Deuterium Fusion Research Articles

Analysis of water activation in fusion and fission nuclear facilities

Water is used as a cooling fluid of certain systems in operational fusion reactors and will also be used in the ITER tokamak. During cooling the water is exposed to high energy neutrons emitted from fusion of deuterium and tritium and becomes activated. The main contributors to the activity of the cooling water are radioactive isotopes of oxygen and nitrogen produced by activation of oxygen isotopes in the cooling water, i.e. 16N, 17N and 19O. As currently few experiments for water activation in fusion reactors exist, computational methods are needed to determine water activation and consequent dose rates in fusion reactors. The calculated activation of oxygen isotopes strongly depends on the cross sections in evaluated nuclear data libraries. For fusion reactors there are two reference nuclear data libraries: FENDL-2.1 and FENFL-3.1b. The calculated activities of nuclides in water have an uncertainty, which depend on the uncertainty of calculated neutron spectra and uncertainty in reaction cross sections. For the reference fusion libraries the uncertainty for activation of water isotopes, due to uncertainty in reaction cross section, is around 8% for isotope 16O, around 12% for the isotope 17O and around 12% for isotope 18O. The uncertainty in oxygen activation due to the uncertainty of activation cross sections is thus in the order of several percent. Hence statistical uncertainty of neutron fluxes calculated with the Monte Carlo method can be of the same order of magnitude.

Diamond fast-neutron detector applied to the KSTAR tokamak

To demonstrate the potential value of a diamond detector as a neutron spectrometer on KSTAR, simultaneous measurements of the KSTAR deuterium-deuterium (D-D) fusion neutron energy, and time-dependent neutron emissions were performed with a diamond based neutron spectrometer during the 2018 KSTAR D-D plasma campaign. For the work, the diamond based neutron spectrometer was placed on a viewport located at the mid-plane of port P outside the KSTAR vacuum vessel. The results of the work not only demonstrated the satisfactory performance of the diamond detector in the harsh environment of a mixed neutron-gamma high radiation field, and strong electromagnetic field, but also its applicability as a neutron spectrometer for fusion deuterium-plasma experiments.

A Review of Radioactive Wastes Production and Potential Environmental Releases at Experimental Nuclear Fusion Facilities

The development of experimental nuclear fusion facilities and the systems connected to them currently involves the operation (or advanced design) of some large plants in the national territory. Devices such as neutron generators and plasma focus systems are also included. The machines developed to test the main components of these systems such as neutral beam generators (Neutral Beam Injector) and the experimental plants for thermonuclear fusion, mainly in the Tokamak configuration (toroidal geometry), are in the list. These applications are characterized by high neutron fluxes of high energy (typically 2.5 and 14 MeV from deuterium-deuterium and deuterium-tritium fusion reactions, respectively). They involve the production of radionuclides in the components of the machines and in the fluids used for targets’ cooling and in the primary containments. In many cases, the atmosphere of the rooms containing these structures is activated and may be affected by the dispersion of powders that are more or less radioactive. The present work addresses the issues mentioned so far, taking into consideration the real cases relating to the devices and the facilities in operation, under construction, and in the advanced design phase. The conclusions highlight the critical aspects related to the management of these types of waste, as well as the low or very low environmental impact, from a radiological point of view, of the examined facilities.

2-D Evaluation of Bred Tritium Using Neutron Imaging Plate

Tritium breeding performance of a fusion blanket is a key parameter for the self-sufficient fueling of a fusion reactor, and thus designed to validate the performance of a neutronics experiment. Measuring the 2-D distribution of bred tritium is challenging via conventional methods such as $\beta $ -ray counting from an irradiated lithium sample using a liquid scintillation counter (LSC) and a single-crystal diamond detector with a thin 6LiF film, because they are point detectors which require many measurements. In this article, 2-D distribution of the low quantity produced tritium was evaluated with a neutron imaging plate (NIP) with a Gd convertor by estimating the loss of neutrons via a capture reaction by Li. Deuterium–deuterium (DD) fusion neutrons were generated using a compact fusion device at an average neutron production rate of $1.5 \times 10 ^{5}$ n/s by applying high voltages. A neutron image with “shadows” projected by thermal neutron capture reactions of 6Li(n, $\alpha$ ) and 10B(n, $\alpha$ ) was successfully obtained. The experimentally evaluated values were confirmed to be consistent with the total number of capture reactions calculated using a neutron transport code. The results suggest that the approach could be a facile method for the 2-D evaluation of bred tritium.

