核设施周围大气中多形态氚的测量

大气中氚主要以氚化水（HTO）、氚化氢（HT）以及氚化甲烷（CH₃T）的形态存在,其危害与其化学形态相关。为了准确评价核设施周围大气中不同化学形态的氚水平,基于高温催化氧化和低温冷阱捕集的原理,建立了一套适用于核设施周围大气中多形态氚的取样及测量方法,并对秦山核电站周围大气中不同形态氚进行了初步测量。该方法中催化剂在大气环境下对HT和CH₃T的催化氧化效率≥99%,冷阱对水样的收集效率≥95%,具备了同时采集和测量HTO、HT和CH₃T的功能。基于秦山核电站周围大气中氚的初步测量结果发现:秦山核电站周围大气中存在HTO、CH₃T和HT三种形态的氚,且HTO>CH₃T>HT,CH₃T和HT浓度与环境本底水平相当,由此表明,建立的取样和测量方法有较高的灵敏度,可以用于核设施周边大气中环境水平氚的采样测量。     

氚化水蒸气硅胶取样方法研究

本文研究了用硅胶取样空气中氚化水蒸气的简便方法。提出两个估算空气中氚化水蒸气浓度的公式,一个不包括取样效率,适用于快速取样或直接暴露取样,另一个不包括相对湿度,适于对结果要求更加准确的场合。     

秦山核电基地大气多形态氚的分布

氚对环境和生命体的危害不仅与氚活度相关,而且与氚的化学形态有关,秦山核电基地作为中国最大的产氚地之一,本文对不同年份、不同季节秦山基地周围不同形态氚进行监测和测量分析,实验结果表明:秦山核电基地大气中存在三种形态的氚,氚化水(Tritiated water,HTO)平均浓度为78.24～8 324.16 mBq·m~(-3);氚化氢(Tritiated hydrogen,HT)和氚化甲烷(Tritiated methane,CH_3T)浓度范围分别为15.35～2 763.12 mBq·m~(-3)和5.68～163.96 mBq·m~(-3);大气中HTO浓度随着核电基地的运行逐年增加,随与重水堆距离的增加逐渐减小;HTO、HT浓度呈现明显的夏季高、冬季低的季节性分布特征;CH3T则没有较为明显的季节性分布规律。     

氚化水蒸气短期暴露后胡萝卜中氚的浓度

为了研究气态氚化水(HTO)事故释放后胡萝卜对HTO的吸收和有机结合氚(OBT)的形成,在4个不同的生长发育期把盆栽的胡萝卜暴露于氚化水蒸气1 h,并于试验结束和收获时分别测量胡萝卜地上部和地下部的组织自由水氚(TFWT)和有机结合氚(OBT)的含量。结果表明大部分情况下胡萝卜地上部分的TFWT浓度在一小时内就能与周围空气中HTO的浓度达到平衡。收获时地上部和地下部的相对TFWT浓度均低于试验结束时的值,收获时的值分别为试验结束时值的1/389~1/86和1/116~1/3,地下部减少的幅度小于地上部。试验在地上部和地下部的生长旺盛期进行,试验结束和收获时相应的这两部分OBT浓度也最高。收获时地上部和地下部OBT浓度小于试验结束时的值,但是肉质根膨大期时期进行试验,收获和试验结束时地上部和地下部相对OBT的浓度差异不大。收获时地下可食部分中OBT与TFWT的比值范围为2.79~20.73,在食入剂量评价中OBT的贡献要大于TFWT。     

元素状态氚常温取样方法的研究

本文对元素状态氚(HT)的常温取样方法进行了研究。给出计算空气中元素状态氚浓度的公式。用本文提供的办法,在常温下可实现空气中氧化物状态氚(HTO)和元素状态氚的分别收集。     

