Development of In-Situ Gas Analyzer for Hydrogen Isotopes in Fusion Fuel Gas Processing

To develop a real time and in-situ process gas analyzer for fusion fuel gas processing systems, application study of laser Raman spectroscopy was performed by measurement of hydrogen isotopes. Using an Ari on type laser of which wavelength 488 nm, power 0.7 W, and single pass irradiation method, Raman spectra of hydrogen isotopes were measured and intensities of the Stokes rotational lines and Q-branch were quantitatively analyzed. The Stokes rotational lines at 587, 443 and 415 cm¹ were selected as suitable ones for quantitative analysis of H₂, HD and D₂. Normalizing the Raman intensity of partial pressure H₂ as 100, relative Raman intensity ratio of H₂:HD:D₂ was obtained as 100:58:47. The detection limit for hydrogen was estimated as 0.05 kPa in partial pressure and 500 ppm in concentration. But multiple pass method further improved the detection limit to 100 ppm.     

A Review of Confinement Requirements for Advanced Fuels

The energy confinement requirements for burning D-³He, D-D, or P-¹¹B are reviewed, with particular attention to the effects of helium ash accumulation. It is concluded that the DT cycle will lead to the more compact and economic fusion power reactor. The substantially less demanding requirements for ignition in DT (the n_{e E} T required for ignition in DT is smaller than that of the nearest advanced fuel, D-³He, by a factor of 50) will allow ignition, or significant fusion gain, in a smaller device; while the higher fusion power density (the fusion power density in DT is higher than that of D-³He by a factor of 100 at the same plasma pressure) allows for a more compact and economic device at fixed fusion power.     

Impurity Transport in a Simulated Gas Target Divertor

Future generation fusion reactors and tokamaks will require dissipative divertors to handle the high particle and heat loads leaving the core plasma (100–400 MW/m² in ITER). A radiative divertor is proposed as a possible scenario, utilizing a hydrogen target gas to disperse the plasma momentum and trace impurity radiation to dissipate the plasma heat flux. Introducing an impurity into the target hydrogen gas enhances the radiative power loss but may lead to a significant impurity backflow to the main plasma. Thus, impurity flow control represents a crucial design concern. Such impurity flows are studied experimentally in this thesis. The PISCES-A linear plasma device (n 3 × 10¹⁹ m^–3, kT _e 20 eV) has been used to simulate a gas target divertor. To study the transport of impurities, a trace amount of impurity gas (i.e., neon and argon) is puffed near the target plate along with the hydrogen gas. Varying the hydrogen gas puffing rate permits us to study the effects of various background plasma conditions on the transport of impurities. A 1-1/2-D fluid code has been developed to solve the continuity and momentum equations for a neutral and singly ionized impurity in a hydrogen background plasma. The results indicate an axial reduction in the impurity concentration upstream from the impurity puffing source. Impurity entrainment is more effective for higher hydrogen target pressures (and for higher hydrogen plasma densities). However, if there is a reversal of the background plasma flow, impurity particles can propagate past the plasma flow reversal point and are then no longer entrained.     

Reaction balance and efficiency analysis of a D-D fusion/fission hybrid with satellite D-3He reactors

Selected reactor physics and isotope balance characteristics of a fusion hybrid supported D-³He satellite nuclear energy system are formulated and investigated. The system consists of two types of reactors: a parent D-fueled fusion device and a number of smaller reactors optimized for D-³He fusion. The parent hybrid station breeds the helium-3 for the satellites and also breeds fissile fuel for an existing fission reactor economy. Various hybrid operational regimes are examined in order to determine favorable reactorQ values and effective fusion and fission efficiencies. A number of analytical correlations between power output, plasma energetics, blanket neutronics, breeding capacity, and energy conversion cycles are established and evaluated. Numerical examples of performance parameters such as fission-to-fusion power, overall conversion efficiency, and the ratio of satellite to parent fusion power are presented. The range of reactor efficiencies is elucidated as affected by the internal plasma power balances. As an upper bound based on optimistic injection and direct conversion efficiencies, we find the D-³He satellite system power output attaining at best 1/3 of the parent fusion power.     

Preliminary Study of Isotopic Methanes Analysis by Laser Raman Spectroscopy for In-Situ Measurement at Fusion Fuel Gas Processing

Application of laser Raman spectroscopy for fusion fuel gas processing was studied by measuring isotopic methanes exchanged with hydrogen isotopes, which are considered to be a major impurities in the processing. For experimental gases, isotopically equilibrated deuterium and methane were prepared in the presence of solid catalyst. Large Raman scattering peaks of v ₁, bands were observed at 2,917 cm^?1 for CH₄ and at 2,100-2,200 cm_?1 for deuterated derivatives of methane C(H,D)₄. Under a spectral resolution of 5 cm_?1, the v ¹ bands of CH₃D and CH₂D₂ were observed as an overlapped peak, the relative absolute Raman intensity ratio of each isotopic methane was obtained as CH₄: CH₃D+CH₂D₂: CHD₃: CD₄=230: 74: 144: 100. On the other hand, the Raman intensity ratio obtained from pure deuterated standard methane was CH₄: CH₃D: CH₂D₂: CHD₃: CD₄=230: 53: 33: 115: 105. It was confirmed that isotopically equilibrated hydrogen isotopes and methane mixed gas would be applicable for an alternative standard gas for fusion fuel processing gas analyzing system.     

