Background Levels of the Radiation Parameters of Soil

A method is proposed for determining the background levels of the radiation parameters of soil: exposure dose rate of the sample and the count rate in radiometry of a thick-layered preparation. Comparing an actually detected radiation parameter of a soil sample and the background level of the same parameter makes it possible to establish the presence and degree of radioactive contamination of the soil and to determine the predominant composition ( or emitters) of the radionuclides present in the soil. The method can be used to perform radiation monitoring of land to be used for a particular purpose.     

Methods for preparing ions of short-lived isotopes

Conclusions A source with thermal ionization in a cavity is extremely convenient for obtaining ion beams with an ultralow quantity of the starting material. Its efficiency with ionization potentials of the starting atoms V_i<6 eV is equal to 100% and drops to 1% for V_i=8 eV [7]. This makes it possible to use it in the study or more than two-thirds of the periodic system of elements, including the actinides. Thus for 10¹² uranium and plutonium atoms ^*9% and 50%, respectively; for 10⁶ curium atoms ^*70%; and, for 10⁵ californium atoms ^*37% [13]. It was shown in [14] that this source can be successfully used in mass spectroscopy to analyze trace quantities of different elements in the solid phase. With its help yttrium isotopes with _1/2=0.4 sec were detected in [16].This source is now widely used in our country, where with its help tens of new isotopes have been discovered [15, 17], and abroad (for example, [16]). The source is effective for short-lived isotopes with _i/_1/2<10 and V_i<7 eV. To study isotopes with _i/_1/2<10 and V_i>7 eV but with _i/_1/2>10 it is desirable to develop sources with thermal and photoionization in the cavity. For elements whose atoms have a long residence time on the surface, these sources, just as the gas-discharge sources, are inefficient. Means must be developed for raising the rate of desorption of the indicated atoms from the surface within the framework of the techniques examined here.Translated from Atomnaya Énergiya, Vol. 60, No. 2, pp. 114–119, February, 1986.     

Immobilization of Radionuclides in Irradiated Reactor-Graphite Blocks

The immobilization of radionuclides in samples of GR-280 reactor graphite by the fixative atomik is described. A graphite block extracted from RBMK masonry after 17 years of operation is used for the investigations.The investigations showed that the strength of the fixative samples increases only with irradiation doses above 15000 Mrad. The radiation–chemical yield of gaseous products of radiolysis from samples of the fixative under irradiation in vacuum is 12·10^–10 cm³/(g·rad). , , and -emitting nuclides are leached from the samples of irradiated graphite; this process proceeds continually. When the irradiated graphite samples are permeated with the fixative atomik, no release of radionuclides is observed at 20°C for 2 yr.     

Analysis of the composition of a mixture of249Bk+249Cf on the basis of x rays

Conclusion The results of the study enable us to conclude the following: the decay of²⁴⁹Bk is accompanied by an L series of x rays from the daughter product Cf. The yield of this radiation is low: (L+L+ L) 10^–4 ( disintegration)^–1, but because of the high specific activity of²⁴⁹Bk, 1 g of this isotope emits 3.7·10⁵ x-ray quanta per minute. This enables us to detect a fairly small amount of Bk (0.01 g) on the basis of x rays in a period of 5–10 min. The rapid accumulation of the daughter product²⁴⁹Cf does not interfere with the determination of the²⁴⁹Bk on the basis of x rays. Even when the mixture contains equal numbers of Bk and Cf nuclei, the ratio of the L lines corresponding to them is 0.46. Therefore the composition of a mixture of²⁴⁹Bk+²⁴⁹Cf can be determined on the basis of x rays over broad ranges of variation of the relative concentrations of Bk+Cf, roughly from 0.03 to 80. It is important to note that for relative measurements it is not necessary to prepare special specimens, since x rays with energies of 15–20 keV are not strongly absorbed in the solution and in the walls of the chemical vessel.Translated from Atomnaya Énergiya, Vol. 48, No. 2, pp. 106–108, February, 1980.     

Ignition in a tokamak reactor with INTOR-like parameters

The requirements for ignition in a tokamak reactor with INTOR-like parameters were studied using a one-dimensional transport code. With empirical electron energy diffusivity _e , ignition was obtained with 60–75 MW of neutral beam injection at a volume average pressure ratio =4–5% under a variety of conditions. Changing _e gave ignition at the same if the plasma minor radius varied asa _e ^1/2 . The maximum impurity concentration which allows ignition was found to be comparable to that for the much simpler case of a homogeneous plasma with radiative losses only. In long pulse simulations with efficient helium pumping, the maximum toroidal field ripple which allowed ignition was 2.0% (peak-to-peak) at the plasma edge. Ignition was maintained with over 99% recycling of helium ash using 5% less than maximum ripple.     