Investigation of light ion fusion reactions with plasma discharges

The scaling of reaction yields in light ion fusion to low reaction energies is important for our understanding of stellar fuel chains and the development of future energy technologies. Experiments become progressively more challenging at lower reaction energies due to the exponential drop of fusion cross sections below the Coulomb barrier. We report on experiments where deuterium-deuterium (D-D) fusion reactions are studied in a pulsed plasma in the glow discharge regime using a benchtop apparatus. We model plasma conditions using particle-in-cell codes. Advantages of this approach are relatively high peak ion currents and current densities (0.1 to several A/cm2) that can be applied to metal wire cathodes for several days. We detect neutrons from D-D reactions with scintillator-based detectors. For palladium targets, we find neutron yields as a function of cathode voltage that are over 100 times higher than yields expected for bare nuclei fusion at ion energies below 2 keV (center of mass frame). A possible explanation is a correction to the ion energy due to an electron screening potential of 1000 ± 250 eV, which increases the probability for tunneling through the repulsive Coulomb barrier. Our compact, robust setup enables parametric studies of this effect at relatively low reaction energies.

Nuclear recoil scintillation linearity of a high pressure 4He gas detector

We investigate scintillation linearity of a commercial high pressure 4He gas detector using monoenergetic 2.8 MeV neutrons from a deuterium-deuterium fusion neutron generator. The scintillation response of the detector was measured for a range of recoil energies between 83 keV and 626 keV by tagging neutrons scattering into fixed angles with a far-side organic scintillator detector. Detailed Monte Carlo simulations were compared to experimental data to determine the linearity of the detector response by comparing the scaling of the energy deposits in the simulations to the detector output. In this analysis, a linear scintillation response corresponds to a consistent value for the scaling factor between simulated energy deposits and experimental data for several different scattering angles. We demonstrate that the detector can be used to detect fast neutron interactions down to 83 keV recoil energies and can be used to characterize low-energy neutron sources, one of its potential applications.

Nuclear Reactions under Irradiation of Deuterated Structures by X Rays

Measurements of emission from nuclear reaction products (neutrons and protons) have been carried out appearing in the deuterated structures of textured CVD diamond, palladium, titanium, and zirconium under irradiation with a beam of X rays using independent methods (neutron detector based on He-3 counters, Si surface-barrier semiconductor detectors and CR-39 track detector). The possibility of enhancement of both DD reaction and multi-particle deuterium fusion by the beam of X rays with energy ranging 20–30 keV in solid deuterated targets has been established. Analysis of X-ray fluorescence spectra of the target bombarded by beams of ions has revealed “additional” peaks, the occurrence of which cannot be related to any of the known elements, and requires separate study.

Challenges for plasma-facing components in nuclear fusion

The interaction processes between the burning plasma and the first wall in a fusion reactor are diverse: the first wall will be exposed to extreme thermal loads of up to several tens of megawatts per square meter during quasistationary operation, combined with repeated intense thermal shocks (with energy densities of up to several megajoules per square meter and pulse durations on a millisecond time scale). In addition to these thermal loads, the wall will be subjected to bombardment by plasma ions and neutral particles (D, T, and He) and by energetic neutrons with energies up to 14 MeV. Hopefully, ITER will not only demonstrate that thermonuclear fusion of deuterium and tritium is feasible in magnetic confinement regimes; it will also act as a first test device for plasma-facing materials (PFMs) and plasma-facing components (PFCs) under realistic synergistic loading scenarios that cover all the above-mentioned load types. In the absence of an integrated test device, material tests are being performed primarily in specialized facilities that concentrate only on the most essential material properties. New multipurpose test facilities are now available that can also focus on more complex loading scenarios and thus help to minimize the risk of an unexpected material or component failure. Thermonuclear fusion—both with magnetic and with inertial confinement—is making great progress, and the goal of scientific break-even will be reached soon. However, to achieve that end, significant technical problems, particularly in the field of high-temperature and radiation-resistant materials, must be solved. With ITER, the first nuclear reactor that burns a deuterium–tritium plasma with a fusion power gain Q ≥ 10 will start operation in the next decade. To guarantee safe operation of this rather sophisticated fusion device, new PFMs and PFCs that are qualified to withstand the harsh environments in such a tokamak reactor have been developed and are now entering the manufacturing stage.