Neutronic analysis of an inertial fusion energy breeder with SiCf/SiC

Neutronic performance of a blanket driven ICF (Inertial confinement fusion) neutron based on SiC_f/SiC composite material is investigated for fissile fuel breeding. The investigated blanket is fueled with ThO₂ and cooled with natural lithium or (LiF)₂BeF₂ or Li₁₇Pb₈₃ or ⁴He coolant. MCNP4B Code is used for calculations of neutronic data per DT neutron. Calculations have show that values of TBR (tritium breeding ratio) being one of the main neutronic paremeters of fusion reactors are greater than 1.05 in all type of coolant, and the breeder hybrid reactor is self-sufficient in the tritium required for the DT fusion driver. Calculations show that natural lithium coolant blanket has the highest TBR (1.298) and M (fusion energy multiplication) (2.235), Li₁₇Pb₈₃ coolant blanket has the highest FFBR (fissile fuel breeding ratio) (0.3489) and NNM (net neutron multiplication) (1.6337). ⁴He coolant blanket has also the best Γ (peek-to-average fission power density ratio) (1.711). Values of neutron leakage out of the blanket in all type of coolants are quite low due to SiC reflector and B₄C shielding.     

C<Subscript>60</Subscript>-Fullerene Hyper-Velocity High-Density Plasma Jets for MIF and Disruption Mitigation

We present an innovative idea to use hyper-velocity (>30 km/s) high-density (>10¹⁷ cm⁻³) plasma jets of D-T/H and C₆₀-fullerene for magneto-inertial fusion (MIF), high energy density laboratory plasma (HEDLP), and disruption mitigation in magnetic fusion plasma devices. The mass (~1–2 g) of sublimated C₆₀ and hydrogen (or D-T fuel) produced in a pulsed power source is ionized and accelerated as a plasma slug in a coaxial plasma accelerator. For MIF/HEDLP we propose to create a magnetized plasma target by injecting two high-Mach number high-density jets with fuel (D-T) and liner (C₆₀/C) structure along the axis of a pulsed magnetic mirror. The magnetized target fusion (MTF) plasma created by head-on collision and stagnation of jets is compressed radially by a metallic liner (Z-pinch) and axially by the C₆₀/C liner. For disruption mitigation, the C₆₀ plasma jets were shown to be able to provide the required impurity mass (J Fusion Energy 27:6, 2008).     

Tritium Released from Mantle Source: Implications for Natural Nuclear Fusion in the Earth’s Interior

This paper summarizes the observation results of mantle tritium (³H) in two volcanic lakes, Lakes Nemrut (Turkey) and Laacher (Germany). The presence of excess ³H in the lakes can be explained as material released from mantle source because of the correlation of excess ³H with mantle ³He and ⁴He. We conclude that excess ³H in these two lakes, after the origin of the excess ³H from atmosphere and conventional nuclear reactions are excluded and the correlation of the excess ³H and mantle ³He is considered, might be from a mantle source and produced by nuclear fusion (d–d reaction) in the deep Earth. We have also investigated helium isotopes in the hydrothermal vent fluids at Mid-Ocean Ridge (MOR). The results show nearly constant ³He/⁴He ratio (³He/⁴He = 1.12 ± 0.13 × 10⁻⁵) and approximately constant ³He/heat ratios ((5–10) × 10⁻¹⁸ mol/J). The correlation of ³He with ⁴He and heat suggests that it is reasonable to suppose ³He is produced by nuclear fusion (d–d reaction) and ⁴He from α-decay of U and Th in the deep Earth. Based on that, ³He/⁴He ratios for 10 hydrothermal vent fluids are calculated. The results agree with the measurement at hydrothermal vent fluids and Mid-Ocean Ridge Basalts (MORB) on the average. We concludes that the narrow distribution of ³He/⁴He ratio peaked at ∼8 R_A in MORB can be explained by the hypothesis that ³He is produced in nuclear fusion.     

