Neutron sources and spectra from cold fusion

Deterministic methods are used to calculate the neutron and photon sources and spectra that would develop if fusion reactions were occurring in cold fusion experimental devices. The results from the calculations give the neutron and gamma spectra resulting from a 2.45-MeV and a 14.1 MeV neutron source. The neutron source strength from certain (gamma,n) and (alpha,n) reactions are also determined.     

Effect of outside tritium source on tritium balance of a D-T fusion reactor

Attainable tritium breeding ration in the blanket system must be larger than the required breeding ratio when no effective tritium resources from outside are expected. It is revealed recently that a considerable amount of tritium can be trapped to the re-deposition layer of the first wall materials and that the time constant of this phenomenon is rather long. Then, the tritium breeding ratio around 1.1 is required in the blanket system when 3 years is claimed for the tritium doubling time to prepare tritium for the initial inventory of a next reactor. Construction of an outside tritium supply is one of the possible ways to compensate the lack of tritium because it is generally considered that the attainable tritium breeding ratio in the solid breeder system is around 1.05. It is reported recently that a high-temperature gas-cooled reactor can produce 10 kg of tritium per year. The preferable amount of tritium production rate of the outer tritium supply is discussed in this study from the viewpoint of tritium balance in a D-T power reactor.     

利用静电加速器质谱技术测定氚

本工作描述基于2.5MV静电加速器建立的加速器质谱计的基本原理、实验装置以及重水样品中氚浓度(T/D)的测定。为了比较,还用放射性法进行了测量。实验结果表明,基于一台能量约1—2MeV加速器测定氚的灵敏度已达到10~(-14),而潜在灵敏度还可能高2—3个量级。本文还讨论了这种技术的前景和问题。     

Chemical thermodynamics of fusion reactor breeding materials and their interaction with tritium

Liquid lithium, lithium alloys (solid and liquid) and ceramic lithium compounds are candidate breeding materials for (D,T) fusion reactors.Besides their tritium breeding capability, which results from neutron capture, their thermochemical properties and their interaction with tritium are of particular interest. A good knowledge of the physical and chemical properties of liquid lithium exists; and the systems Li-LiH, Li-LiD and Li-LiT have been studied in great detail. For dilute solutions of D₂ in liquid lithium, Sieverts' law was found to be valid down to an atom fraction of $\text{x}{}_{\mathrm{D}}\text{= 10}{}^{-6}$; in the vapor, lithium polymers up to Li₄ and lithium deuterides are found.In the system liquid Li-Pb, the solubility of D₂ was measured as a function of temperature and alloy composition, and correlated with the activities of the constituent metals. The solubility of D₂ was found to obey Sieverts' law at low concentrations, and is many orders of magnitude smaller than that in liquid lithium. This holds also for solid “Li₇ Pb₂”.Vaporization studies yielded data on the thermal stability of the oxides: Li₂0, γ-LiAlO₂, β-Li_sAlO₄, LiAl₅O₈, Li₂ZrO₃, Li₄ZrO₄, Li₈ZrO₆, Li₂SiO₃ and Li₄SiO₄. Tritium diffusivity was studied in Li₂O, γ-LiAlO₂, β-Li₅AlO₄ and Li₄SiO₄. A large number of gaseous lithides were detected during these studies.     

The production of tritium in fission and fusion reactors

Conclusions It follows from the published data on the selection of lithium materials for the breeding zone of a thermonuclear reactor [43–45] that the tritium production involves large-scale radiochemical installations for the conversion of the irradiated material and the extraction of the pure isotope which is present in extreme dilution. When such radiochemical installations are built, a set of basic technological problems must be solved (continuously maintaining the purity of the lithium materials, removing the radiolysis products, stabilization of the physicochemical properties of the material, removing the corrosion products of the materials used for the construction); one must also solve problems related to personnel safety and the protection of the environment from the emission of the radioactive isotope. Problems related to the construction of apparatus for the processes occurring at a high temperature must be solved.When from this viewpoint lithium materials and their irradiation conditions are selected, one must recall that solid lithium materials (ceramics, alloys) and melts of salts have advantages over metallic lithium for the very reason that they eliminate operations involving a flammable material.The use of solid lithium materials or of molten systems as a neutron-absorbing material in the breeding zone of the blanket depends upon the characteristics of the tritium-breeding zone in terms of neutron physics and upon the thermophysical parameters.At the present time nuclear physics research, physicochemical research, and radiochemical research is done on systems with irradiated lithium materials. Methods are developed for separating the tritium which is present in various states at relatively low concentrations. The goal of this work is not only to obtain answers to the technological problems with the greatest reliability but also to effectively select a lithium material suitable for building the tritium cycle of a thermonuclear station as a whole.In the ensuing stage of the research work, when the blanket zone will be drafted, one must evaluate the various conditions of operation of the breeding zone with metallic lithium, diluted fluorine systems, and solid ceramic materials. At the present time, the selection of the blanket design and the construction of the breeding zone, as well as the selection of the lithium material providing the highest tritium production coefficient, are the basic problems among the engineering problems of thermonuclear fusion and the technological and economical aspects of the forthcoming developments.Translated from Atomnaya Énergiya, Vol. 44, No. 5, pp. 440–446, May, 1978.     

