Feasibility study of applying the passive safety system concept to fusion–fission hybrid reactor

The fusion–fission hybrid reactor can produce energy, breed nuclear fuel, and handle the nuclear waste, etc., with the fusion neutron source striking the subcritical blanket. The passive safety system consists of passive residual heat removal system, passive safety injection system and automatic depressurization system was adopted into the fusion–fission hybrid reactor in this paper. Modeling and nodalization of primary loop, partial secondary loop and passive core cooling system for the fusion–fission hybrid reactor using relap5 were conducted and small break LOCA on cold leg was analyzed. The results of key transient parameters indicated that the actuation of passive safety system could mitigate the accidental consequence of the 4-inch cold leg small break LOCA on cold leg in the early time effectively. It is feasible to apply the passive safety system concept to fusion–fission hybrid reactor. The minimum collapsed liquid level had great increase if doubling the volume of CMTs to increase its coolant injection and had no increase if doubling the volume of ACCs.     

Feasibility studies of D—^3He fusion power in China

The systematic study on D-3He advanced fuel fusion in China has been performed.Comparisons between D-3He and D-T fuel cycles in physics,engineering,environmental safety and so on have been made.D-3He fusion offers significant adavantages for reducing the neutron yield by a factor of 10-60,The 3He resource and mining possibility are investigated.The energy payback factor of 97 for mining lunar 3He resource is calculated.The operating parameter scope for D-3He fueled Tokamak reactor is analyzed.The prompt energy broadening for fusion products is calculated and results are consistent with those obtained by Lehner using a different method.Centrally peaked current drive with high efficiency is studied utilizing plasma synchrotron radiation.Centrally peaked current drive with gigh efficiency is studied utilizing plasma synchrotron radiation.More than 80% of plasma current required can be driven passively.A D-^3He fueled Tokamak commercial reactor-Mooncity was designed.Neutronics calculations show that the radioactivity,afterheat,BHP value for Mooncity are 10-60 times less than those for D-T fusion.     

A three-dimensional thermal and fluid dynamics analysis of a gas cooled subcritical fast reactor driven by a D–T fusion neutron source

The entire nuclear fuel cycle involves partitioning classification and transmutation recycling. The usage of a tokamak as neutron sources to burn spend fuel in a gas cooled subcritical fast reactor (GCSFR) reduces the amount of long-lived radionuclide, thus increasing the repository capacity.     

Improved activation tests of fusion structural materials with a deuteron–beryllium neutron source

In the framework of the European Activation File (EAF) task of the European Fusion Technology Programme, the EAF data relevant to the steel types F82H-mod and MANET-2 were benchmarked experimentally. Samples were activated in an intense neutron field produced in a thick beryllium target by a 19-MeV deuteron beam of the Karlsruhe Isochron-Zyklotron. The irradiated samples were investigated by γ spectrometry. The results were compared with calculations using the FISPACT code, the EAF-4.1 library and the source neutron spectrum as measured by activation foil dosimetry. Calculation-over-experiment ratios between 0.96 and 1.19 are found for the more important medium-halflife radionuclides produced in F82H-mod. Similar values are found for MANET-2.     

“Cold nuclear fusion”: A hypothetical model to probe an elusive phenomenon

The natural tendency of identical bosons to clump in ordinary space is ascribed to a symmetry force, whose action is equivalent to the effects of the wavefunction for a collection of degenerate bosons. The symmetry force is hypothesized to produce clusters of deuterons in the lattice for a high enough stoichiometric ratio of deuterons to Pd atoms and to catalyze tunneling to achieve cold fusion. A semiempirical power law is derived as a function of the number of deuterons,N, in a representative cluster: for large enoughN the fusion products are He⁴ plus heat, while for small clusters the fusion rate is much lower and the Oppenheimer-Phillips process favors the production of tritium over neutrons. Pulsed production of heat and neutrons is suggested. Finally, three additional roles in physics for the symmetry force are hypothesized.     

