Equilibrium of a toroidal pinch in a magnetic field

We obtain the equilibrium conditions for an axially symmetric toroidal pinch by expanding in powers of a/R (a and R are the minor and major radii of the toms) without specifying the distribution of current or longitudinal magnetic field over the cross section of the pinch. The only assumption is that the pinch exhibits cylindrical symmetry in the zeroth approximation (R = 8).We present relations for the displacement of a pinch in a conducting chamber that are correct to second order, i.e., terms of order b²/R² are taken into account, whereb is the chamber radius.Translated from Atomnaya Énergiya, Vol. 13, No. 6, pp. 521–529, December, 1962.     

Passage of a plasma burst through a magnetic mirror machine

A study has been made of the behavior of plasma bursts as they move along the axes of an Ogrenok magnetic mirror machine, The bnrsts were accelerated by a coaxial ptasma injector. For the parameters chosen, the main plasma current was injected in the form of two bursts with velocities of 10⁷ and 2·10⁵ cm/sec, In passing through the first magnetic mirror, both bursts were broken up into streams. This occurred to a larger extent in the burst with the lower velocity. The first burst passed through 380 cm of machine in a time of the order of 90 sec. The luminescence from the streams in the machine lasted 700 sec.Translated from Atomnaya Énergiya, Vol. 14, No. 4, pp. 354–358, April, 1963     

Design of a fuel element for a lead-cooled fast reactor

The options of a lead-cooled fast reactor (LFR) of the fourth generation (GEN-IV) reactor with the electric power of 600 MW are investigated in the ELSY Project. The fuel selection, design and optimization are important steps of the project. Three types of fuel are considered as candidates: highly enriched Pu-U mixed oxide (MOX) fuel for the first core, the MOX containing between 2.5% and 5.0% of the minor actinides (MA) for next core and Pu-U-MA nitride fuel as an advanced option. Reference fuel rods with claddings made of T91 ferrite-martensitic steel and two alternative fuel assembly designs (one uses a closed hexagonal wrapper and the other is an open square variant without wrapper) have been assessed. This study focuses on the core variant with the closed hexagonal fuel assemblies. Based on the neutronic parameters provided by Monte-Carlo modeling with MCNP5 and ALEPH codes, simulations have been carried out to assess the long-term thermal-mechanical behaviour of the hottest fuel rods. A modified version of the fuel performance code FEMAXI-SCK-1, adapted for fast neutron spectrum, new fuels, cladding materials and coolant, was utilized for these calculations. The obtained results show that the fuel rods can withstand more than four effective full power years under the normal operation conditions without pellet-cladding mechanical interaction (PCMI). In a variant with solid fuel pellets, a mild PCMI can appear during the fifth year, however, it remains at an acceptable level up to the end of operation when the peak fuel pellet burnup ∼80 MW d kg⁻¹ of heavy metal (HM) and the maximum clad damage of about 82 displacements per atom (dpa) are reached. Annular pellets permit to delay PCMI for about 1 year. Based on the results of this simulation, further steps are envisioned for the optimization of the fuel rod design, aiming at achieving the fuel burnup of 100 MW d kg⁻¹ of HM.     

Ignition of a Deuterium Micro-Detonation with a Gigavolt Super Marx Generator

The Centurion–Halite experiment demonstrated the feasibility of igniting a deuterium–tritium micro-explosion with an energy of not more than a few megajoule, and the Mike test, the feasibility of a pure deuterium explosion with an energy of more than 10⁶ MJ. In both cases the ignition energy was supplied by a fission bomb explosive. While an energy of a few megajoule, to be released in the time required of less than 10⁻⁹ s, can be supplied by lasers and intense particle beams, this is not enough to ignite a pure deuterium explosion. Because the deuterium–tritium reaction depends on the availability of lithium, the non-fission ignition of a pure deuterium fusion reaction would be highly desirable. It is shown that this goal can conceivably be reached with a “Super Marx Generator”, where a large number of “ordinary” Marx generators charge (magnetically insulated) fast high voltage capacitors of a second stage Marx generator, called a “Super Marx Generator”, ultimately reaching gigavolt potentials with an energy output in excess of 100 MJ. An intense 10⁷ Ampere-GeV proton beam drawn from a “Super Marx Generator” can ignite a deuterium thermonuclear detonation wave in a compressed deuterium cylinder, where the strong magnetic field of the proton beam entraps the charged fusion reaction products inside the cylinder. In solving the stand-off problem, the stiffness of a GeV proton beam permits to place the deuterium target at a comparatively large distance from the wall of a cavity confining the deuterium micro-explosion.

