new Disruption Mitigation System for deuterium–tritium operation at JET

Disruptions, the fast accidental losses of plasma current and stored energy in tokamaks, represent a significant risk to the mechanical structure as well as the plasma facing components of reactor-scale fusion facilities like ITER. At JET, the tokamak experiment closest to ITER in terms of operating parameters and size, massive gas injection has been established as a disruption mitigation method. As a “last resort” measure it reduces thermal and electromagnetic loads during disruptions which can potentially have a serious impact on the beryllium and tungsten plasma-facing materials of the main chamber and divertor. For the planned deuterium–tritium experiments, a new Disruption Mitigation System (DMS) has been designed and installed and is presented in this article. The new DMS at JET consists of an all metal gate valve compatible with gas injections, a fast high pressure eddy current driven valve, a high voltage power supply and a gas handling system providing six supply lines for pure and mixed noble and flammable gases (Ar, Ne, Kr, D2, etc.). The valve throughput varies with the injection pressure and gas type (efficiency – injected/charged gas 50–97%); the maximum injected amount of gas is approximately 4.6kPam3 (at maximum system pressure of 5.0MPa).

The Project 8 Radiofrequency Tritium Neutrino Experiment

The Project 8 experiment aims to determine the electron neutrino mass by measuring the spectrum of tritium beta decay electrons near the 18.6 keV endpoint. Unlike past tritium experiments, which used electrostatic and magnetostatic spectrometers, Project 8 will detect decay electrons nondestructively via their cyclotron radiation emission in a magnetic field. An individual electron is expected to emit a detectable pulse of microwaves at a frequency which depends on the electron energy. Precise measurement of these pulse frequencies is a novel spectroscopy technique particularly well-suited for the high rate, high precision, low background needs of a tritium experiment. The collaboration is currently operating a prototype designed to detect single 83mKr conversion electron decays in an 0.9T magnetic field. We report on recent activities on the prototype, and on progress towards the design of a large tritium experiment with new neutrino-mass sensitivity.

TSTA piping and flame arrestor operating experience data

The Tritium Systems Test Assembly (TSTA) was a facility dedicated to tritium handling technology and experiment research at the Los Alamos National Laboratory. The facility was operated with tritium for its research and development program from 1984 to 2001, running a prototype fusion fuel processing loop with ∼100g of tritium as well as small experiments. There have been several operating experience reports written on this facility's operation and maintenance experience. This paper describes reliability analysis of two additional components from TSTA, small diameter copper gas piping that handled tritium in a nitrogen carrier gas, and the flame arrestor used in this piping system. The component failure rates for these components are discussed in this paper. Comparison data from other applications are also presented.

Neutron spectroscopy measurements of tritium beam transport at JET

A detailed description of the 14 MeV neutron emission in plasmas heated by neutral beam injection has been carried out by coupling Monte Carlo calculations of the neutron emission spectrum with TRANSP modelling of the beam ion energy distributions. The model is used to study tritium beam injection experiments of the JET trace tritium campaign for internal transport barrier (ITB) and H-mode discharges. For ITB discharges, the measured neutron emission spectrum is well described by modelling using as input the beam ion distribution calculated with TRANSP. For H mode discharges the neutron spectrum can be reproduced only if high energy tritons are lost from the plasma, suggesting the possible role of low frequency tearing modes on the beam ions. The presented results are of relevance for tritium beam transport studies in trace tritium experiments and, more generally, for deuterium and tritium transport studies in high power experiments using neutron emission spectroscopy.

An overview of organically bound tritium experiments in plants following a short atmospheric HTO exposure

The need for a less conservative, but reliable risk assessment of accidental tritium releases is emphasized in the present debate on the nuclear energy future. The development of a standard conceptual model for accidental tritium releases must be based on the process level analysis and the appropriate experimental database. Tritium transfer from atmosphere to plants and the subsequent conversion into organically bound tritium (OBT) strongly depends on the plant characteristics, seasons, and meteorological conditions, which have a large variability. The present study presents an overview of the relevant experimental data for the short term exposure, including the unpublished information, also. Plenty of experimental data is provided for wheat, rice, and soybean and some for potato, bean, cherry tomato, radish, cabbage, and tangerine as well. Tritiated water (HTO) uptake by plants during the daytime and nighttime has an important role in further OBT synthesis. OBT formation in crops depends on the development stage, length, and condition of exposure. OBT translocation to the edible plant parts differs between the crops analyzed. OBT formation during the nighttime is comparable with that during the daytime. The present study is a preliminary step for the development of a robust model of crop contamination after an HTO accidental release.