The design of “multiple energies from one source” in D-T neutron tube

To obtain multiple monoenergetic neutron sources and realize the on-site calibration of radiation monitoring equipment for nuclear-involved places,the structural characteristics and neutron source features of D-T neutron tube were analyzed;Monte Carlo method was adopted to simulate the effect of interaction between typical materials and different energy neutrons;multilayered shielding materials were combined and optimized to acquire the optimal scheme to shield the neutron sources from the neutron tube.On the base,a tapered alignment filtration construction was designed and Monte Carlo method was employed to simulate the effect of alignment construction.The result showed that the tapered alignment filtration construction can create monoenergetic neutrons including14.1 MeV,0.18 MeV and thermal neutrons and demonstrated good monochrome performance which provides multiple monoenergetic sources for the on-site calibration.     

Neutron flux determination in irradiation sites of an Am–Be neutron source at NNRI

Neutron flux measurements and flux distribution parameters for two irradiation sites of an Am–Be neutron source irradiator were measured by using gold (Au), zirconium (Zr) and aluminum (Al) foils. thermal neutron flux Φ_th = 1.46 × 10⁴ n cm⁻² s⁻¹ ± 0.01 × 10², epithermal neutron flux Φ_epi = 7.23 × 10² n cm⁻² s⁻¹ ± 0.001, fast neutron flux Φ_f = 1.26 × 10² n cm⁻² s⁻¹ ± 0.020, thermal-to-epithermal flux ratio f = 20.5 ± 0.36 and epithermal neutron shaping factor α = −0.239 ± 0.003 were found for irradiation Site-1; while the thermal neutron flux Φ_th = 4.45 × 10³ n cm⁻² s⁻¹ ± 0.06, the epithermal neutron Φ_epi = 1.50 × 10² n cm⁻² s¹ ± 0.003, the fast neutron flux Φ_f = 1.17 × 10 n cm⁻² s⁻¹ ± 0.011, thermal-to-epithermal flux ratio f = 29.6 ± 0.94, and epithermal neutron shaping factor α = 0.134 ± 0.001 were found for irradiation Site-2. It was concluded that the Am–Be neutron source can be used for neutron activation analysis (NAA). The Am–Be source can be used for neutron activation analysis thereby reducing the burden on GHARR-1 and increasing the research output of the nation.     

Optimization of the steady neutron source technique for absorption cross section measurement by using an 124Sb–Be neutron source

An improved experimental approach has been developed to determine thermal neutron absorption cross sections. It uses an ¹²⁴Sb–Be neutron source which has an average neutron energy of only about 12 keV. It can be moderated in either a water tank or a paraffin filled box and can be used for aqueous or powder samples. This new design is first optimized by MCNP simulation and then benchmarked and calibrated with experiments to verify the simulations and realize the predicted improved measurement sensitivity and reproducibility. The ¹²⁴Sb–Be source device is from 1.35 to 1.71 times more sensitive than the previous method based on the use of a ²⁵²Cf source.     

Verification of a fusion neutron diagnostic Bonner sphere spectrometer on measurement of a ~(241)Am–Be neutron source

A Bonner sphere spectrometer(BSS) was developed for neutron diagnostic on HL_2A Tokamak.It contains eight polyethylene spheres embedded with SP9~3 He proportional counter.Before setting up on the Tokamak experimental hall,a verification experiment was arranged on a~(241)Am–Be neutron source to test its spectrometry capability.The neutron response functions were calculated by Monte Carlo code Geant4 to simulate the real measurement environments.By least square method,the neutron spectrum was finally unfolded on log domain from0.1 e V to 11 Me V.It has a remarkable consistency to the ISO 8529-1 standard~(241)Am–Be neutron spectrum.This shows that the BSS is effective and reliable for neutron spectrum determination.     