Light ion bombardment sputtering,stress buildup,and enhanced surface contamination

Several effects of high fluence light ion bombardment which are relevant to fusion reactor inner wall problems are under investigation. The impurity loading and lateral stress from high fluence ion bombardments can alter sputtering yields markedly. This is demonstrated with sputtering measurements of 45 keV Kr incident upon Au. Sputtering yields for 150 keV⁴ He onto Au are presented for two different background hydrocarbon partial pressures during bombardment. It is shown that there is a polymerized hydrocarbon buildup on the surface for hydrocarbon partial pressures greater than $\text{1 × 10}{}^{\mathrm{?10}}\text{mm Hg}$ even for ion current densities ranging as high as 4 μA/cm²; true sputtering of the Au has been observed only for lower hydrocarbon partial pressures. Additional effects of oxidizing background gases on sputtering measurements of reactive metals are discussed.It is concluded that the background gas partial pressures, temperatures, and particle fluxes in a fusion device and in simulation experiments must be well defined before sputtering effects can be understood.     

Charge exchange of medium energy H and He ions emerging from solid surfaces

Charge exchange of medium energy H and He ions emerging from clean solid surfaces is studied extensively using a toroidal electrostatic analyzer with an excellent energy resolution. The charge distributions of He ions scattered from sub-monolayers near a surface are non-equilibrated, resulting in a surface peak even for poly-crystal solids. By solving simultaneous rate equations numerically, we derive electron capture and loss cross sections for Ni and Au surfaces. Based on a free electron gas model, non-equilibrated He⁺ fractions dependent on emerging angle reveals uniform electronic surfaces for metals and corrugated surfaces for Si and graphite with covalent bonds. It is also found that equilibrium charge fractions of H⁺ are independent of surface materials (Z₂) and in contrast equilibrium He⁺ fractions depend pronouncedly on Z₂. The data obtained are compared with semi-empirical formulas.     

Low Radioactivity Fusion Reactor Based on the Spherical Tokamak with a Strong Magnetic Field

The most important feature of the spherical tokamak is the possibility of high-β plasma confinement (β is the ratio of plasma pressure to magnetic field pressure). So, spherical tokamak can be considered as a possible confinement system for D–³He fusion reactor. Present paper study the ability to develop powerful D–³He reactor based on a spherical tokamak (fusion power about 3 GW). The following parameters are considered as optimization criteria: (1) the ratio of confinement time to the value predicted by ITER98y2 scaling; (2) the neutron flux from the plasma.     

Evaluation of leak flow rate and jet impingement related to leak before break

Leak flow rate and jet impingement load are experimentally evaluated using very narrow and short artificial slits which simulate a through-wall fatigue crack. The following items are clarified in the experiments under BWR fluid conditions: (1) the leak flow rate from the rectangular slit is experimentally clarified and it agrees well with the analytical result when the estimated thermodynamic nonequilibrium parameter N in the present experiment is introduced; (2) the orifice effects are experimentally evaluated concerning the through-wall fatigue crack, in which the discharge coefficients C_D between 0.75 and 0.25 are obtained as a function of the exit to the stagnation area ratio A_e/A_o; (3) when very narrow and short slits are used in the jet impingement experiments, the maximum pressure on the target is higher than that of a large diameter pipe and it increases with the decrease of the flow path length to hydraulic diameter ratio L/D of the slit because of the thermodynamic nonequilibrium effect.     

Comparison of High-Energy He+ and D+ Irradiation Impact on Tungsten Surface in the IR-IECF Device

Polycrystalline tungsten specimens were irradiated in the Iranian Inertial Electrostatic Confinement Fusion device (IR-IECF) by high energy (~100 keV) and high fluency (~10¹⁹ ions/cm²) helium and deuterium plasma to investigate the implantation impact of high energetic ions on tungsten as a candidate for fusion first wall material. Comparison of the exposure by He and D₂ plasma and influence of high temperature (~1,100 °C) implantation of each ion has been examined. Scanning electron microscopy was used to investigate surface morphology changes for various ion fluencies. Results showed the onset of visible surface pores formation especially for helium implanted samples which increased with higher implant fluencies, eventually resulting in a rough and flaky surface structure, unlike deuterium implanted samples on which smoothening of the surface occurred. Microhardness measurements were used to evaluate mechanical properties of implanted tungsten. Each specimen sustained surface hardening after implantation which was observed to increase with greater ion dose. The phase formation and structural evolution were studied by X-ray diffractometry method.     

Cold fusion experiment at Department of Nuclear Engineering,National Tsing-Hua University

We have repeated the so-called cold fusion experiment by electrolyzing heavy water, with 0.1M LiOD, with palladium rod as the cathode and platinum wire as the anode. The purpose of our experiment is to dectect the neutrons that are produced from the fusion process of deuterium if fusion does occur. We use one³He detector and one BF₃ detector to detect the thermal neutrons coming out of the water bath that surrounds the heavy water cell. Possible neutron bursts are detected by the³He detector during a period of about 7 h after electrolyzing for 11 days.     