Fuel ion ratio measurements in reactor relevant neutral beam heated fusion plasmas

In this paper, we present a method to derive n(t)/n(d) using the ratio of the thermonuclear neutron emission to the beam-target neutron emission. We apply it to neutron spectroscopy data from the magnetic proton recoil spectrometer taken during the deuterium tritium experiment at JET. n(t)/n(d)-values obtained using neutron spectroscopy are in qualitative agreement with those from other diagnostics measuring the isotopic composition of the exhaust in the divertor.

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

In the so-called ‘alpha-heating’ experiment performed on the JET tokamak during the deuterium–tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s.Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code.We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the so-far-unexplained anomalous ion heating observed in the JET alpha-heating experiment of 1997.Through the formulation of an empirical criterion for ion-drift-wave turbulence stabilization by fusion-born alpha particles, we also show why similar observations were not made in the other deuterium–tritium experiments run so far in JET and TFTR. This allows assessing the operational domain for this stabilization mechanism for ion-drift-wave turbulence in future burning plasma experiments such as ITER, which may open a new path towards the sustainment of a high energy gain in such forthcoming devices.

Overview of Recent Tritium Experiments in TPE

Tritium retention in plasma-facing components influences the design, operation, and lifetime of fusion devices such as ITER. Most of the retention studies were carried out with the use of either hydrogen or deuterium. Tritium Plasma Experiment is a unique linear plasma device that can handle radioactive fusion fuel of tritium, toxic material of beryllium, and neutron-irradiated material. A tritium depth profiling method up to mm range was developed using a tritium imaging plate and a diamond wire saw. A series of tritium experiments (T2/D2 ratio: 0.2 and 0.5 %) was performed to investigate tritium depth profiling in bulk tungsten, and the results shows that tritium is migrated into bulk tungsten up to mm range.

Short-baseline electron neutrino disappearance, tritium beta decay, and neutrinoless double-beta decay

We consider the interpretation of the MiniBooNE low-energy anomaly and the Gallium radioactive source experiments anomaly in terms of short-baseline electron neutrino disappearance in the framework of 3+1 four-neutrino mixing schemes. The separate fits of MiniBooNE and Gallium data are highly compatible, with close best-fit values of the effective oscillation parameters Delta m^2 and sin^2 2 theta. The combined fit gives Delta m^2 >~ 0.1 eV^2 and 0.11 < sin^2 2 theta < 0.48 at 2 sigma. We consider also the data of the Bugey and Chooz reactor antineutrino oscillation experiments and the limits on the effective electron antineutrino mass in beta-decay obtained in the Mainz and Troitsk Tritium experiments. The fit of the data of these experiments limits the value of sin^2 2 theta below 0.10 at 2 sigma. Considering the tension between the neutrino MiniBooNE and Gallium data and the antineutrino reactor and Tritium data as a statistical fluctuation, we perform a combined fit which gives Delta m^2 \simeq 2 eV and 0.01 < sin^2 2 theta < 0.13 at 2 sigma. Assuming a hierarchy of masses m_1, m_2, m_3 << m_4, the predicted contributions of m_4 to the effective neutrino masses in beta-decay and neutrinoless double-beta-decay are, respectively, between about 0.06 and 0.49 and between about 0.003 and 0.07 eV at 2 sigma. We also consider the possibility of reconciling the tension between the neutrino MiniBooNE and Gallium data and the antineutrino reactor and Tritium data with different mixings in the neutrino and antineutrino sectors. We find a 2.6 sigma indication of a mixing angle asymmetry.

A parametric model for fusion neutron emissivity tomography for the KN3 neutron camera at JET

A parametric model for fusion neutron emissivity is presented and applied to the KN3 neutron camera data collected during the trace tritium experiment at the Joint European Torus. This work is aimed at achieving a good compromise between accuracy of tomographic reconstruction and low model complexity. This means low numerical degeneracy and good time consistency of the results. The model is compared both with plasma simulation codes and other tomographic techniques, which use KN3 line integrated emissivity data, showing good agreement over the entire data set analysed (≈500 plasma discharges).