Heat transfer in a region of thermal stabilization in the turbulent flow of liquid metals in a tube

In the work described here, local heat-transfer coefficients were determined for turbulent flows of liquid metals (Pr 0.02) in a region of thermal stabilization ( _t equal to 5, 10, 15 d) for Reynolds numbers Re = 10⁴-2·10⁵. The determinations were made by two methods: by the measurement and analysis of temperature profiles in the flow without taking into account the thermal contact resistance, and by directly measuring the temperature changes in the wall, taking into account the thermal contact resistance. Hydrodynamic stabilization of the flow was maintained during the experiments ( _t 30 d).     

The reversed-field-pinch (RFP) fusion neutron source: A conceptual design

The conceptual design of an ohmically heated, reversed-field pinch (RFP) operating at 5-MW/m² steady-state DT fusion neutron wall loading and 124-MW total fusion power is presented. These results are useful in projecting the development of a cost effective, low-input-power (206 MW) source of DT neutrons for large-volume (10 m³), high-fluence (3.4 MW yr/m²) fusion nuclear materials and technology testing.Work supported by U.S. DOE.     

Investigation of the isotopic composition of uranium in rare-earth minerals

The isotopic composition of the uranium of rare-earth minerals (orthite, xenotime, and gadolinite) was investigated for the detection of possible traces of Cm²⁴⁷ in nature,by means of an ionization chamber with a multichannel analyzer of the pulse amplitudes. The results of the measurements are discussed. A method is given for the accurate, calculation of distortions of the spectrum of particles in ionization chambers with electron collimation. It is shown that during the investigation of samples of low intensity (0.2–1 mg of uranium), the relative content of U²³⁵/U²³⁸ isotopes can be measured by an -spectrometric method with an error up to 1%.In conclusion, the authors with to express their thanks to A. P. Komar and V. I. Baranov for the interest they have shown in this work.     

Nuclear fusion from crack-generated particle acceleration

Summary In summary, the high-voltages necessary to accelerate deuterons to energies sufficient to produce modest numbers (10⁴–10⁵/sec) of d-d neutrons appears to be possible as a result of cracking or fracture of the metal lattice in the cold fusion experiments.This mechanism requires neither massive electrons nor exotic nuclear reactions to explain the apparent cold fusion d-d neutron production results. Instead, it is possible that high voltage electrostatic fields, known to be associated with cracking, can reside across a crack gap long enough for the deuterons to be accelerated to sufficiently high energy to produce the d-d reactions. Interestingly, the electrostatic acceleration is quite similar to that of laboratory accelerators except for its submicron scale. Clearly, much work is still required to determine whether such a crack-generated acceleration mechanism, a quasi-particle mechanism, some combination of these, or some other, as yet unidentified mechanism is responsible for the nuclear effects seen in cold fusion experiments.Presented at the Workshop on Cold Fusion Phenomena, Sante Fe, New Mexico, May 23–25, 1989.     

Problem of the iodine method of purification of zirconium

A method is proposed for the determination of the equilibrium constantsk and k' for the reactions Zr+2I₂–ZrI₄=0 and 2I–I₂=0, which is based on the measurement of the amount of iodine or zirconium liberated in the decomposition of zirconium tetraiodide on a heated surface in the process of establishing equilibrium. The decomposition of the tetraiodide was carried out at 900–1600C on a tungsten filament. The temperature distribution between filament and vessel walls was neglected.The dependence of the sum of atomic and molecular iodine pressures on zirconium tetraiodide pressure was determined at 1430C, and on temperature for 50 mm Hg. The values of kk'² 35 (mm Hg)³ at 1430C and k0.07 mm Hg at 400C, found from the results, differ substantially from known thermodynamic data, but give good agreement between the authors' formula [1] and experimental results on the iodide process of zirconium purification.     