冷聚变实验探索

采用电解法和氘气吸附法研究了冷聚变现象。在一次电解实验中,电解开始后约90h,长中子计算器和液体闪烁中子计数器中都同时观察到一个持续时间达4h、峰值强度为400聚变/s的中子讯号。长中子计数器和液体闪烁计数器的计数均比本底高15倍,液体闪烁计数器同时记录了2.45MeV中子的反冲质子能谱。     

Enhancement of cold fusion reaction rates

Although major controversy still remains as to the source of the excess thermal power output reported from diverse successful cold fusion calorimetry experiments, considerable independent evidence does exist that low-level, deuterium fueled, cold fusion reactions can occur based upon reported neutron and tritium measurements. Because the specific fusion power output may be very low in present cold fusion experiments, there are numerous features and conditions associated with cold fusion experiments which might enhance fusion reaction rates.The principal focus of attention in enhancing cold fusion reactions occurring in an electrolytic cell is the palladium cathode where deuterium is preferentially absorbed into the cathode. The cathode's physical, metallurgical, and chemical characteristics such as purity, lattice cell size and orientation, chemical and hydrodynamic properties, and its electrical surface conditions and prevailing reactions are known to be important for maximizing deuterium loading. Even the geometrical size and configuration of the cathode and the crystalline grain size and conditioning are apparently important. The composition, pH, flow of the electrolyte, electrolysis employing rapidly time varying electrical potential and current and very high pressure and low temperature operation may also enhance fusion reaction rates.     

Alternate approach to inertial confinement fusion with low tritium inventories and high power densities

A low-tritium-inventory, high-power-density, pool-type chamber approach to inertial confinement fusion is introduced. The concept uses target designs with internal tritium and³He breeding, eliminating the need for a lithium-breeding blanket. The fraction of the fusion energy carried out by neutrons is estimated as 10%, compared with 70% in a typical D-T system, and the neutron spectrum is softer. Liquid metals other than lithium that are less chemically reactive, such as lead, can be used for first-wall protection. The reduced neutron component and the elimination of the need for a thick lithium blanket for tritium breeding lead to higher power densities and more compact chamber designs. The radiation damage at the first structural wall is reduced, leading to potentially longer wall lifetimes. A significant environmental advantage in terms of reduced radioactive release risks under operational and accident conditions is identified, primarily due to the one to two orders of magnitude reduction in the tritium inventories compared with D-T-based systems.     

Limits of chemical effects on cold fusion

Cold fusion enhanced by chemical confinement of deuterons has been suggested as an explanation of recent reports of the production of neutrons in electrochemically-generated palladium deuterides. To test this suggestion local-density-functional cluster calculations were used to study the coulomb barrier between two deuterons within the octahedral cage in crystalline palladium. The calculated repulsive forces were always greater than the corresponding forces between deuterons in molecular D₂. These results imply that the room temperature fusion rate at this site is negligible.     

Release of tritium from boron carbide irradiated with reactor neutrons

The release of tritium from irradiated boron carbide in a pure Ar atmosphere was investigated between 500 and 900°C. The sintered B₄C samples with densities between 75 and 95% of the theoretical density were irradiated with reactor neutrons with total neutron doses up to 5 × 10²⁰/cm². Effective diffusion coefficients, D_eff, were derived from the release data using the model “diffusion out of a sphere”. D_eff decreases by about 3 orders of magnitude with increasing total neutron dose, levels off at about 10¹⁸n/cm² and increases at very high doses ( > 10²⁰ n/cm²). The decrease in the tritium mobility is attributed to the radiation defects formed in the B₄C. The activation energy of 210 ± 30 kJ/mol for the tritium diffusion in the irradiated B₄C is much higher than the value found for unirradiated material. D_eff depends also very strongly on the density of the sintered material.     