氚废气的回收技术研究

采用了高温催化氧化法处理含氚废气。处理过程如下:在干燥氩气(含少量H2)的载带下,含氚废气通过高温催化氧化床转化为氚水,然后用蒸馏水或合适的干燥剂吸收。在400℃,氧化床穿透之前,Hopcalite氧化剂对H2的氧化效率接近100%;在500℃,Hopcalite氧化床对HT的氧化效率大于99%。实验测定了回收氚的分子筛在存放过程中,不同规格分子筛的氚释放系数以及存放条件与释放系数的关系。结果表明,3种分子筛在吸收氚水后的氚释放系数为(1.9～5.5)×10-6d-1·g-1。其中,4A钠型分子筛的氚释放系数最小,5A钙型分子筛的氚释放系数最大;3种分子筛在吸收氚水后释放的氚的化学形式绝大部分是氚化水(HTO),氚气(HT)含量不超过1.2%;含氚分子筛的贮存气氛对氚的再释放有一定影响,在纯氩气中氚释放系数比在含2%氢的氩气中的低。     

空气中氚监测仪刻度器

空气中氚监测仪刻度器是参照加拿大 Osborne,R.V.工作研制的实验室专用刻度装置。其鼓泡器是一个φ40×300mm 的铜室,内装150ml 氚水,置于半导体冷阱中,冷阱工作温度在8—12℃之间时,恒温精度在±0.03℃以内。空气流速可高达61/min,鼓出空气中 HTO 的浓度在室温(15—30℃)下可在±3.1%以内预先确定。本文介绍了该刻度器的原理,结构性能及其在国产氘监测仪刻度中的实际应用。     

空气中氡甄别型氚监测仪的研制

介绍了一种可甄别空气中惰性气体氡的高灵敏度氚实时连续监测仪,其一体化的平行板型丝壁测氚电离室和镀铝聚酯膜窗平行板型测氡密闭电离室,实现了空气中氚监测过程中氡干扰的实时、同步测量与补偿。该氡甄别型氚监测仪不仅在一般使用环境条件下减少了环境氡的影响．提高了氚监测仪的探测灵敏度,而且可在氡浓度比环境高100倍的场所探测到100Bq／L的氚浓度。对于监测环境中其他8放射性惰性气体．这种新型的氚监测仪预期将会有更好的甄别补偿性能。     

核素氚导出空气浓度控制限值的发展及其应用研究

氚是核设施运行过程中释放的放射性物质之一,对人体的内照射危害不仅与其活度有关,而且与氚的化学形态、摄入途径密切相关.针对目前国内涉及氚的控制标准较多,氚化水(HTO)与元素氚(HT)的控制限值均存在不一致的问题,梳理分析了氚浓度控制限值的发展及相关标准的制定依据.根据我国现行辐射防护有关标准,结合国际原子能机构(Int...     

氚标记八厘麻毒素的制备

一、问题的提出据统计,我国成年人中有5%—10%的高血压病患者。严重高血压患者可导致脑溢血、心力衰竭、肾功能衰竭等严重后果而构成我国人口中死亡率最高的疾病之一。然而,对这大量的危重高血压患者却缺少理想的降压药物。八厘麻是我国民间常用的中草药,是主要用于治疗跌打损伤的外用药。1977年武汉医     

Environmental Tritium in the Vicinity of Tokai Reprocessing Plant

The distribution of ³H in the atmosphere, vegetations and soil water was observed in the vicinity of Tokai reprocessing plant (TRP) over the period 1990–2004. The annual means of the atmospheric HTO and HT concentrations were in the range of 12–40 mBqm^?3 with a significant seasonal variation and 14–51 mBqm^?3 with no seasonal variation, respectively. Long-term atmospheric dilution factors, defined as the annual mean of the atmospheric HTO concentration divided by the discharge rate of HTO from the TRP, were estimated to be 10^?8–10^?6 sm^?3. The atmospheric HTO concentrations decreased with distance from the TRP, falling to the current background level in Japan at 5 km off-site. The HTO concentrations observed were compared with those calculated by a simple mathematical model with input data of the monthly ³H discharge rates and actual meteorological conditions. The calculations were correlated well with the observations even for only a little HTO-elevated situation, considering the naturally occurring ³H level in atmospheric vapor around the TRP. Tritium concentrations in vegetation and soil water samples were roughly the same as the atmospheric HTO concentrations, suggesting the rapid equilibrium of ³H concentrations in the atmosphere-soil-vegetation system around the TRP.     

