Some comments on energy and particle confinement in advanced fuel EBT reactors

Results of a point model calculation for advanced fuel (cat. D and D³He) EBT reactors are used to determine some of the limitations on the ratio of ion particle to energy confinement time. The greater fraction of charged fusion products produced in the advanced fuel reactions and the greater fraction of their energy radiated cause the effect of on ash buildup to be a factor of 4 greater for the advanced fuels than that of DT fuel. Hence it is found that<5 for steady state ignited advanced fuel EBT reactors, whereas 22 is the restriction for DT fueled EBT reactors. A survey of for neoclassical bumpy torus ions reveals that in the plateau regime,<5 appears possible but is critically dependent on the nature of the electric field.     

Graphite-moderated,gas-cooled,and water-moderated,water-cooled reactors as power units in nuclearelectric power stations

The present article reviews a number of papers submitted at the Second International Conference on the Peaceful Uses of Atomic Energy bearing on water-cooled, water-moderated, graphite-moderated, and gas-cooled reactors abroad.The basic characteristics of all of the operational power reactors, as well as of the high-power, graphite-gas water-cooled, and water-moderated reactors built abroad are cited in the article.Differences in the pathways and means of development of nuclear power in different countries are given due acknowledgement. In Britain, for example, after the first generation reactors (Calder Hall type) were built, advanced second generation reactors (Hinkley Point, etc.) were introduced, and intensive studies are now underway on third generation reactors. The ultimate purpose of the research in progress is the development of a high- temperature reactor operating in a unit with the associated gas turbine. A transition in the USA from the classical pressurized-water reactor concept (PWR) to that of the boiling water reactor with direct steam feed to the turbine is planned.The continuous improvement in the efficiency of graphite-moderated, gas-cooled reactors and water-cooled, water-moderated reactors and the reduction in capital costs per unit rated power and in cost of power developed is shown.     

Study of the zirconium apex op the Zr-Ta-Nb phase diagram

Metallographical examination thermal analysis and electrical resistance measurements have been applied to a study of the zirconium apex, up to 82% zirconium and a temperature of 1200C, of the ternary system Zr-Ta-Nb, with limited solubility of tantalum and niobium in -zirconium ( phase), limited solubility and complete solubility of niobium in -zirconium, with eutectoid decomposition of the \ solid solution and three-phase eutectoid equilibrium + between - and-zirconium. In the investigated portion of the Zr-Ta-Nb phase diagram, the following phase regions were found: a) two one-phase regions and ; b) three two-phase regions + , + and + : c) one three-phase region + + ; the region contracts as the temperature falls below 1200 C.The solubility of tantalum and niobium in -zirconium in the system Zr—Ta—Nb is about 0.5%. On passing from Zr—Ta to Zr—Nb, the + and + regions are displaced toward lower temperature and high niobium concentrations; the boundaries of the + and + + regions are lowered from 790 for Zr—Ta to 612 C for Zr-Nb. Passing between the + and + regions is a binary eutectoid line which, from Zr-Ta to Zr-Nb is displaced toward lower temperatures and higher niobium concentrations. The solubility of niobium in ot zirconium in the Zr-Nb system is about 0.5%by weight. Eutectoid decomposition in the Zr-Ta system shifts the maximum of the martensitic-like transformation to the left and results in an increase in the stability of the phase at room temperature in quenched alloys.     

Radiation Conditions during Decontamination of an Experimental Facility for Reprocessing Nuclear Fuel

The basic characteristics of the changes occuring in the radiation conditions in an experimental facility for reprocessing spent nuclear fuel during decontamination of the facility after reprocessing irradiated uranium and uranium–plutonium BOR-60 reactor fuel and plutonium tetrafluoride into dioxide by the pyroelectrochemical method are examined. An expression is obtained experimentally for calculating the decrease in the power of photon radiation from contaminated surfaces as a function of the number of decontamination cycles. It is shown that for one-time processing of the surfaces of stainless steel equipment by the two-bath method the decontamination coefficient varies over the range 2.5–25 for emitters and 5–30 for and , emitters.     