A study on the feasibility of fast neutron imaging using the D–D fusion neutrons of the KSTAR tokamak

Abstract In the 2015 Annual Plasma Campaign of the Korea Superconducting Tokamak Advanced Research (KSTAR), which mainly used neutral beam injection (NBI) as auxiliary heating, the yield by the Deuterium–Deuterium (D–D) fusion neutrons of 2.45 MeV energy from the KSTAR plasma was estimated to have reached about 1014 n/s. Apart from the primary goal, which is energy production by nuclear fusion, these fusion neutrons may be used in other applications such as aerospace, defense, material, and electronic component research and testing, as well as battery and fuel cell research in the fields of archeology and security. This is because the tokamak is huge and intense as a volumetric neutron source. This work aims to investigate the feasibility of fast neutron imaging using the D–D fusion neutrons emitted from the KSTAR tokamak. For this work, we adopted a fast neutron imaging technique based on a CCD camera in combination with a fiber–optical scintillator (FOS). The first experimental results about the feasibility of fast neutron imaging obtained from the KSTAR Tokamak will be described in this paper.

Cheating the death of the sun by relativistic interstellar spaceflight

For the human species and its unique culture to survive the death of the sun, a bridge must be built to other solar systems with earthlike planets. The Kepler space telescope has discovered a large number of extrasolar planets, but only a few with earthlike conditions, and those are many light years away. Assuming that no new fundamental laws of physics which would greatly facilitate interstellar spaceflight are awaiting discovery, one can only see two avenues:First, at 10% of the speed of light via deuterium fusion bomb propulsion, harvesting the deuterium in the comets of the Oort clouds surrounding our and other suns, and by hopping from comet to comet. Second, with relativistic velocities by matter-antimatter generated GeV laser beams released from relativistically stabilized hydrogen-antihydrogen super-pinch discharges, transmitting the recoil of the laser beam by the Mössbauer effect to the spacecraft. The production of the anti-hydrogen can be done with solar energy in robotic factories on the planet Mercury. For the first, but much more for the second possibility, very large masses must be lifted in one stage into low Earth orbit. This can conceivably be done by chemically ignited pulsed pure fusion bomb propulsion.

Contribution of random noise in the ITER RNC diamond neutron detectors pulses to the counting rate uncertainty

The main goal of the ITER Radial Neutron Camera (RNC) is to provide the plasma neutron emission profile (neutron emissivity) through measurement of the uncollided 14 MeV and 2.5 MeV neutrons from deuterium-tritium (DT) and deuterium-deuterium (DD) fusion reactions. The system is based on an array of detectors (diamonds are among the candidate detectors) located in collimated lines of sight (LOS) viewing the plasma through the ITER Equatorial Port Plug #1. Tomographic reconstruction techniques are used to calculate the neutron emissivity.The contribution of random noise on diamond detector pulses to the count rate uncertainty is investigated in this paper. The energy spectrum of the neutrons impinging on the detector has been calculated by means of MCNP calculations for one line of sight of the RNC In-Port system. The spectrum has been convoluted with the diamond detector response functions and the Pulse Height Spectrum (PHS) has been obtained. Experiments have been carried out with the CAEN™ 5810D detector emulator, that is able to produce arbitrary pulse height distributions as those expected in the ITER RNC. Random noise has been added on each detector pulse of the distribution using the detector emulator. The resulting uncertainty produced on the count rate has been evaluated as a function of the random noise level.