The Somma–Vesuvius complex and the Phlaegrean Fields caldera: New chronological data of several eruptions of the Copper–Middle Bronze Age period

Radiocarbon dating of short-lived sample materials is a useful tool applied to date deposits of volcanic eruptions. Several archaeological sites discovered and excavated in Campania witnessed important volcanic eruptions, which occurred in the Copper and Middle Bronze Ages. These eruptions come from the Somma–Vesuvius complex and the Phlaegrean Fields caldera. At least four Plinian eruptions have been identified in the eruptive history of Somma–Vesuvius, interspersed by interplinian events, called protohistoric, which occurred between Avellino and Pompeii. At S. Paolo Belsito a stratigraphic sequence below Avellino and above the first two protohistoric events after Avellino were highlighted; while Nola (Naples) gives new information on the chronology of Avellino. Sites like Caivano and Gricignano D’Aversa, involved by the Agnano 3, Paleoastroni 2 and Agnano Monte Spina eruptions were highlighted and investigated. In this work, we want to clarify the chronology of some eruptions by comparing our results with previous data. Charcoal, bone and seed samples were collected, treated and measured at the CIRCE laboratory in Caserta.     

Modelling of a supercritical CO2 power cycle for nuclear fusion reactors using RELAP5–3D

A supercritical recompression CO₂ power cycle has been simulated using the system code RELAP5–3D. This code is being developed by INL and has traditionally been used in the simulation of operational and accidental transients in fission nuclear plants. The aim of the work presented here, developed within the framework of the Spanish Fusion Technology Program Consolider TECNO_FUS, is to take advantage of the simulation capabilities of RELAP5–3D in a field where little if any experience exists in the use of the code; i.e., the simulation of the heat fluxes and the thermodynamic cycle that, in a fusion power plant, will convert thermal power from plasma into mechanical power as a previous step to electricity generation. Code capabilities that make it suitable for this purpose are, for instance, the compressor model and the libraries of fluid properties (among them CO₂ and LiPb).The reference plant for the simulation is the one being designed under TECNO_FUS, which is the Spanish proposal for DEMO. The model of the plant includes the primary coolant systems, i.e. helium and LiPb in the Spanish dual coolant modular design (doble refrigerante modular, DRM), compressors, turbine and heat exchangers (Printed Circuit type).After the model has been set-up, several steady-state calculations have been run to test the performance of the model. After designing some minimal control features and adjusting their parameters, a few transient calculations have been run in order to demonstrate the capabilities of code and model. Finally, strengths and weaknesses of code and model are highlighted, along with some conclusions on their suitability for fusion technology applications.     

A chemical interpretation of heat generated in “cold fusion”

It is concluded from a thermochemical analysis that the steady-state excess heating observed in calorimetric experiments¹ is attributable to the heat of formation of liquid D₂O resulting from recombination of D₂ and O₂ gases generated in the electrolytic cell. The recombination is catalyzed by both electrodes and the extent of the reaction increases on stirring, especially when D₂ gas sparging is used for this purpose. Thermal effects of stored chemical energy, which include thermal power output exceeding electrical input in the short term and cathode meltdown from total sudden release, arise from storage of D atoms in supersaturated solid solution within the cathode volume. Their recombination to form D₂ builds up high internal pressures, causing multiple fracture. Excess heat is liberated as D atoms and D₂ molecules fall into deep traps created on fresh Pd surfaces, supplemented by D recombination heat. Postulation of unknown nuclear processes to account for the heat is not necessary.     

The study of aeroball system for measuring 3D neutron flux distribution in reactor core

Aeroball system is attractive in several aspects because it can easily transport the map of neutron flux distribution to be measured from incore to outside of a reactor vessel.However,before the aeroball system is put to practical use in the heating reactor.there are four topics that have to be further studied.They are the stability of the activated positions,enhancement of signal/noise(S/N)ratio,distributed control and data-acquisition system and on-lin nbeutron flux distribution reconstruction.Besides describing the rasons for them,this paper gives out the theory,concept and solution about the first two topics and it is helptul to give the possibility to enhance the reactor-power.     

