Ballistic properties of multilayered concrete shields

We investigate theoretically the effect of layering of concrete shields using a wide class of semi-empirical models. We have found that (i) the ballistic limit velocity (BLV) of the multilayered shield does not depend on the order of the plates in the shield, (ii) monolithic shield is superior to any layered shield with the same thickness, and (iii) the largest decrease of the BLV occurs when a shield is divided into a number of plates having the same thickness.     

Radiation leakage from narrow gaps in shields

Clearance gaps around plugs and other movable components can be a significant source of radiation leakage from large casks. There is, however, a lack of quantitative information upon which a designer can base his choice of clearance dimension. The factors underlying this problem are discussed, and expressions based on a single-scatter approximation are derived from some typical geometries. Calculated data is presented for iron, lead and uranium shields, for cobalt-60 and caesium-137 gamma radiation. Experiments to check the expressions are described. It is shown that the accuracy of this method is sufficient for dealing with practical problems.     

Determination of heat generation in double layer shields

In this paper theoretical and experimental calculation of direct heat generation from the penetration of 6.12 MeV photons energy, emitted from an N-16 disk source, through double shielding layers combined of concrete, steel and lead shields is described. This work is a continuation of the work reported by Bakos (Bakos G.C., 1999. Ann. Nucl. Energy 26, 69–73) and is based on the analysis of experimentally determined photon flux spectra and the use of build up factor method.     

Geometrical aspects of cylindric magnetic shields in strong static fields

Motivated by rrER (the International Thermonuclear Experimental Reactor),research on a magnetic shield against a strong field has been carried out.In this paper,a cylindric magnetic shield is studied by using the finite element method with a nonlinear magnetization curve.The geometrical aspects of shielding performance are identified and corresponding suggestions for application are provided.Among them,the effects of the edge and cover thickness have not been mentioned elsewhere to our knowledge.     

含硼卟啉在硼中子捕获治疗中的研究进展

硼中子捕获治疗(boron neutron capture therapy,BNCT)是利用10B(n,α)7Li反应产生的高能α粒子和反冲7Li原子进行治疗的高传能线密度辐射治疗方式,含硼化合物是硼中子捕获治疗的重要方面,其中含硼卟啉是上世纪90年代起广受关注的含硼化合物.介绍了硼中子捕获治疗及含硼卟啉的特点,阐述了...     

Calculation of the cross-sections for fast neutrons and gamma-rays in concrete shields

This work is concerned with the theoretical calculation of both the total mass attenuation coefficients (μ/ρ) for gamma rays and the effective removal cross-sections (Σ_R) for fast neutrons. Calculations were carried out for four types of concrete of different densities namely (1) dolomite–sand ρ=2.5 g.cm⁻³, (2) barite–barite ρ=3.49 g.cm⁻³, (3) magnetite–limonite ρ=3.6 g.cm⁻³ and (4) ilmenite–ilmenite ρ=3.69 g cm⁻³. The total mass attenuation coefficients have been calculated at energies from 10 keV to 1 GeV using the XCOM (version 3.1) computer program and cross- section database for elements from Z=1 to 100. Also the effective removal cross-section have been calculated using the elemental composition of the concrete mixes. The calculated values are widely needed and used as a database for radiation shielding design of research reactors, power station and particle accelerators. The results were displayed in tables and figures. Calculated results were compared with those previously measured and a reasonable agreement was found between them.     

Voids in boron carbide

Two different void morphologies have been observed in the commercial grades of boron carbide that are currently undergoing assessment as candidates for the control rod material in fast breeder reactors. Some grains in unirradiated powders contain dodecahedral voids which are closely associated with iron-rich precipitates believed to be cementite, and neutron-irradiated powders also contain plate-shaped voids oriented parallel to {110} planes (rhombohedral indices). These latter voids are believed to contain fission gas and their plate-like morphology is attributed to work which the gas can do in elastically deforming the matrix if their shape is changed from spherical to disc-shape.