Code O-SUKI: Simulation of direct-drive fuel target implosion in heavy ion inertial fusion

The Code O-SUKI is an integrated 2-dimensional (2D) simulation program system for a fuel implosion, ignition and burning of a direct-drive nuclear-fusion pellet in heavy ion beam (HIB) inertial confinement fusion (HIF). The Code O-SUKI consists of the four programs of the HIB illumination and energy deposition program of OK3 (Comput. Phys. Commun. 181, 1332 (2010)), a Lagrangian fluid implosion program, a data conversion program, and an Euler fluid implosion, ignition and burning program. The OK3 computes the multi-HIBs irradiation onto a spherical fuel target. One HIB is divided into many beamlets in OK3. Each heavy ion beamlet deposits its energy along the trajectory in a deposition layer depending on the particle energy. The OK3 also has a function of a wobbling motion of the HIB axis oscillation, and the HIBs energy deposition spatial detail profile is obtained inside the energy absorber of the fuel target. The spherical target implosion 2D behavior is computed by the 2D Lagrangian fluid code coupled with OK3, until just before the void closure time of the fuel implosion. After that, all the data by the Lagrangian implosion code are converted to them for the Eulerian code. The fusion Deuterium (D)–Tritium (T) fuel and the inward moving heavy tamping material are imploded and deformed seriously at the stagnation phase. The Euler fluid code is appropriate to simulate the fusion fuel compression, ignition and burning. The Code O-SUKI 2D simulation system provides a capability to compute and to study the HIF target implosion dynamics. Program summaryProgram Title: O-SUKIProgram Files doi:http://dx.doi.org/10.17632/h8n474wvf5.1Licensing provisions: CC BY NC 3.0Programming language: C++Nature of problem: The nuclear fusion energy would provide one of energy resources for our human society. In this paper we focus on heavy ion beam (HIB) inertial confinement fusion (HIF). A spherical deuterium (D)–tritium (T) fuel pellet, whose radius may be about several mm, is irradiated by HIBs to be compressed to about a thousand times of the solid density. The DT fuel temperature reaches ∼5–10 KeV to be ignited to release the DT fusion energy. The typical HIBs total input energy is several MJ, and the HIBs pulse length is about a few tens of ns. The DT fuel compression uniformity is essentially important to release the sufficient fusion energy output. The DT fuel pellet implosion non-uniformity should be kept less than a few %. The O-SUKI code system provides an integrated tool to simulate the HIF DT fuel pellet implosion, ignition and burning. The HIBs energy deposition detail profile is computed by the OK3 code (Comput. Phys. Commun. 181, 1332 (2010)) in an energy absorber outer layer, which covers the DT fuel spherical shell. The DT fuel is compressed to the high density, and so the DT fuel spatial deformation may be serious at the DT fuel stagnation. Therefore, the O-SUKI system employs a Lagrangian fluid code first to simulate the DT fuel implosion phase until just before the stagnation. Then all the simulation data from the Lagrangian code are converted to them for the Euler fluid code, in which the DT fuel ignition and burning are simulated.Solution method: In the two fluids codes (Lagrangian and Euler fluid codes) in the O-SUKI system the three-temperature fluid model (J. Appl. Phys. 60, 898 (1986)) is employed to simulate the pellet dynamics in HIF. The HIBs energy deposition detail profile is computed by the OK3 code (Comput. Phys. Commun. 181, 1332 (2010)).

Ab initio predictions for polarized deuterium-tritium thermonuclear fusion

The fusion of deuterium (D) with tritium (T) is the most promising of the reactions that could power thermonuclear reactors of the future. It may lead to even more efficient energy generation if obtained in a polarized state, that is with the spin of the reactants aligned. Here, we report first-principles predictions of the polarized DT fusion using nuclear forces from effective field theory. By employing the ab initio no-core shell model with continuum reaction method to solve the quantum mechanical five-nucleon problem, we accurately determine the enhanced fusion rate and angular distribution of the emitted neutron and 4He. Our calculations demonstrate in detail the small contribution of anisotropies, placing on a firmer footing the understanding of the rate of DT fusion in a polarized plasma. In the future, analogous calculations could be used to obtain accurate values for other, more uncertain thermonuclear reaction data critical to nuclear science applications.