Estimate of the Efficiency of Hydrogen–Metal Hydride (Intermetallic Compound) Systems in the Separation of the Three-Isotope Mixtures H–D–T

A method is developed for calculating apparatus for separating a three-isotope mixture H–D–T by the sorption method using hydrides of metals or intermetallic compounds. Relations are established between the partition coefficients and mass-transfer characteristics, determined for binary isotopic mixtures of hydrogen, and the parameters determining the isotopic equilibrium and the kinetics of mass transfer in the system gas–solid hydride phase with three isotopes. The efficiencies of various sorbents for deprotization of deuterium–tritium mixture are compared. 4 figures, 2 tables, 7 references.     

Impact of Resonance Treatment on Minor Actinide Incineration in a D–T Thorium Fusion Concept

Resonance treatments have an essential role to reliable neutronic calculations with different neutronic parameters. In this study presents the effect of resonance treatment and various tritium breeder materials on the incineration of the nitride fuels containing minor actinide mixed thoria in the Deuterium–Tritium fusion driven hybrid reactor as time dependent. Neutron transport calculations under resonance treatment and without resonance treatment are performed by using XSDRNPM/SCALE 5 codes. The impact of resonance treatments and various tritium breeder materials on tritium breeding, energy multiplication, total fission rate (∑_f), cumulative fissile fuel enrichment, fissile fuel breeding, average burn up values are comparatively investigated. It is observed that the neutronic results affect from both resonance treatment and the tritium breeder materials as time dependent.     

Summary of US–Japan Exchange 2004: New Directions and Physics for Compact Toroids

Scientists from research institutions in the United States of America and Japan attended a USA Department of Energy sponsored joint international workshop on the subject of Compact Toroids (CT) in Santa Fe, NM, USA in September 2004. We outline here a summary of the topics that were discussed, some of the implications, and new directions that are likely to follow from this research. Experimental, theoretical and computational results were presented. The experimental devices and concepts, along with the theory and computational models comprise investigations of fundamental plasma physics, fusion science, and approaches to fusion energy that require magnetized plasmas.     

In vitro study of nonthermal atmospheric pressure plasma in improving the durability of the dentin–adhesive interface with an etch-and-rinse system

In this study, we employed a nonthermal atmospheric pressure plasma (NTAPP) jet to evaluate the effect of plasma treatment on the durability of resin–dentin bonding under a thermocycling challenge. Furthermore, we assessed the degradation resistance of plasma-treated collagen under a sodium hypochlorite (NaClO) challenge. We assessed the beneficial effect of NTAPP treatment on the acid-etched dentin–bonding interface by testing the micro-tensile bond strength and examining the morphology. We found that the immediate bonding strength of the dentin significantly increased after NTAPP treatment. Compared with the control group, NTAPP resulted in a more prominent effect on the bonding durability of the dentin–adhesive interface after treatment for 5 or 10 s. Simultaneously, the mechanical strength of dentin collagen under the NaClO challenge was improved. Our results indicate that, in optimal conditions, NTAPP could be a promising method to protect dentin collagen and to improve the bonding durability between dentin and etch-and-rinse adhesives.     

Effect of radiolysis of TODGA on the extraction of TODGA/n-dodecane toward Eu(Ⅲ): an experimental and DFT study

N,N,N′,N′-Tetraoctyl diglycolamide (TODGA) is one of the most promising extractants tailored for high-level liquid radioactive waste treatment during nuclear fuel reprocessing.The γ-radiolysis of TODGA (0.2 mol/L) in n-dodecane (n DD) solution with and without pre-equilibrated 3.0 mol/L HNO₃ was investigated using HPLC and UPLC-QTOF-MS and compared with the γ-radiolysis of neat TODGA in this study.With increased absorbed doses,the concentration of TODGA decreased exponentially for the...