D-T experiments on TFTR

Temperatures, densities and confinement of deuterium plasmas confined in tokamaks have been achieved within the last decade that are approaching those required for a D-T reactor. As a result, the unique phenomena present in a D-T reactor plasma (D-T plasma confinement, alpha confinement, alpha heating and possible alpha driven instabilities) can now be studied in the laboratory. Recent experiments on the Tokamak Fusion Test Reactor (TFTR) have been the first magnetic fusion experiments to study plasmas with reactor fuel concentrations of tritium. The injection of 20 MW of tritium and 14 MW of deuterium neutral beams into the TFTR produced a plasma with a T/D density ratio of 1 and yielded a maximum fusion power of 9.2 MW. The fusion power density in the core of the plasma was 1.8 MW m^–3 approximating that expected in a D-T fusion reactor. In other experiments TFTR has produced 6.4 MJ of fusion energy in one pulse satisfying the original 1976 goal of producing 1 to 10 MJ of fusion energy per pulse. A TFTR plasma with T/D density ratio of 1 was found to have 20% higher energy confinement time than a comparable D plasma, indicating a confinement scaling with average ion mass, A, of _E. The core ion temperature increased from 30 keV to 37 keV due to a 35% improvement of ion thermal conductivity. Using the electron thermal conductivity from a comparable deuterium plasma, about 50% of the electron temperature increase from 9 keV to 10.6 keV can be attributed to electron heating by the alpha particles. At fusion power levels of 7.5 MW, fluctuations at the Toroidal Alfvén Eigenmode frequency were observed by the fluctuation diagnostics. However, no additional alpha loss due to the fluctuations was observed. These D-T experiments will continue over a broader range of parameters and higher power levels.Work supported by U.S. Department of Energy Contract No. DE-AC02-76-CHO-3073.     

Ion beam propagation and focusing

Inertial confinement fusion with ion beams requires the efficient delivery of high energy (1 MJ), high power (100 TW) ion beams to a small fusion target. The propagation and focusing of such beams is the subject of this paper. Fundamental constraints on ion beam propagation and focusing are discussed, and ion beam propagation modes are categorized. For light ion fusion (LIF), large currents (2–33 MA) of moderate energy (3–50 MeV) ions of low atomic number (1A12) must be directed to a target of radius 1 cm. The development of pulsed power ion diodes for LIF is discussed, and the necessity for virtually complete charge neutralization during transport and focusing is emphasized. Fornear-term LIF experiments, the goal is to produce pellet ignition without the standoff needed for the ultimate reactor application. Ion diodes for use on Sandia National Laboratories Particle Beam Fusion Accelerators PBFA-I (2–4 MV, 1 MJ, 30 TW, operational) and PBFA-II (2–16 MV, 3.5 MJ, 100 TW, scheduled for operation in 1985) are discussed. Ion beam transport from these diodes to the pellet is examined in reference to the power brightness . While values of =2–5 TW/cm²/sr have been achieved to date, a value of 100 TW/cm²/sr is needed for breakeven. Research is now directed toward increasing , and means already exist (e.g., scaling to higher voltages, enhanced ion diode current densities, and bunching), which indicate that the required goal should be attainable. Forfar-term LIF applications, the goal is to produce net energy gain with standoff suitable for a reactor. This may be achieved by ion beam transport in preformed, current-carrying plasma channels. Channel transport research is discussed, including experiments with wire-initiated, wall-initiated, and laser-initiated discharge channels, all of which have demonstrated transport with high efficiency (50–100%). Alternate approaches to LIF are also discussed, including comoving electron beam schemes and a neutralized beam scheme. For heavy ion fusion (HIF), moderate currents (10 kA) of high energy (10 GeV) ions of high atomic number (A200) must be directed to a target of radius 0.3 cm. Conventional accelerator drivers for HIF are noted. For a baseline HIF reactor system, the optimum transport mode for low charge state beams is ballistic transport in near vacuum (10^–4–10^–3 Torr lithium), although a host of other possibilities exists. Development of transport modes suitable for higher charge state HIF beams may ultimately result in more economical HIF accelerator schemes. Alternate approaches to HIF are also discussed which involve collective effects accelerators. The status of the various ion beam transport and focusing modes for LIF and HIF are summarized, and the directions of future research are indicated.     

