STUDY OF INTERACTION BETWEEN ACTINOIDS AND COLLOIDAL MATTER IN GROUND WATER

了解具有长期放射性毒性的放线类物质在搁浅水中胶体物质上的吸附机理是进行放射性废物地下处置安全评估的核心。为了建立一种在不干扰实验系统条件的情况下分析胶体吸附放线体组分的方法，在东北大学的单端式动能加速器上安装了垂直空气中粒子诱导X射线发射(PIXE)系统，并建立了PIXE谱的自动分析方法。空气对含有挥发性成分的精致样品提供了很好的散热作用。在考虑束流、束流直径和能量损失的情况下，分析了Kapton箔作为空气中PIXE系统出射窗口的寿命，为估算Kapton箔在不同辐照条件下的寿命提供了依据。建立了一种用于可溶性…的X射线光电子能谱分析方法水样中含有更多的e和不溶性成分。用3 MeV质子束PIXE系统制备了三种靶材，并进行了分析。不溶组分在0.4-PM孔径的核孔过滤器上过滤，氢氧化铁胶体的最低检测下限为几十ppb，累积电荷为3mug。用3mug辐照靶材可精确测定高于40 ppb的钍和铀的浓度。靶材由用户自制的聚碳酸酯薄膜上蒸发的含有镓内标的0.12毫升溶液制成。采用二苄基二硫代氨基甲酸盐络合和随后缩合成二亚甲基-D-山梨醇凝胶相结合的方法，将25-mI样品中的铀(VI)离子预富集到以钯为内标的薄而均匀的靶中，通过PIXE测量，很容易测定低浓度的4 ppb。然而，这种方法不适用于痕量钍离子的浓缩。同时测定了从钠到铅的广泛存在的-24种元素的浓度(几十ppb到几十ppm)，其精密度足以揭示河流水中可溶和不溶部分之间的元素分布。该方法还具有良好的灵敏度和精密度，足以确定9种浓度低于放射性同位素精制装置排水中允许浓度的钍和铀。较少

Understanding the sorption mechanism of actinoids having long-term radiological toxity onto colloidal matter in aground water is central to the safety assessment of underground disposal of radioactive wastes. In order to develop a methodology for analyzing compositions of colloids sorbing actinoids without disturbing conditions of an experimental system, a vertical in-air Particle Induced X-ray Emission (PIXE) system has been installed at a single-ended type Dynamitron accelerator in Tohoku University, and we have developed a method for auto-analysis of PIXE spectrum. The air offers a good heat removal from a delicate specimen containing a volatile component. Endurance of Kapton foil used as an exit window of in-air PIXE system for beam irradiation was analyzed in consideration of beam current, diameter and energy loss, which enables us to estimate the lifetime of the Kapton foil under various irradiation conditions. A procedure has been developed and tested for PIXE analysis of solubl … More e and insoluble constituents in a water sample. Three kinds of targets were prepared and analyzed with the PIXE system of 3-MeV proton beam. Insoluble components were filtered on a Nuclepore filter of 0.4-pm pores, and the lower detection limit for ferric hydroxide colloids was a few tens of ppb at an accumulated charge of 3 muG.The concentrations of thorium and uranium higher than 40 ppb were precisely determined by 3-muG irradiation on targets which were made from a 0.12-ml solution containing Ga-internal standard evaporated on a user-madepolycarbonate foil. Uranium(VI) ions in a 25-mi sample were preconcentrated into a thin uniform target containing Pd as an internal standard by means of a combination of dibenzyldithiocarbamate complexation with subsequent condensation into dibenzylidene-D-sorbitol gels, and the low concentration of 4 ppb was easily determined by the PIXE measurement. However this method did not work for concentrating trace thorium ions. The widespread concentrations (several tenths of ppb to a few tens of ppm) of -24 elements from Na to Pb were determined simultaneously in a precision sufficient to reveal the elemental distribution between the soluble and insoluble fractions of riverwaters. The methodology also had good sensitivity and precision enough to detennine concentrations of thorium and uranium lower than their permissible concentrations in drainage from a radioisotopelaboratory. Less