Universal apparatus with a Co60 γ-ray source with an activity of 60,000 g-eq of Ra for simulating radiation-chemical apparatus,and investigations (the “K-60,000”)

The article describes a universal apparatus for radiation-chemical investigations with a Co⁶⁰ -ray source possessing an activity of about 60,000 g-eq of Ra. The design of the apparatus makes it possible to simulate radiation-chemical apparatus with powerful isotopic -ray sources of various configurations and dimensions: a cylindrical radiating element, a radiating element in the form of two plates, a radiating element in the form of a heat exchanger, and a radiating element in the form of one or more rods. The dosage rate (without taking into account the attenuation in the protective vessels) varies from250 r/sec in a volume of 36 liters to 3000 r/sec in a volume of 0.1 liter. The apparatus is designed for carrying out radiation-chemical investigations under practically any physicochemical parameters; it ensures the possibility of remote control and observations both of the experimental conditions and the processes taking place in the investigated systems during irradiation.The authors wish to express their thanks to V. I. vainshtein, M. A. Dembrovskii, and N. P. Syrkus, who took part in the discussionof individual problems of the design of the apparatus, and also to A. I. Dombrovskii, V. M. Kasatkin, A. V. Tatov, D. V. Yasinskii, I. A. Gromov, V. G. Ivanov, M. N. Demichev, V. V. Serebryakobaya, N. V. Troinov, and others, who took part in the construction and assembly of the apparatus.     

Measurement of neutron emission from Ti and Pd in pressurized D2 gas and D2O electrolysis cells

Experiments using high-efficiency neutron detectors have detected neutron emission from various forms of Pd and Ti metal in pressurized D₂ gas cells and D₂O electrolysis cells. Four independent neutron detectors based on³He gas tubes were used. Both random neutrons (0.05–0.2 n/s) and time-correlated neutron bursts (10–280 n) of 100-s duration were measured using time-correlation counting techniques. The majority of the neutron burst events occurred at –30°C as the samples were warming up from the liquid nitrogen temperature.     

Resonance scattering of γ-rays in Mg24

Resonance scattering of -rays With energies E₁=1.38 Mev, corresponding to the transition to the ground state in Mg²⁴. have been observed in metallic magnesium. The energy given off by the -ray (E₁=1.38 Mev) in emission and collision with the nucleus, is compensated for by the energy obtained due to recoil associated with the emission of the preceding -ray with an energy E₂ = 2.76 Mev. Using a fast coincidence method and amplitude discrimination, coincidences were recorded between the -rays with energies E₁=1.38 Mev and E₂=2.76 Mev. Scattercrs of magnesium and aluminum were alternately placed in the path of the 1.38 Mev -rays. The source was radioactive Na²⁴ in a water solution of NaOH. At an angle of 120 ° between the -rays a strong attenuatlon of the 1.38 Mev -rays was observed; this is attributed to resonance scattering. When the angle between the -rays was varied by 5 °. the strong attenuation of the flux disappeared. The width of the level at 1.38 Mev in Mg²⁴ has been estimated at > 1.6· in^–4 Mev.     

Slowing down of fission neutrons by water

In this articie we describe the method and results of measurement offor U²³⁵ fission neutrons slowed down by water to energies of 1.46 ev. The value obtained for _{1.46 ev} = 294 ± 1.5 cm² In conclusion, the authors express their sincere gratitude to I. I. Gurevich and D. V. Timoshuk for reviewing the results, to A. P. Venediktov for help in the work, and to G. R. Golbek for lending the -apparatus with low background.     

The distribution of ionization along a beam of γ-radiation and the determination of radiation dose with normal ionization chambers

It was established that the ionization effect, measured in normal ionization chambers for determining the dose in a region of -radiation, must be referred to a point in space, displaced by a distance of about from the center of the measuring electrode of the chamber towards the source. The corrections for displacement of the measuring volume for the -radiation of Cs¹³⁷ and Co⁶⁰, respectively, equal 0.996 and 0.992.     

Investigation of the Effect of Radiation and High-Temperature Treatment on the x-Ray Luminescence of Quartz Glasses

The x-ray luminescence of KI, KV, and KU-1 quartz glasses, irradiated with and n– radiation in the dose range 10²–10⁷ Gy and neutron fluence range 10¹⁵–10¹⁷ cm^–2 and subjected to high-temperature annealing in air at 450 and 900°C is investigated. It is shown that the spectra of the nonirradiated and the and n– irradiated glasses of the first two types are a superposition of bands with _max = 410 and 460 nm, which are due to an impurity center initially present in the glasses (_max = 410 nm) and the initial and radiation-generated with dose 10⁶ Gy and fluence 10¹⁶ cm^–2 E' centers (_max = 460 nm). X-Ray luminescence is not observed in nonirradiated KU-1 glasses; a band with _max = 460–470 nm, due to radiation-generated E' centers, appears in the spectra of and n– irradiated glasses. As the radiation dose and the neutron fluence increase, the number of impurity centers decreases and the number of E' centers increases. It is established that the 410 nm band is due to the component of the n– radiation. High-temperature annealing in air at 900°C induces in the spectra new bands with _max = 470 and 520–540 nm, which are believed to be due to interstitial defects of the type O^– and O₂ ^–, formed when oxygen from air diffuses into the glass and localizes in interstices. 6 figures, 7 references.     