A novel method for trace tritium transport studies

A new method combining a free-form solution for the neutron emissivity and the ratio method (Bonheure et al 2006 Nucl. Fusion 46 725–40) is applied to the investigation of tritium particle transport in JET plasmas. The 2D neutron emissivity is calculated using the minimum Fisher regularization method (MFR) (Anton et al 1996 Plasma Phys. Control. Fusion 38 1849, Mlynar et al 2003 Plasma Phys. Control. Fusion 45 169). This method is being developed and studied alongside other methods at JET. The 2D neutron emissivity was significantly improved compared with the first MFR results by constraining the emissivity along the magnetic flux surfaces. 1D profiles suitable for transport analysis are then obtained by subsequent poloidal integration.In methods on which previous JET publications are based (Stork et al 2005 Nucl. Fusion 45 S181, JET Team (prepared by Zastrow) 1999 Nucl. Fusion 39 1891, Zastrow et al 2004 Plasma Phys. Control. Fusion 46 B255, Adams et al 1993 Nucl. Instrum. Methods A 329 277, Jarvis et al 1997 Fusion Eng. Des. 34–35 59, Jarvis et al 1994 Plasma Phys. Control. Fusion 36 219), the 14.07 MeV D–T neutron line integrals measurements were simulated and the transport coefficients varied until good fits were obtained. In this novel approach, direct knowledge of tritium concentration or the fuel ratio nT/nD is obtained using all available neutron profile information, e.g both 2.45 MeV D–D neutron profiles and 14.07 MeV D–T neutron profiles (Bonheure et al 2006 Nucl.Fusion 46 725–40). Tritium particle transport coefficients are then determined using a linear regression from the dynamic response of the tritium concentration nT/nD profile.The temporal and spatial evolution of tritium particle concentration was studied for a set of JET discharges with tritium gas puffs from the JET trace tritium experiments. Local tritium transport coefficients were derived from the particle flux equation Γ = −D∇nT + VnT, where D is the particle diffusivity and V the convection velocity.Tritium transport in the plasma core approaches the neoclassical level in some cases. For the set of plasmas analysed and within the uncertainty, tritium particle confinement follows the ITER IPB98(y,2) particle scaling confinement.

Anomalous and classical neutral beam fast ion diffusion on JET

Trace tritium experiments (TTE) on JET were analysed using Monte Carlo modelling of the neutron emission resulting from the neutral beam injection (NBI) of short (∼300 ms) tritium (T) beam blips into reversed shear, hybrid ELMy H-mode and L-mode deuterium plasmas for a wide range of plasma parameters. The calculated neutron fluxes from deuterium–tritium (DT) reactions could only be made consistent with all plasmas by applying an artificial reduction of the T beam power in the modelling of between 20% and 40%. A similar discrepancy has previously been observed in both JET (Gorini et al 2004 Proc. 31st EPS Conf. on Plasma Physics (London, UK) vol 28G (ECA)) and TFTR (Ruskov et al 1999 Phys. Rev. Lett. 82 924), although no mechanism has yet been found that could explain such a difference in the measured T beam power. Applying this correction in the T beam power, good agreement between calculated and measured DT neutron emission profiles was obtained in low to moderate line averaged density ELMy H-Mode plasmas assuming that the fast beam ions experience no, or relatively small, anomalous diffusion (Dan ≪ 0.5 m2 s−1). However, the modelled neutron profiles do not agree with measurements in higher density plasmas using the same assumption and the disagreement between the measured and calculated shape of the neutron profile increases with plasma density. In this paper it is demonstrated that large anomalous losses of fast ions have to be assumed in the simulations to improve agreement between experimental and simulated neutron profiles, characterized by the goodness of fit. Various types of fast ion losses are modelled to explain aspects of the data, though further investigation will be required in order to gain a more detailed understanding of the nature of those anomalous losses.

