Analysis of stresses in GCFR cladding under normal operating conditions

A modified version of the LIFE-III code, LIFE-GCFR, and classical stress analysis techniques have been employed to calculate the stresses in GCFR cladding under normal reactor operating conditions. Several types of loadings on the cladding which occur during normal operation have been considered. These include fuel-cladding mechanical interaction, thermal stresses induced by radial and axial temperature gradients, and stresses induced by swelling gradients. The combined and individual effects of these loadings as well as the effect of creep on cladding stresses have been assessed. Results obtained from this study have provided input to the experimental GCFR cladding development work at Argonne National Laboratory.     

Overview of recent developments in pellet injection for ITER

Pellet injection is the primary fueling technique planned for core fueling of ITER burning plasmas. Also, the injection of relatively small pellets to purposely trigger rapid small edge localized modes (ELMs) has been proposed as a possible solution to the heat flux damage from larger natural ELMs likely to be an issue on the ITER divertor surfaces. The ITER pellet injection system is designed to inject pellets into the plasma through both inner and outer wall guide tubes. The inner wall guide tubes will provide high throughput pellet fueling while the outer wall guide tubes will be used primarily to trigger ELMs at a high frequency (>15 Hz). The pellet fueling rate of each injector is to be up to 120 Pa m³/s, which will require the formation of solid D–T at a volumetric rate of ～1500 mm³/s. Two injectors are to be provided for ITER at the startup with a provision for up to six injectors during the D–T phase. The required throughput of each injector is greater than that of any injector built to date, and a novel twin-screw continuous extrusion system is being developed to meet the challenging design parameters. Status of the development activities is presented, highlighting recent progress.     

Railgun pellet injection system for fusion experimental devices

A railgun pellet injection system has been developed for fusion experimental devices. Using a low electric energy railgun system, hydrogen pellet acceleration tests have been conducted to investigate the application of the electromagnetic railgun system for high speed pellet injection into fusion plasmas. In the system, the pellet is pre-accelerated before railgun acceleration. A laser beam is used to induce plasma armature. The ignited plasma armature is accelerated by an electromagnetic force that accelerates the pellet. Under the same operational conditions, the energy conversion coefficient for the dummy pellets was around 0.4%, while that for the hydrogen pellets was around 0.12%. The highest hydrogen pellet velocity was 1.4 km s⁻¹ using a 1 m long railgun. Based on the findings, it is estimated that the hydrogen pellet has the potential to be accelerated to 5 km s⁻¹ using a 3 m long railgun.     

Theoretical magnitude of the stresses produced in fuel cladding by the expansion of cracked pellets: Effect of interfacial dislocations (interfaceons) and pellet relaxation

Because the stresses to which metals are subjected in service are a much smaller proportion of the elastic modulus than are the stresses commonly imposed on rubbery polymers, the coefficient of friction when interfacial dislocations (interfaceons) are present is much lower for metals than for rubber. It is also much lower than the coefficient of friction for ordinary sliding (in the absence of interfaceons) and so the stress concentration predicted to be produced by pellet cracks is negligible if there are interfaceons present. If they are absent then the stress concentration is significant. In either case a low rate of power increase causes the lowest stresses and stress concentrations in the clad. This is shown to be due to relaxation creep in the pellet.     

Model of nanotube formation in solution under molecular sorption conditions

Reliable disposal of radioactive wastes in nanosize containers which ensure that the wastes are isolated and strongly contained is investigated. A model of the process of incorporating impurity components into solutions where nanotubes are formed is presented to substantiate the possibility considered. An attempt is made to describe the rolling up of nanotubes in a liquid medium from the standpoint of the energy balance in a system that consists of a nanometer-size thin film and molecules which are sorbed on its surface from solution. The results show that when molecules are sorbed from solution onto a nanolayer surface the layer rolls up. The possibility that a roll or nanotube loses stability when sorbed molecules are present in them must be taken into account when studying the final state of the nanolayer.     

The conditions of formation and classification of exogenous uranium deposits

Some previously published schemes are given for the classification of exogenous uranium deposits; a brief ctitical review is given of the main principles of the classification; the stages of ore formation are described corresponding to the stages of formation of the ore-containing sedimentary rocks. Finally, a scheme is proposed of a classification which takes into account the conditions of formation and the composition of the ore-containing rocks, and also the dynamics of the ore-forming processes.Translated from Atomnaya Énergiya, Vol. 14, No. 3, pp. 296–308, March, 1963     

Asymptotic and reference stresses for design by analysis

Difficult computational problems can arise when analysing structures constructed from materials which are non-linear. It has also to be recognised that the parameters in the relationships which define the latter may show some variability. This can de-value the usefulness of findings which take no account of such variability. Information concerning effects of the latter is obtainable by envisaging the dependent variables as function of a parameter h, the value of which varies from zero for linearly elastic/viscous behaviour to unity for a plasto-rigid material.Generally applicable methods have thus been established for estimating the sensitivity of the stress distribution in a structure and the associated deflections as functions of h. Use has been made of the asymptotic solutions when h → 0 both for this purpose, and to automate computation of so-called reference stresses for structures which may behave in a non-linear fashion, as a result of creep, for example. It is further conjectured that such a development has a potential for affecting the direction of developments from the current position on design by analysis for components and structures which are required to operate under such conditions.     