Alternating-gradient focusing in linear accelerators

A linear theory for alternating-gradient (strong) focusing in linear ion accelerators is presented.Presented at the All-Union Conference on the Physics of High Energy Particles, May 18, 1956.     

Monitoring the radiation conditions in reactors by semiconductor spectrometry methods

Conclusions 1. Semiconductor spectrometry of the radiation facilitates the analysis of the radiation conditions in nuclear reactors for power generation and research:identification of the radiation sources (radionuclides, nuclear reactions); andquantitative determination of the intensity of the radiation from the identified radionuclides and from nuclear reactions in units of H.2. The information makes it possible to determine the origin of the radioactive contamination by man-made radionuclides on industrial sites and the degree of radionuclide migration and allows a comparison of the radiation conditions on inspected objects.3. The total H values of the monoenergetic radiation do not exceed 25% of the maximum admissible amounts in the reactor halls inspected [4].Translated from Atomnaya Energiya, Vol. 68, No. 5, pp. 385–386, May, 1990.     

The measurement of the resonance absorption of neutrons in an atomic power station reactor

One of the most important quantities determining the possibility of the development of a nuclear chain reaction in the system uranium-moderator is 1- — the probability of the resonance absorption of neutrons by U²³⁸ in the process of their slowing down from the fission to thermal energies. Up to the present time the calculation of 1- for heterogeneous reactors is not sufficiently accurate; there arises, in this connection, the necessity for an experimental determination of 1- directly in the reactor lattice. In this paper the experimental methods for the determination of the resonance absorption are discussed. Various corrections are considered, taking into account the neutron loss, the fission of the uranium and the neutron capture in the resonance region. For an atomic power station reactor employing enriched uranium (5% U²³⁵) these corrections are found to be significant. Three methods are used to calculate — the resonance escape probability — for an atomic power station reactor. was found to be equal to 0.900±0.015.The authors consider it necessary to express their gratitude to Dr. A.K. Krasin for the continual interest in the work, for valuable advice and help, to M.E. Minashin for valuable comments, and also to the collective of the atomic power station associates, who created the necessary conditions for the work.     

Reactivity Behavior During RBMK Startup

During startup of an RBMK reactor, the reactivity varies from –(4–7)_eff to 0–0.1_eff. Positive reactivity is introduced locally – by extracting control rods. Since the physical dimensions of an RBMK reactor are large, a local change in the properties can produce a large change in the spatial distribution of the neutron flux in the core. The possible range of variation of the reactivity of a subcritical and a critical reactor with one control rod extracted is analyzed for the actual states of the power-generating units of a nuclear power plant with RBMK reactors. It is shown that the extraction of some rods in an RBMK reactor in subcritical and critical states can increase the reactivity by 1_eff or more.     

Experimental results of the erosion of molybdenum due to blistering by He+ bombardment

We report some preliminary measurement of the erosion rate of plasma dumps when bombarded with 100 keV He⁺ ions at high power density ( 1 MW/m²). The expected erosion rates, based on measurements of He blistering that were made at lower power density ( 0.3 MW/m²), indicate a potentially serious problem for fusion reactors. Our tests use a reactorlike power density and produce He blisters at a rate that is slower than predicted by 2 to 4 orders of magnitude, depending on the temperature of the molybdenum target.     