Behavior of Solid Polymer Membrane Electrolyzers in Use with Highly Tritiated Water

These days more and more modern electrolysis cells are operated with new solid polymer membranes. These membranes prevailing DuPont’s Nafion® are not only used for electrolysis but as well for the wide spectrum of fuel cells due to their good mechanical and chemical stability and the high proton conductivity. For that reason it is intended to use these solid polymer membranes for the electrolyzer units in the ITER Water Detritiation System (WDS). The influence of Tritium during water electrolysis to the membrane material is still not sufficiently investigated. Therefore long-term experiments of solid polymer membranes were performed at Tritium Laboratory Karlsruhe (TLK). The chemical degradation and durability behavior of the used Nafion® 117 membrane are investigated in details under tritiated water conditions. For comparison a second cell was operated with demineralized water for the same period.In addition to the experimental rigs with single Nafion® membranes, two industrial electrolyzer units equipped with Nafion® membranes were operated during different tritium experiments at TLK. Before operation they had been modified to be compatible for tritium operation. After long operation period no degradation in the performance of the electrolyzers is observable.

First Tritium Results of the KATRIN Test Experiment Trap

The TRAP experiment (TRitium Argon frost Pump) has been built at the Tritium Laboratory Karlsruhe (TLK) as a test rig for the Cryogenic Pumping Section (CPS) of the KArlsruhe TRItium Neutrino Experiment (KATRIN). TRAP employs a heterogeneous layer of pre-condensed argon to adsorb hydrogen isotopes at ~ 4.2 K. This paper presents results obtained in the first three tritium experiments with TRAP.

Surface Enhanced Exchange Reactions of Hydrogen Isotopes with Water and Fomblin Oil

Maintaining isotopic purity of tritium is one of the major tasks in several new large facilities such as ITER (International Thermonuclear Experimental Reactor), KATRIN (Karlsruhe Tritium Experiment) and NEXTEX (Texas Neutrino Mass Experiment). Working with multiple isotopes and isotopomers is always accompanied by isotope exchanges, which are accelerated by catalysts. These are provided by surfaces of various materials, which are used in the recycling systems. Here new results are reported of the solubility of hydrogen in Fomblin oil and kinetics for reactions between D2O, HDO, H2O and D2, HD and H2 taking place at the surface of a stainless steel (SS304) vessel at pressures of about 350 Pa. The kinetics of hydrogen isotopes were measured by Raman spectrometer. The water isotopomers were monitored by mass spectrometry. The solubility of hydrogen in Fomblin oil was determined at several H2 pressures using NMR spectroscopy. The results can be extended to lower pressures using Henry’s law.

Prospects for cosmic neutrino detection in tritium experiments in the case of hierarchical neutrino masses

We discuss the effects of neutrino mixing and the neutrino mass hierarchy when considering the capture of the cosmic neutrino background (CNB) on radioactive nuclei. The implications of mixing and hierarchy at future generations of tritium decay experiments are considered. We find that the CNB should be detectable at these experiments provided that the resolution for the kinetic energy of the outgoing electron can be pushed to a few 0.01 eV for the scenario with inverted neutrino mass hierarchy, about an order of magnitude better than that of the upcoming KATRIN experiment. Another order of magnitude improvement is needed in the case of normal neutrino mass hierarchy. We also note that mixing effects generally make the prospects for CNB detection worse due to an increased maximum energy of the normal beta decay background.

Anticipated X-ray and VUV spectroscopic data from ITERwith appropriate diagnostic instrumentation