Uncertainty and range of alternatives in estimating tritium emissions from proposed fusion power reactors and their radiological impact

A review of technology assessment studies as well as original research papers is presented in two diagrams with respect to estimating (1) the performance of fusion reactors in containing tritium, and (2) the radiological consequences of normal operational losses as well as accidental releases of tritium. Predictions are shown to vary over several orders of magnitude.This paper is based on a more comprehensive study.²³     

A molecular dynamics study of diamond exposed to tritium bombardment for fusion applications

Diamond, with its low atomic number and high thermal conductivity, is being assessed as a possible plasma facing material within a fusion reactor. Molecular dynamics simulations using the AIREBO potential were performed simulating the exposure of diamond to a plasma in conditions similar to those of the divertor region of a tokamak. Diamond surfaces at temperatures of 300 and 600 K were bombarded with 15 eV tritium at a high flux (10²⁹ ions m⁻² s⁻¹). A layer-by-layer etching process was observed which, with the lack of any tritium diffusion though the remaining diamond structure, was responsible for limiting damage, and thus tritium retention, to the top 4-5 diamond layers. Analysis of this damaged region also showed a large amount of residual structure suggesting that bombardment below the physical sputtering threshold (∼30 eV) may not lead to amorphisation of the surface.     

Interaction of tritium with graphite

Translated from Atomnaya Énergiya, Vol. 64, No. 3, pp. 206–209, March, 1988.     

The preparation of palladium for cold fusion experiments

Techniques have been established to prepare palladium specimens for cold fusion experiments using an ultra-high-vacuum, allmetal, high-temperature furnace to melt palladium metal in high purity alumina molds having a test tube shape. To date 6-mm and 15-mm cylinders have been fabricated, the latter being used to fabricate a sphere 12.5-mm in diameter. Techniques and facilities used for palladium-hydrogen isotope pressure-volume-temperature measurements^1–4 have been used to anneal these palladium specimens after machining and, in some cases, to charge these specimens with deuterium to PdD_0.63 stoichiometry prior to their use in electrochemical cells. The modeling of palladium-hydrogen isotope pressure-composition-temperature curves is described wherein existing data^5,6 is used to derive models that accurately describe the existing data and that extrapolate to high compositions. Experiments for reacting⁶LiD with Pd rods at 700°C to 800°C, in an attempt to precharge⁶Li into the Pd rods, are being prepared.Operated for the U.S. Department of Energy by Martin Marietta Energy Systems, Inc. Under Contract no. DE-AC05-84OR21400.     

Estimates of routine tritium discharges from ETHEL

The European Tritium Handling Experimental Laboratory (ETHEL) at JRC-Ispra is constructed within the ESSOR reactor complex and is therefore required to be consistent with the existing site license agreement. This paper summarizes the status of ETHEL under the Italian licensing legislation and focuses, in particular, on the problem of tritium discharges under routine conditions. First, the available margins for additional tritium releases from the ESSOR complex are established by taking into account the existing operational requirements. The discharge requirements of ETHEL are then estimated by analyzing the various in-plant routes by which tritium may be released to the environment under normal operation conditions. An analysis is also undertaken for assessing the radiological impact on the population due to exposure and ingestion pathways. It is shown that the expected gaseous releases and tritiated aqueous discharges comply comfortably with the existing site limits and the fraction available for ETHEL.     

The efficiency of liquid scintillators in the determination of the tritium concentration of A water sample

Scientific Production Company Monokristallreaktiv. Khar'kov State University. Translated from Atomnaya Énergiya, Vol. 72, No. 4, pp. 405–407, April, 1992.     

金属电极间冷聚变中量子效应分析

分析了金属电极间的冷聚变现象,采用量子力学方法,导出在微观外场作用下反应核的穿透几率以及相应的核聚变截面公式,阐释了在核聚变中也存在共振隧穿现象,并给出了冷聚变实验结果的半定量解释,从而提出了一种新的聚变机理。