Tritium diffusivity in crystal grain of Li2TiO3 and tritium release behavior under several purge gas conditions

It has been reported by the present authors that behavior of tritium release from solid breeder grain is consisted of diffusion in grain, tritium transfer at surface layer and surface reactions on grain surface such as adsorption or isotope exchange reactions. Tritium release curves estimated using the tritium release model gave good agreement with observed tritium release curves from Li₄SiO₄, Li₂ZrO₃ or LiAlO₂.

Tritium release behavior from Li₂TiO₃ under humid purge gas, dry purge gas and dry purge gas with hydrogen conditions is discussed in this study, tritium release curves using the release model that we proposed previously give a good agreements with experimental tritium release curves. Tritium effective diffusivity in the crystal grain of Li₂TiO₃ is also estimated in this study using a curve-fitting method applied to the release curves obtained under the humid purge gas condition. It is discussed that change of color of Li₂TiO₃ surface under hydrogen purge gas condition is observed and this phenomenon might affect tritium release behavior from Li₂TiO₃.     

化学交换反应法分离硼同位素的数学模型

采用化学交换反应法,针对三氟化硼-苯甲醚分离体系,研究了硼同位素分离生产过程的特点,建立了交换精馏塔的稳态数学模型,并利用Matlab程序进行模型求解,得到了不同分离要求和操作条件对交换精馏塔理论塔板数的影响.当增大所需同位素丰度或改变分离温度以及回流比时,都会使得理论塔板数增加或减少.该数学模型可以指导工艺设备的改进和优化,为下一步的放大和操作过程提供了理论依据.     

Evaluation of Reactivity Worth of Air Filled Beam Tubes in a Small Neutron Source Reactor by 3-D Transport Calculations

Four air filled beam tubes are present in the small pool type ²³³U fuelled, BeO and water reflected neutron source reactor KAMINI under construction in IGCAR, Kalpakkam. The positive reactivity insertion possible due to the accidental ingress of surrounding water into these empty beam tubes was estimated using the 3-D transport code TRITAC. To save computer time and also to highlight the effects caused by filling of air gaps with water, a similar but symmetrical core with more beam tubes was also studied in detail. Microscopic cross sections were derived from WIMS library and assembly homogenization was performed using a computer code SMAXY. Condensed eight group cross sections were used in TRITAC.

During the study reported here, need was found for the use of tight flux convergence criterion in TRITAC for getting reliable estimates of air to water worths. From the study of the symmetrical core, it is found that the presence of outer water reflector significantly reduces the air to water worth of these beam tubes. Further, the air to water worth of these beam tubes is quite small when the region where water replaces air is, beyond 15 cm from core boundary. Thus it is inferred that the total air to water worth of all beam tubes in the KAMINI reactor will be small compared to the total delayed neutron fraction of ²³³U.     

Theoretical prediction of S Kβ fine structures in PIXE-induced XRF spectra

Sulfur is one of the most important elements found in air pollutants. A PIXE-induced XRF system equipped with a crystal spectrometer is a candidate to analyze chemical states of S in the pollutants. To aid in the design of the spectrometer for this purpose, fundamental data have been collected by calculating S Kβ spectra by use of the discrete variational Xα (DV-Xα) method for molecular orbital calculations. The calculated spectra have very faithfully reproduced XRF spectra observed for mixtures of Na₂SO₄, Na₂SO₃ and ZnS using a Ge (1 1 1) flat crystal spectrometer, which were used as representative chemical species including SO₄²⁻and SO₃²⁻, and as an example of sulfides in the air pollutants.