Development and testing of an integrated combustion and gas ion source system for AMS

A method for interfacing an automated combustion unit to a gas ion source for ¹⁴C analysis is described. This method makes use of an actively controlled transfer line which accommodates the relatively fast flow of the output He carrier gas and short time duration during which the CO₂ is released from the combustion unit, and provides a constant ratio of CO₂ to He carrier gas to the ion source. Details of the active control system are presented and results from the testing of this control are provided.     

Plasma Focus Device as a Breeder of 14.66 MeV Protons to Produce Short-Lived Radioisotopes

In plasma focus devices filled deuterium gas with low pressure admixture gas, ³He, the deuterium creates high energy protons of 14.66 MeV through the ³He(d, p) ⁴He(Q = 18.35 MeV) fusion reaction. This reaction takes place due to the thermal and non-thermal (beam-target) mechanisms. The proton yield production for deuterium filling gas is determined by using the beam-target character of the pinched plasma and moving boiler model. If we use a low pressure admixture gas like ¹¹B, these high energy protons in turn, could generate short-lived radioisotopes like ¹¹C (used in positron emission tomography) via the ¹¹B(p, n)¹¹C reaction. Calculations indicate the influence of drive parameter to the final yield for a Mather type device.     

Analytical Study of Quantum Magnetic and Ion Viscous Effects on p11B Fusion in Plasma Focus Devices

In this article we studied the feasibility of proton-boron (p¹¹B) fusion in plasmoids produced by plasma pinch devices like plasma focus facility as commercially sources of energy. In plasmoids fusion power for 76 keV < T_i < 1,500 keV exceeds bremsstrahlung loss (W/P_b = 5.39). In such situation gain factor and the ratio of Te to Ti for a typical 150 kJ plasma focus will be 7.8 and 4.8 respectively. Also with considering the ion viscous heating effect W/P_b and T_i/T_e will be 2.7 and 6 respectively. Strong magnetic field will reduces ion–electron collision rate due to quantization of electron orbits. While approximately there is no change in electron–ion collision rate, The effect of quantum magnetic field makes ions much hotter than electrons which enhances the fraction of fusion power to bremsstrahlung loss.     

An efficient analytical form for the period-reactivity relation of beryllium and heavy-water moderated reactors

A new mathematical form of the period-reactivity equation for heavy-water- and beryllium-moderated reactors has been developed. This form is represented in a polynomial form with a degree of G+1 for G-th group of delayed neutrons and photoneutrons. A general formula for the coefficients of such polynomial is derived. These coefficients have a linear dependence on the step reactivity insertion. The related constants of this linear dependence are calculated for both types of reactors. In addition, a comparison has been made for the stable reactor periods of an infinite U²³⁵-fueled, D₂O- or Be-moderated reactors, following step reactivity insertion, with and without delayed photoneutrons taken into consideration. Also, a comparison was made for the reactor response to reactivity changes when evaluated using fast and thermal fission delayed neutron group constants combined with and without D₂O- and Be-moderated reactors.     

Preliminary Results of Experimental Studies from Low Pressure Inertial Electrostatic Confinement Device

In this study, Turkey’s first low pressure inertial electrostatic confinement (IEC) device, constructed at the Saraykoy Nuclear Research and Training Center (SNRTC-IEC), is introduced and the first results are reported. This device was designed for neutronic fusion studies in terms of D–D reaction. The SNRTC-IEC device consists of spherical chamber 300 mm in diameter and a grid-type spherical cathode in which high negative voltage is applied at the center of chamber. The outer surface of the device held at ground potential has 10 ports to connect the vacuum pump, high voltage load, residual gas analyzer, ion sources and other peripherals. Cathode voltage is 85 kV and it is particularly emphasized that the SNRTC-IEC device is studied at low pressure (1?10 × 10^?4 mbar). The maximum total neutron production rate is measured at around 2.4 × 10⁴ neutrons per second for the medium grid cathode.     

Experimental Study of the Iranian Inertial Electrostatic Confinement Fusion Device as a Continuous Neutron Generator

Among many facilities in the field of nuclear fusion devices, inertial electrostatic confinement (IECF) device has the specific character of tendency to generate fusion products continuously. Besides the distinctive characteristics, it has become an outstanding focus of interest for many scientists because of several applications such as the ability of performing hydrogen boron fusion. This paper summarizes primary results of the design and construction of the first Iranian IECF device (IR-IECF). It consists of 13.5 cm diameter stainless steel cathode, 41 cm diameter anode with a 60 cm diameter and 60 cm height vacuum chamber. The outcomes of neutron detection represent more than 10⁷ neutron/s at the maximum biased voltage of −140 kV and 70 mA current with deuterium operational filling gas in the steady state regime.