萨瓦甫齐铀矿床成矿古水文地质分析

萨瓦甫齐铀矿床地处南天山褶皱带狭长的库尔干山间盆地内。根据区域构造、古地理和古气候等资料,将山间盆地划分为3个大的古水文地质旋回;从古水文地质条件演化的角度,分析了各旋回与铀成矿的关系,并建立了强构造背景下砂岩型铀矿古水文地质成矿模式。     

A repetitive pellet injection system for steady state fuelling in EAST superconducting tokamak

A new hydrogen/deuterium pellet injector has been developed for Experimental Advanced Superconducting Tokamak (EAST). The pellet injector based on a screw extruder is able to fire pellets (∅2 mm × 2 mm; frequency 1–10 Hz and velocity 150–300 m/s) in steady state mode with reliability greater than 95%. An injection line was designed for pumping propellant gas and for diagnostic purpose also. A guide tube for magnetic high-field side (HFS) injection was developed and theoretical calculation has been done. After successful engineering commissioning, the injection system served at EAST 2012 campaign and first experimental results were obtained.     

An improved thermometer for intermediate-mass fragments

An improved thermometer (TIB) is proposed for intermediate-mass fragments via the difference between isobaric yield ratios. The residual free energy of three isobars is replaced by that of the binding energy. The measured fragments in the 140A MeV 40, 48Ca+ 9Be (181Ta) and 58, 64Ni+ 9Be (181Ta) reactions are analyzed to obtain TIB ranging from 0.6 to 3.5 MeV. TIB is suggested to be a direct determination of temperature avoiding the fit-ting procedure.     

库米什盆地木拉阿米特凹陷铀成矿水文地质条件分析

在综合分析资料的基础上,从基础地质条件出发,全面分析了木拉阿米特凹陷的水文地质条件、含水岩组特征、水文地球化学特征与层间氧化带及铀矿化的关系,初步认为库鲁克塔格山前地带具有较好的发育层间氧化带及铀矿化的前景。     

新疆布雅盆地铀成矿条件分析

布雅盆地是塔里木盆地南缘有利的铀成矿地段。在简析布雅盆地区域地质背景、已知铀矿化特征的基础上,着重宏观地分析了盆地形成铀矿化的地层、构造、水文地质及铀源等条件,以构造为主线初步总结出该区铀成矿的载体形成、初始铀富集、相对停滞和破坏及叠加富集4个阶段,独特的构造演化促成了铀矿化的形成。     

Thermal stresses in reactor constructions

Conditions for the appearance of thermal stresses in reactors are investigated; also their magnitude and the danger they create are estimated. The influence of the form of the heat-generating elements (HGE) on the temperature drop and magnitudes of thermal stresses is analyzed; recommendations are given with the aim of decreasing the harmful effect of thermal stresses.The methods from the theory of elasticity employed in the calculation of thermal stresses have significant limitations. In many cases when estimating the magnitude and degree of danger created by the thermal stresses, when combining such stresses with mechanical stresses, and also when seeking a way to decrease them, other effects such as fluidity, creep, initial breakdown, and microscopic processes must be taken into consideration.     

SPAGINS: semiempirical parameterization for fragments in gamma-induced nuclear spallation

From the empirical phenomena of fragment distributions in nuclear spallation reactions, semiempirical formulas named SPAGINS were constructed to predict fragment cross-sections in high-energy γ-induced nuclear spallation reactions(PNSR).In constructing the SPAGINS formulas, theoretical models, including the TALYS toolkit, SPACS, and Rudstam formulas,were employed to study the general phenomenon of fragment distributions in PNSR with incident energies ranging from 100 to 1000 MeV. Considering the...     

Thermal and mechanical stresses in nuclear reactor vessels

This paper is concerned with stress and deformation analysis of a circular cylindrical, thin, elastic shell, representing a nuclear reactor vessel, with an insulated cutout of arbitrary shape subjected to mechanical and thermal loads. The analysis is based on the method of superposition. The actual stresses in the shell may be considered as the sum of the following two parts:

1.

(a) Stresses caused by the given heat flow and mechanical loads in a similar shell without a hole (nominal stress solution);