An optimization study for shielding design of D-D and D-T neutron generators

Neutron generators (NG) are being increasingly used in various industrial and research areas such as neutron activation analysis, neutron radiography, and neutron capture therapy. In such applications of neutron generators, compactness is one of the most important issues. Since a neutron source is generated by deuterium-deuterium (D-D) or deuterium-tritium (D-T) fusion reaction, a relatively thick shield for both fast neutrons and related photons is usually required. In this study, optimization of shielding designs for D-D and D-T neutron generators were investigated by adopting appropriate moderator and shielding materials. Based on the optimized moderator and shield thicknesses, the final dimensions of neutron generators were derived for various source strengths of D-D and D-T neutron conditions. Considering conventional condition of a container, we concluded that a 1010 n/sec D-D source and a 108 n/sec D-T source could be a portable NG.

Characteristics of fast 3He ion velocity distribution exciting ion cyclotron emission on JT-60U

Ion cyclotron emission (ICE) is probably excited by non-thermal ion velocity distribution. Identifying characteristics of the ion velocity distribution that excites the ICE can contribute to understanding its emission mechanism. The characteristics of fast helium-3 (3He) ion velocity distribution that excites 3He ICE [ICE(3He)] on JT-60U are investigated. First, fast deuterium ion distributions, which mainly contribute to deuterium–deuterium fusion reactions, are calculated with a fast ion orbit following Monte-Carlo code (OFMC code) under realistic conditions to evaluate birth spatial and velocity distributions of the 3He ions. Then, the fast 3He ion distributions are evaluated with the OFMC code using the birth distributions and compared between cases when the ICE(3He) is observed and not. The evaluated fast 3He ion distributions at the midplane edge of the plasma on the low field side have strong pitch-angle anisotropy in both cases. In the case with the ICE(3He) excitation, a relatively peaked bump-on tail structure in the energy direction is formed in the distributions. The formation of the relatively peaked bump-on tail structure is localized at the plasma edge on the low field side. On the other hand, the distributions at the plasma edge on the low field side have a broader structure in the energy direction in the case without the excitation. The comparison results show that the formation of the relatively peaked bump-on tail structure in the fast 3He ion distribution makes a key contribution to the excitation of the ICE(3He) on JT-60U.

Numerical simulation of deuterium-tritium fusion reaction rate in laser plasma based on Monte Carlo-discrete ordinate method

Inertial confinement fusion (ICF) is one of the possible ways to realize controlled thermonuclear fusion. The fusion neutron source term is one of the important parameters in the physical design and analysis of laser plasma. The accuracy of the fusion neutron source term directly affects the reliability of the analysis results. At present, the neutron source term of deuterium-tritium fusion reaction in ICF is mainly based on formula method. It has limited applications in temperature and reaction type. Because of a large quantity of data, it is impossible to simulate the fusion reaction of each particle. In this paper, the concept of particle cloud is introduced, that is, the collection of the like particles with the same position and speed, and it is considered that the action of particle cloud is the same reaction. Because the particles should satisfy the Maxwell velocity distribution at a certain temperature and the direction is all around the circumference angle, the collision cross sections between the incident particle and different target particles are different. Therefore, the design program takes all the possible velocities, polar angles and direction angles, reads the collision cross sections between deuterium and tritium and makes corrections, and obtains the multi-temperature differential correction cross sections of deuterium and tritium fusion with Doppler energy broadening. On these bases, Monte Carlo method and discrete ordinate method method are used. A numerical simulation program for the fusion rate of D-T particles in laser plasma is developed in this paper. It is found that there are significant differences between the DT, DD, TD cross sections and the original cross sections after Doppler broadening. In a range of plasma temperature between 20 keV and 100 keV, the simulation results are more consistent with the cross section data of ENDF/B-VI and ENDF/B-VII databases of deuterium-tritium fusion reaction than those from the analytical formula method. There is a large error between the numerical simulation results and the analytical formula method in the low energy region. It may be caused by the difference of calculation methods and too big difference among the used fusion cross sections at low temperature.