Effect of a transverse magnetic field on a toroidal discharge in a strong longitudinal magnetic field

The effect of a transverse magnetic field on a toroidal discharge in a strong longitudinal magnetic field was studied. It was found that, for a definite value of the pinch displacement caused by the 1/c [I,B], force, the oscillations on the oscillograms of the electrical characteristics of the discharge had minimum amplitude, while the mean plasma conductivity reached a maximum. It was shown that the effect of the transverse component of the magnetic field could, in general, be explained from the concept of the equilibrium of the plasma pinch inside the conducting sheath.Translated from Atomnaya Énergiya, Vol. 17, No. 3, pp. 177–184, September, 1964.     

Use of a subminiature storage ring in a weak-current regime

The use of a subminiature electron storage ring in the weak-current regime (I _b = 0.02 mA) as a source of coherent mm-range synchrotron radiation and a laboratory facility for studying electron scattering in a bunch is studied. The weak-current regime considerably simplifies the construction of a magnetic system and decreases the likelihood of the development of bunch instabilities. To make a more accurate assessment of some basic parameters of a subminiature storage ring, a calculation of the effective accelerating voltage was performed taking account of the transit factor of the rf-system cavity.     

Longitudinal instability of a continuous beam in a proton synchrotron

The results of a calculation of the threshold for longitudinal coherent instability of a continuous beam circulating in a proton synchrotron and constant energy are presented. A beam in an intermediate state — not bunched into bunches but not uniform over the azimuth — is said to be continuous. Such a beam moves outside (possibly, near) empty rf separatrices of the longitudinal sinusoidal electric field and has a ribbon portrait in the longitudinal phase plane. The computational method is used for the U-70 synchrotron at the Institute of High Energy Physics, where in the course of stochastic slow extraction of a circulating beam is continuous in the sense indicated. It bends around empty separatrices of the 200-MHz accelerating field and for several seconds interacts with the electromagnetic fields of the working oscillations of the disconnected resonators of the main accelerating system with frequency 5.5–6 MHz, which can result in a loss of longitudinal stability. __________ Translated from Atomnaya énergiya, Vol. 104, No. 1, pp. 26–33, January, 2008.     

A study of life prediction differences for a nickel-base Alloy 690 using a threshold and a non-threshold model

In this paper we compare and contrast the crack growth rate of a nickel-base superalloy (Alloy 690) in the Pressurized Water Reactor (PWR) environment. Over the last few years, a preponderance of test data has been gathered on both Alloy 690 thick plate and Alloy 690 tubing. The original model, essentially based on a small data set for thick plate, compensated for temperature, load ratio and stress-intensity range but did not compensate for the fatigue threshold of the material. As additional test data on both plate and tube product became available the model was gradually revised to account for threshold properties. Both the original and revised models generated acceptable results for data that were above 1 × 10⁻¹¹ m/s. However, the test data at the lower growth rates were over-predicted by the non-threshold model. Since the original model did not take the fatigue threshold into account, this model predicted no operating stress below which the material would effectively undergo fatigue crack growth. Because of an over-prediction of the growth rate below 1 × 10⁻¹¹ m/s, due to a combination of low stress, small crack size and long rise-time, the model in general leads to an under-prediction of the total available life of the components.     

Simulation of the Radioactive Contamination of a Bukhta after a Radiation Accident

A mathematical model is developed for transport of radionuclides in the system consisting of water–hot particles in bottom deposits–particles of bottom deposits. This model is used to study the consequences of the radiation accident in bukhta Chazhma in 1985. The escape of ⁶⁰Co into the bukhta water from bottom deposits is estimated. Although the fraction of ⁶⁰Co escaping is small (about 10^–5), estimates show that its concentration in water can reach hundreds Bq/m³. The time dependence of the ⁶⁰Co concentration in the upper layer of bottom deposits is estimated.     

Application of a local approach to ductile-brittle transition in a low-alloyed steel

Both tensile tests on notched specimens and fracture mechanics experiments on axisymmetrically cracked specimens were performed on one heat of A508 steel (AFNOR: 16MND5). Tensile tests on notched geometries were made to determine the characteristic parameters used in a statistical analysis of cleavage fracture proposed previously [1]. Tests on cracked specimens were carried out between −80°C and −20°C to investigate the critical values of stable crack growth, Δa_c, occurring before unstable cleavage fracture. At a given temperature a large scatter in the values of critical crack growth, Δa_c, was observed.To interpret these results a model derived previously for cleavage crack initiation [1] is used. In this model the Weibull stress is calculated by the finite element method for three different initial crack lengths covering stable growth increments observed experimentally. It is shown that this model accounts reasonably well for the observed effects.     