The radiation characteristics of anticipated sample elements, from H through W, in the International Thermonuclear Experimental Reactor (ITER) have been modelled using the diffusion equilibrium model SANCO for the ion concentrations coupled with the spectral signature of the ions, throughout the X-ray and VUV regions (0.1–100 keV), using the Atomic Data and Analysis Structure population code and database, ADAS. The spectral signature varies greatly depending on whether the viewing line-of-sight (LOS) encompasses the divertor and (or) core regions of the plasma volume. Bound–bound transitions required for line profile analyses of nonfuel core ions can locally dominate the continuum spectrum in the 0.1–10 keV region at acceptably low elemental concentrations. While the background continuum is the main source of noise in the line profile analyses, the intensity and features of the continuum when divided into many spectral bands covering 0.1–100 keV are themselves powerful diagnostics of the plasma composition, Zeff, and the electron temperature. The spectral signature of the divertor LOSs where 1 &lt; Te &lt; 300 eV is dominated typically and exclusively by lines in the XUV–VUV region, restricted in the case of W to λ &gt; 40 Å. Appropriate instrumentation, relying on imaging Bragg reflectors and diffractors and position-sensitive energy-resolving detectors, is designed to cover the full spatial extent of the core plasma. Estimates of the core signal/noise based on experience with tritium experiments on the Joint European Torus indicates substantial signal levels with tolerable neutron-induced noise and component degradation. The divertor diagnostics make use of a suite of aspheric diffraction grating spectrometers designed to measure impurity ion influxes and are essential for plasma control. The EBIT could be conceived as a neutron-free adjunct facility to the ITER spectroscopic programme. At its simplest level, it provides standards for instrument performance and for the spectroscopic signature of selected ions subjected to electronic and atomic collisions over a wide range of ITER-relevant impacting energies.PACS Nos.: 52.58.Lq, 52.55.Fa, 52.70–m, 52.25.Vy, 87.64.Gb

Modelling of alpha-particle behaviour in H-mode plasmas with trace tritium at JET

Recently gamma(γ)-ray emission measurements have been performed for the first time in trace tritium experiments in the Joint European Torus (JET) [Kiptily et al 2004 Phys. Rev. Lett. 93 115001]. The decay in the γ-ray emission has been measured after a short duration tritium neutral beam injection (NBI) into deuterium plasmas. The measured γ-ray emission is produced in the reaction between the α-particles and intrinsic beryllium impurity, and therefore it carries information about the α-particle behaviour. The interpretation of the γ-ray emission decay after the tritium NBI and short single gas puff into H-mode plasmas, based on the modelling of the α-particle evolution with the TRANSP code, is given here. It is shown that the α-particle confinement may determine the decay time of the γ-ray emission during the very short post-NBI phase (∼150–200 ms) unresolved with present diagnostics (time resolution of γ-ray emission measurements is 250 ms). The later γ-ray decay correlates with the confinement of thermalized tritium (i.e. with the decay of the α-particle source). An upper estimate of the α-particle confinement time is determined, but this estimate exceeds the α-particle slowing down time giving a large uncertainty in the estimation of anomalous (non-collisional) losses in these plasmas. The α-particle behaviour is analysed also in discharges with tritium gas puffs with the goal of finding a scenario where the α-particle production and losses could be clearly distinguished. It is found that a large time delay between the decay of the α-particle source and its products occurs in discharges performed at high plasma density due to the large transient orbit losses of α-particles. These scenarios are proposed for testing α-particle orbit losses in future deuterium–tritium experiments.

The dissolution kinetics of major elements in municipal solid waste incineration bottom ash particles

Leaching and tracer experiments in batches at L/S 20 were performed with 3-month-old MSWI bottom ash separated into eight different particle sizes. The time-dependent leaching of major elements (Ca 2+, K +, Na +, Cl − and SO 4 − 2 ) was monitored for up to 747 h. Physical properties of the particles, the specific surface (BET), pore volume and pore volume distribution over pore sizes (BJH) were determined for all particle classes by N 2 adsorption/desorption experiments. Some common features of physical pore structure for all particles were revealed. The specific surface and the particle pore volume were found to be negatively correlated with particle size, ranging from 3.2 m 2/g to 25.7 m 2/g for the surface area and from 0.0086 cm 3/g to 0.091 cm 3/g for the pore volume. Not surprisingly, the specific surface area was found to be the major material parameter that governed the leaching behavior for all elements (Ca 2+, K +, Na +, Cl − and SO 4 − 2 ) and particle sizes. The diffusion resistance was determined independently by separate tracer (tritium) experiments. Diffusion gave a significant contribution to the apparent leaching kinetics for all elements during the first 10–40 h (depending on the particle size) of leaching and surface reaction was the overall rate controlling mechanism at late times for all particle sizes. For Ca 2+ and SO 4 − 2 , the coupled effect of diffusion resistance and the degree of undersaturation in the intra particle pore volume was found to be a major rate limiting dissolution mechanism for both early and late times. The solubility control in the intra particulate porosity may undermine any attempt to treat bottom ash by washing out the sulfate. Even for high liquid/solid ratios, the solubility in the intra-particular porosity will limit the release rate.