Distribution of the ratio of radiation capture and fission cross sections for Pu239 with respect to height in the BR-5 reactor

A study was made of the distribution of the ratio of radiation capture and fission cross sections for Pu²³⁹ with respect to height in the BR-5 reactor. The distribution of neutron capture reactions was measured by determining the concentration of Pu²⁴⁰ from the rate of spontaneous fissions in plutonium samples irradiated in the reactor with an integral flux of 10²¹ to 10²² neutrons/cm². As initial material for irradiation, almost isotopically pure Pu²³⁹ (Pu²⁴⁰ content 5·10^–3% was used. The values of obtained rose from 0.1 to 0.8 on moving away from the center of the reactor. The data corresponding to equilibrium neutron spectra in the active zone and the outer region of the reflector agree with the results of measuring and _f in monoenergetic neutrons.Translated from Atomnaya Énergiya, Vol. 16, No. 6, pp. 497–500, June, 1964     

Thin-foil electrochemical cells: High-sensitivity fusion tests andin-situ ion beam measurements of deuterium loading

Electrochemical cells constructed with a thin Pd or Ti foil electrode mounted at one wall of the cell have been used both to test for the existence of cold fusion and to measure directly DPd loading ratios in an operating cell. The first type of experiment used a surface-barrier particle detector positioned a few millimeters from the foil to provide a very sensitive monitor for possible fusion-generated protons at 3.02 MeV. The detection limit for this arrangement is estimated to be 10^–24 fusions/deuterium/s, assuming a bulk fusion effect. These experiments included cells with 5- and 25-m-thick Pd foils, 10-m Ti foils, parallel experiments with 0.1M LiOD (heavy water) in one cell and LiOH (light water) in another, current densities up to 0.5 A/cm², and run times as long as 22 days. No evidence for fusion products was seen. The second type of experiment using these cells, both as an adjunct to the fusion tests and to provide new information, was the use of external beam nuclear reaction analysis to monitor directly the loading and unloading of deuterium in the foil of an operating cell. Using a 1.5-MeV³He ion beam in air, the deuterium in the outer 2 m of the exposed Pd foil was measured for the first time using the D(³He,p) nuclear reaction. The maximum DPd ratios observed using this technique were 0.8–0.9.     

The fusion-supported decentralized nuclear energy system

A decentralized nuclear energy system is proposed comprising mass-produced pressurized water reactors in the size range 10 to 300 MW (thermal), to be used for the production of process heat, space heat, and electricity in applications where petroleum and natural gas are presently used. Special attention is given to maximizing the refueling interval with no interim batch shuffling in order to minimize fuel transport, reactor downtime, and opportunity for fissile diversion. The smallest reactors could be deployed as nuclear batteries, kept in the equivalent of spent-fuel shipping casks and returned to nuclear fuel centers for refueling. These objectives demand a substantial fissile enrichment (7 to 15%). The preferred fissile fuel is U-233, which offers an order of magnitude savings in ore requirements (compared with U-235 fuel), and whose higher conversion ratio in thermal reactors serves to extend the period of useful reactivity and relieve demand on the fissile breeding plants (compared with Pu-239 fuel). Application of the neutral-beam-driven tokamak fusion-neutron source to a U-233 breeding pilot plant is examined. This scheme can be extended in part to a decentralized fusion energy system, wherein remotely located large fusion reactors supply excess tritium to a distributed system of relatively smallnonbreeding D-T reactors.     

An investigation of γ-emission associated with thermal neutron capture

A number of spectra of -rays from the (n, ) reaction brought about by irradiation by thermal neutrons were investigated with the use of a magnetic Compton spectrometer at the VVR reactor of AN SSSR. The conditions of the experiment are described, as well as the results of measurements made on the -spectra of tin and antimony.In conclusion, we wish to thank A. S. Volkov for constructing the electronic apparatus and providing for its stable operation; also, we thank the maintenance organization of VVR AN SSSR.     