Gravitational flow of a thin film of liquid metal in a strong magnetic field

The influence of a poloidal magnetic field of the spherical Tokamak on super thin (h ≈ 0.1 mm) film flow of liquid metal driven by gravity over the surface of the cooled divertor plate is addressed. The experimental setup developed at the Institute of Physics, University of Latvia (IPUL) is described, which makes it possible to drive and visualize such liquid metal flows in the solenoid of the superconducting magnet “Magdalena”. As applied to the above setup, the magnetic field effect on the operation of the capillary system of liquid metal flow distribution (CSFD) is evaluated by using molten metal (lithium or eutectic InGaSn alloy) with a very small linear flowrate q ≤ 1 mm²/s, spread uniformly across the substrate. The magnetic field effect on the main parameters of the fully developed film flow is estimated for the above-mentioned liquid metals.An approximation technique has been proposed to calculate the development of the gravitational film flow. A non-linear differential second order equation has been derived, which describes the variation of the film flow thickness over the substrate length versus the flowrate q, magnetic field B and the substrate sloping α.Results of InGaSn film flow observations in a strong (B = 4 T) poloidal magnetic field are presented. Analysis of the video records evidences of experimental realization of a stable stationary film flow at width-uniform supply of InGaSn.     

Numerical modeling of focusing of heavy-ion beams on a target in a reactor

Institute of Theoretical and Experimental Physics, Moscow. Translated from Atomnaya Énergiya, Vol. 72, No. 3, pp. 266–272, March, 1992.     

Diffusion coefficient of Xe-133 in a SIMFUEL with a low burnup

Post irradiation annealing tests were performed to obtain the Xe-133 diffusion coefficients in a SIMFUEL which was a simulated irradiated UO₂ fuel with a burnup of 27,300 MWd/t U. Specimens were fabricated as cubic polycrystals with the same composition for a given burnup. Each 300 mg specimen was irradiated in the HANARO research reactor for up to a 0.1 MWd/t U burnup. Post irradiation annealing tests were carried out at 1400 °C, 1500 °C and 1600 °C. The xenon diffusion coefficients for the SIMFUEL were lower than those for UO₂ in near stoichiometric UO₂ due to a relatively higher concentration of the tri-valent additives, which is related to the concentration of a cation vacancy. The activation energy in the SIMFUEL was also lower than that in UO₂ due to the lower formation energy of a cation vacancy and the migration energy. The xenon diffusion coefficient for the SIMFUEL increased with an increasing oxygen potential of the ambient gas.     

A thermal-fluid assessment of a cooled-vessel concept for a VHTR

Flow distribution and thermal analyses of a conceptual design of a cooled vessel for a very high temperature reactor (VHTR), which has a forced vessel cooling with an internal coolant path through a permanent side reflector, have been performed. A computational fluid dynamics (CFD) code was employed to investigate flow distributions at inlet and upper plenums of the proposed cooled-vessel concept. Thermal-fluid analyses of the cooled vessel during a normal operation were carried out by using the CFD code with the boundary conditions provided by the GAMMA system analysis code. The transient analyses during postulated accidents were conducted by the GAMMA code itself. According to the results, the flow deviation at the riser holes due to a change of the inlet flow path to the core inlet is about ±20% which results in about a 3-7% core flow deviation from the average value depending on the upper plenum height. The pressure drops in the inlet and upper plenums are estimated to be from 13 to 25 kPa with a change of the upper plenum height. A cooling flow of more than 4 kg/s is sufficient to maintain the RPV temperature within the required limit during a normal operation. Transient analysis reveals that the reactor vessel is exposed to a temperature above its limit of 371 °C but this duration is shorter than the allowable time for a creep region with a sufficient safety margin. The results suggest that the cooled-vessel concept considered in this paper has the potential to be used for a VHTR but further and more detailed studies are required to realize the proposed concept.     

The structure of turbulent flow through a wall subchannel of a rod bundle

An experimental investigation was performed to establish reliable information on the transport properties of turbulent flow through subchannels of rod bundles. Detailed data were measured of the distributions of the time-mean velocity, the turbulence intensities in all directions and hence, the kinetic energy of turbulence, of the shear stresses in the directions normal and parallel to the walls and of the wall shear stresses for a wall subchannel of a rod bundle of four parallel rods. The pitch to diameter ratio of the rods equal to the wall to diameter ratio was 1.07, the Reynolds number of this investigation was Re = 8.7 × 10⁴.On the basis of the data measured the eddy viscosities in the directions normal and parallel to the walls were calculated. Thus, detailed data of the eddy viscosities in direction parallel to the walls in rod bundles were obtained for the first time. The experimental results were compared with predictions by the VELASCO code. There are considerable differences between calculated and measured data of the time-mean velocity and the wall shear stresses. Attempts to adjust the VELASCO code against the measurements were not successful. The reasons of the discrepancies are discussed.     