Containment of plasma in a trap with combined magnetic field

The containing properties of an adiabatic trap with a magnetic field increasing in the longitudinal and radial directions are investigated. This field is obtained from a combination of the ordinary mirror field configuration (main field H0) and the field of a system of current-carrying conductors laid parallel to the axis of the trap (stabilizing field H). The conductors are placed uniformly in azimuth around the side walls. The trap is filled with plasma of density n10⁹–10¹⁰ cm^–3 and proton energy T_i5eV (T_e20 eV). The plasma lifetime is measured as a function of H. and the neutral gas pressure. From the results obtained, it is concluded that such combined fields ensure stable containment of the plasma, unbroken by magnetohydrodynamic instabilities [at any rate for = nI/(H²/8) 10^–4]. The stabilization of the instability is confirmed by analysis of the plasma oscillations for various values of H. The disintegration of the plasma is determined by the charge exchange of fast ions in the residual gas; the maximum containment time which can be achieved is 0.06 sec for p = 7.10^–9mmHg. A qualitative picture of the plasma density over the radius of the trap is obtained.Translated from Atomnaya Énergiya, Vol. 17, No. 5, pp. 366–375, November, 1964     

Some characteristics ofγ-ray scattering at the boundary of two media

The characteristics of -ray scattering (0.33 E 1,25 MeV) at the boundary between two media were experimentally investigated. It was established that the scattered radiation was produced mainly by a narrow beam of primary radiation. The effective scattering area was contained within a region with a radius r 10h (for h z). The contribution to the total energy from radiation scattered by the medium increased for angles of incidence of the primary narrow beam up to 85–88 °, and then decreased monotonically.An estimate was made of the effective dimensions of the area from which scattered quanta were emitted into the backward half-space when an isotropie source was located at the surface of the scatterer.The energy flux of the scattered radiation was measured with a gas counter which had a practically constant sensitivity for -rays of different energies.The authors are deeply grateful to Prof. O. I. Leipunskii and to A. S. Strelkov for assistance and for discussions of the results.     

Direct-Drive Implosion Experiments on the SG-II Laser Facility

SG-II, a 8-beam Nd:glass laser with an output energy capability of 6kJ at 1.053m, was built and direct-drive implosions were successfully performed early in 2000. Both exploding pusher and ablative targets were imploded using glass capsules with diameters of 200 and 500m, and a wall thickness of about 1m. The deuterium and tritium (DT) gas pressure filled in these capsules were 2.0 and 0.5MPa, respectively. Sophisticated diagnostics were deployed to measure laser absorption, hot electron temperature and fraction, thermal electron temperature, neutron yields, ion temperature, temporally resolved x-ray images, fuel areal density, alpha particle image, and so on. Significant results, such as neutron yields up to 4 × 10⁹ for exploding pushers with 100-ps laser pulse irradiation and 6 × 10⁸ for ablative targets with 1-ns pulses and clear x-ray images to see the compression process, were obtained. Numerical simulations were conducted to optimize target and laser parameter design and to duplicate the results afterwards with the specific shot parameters used in the experiment.     

Pulse method of measuring neutron age in graphite

Using a pulse source located within a prism, the age of thermal neutrons from the reactions D-D and D-T in graphite was measured. From the time dependence of the thermal neutron density the author calculated the effective age of D-D neutrons _eff = 355 ± 9 cm², recalculated for a graphite density equal to 1.6 g/cm³.The slowing down of D-T neutrons in graphite can be approximately expressed with the aid of two neutron groups: neutrons suffering but one inelastic collision when slowed down (_eff =600 cm²), and neutrons suffering several inelastic collisions (_eff = 240 cm²). In determining the age the relative contributions of both groups were assumed equal to 0.65 and 0.25, respectively. A third group is composed of neutrons slowed down only by means of elastic collisions. These neutrons may be neglected in the first approximation, since their contribution is small (about 0.1), while the increase is large.This work was carried out at the P. N. Lebedev Physics Institute of the Academy of Sciences of the USSR.In conclusion, the author expresses his gratitude to Corresponding Member of the Acad. of Sei. of the USSR I. M. Frank for suggesting the research topic, for his steadfast interest in the work, and for valuable remarks during the course of discussion.