Angle-energy distribution ofγ radiation scattered in water and iron

In this paper we investigate the detailed characteristics of multiple scattering of rays, in particular the angle-energy distribution, a knowledge of which allows us to calculate the attenuation of radiation in complex geometries. Measurements have been made of the angle-energy distribution of rays from a Co⁶⁰ source in water and iron for a semiinfinite geometry and it has been established that these distributions have a maximum close to the energy corresponding to single scattering at the minimum angle. It is shown that the angular distributions are exponential and that the exponential factor is a linear function of the atomic number of the medium. The energy distributions are compared with calculations carried out by Goldstein and Wilkins [1].In conclusion the author wishes to thank I. I. Bondarenko and V. I. Kukhtevich and S. G. Tsypin for discussion of the present work; the author is also indebted to A. N. Voloshin and V. I. Popov for help in carrying out the experiments.     

Spatiotemporal Energy Distribution in a Pulsed Coupled Reactor System

The basic characteristics of nonstationary neutron transport in a subcritical component of a coupled pulsed reactor system are studied. The investigations are performed on the reactor-laser setup of stand B. The existence of a phenomenon which is unusual for nuclear reactors – a spherical wave of fission – in the subcritical assembly is confirmed experimentally. The basic characteristics of this wave are determined experimentally and confirmed computationally for a three-core pulsed reactor–laser system.     

Circulation loop of a nuclear reactor as a source of radiation,particularly for radiation chemistry

At the present time it is necessary to solve the problems concerned with the use of powerful radiation fluxes from nuclear reactors for irradiation in various scientific and technological fields, and, in particular, for carrying out radiation-chemical processes. In this work we discuss some of the aspects of employing a reactor for these purposes. We examine a circulation loop which transfers -radiation from a reactor to a radiation apparatus for those cases where the activated material forms one radioisotope, without radioactive daughters. The theory is reduced to working formulas and graphs which make it possible to calculate the strength of the -radiation emitted in the apparatus and to choose the parameters which would ensure the most effective use of the loop.     

Activation γ-Spectrometric Method of Determining the Mass of Samples of Nuclear Materials

The possibility of using activation -spectrometry to determine the mass content of nuclear materials in matter is investigated. Irradiation of samples for a short time with moderated neutrons from a ~10⁷ sec^–1 Pu–Be source is used to induce 1436 keV -ray emission from ¹³⁸Cs. These -rays are suitable for measurements; the mass of the nuclear materials is determined from the intensity of the radiation. Three series of experiments are performed with sets of samples consisting of uranium and uranium dioxide with different mass and degrees of enrichment.Experiments showed that the error in determining the mass of uranium samples can reach 1–3% with 30–60 min irradiation and the same measurement duration.Special experiments were performed to investigate the influence of the experimental geometry and the self-absorption of the rays in the sample, which limit the possibility of -spectrometric measurements on samples of nuclear materials.The activation -spectrometric method can be used for analyzing metallic uranium samples, powder samples, samples of fuel micropellets and uranium hexafluoride, and plutonium samples.     

3D Wave Propagation and an Ultra–Low-Frequency Instability in Magnetopause

A model set of equations for the low-frequency electromagnetic perturbations in a magnetized nonuniform plasma is presented. A more convenient and systematic procedure is suggested to treat the fluid equations in order to deduce electrostatic and electromagnetic limits. A general dispersion relation is derived for the waves propagating in 3D under local approximation in nonuniform plasmas, which includes almost all the known modes of cold ion magnetized plasmas in the limit < _i (where _i is the ion cyclotron frequency). Both the limits 1 and O(1) have been discussed briefly. The shear Alfvén waves and electromagnetic ion acoustic waves near ultra low frequency (ULF) range are found unstable in the high plasma of magnetopause. The results are in complete agreement with the satellite observations.