Damage of a candidate CTR material in a high energy fluence deuterium plasma

We have systematically exposed candidate CTR materials to a dense, hot deuterium plasma which approximates the energy and particle fluences expected to bombard the first wall in a contemplated CTR tokamak power reactor. The shock tube produced plasma is characterized by n ~ 10¹⁶ particles · cm^?3, T_ion ~ 600 eV, T_electron ~ 30 eV. Microstructural damage and resulting changes in tensile properties are reported in this paper for Nimonic PE-16, designated as the first wall and structural material for a tokamak power reactor. It is found that the damage sustained includes localized incipient melting; sputter erosion and cracking of grain boundaries; and a high density of deuterium pressurized blisters. Some of the damage is found to penetrate on the order of one grain diameter into the bulk of the material. A significant decrease in tensile ductility is also found to occur, indicative of hydrogen embrittlement.     

On features of the radiation from an electron moving along a helix inside a cylindrical hole in a homogeneous dielectric

The radiation from a charge moving along a helical trajectory inside a cylindrical hole in homogeneous dielectric medium is investigated. Prompted by availability of materials with large dielectric permittivity ε and small absorption, we discuss the features of this type of radiation for media with ε?1. It is shown that there are high peaks in the angular distribution of radiation intensity at well-defined harmonics. The conditions are specified for the cavity-to-helix radii ratio, ρ₁/ρ₀, under which the angle-integrated radiation intensity on some harmonics exceeds that in the empty space. Though the amplification of radiation intensity increases with increasing ε, the corresponding “resonant” values of ρ₁/ρ₀ ratio are practically independent of the dielectric permittivity of surrounding medium. It is shown that an analogous amplification of radiation takes place essentially for the same values of ρ₁/ρ₀ also for the radiation in a cylindrical waveguide with conducting walls. An explanation of this phenomenon is given.     

Experimental Investigation of a Steam-Water Injector with a Tapered Nozzle

Working recommendations for determining the basic parameters and geometry of a steam–water injector with a converging nozzle are presented on the basis of experimental data. Injector startup, operating efficiency, and service life are examined.     

An evaluation of a general venting strategy in a CANDU 6 reactor building

If the reactor building sprays or local air coolers are not available, depressurization by reactor building venting is considered as a useful mitigation strategy for a severe accident management of the Wolsong plants. As the containment filtered vent system is not established in the Wolsong Units, the reactor building isolation system can be a substitute for reactor building venting. The D₂O vapour recovery system which has a 0.76 m (30 in.) diameter penetration is expected to meet the NRC requirements. To investigate the effectiveness of the Reactor Building Venting Strategy, three kinds of accidents are analyzed: a SBO, a Small LOCA and a Large LOCA. The reactor building pressure behavior was analyzed with the ISAAC computer code for four different cases: without venting, 379 kPa(g)/345 kPa(g) (55 psig/50 psig), 345 kPa(g)/276 kPa(g) (50 psig/40 psig) and 345 kPa(g)/207 kPa(g) (50 psig/30 psig) valve open/close pressures. When the reactor building spray or local air coolers can not be operated, a depressurization strategy by using the D₂O Vapour Recovery System could prevent a reactor building failure and reduce the amount of CsI released to the environment. The present study shows that the operation of valves at a pressure of 379 kPa(g)/345 kPa(g) (55 psig/50 psig) is safe and effective. Based on the current study, the strategy of reactor building venting is involved in severe accident management guidance-5.     

Development of a TOF-ERDA measurement system for analysis of light elements using a He beam

A time-of-flight ERDA (TOF-ERDA) measurement system has been developed for the analysis of light elements. He ions are used for the incident beam, and recoil light ions are detected with the system. The system consists of a time detector and a silicon detector, and energy and velocity of recoil ion are measured simultaneously. The depth resolution of 21.6 ± 2.2 nm (FWHM) has been obtained by an ERDA measurement of a thin carbon layer onto a silicon wafer using a 5.7 MeV He beam. The mass resolution is better than 1 for elements up to oxygen. Maximum detectable depth of carbon in a PET film is about 650 nm. An ERDA measurement of implanted carbon in a silicon wafer has been demonstrated.