Concepts for a Deuterium–Deuterium Fusion Reactor

We revisit the assumption that reactors based on deuterium-deuterium (D-D) fusion processes have to be necessarily developed after the successful completion of experiments and demonstrations for deuterium-tritium (D-T) fusion reactors. Two possible mechanisms for enhancing the reactivity are discussed. Hard tails in the energy distribution of the nuclei, through the so-called kappa-distribution, allow to boost the number of energetic nuclei available for fusion reactions. At higher temperatures than usually considered in D-T plasmas, vacuum polarization effects from real $e^+e^-$ and $\mu^+\mu^-$ pairs may provide further speed-up due to their contribution to screening of the Coulomb barrier. Furthermore, the energy collection system can benefit from the absence of the lithium blanket, both in simplicity and compactness. The usual thermal cycle can be bypassed with comparable efficiency levels using hadronic calorimetry and third-generation photovoltaic cells, possibly allowing to extend the use of fusion reactors to broader contexts, most notably maritime transport.

Neutron spectroscopy and spectral unfolding with 4He fast neutron scintillators

Time-of-flight measurements were performed to determine the 4He pressurized fast neutron scintillation detectors response function and the ability of the detectors to be applied as a spectrometer. An experimentally validated neutron energy response function was used in conjunction with an iterative least squares unfolding technique to unfold a 252Cf spontaneous fission spectrum, a PuBe (α, n) spectrum, and a deuterium–deuterium (D–D) fusion reaction spectrum. The ability of the detectors to retain incident neutron energies makes them suitable for applications such as nuclear non-proliferation and spent nuclear fuel monitoring.

Cyclooxygenase‑2‑mediated upregulation of heme oxygenase 1 mitigates the toxicity of deuterium‑tritium fusion radiation.

Utilizing the energy released from the nuclear fusion of deuterium with tritium (D-T) may be an important method of supplying energy in the future. The ionizing radiation emitted from nuclear fusion is a potential health risk to humans, including scientists who are currently performing nuclear fusion experiments and the employees of fusion nuclear plants, in the future. However, there have been few reports on the biological effects of fusion radiation. In the present study, using the High Intensity D-T Fusion Neutron Generator, the DNA damage and its regulation in normal human fibroblasts exposed to fusion radiation were investigated. Heme oxygenase 1 (HO-1), which is reported to induce anti-inflammatory activity, was upregulated in the irradiated cells. Pretreatment with the HO-1 inhibitor, protoporphyrin IX zinc (II), exacerbated double strand break formation following exposure to fusion radiation. The expression of cyclooxygenase-2 (COX-2) contributed to the upregulation of HO-1, as demonstrated by the result that its inhibitor, NS-398, inhibited the induction of HO-1 in irradiated cells. It was further clarified that the ataxia telangiectasia mutated DNA damage response was activated and it stimulated the phosphorylation of p38 mitogen-activated protein kinase, which was responsible for the upregulation of COX-2 and HO-1. These results provide novel information on fusion radiation-induced biological effects and potential targets for decreasing the associated health risks.

Possible Applications of Nanomaterials for Nuclear Fusion Devices

Abstract Conditions of nuclear fusion and nuclear fusion devices were described, and some possible applications of nanomaterials for nuclear fusion devices were presented in the present article. Muon-catalyzed fusion is one of methods for nuclear fusion to cause even at room temperature or lower, and protons or heavy ions with huge energy are irradiated to metals such as beryllium or copper, which results in emission of negative or positive charged muons from the metals. An experiment using a pyroelectric power source using lithium tantalite crystal was also reported to achieve nuclear fusion in a desktop-like device. Hydrogen storage is also important for the fusion devices, and the possibility of hydrogen storage in hydrogen storage metallic alloys was studied by diffusion calculation and potential calculation of deuterium fusion. Enhancement of deuterium diffusion in the Pd alloys would be one of the key points for energy materials. Carbon(C)/copper(Cu)-based composite materials with high thermal conductivity and good stability at high temperatures were also developed by adding a small amount of titanium, which has a low enthalpy of alloy formation with C and Cu. These carbon-based materials could be a candidate material for the plasma facing components of fusion devices.