IMPORTANCE OF STEARATES IN THE FABRICATION OF UO2 AND (U,Pu)O2 PELLETS

Abstract

Eighteen qualities of metallic soaps have been studied, either as lubricants or as additives for the fabrication of UO₂ and (U,Pu)O₂ pellets. Compounds of the same family, such as zinc stearates, differ in their effectiveness as lubricants. This property is strongly dependent on the particle size of the powder and its purity. The behaviour of the dry lubricants when used as admixtures in UO₂ and also when employed for the direct lubrication of the pelletizing tools is discussed.

The efficiency of metallic soaps as additives to lower the density of the sintered pellets is related to the nature of the metallic ion. Thus, zinc stearate has little influence on the fired density of UO₂, whereas barium stearate and other barium compounds are very effective. Barium inhibits sintering, but zinc, which is eliminated at low temperature, does not diminish the sinterability of the oxide powders. In the latter case, the decrease in density is caused by thermal decomposition of the organic molecule.     

甘肃北山地下水中Pu的形态分布及影响因素

利用日本原子力学研究所于2010年9月提供的热力学数据库,运用水文地球化学软件Phreeqc,模拟研究了甘肃北山地下水中Pu的存在形态。其结果表明:Pu在甘肃北山地下水中主要以Pu(OH)4形态为主,Pu(OH)+3占少量;pH和pE对Pu的形态分布有较大的影响。     

A comprehensive appraisal of 241Am in soils around Rocky Flats, Colorado

Soils east of Rocky Flats Plant (RFETS) near Golden, Colorado, were contaminated with actinides because of accidental release of oils laden with plutonium isotopes. Consequently, these soils were contaminated by 241Am due to radioactive decay of 241Pu (t1/2 = 14.4 y). A spatial analysis of 241Am activity in soils east of RFETS was conducted to elucidate the magnitude and the mode of 241Am dispersion in the soil environment. 241Am activity of 178 soil samples ranged from 0.037 Bq kg-1 to 10,004 Bq kg-1 with a mean of 214 Bq kg-1, median of 7.28 Bq kg-1, standard deviation of 942 Bq kg-1, and a coefficient of variation of 4.3. Spatial analysis of 241Am in soils around RFETS was conducted using indicator kriging, which is a nonparametric technique especially suitable to model a conditional cumulative distribution function (ccdf) of highly skewed environmental data such as 241Am. The ccdf was used to generate an E-type (mean of the conditional cdf) surface. The resulted surfaces were consistent with the hypothesis that the westerly winds were the dominant mechanism of americium dispersal. The spatial distribution and dispersal mechanisms of 241Am were similar to those of 239+240Pu. The ccdf was also used to construct probability of exceedence maps of 241Am in soils. For the purpose of this report two threshold values for the probability maps were selected: (1) the mean measured background activity of 241Am (0.4 Bq kg-1), and (2) the programmatic preliminary remediation goal for residential occupancy scenario (87.7 Bq kg-1). The probability-of-exceedance maps provide estimates of spatial uncertainty associated with each threshold. The E-type maps in conjunction with the probability-of-exceedance maps provide a robust framework for future cleanup options and land use decisions.     

37例普外科伤口感染分析

恶性肿瘤发病率逐年增多,是临床常见病和多发病,由于恶性肿瘤患者本身免疫功能低下,加上放化治疗加重患者免疫功能紊乱、缺陷,肿瘤坏死产生的中毒产物导致机体代谢紊乱等均为院内感染的高发因素.针对恶性肿瘤患者,目前不可能为了避免继发感染而终止化疗和放疗,应在提高疗效的同时,加强医务人员的无菌观念,严格消毒隔离,避免医源性感染的发生;加强患者个人卫生护理,配合必要的支持疗法,提高患者的免疫功能.开放引流本身易使皮肤表面的细菌进入体内,因此要严格掌握其适应证.