高速逆流色谱结合制备型高效液相色谱法分离制备大豆皂苷单体

为建立一种有效的同时分离制备多种大豆皂苷单体的方法,先采用高速逆流色谱分离去除大豆皂苷粗提物中的大豆异黄酮,然后对得到大豆总皂苷,优化制备型高效液相的流动相酸(乙酸或三氟乙酸)的含量和梯度洗脱程序,以制备高纯度的大豆皂苷单体。结果表明:流速10mL/min,流动相乙腈(含0.01%三氟乙酸)-水按梯度程序Ⅲ洗脱,出峰数量多、峰形好、分离度高。经高效液相分析与光谱特性、质谱和核磁共振鉴定了11个峰的大豆皂苷种类,包括5种A组、2种B组以及3种2,3-2H-2,5-二羟基-6-甲基-4H-吡喃-4-(DDMP)大豆皂苷。研究结果提供了从含量相对丰富的大豆胚芽中大量分离制备部分或完全乙酰化的A组以及非DDMP和完整DDMP存在的B组大豆皂苷的有效方法。     

无源核子料位计在火电厂应用中关键问题的研究

无源核子料位计因其非接触式测量的优点被广泛运用于国内火电厂除尘器灰斗与输灰仓泵的料位测量中,但在实际使用中出现了测量不准、测量界线模糊、基础测量理论缺失等不足.从河北神华三河发电有限公司实际应用和基础原理角度出发,针对背景辐射变化问题、料种变化问题以及量程问题,对于无源核子料位计在火电厂应用中几个关键问题进行了分析与研...     

核电蒸汽发生器水压试验替代厂内水压试验可行性分析

核电蒸汽发生器水压试验是验证蒸汽发生器一次侧和二次侧强度性能、密封性能的关键试验.由核电站现场水压试验替代蒸汽发生器制造厂内水压试验的可行性分析可知,在实施核电项目时,应从减少超压试验对设备的损害,以及因现场安装需求缩短设备厂内制造周期等方面进行考虑,以期为日后相关工作的顺利实施提供一定的参考借鉴.     

我国环境土壤中的重要超铀核素分布

Pu、Am、Np是3种重要的超铀核素,环境中的这些核素主要来源于人类的核活动,包括大气层核武器试验、核设施排放和核事故释放等。这些超铀核素不仅具有放射性,还兼具化学毒性。我国地域辽阔,环境土壤类型丰富,在当前核电事业蓬勃发展的背景下,建立和扩大我国环境土壤中这些重要超铀核素的“准本底”数据库是辐射环境安全评价的重要组成部分,也是公众关心的热点问题。近30多年来,研究人员对我国不同环境土壤中这几种超铀核素从不同科学角度开展了调查测量研究。本文对此进行整理和分析,对我国环境土壤中这些重要超铀核素（主要是Pu核素,还包括241Am和237Np）的来源、浓度水平和分布特征进行讨论和综述,为辐射环境安全评价奠定基础。     

阳江核电站液态流出物对阳江海域环境影响的计算模拟

本文针对阳江核电站50 km核应急计划区的阳江海域,采用切比雪夫谱方法计算了阳江海域的潮流速度和潮位值,进而采用粒子随机行走模型,模拟计算了阳江核电站正常工况下,液态流出物10 h连续排放后,阳江海域内核素氚的浓度分布。计算结果表明,核素迁移扩散24 d后到达海陵岛附近海域,此时有氚分布的区域常规相对浓度值低于0.005,活度浓度值低于0.70 Bq/L,该值与海陵岛海水氚的监测活度浓度(＜0.97 Bq/L)量级上相符。此结果表明,阳江核电站液态流出物中的核素氚对阳江海域环境无明显影响。     

核电厂应急监测计划的关键问题及探讨

应急监测计划是核电厂应急计划的重要支持性文件,是核电厂应急监测准备和响应的重要依据。本文从核电厂事故应急监测方案、监测方法、监测设施设备配置、应急监测响应、监测能力的保持、质量保证等关键问题进行分析研究,提出相关建议,为核电厂应急监测计划的制订提供参考。     

放射性气载流出物取样代表性分析

为获取核设施放射性气载流出物单点连续监测取样位置,提出基于随机轨道模型(DRW)的气-固多相湍流耦合方法求解代表性取样区域。借助k-epsilon湍流模型模拟连续相,并引入离散颗粒模型(DPM)模拟离散相,建立基于DRW模型的排风管道内流道气-固多相湍流耦合计算模型,计算了核设施气载流出物在管道内流道流场分布规律,分析了内流道流体气旋角、气流速度、示踪气体浓度、气溶胶粒子浓度与管道高度间的关联关系。分析结果表明,随着截面高度的增加,气旋角、气流速度变异系数(COV)、示踪气体浓度COV及示踪气体浓度最大值与平均值的偏差逐渐降低并趋于稳定,气溶胶粒子浓度COV在截面6与截面8满足取样代表性要求;基于计算流体动力学方法可快速地确定出代表性取样位置,为气载流出物单点取样现场试验提供了理论参考依据。     

Experimental study of neutron counting in a zero-power reactor driven by a neutron source inherent in highly enriched uranium fuels

Even a zero-power reactor core containing highly enriched uranium has a weak neutron source inherent in uranium 235, and consequently, a neutron counter placed closely to the core without external neutron source registers a certain counting rate. The study of the counting is very important for zero-power reactor physics experiments with a high precision. In this experimental study, first, at a shutdown state of the UTR-Kinki reactor without start-up neutron source, a pulse height distribution of output signals from a neutron proportional counter was measured to confirm that these signals resulted from neutron detections. At several subcritical states of the UTR, then, the Feynman-α analysis was carried out to confirm that the neutrons detected by the counter must be fission neutrons multiplied by fission chain reactions. The correlation amplitude measured in the Feynman-α analysis was much higher than that measured in a previous drive by start-up source. Further, it was also confirmed that the subcriticality dependence of neutron counting rate followed the source multiplication formula. This feature indicated that the one-point model was very successful in the subcritical range including the shutdown state.     

First nuclear transmutation of 237Np and 241Am by accelerator-driven system at Kyoto University Critical Assembly

This study demonstrates, for the first time, the principle of nuclear transmutation of minor actinide (MA) by the accelerator-driven system (ADS) through the injection of high-energy neutrons into the subcritical core at the Kyoto University Critical Assembly. The main objective of the experiments is to confirm fission reactions of neptunium-237 (²³⁷Np) and americium-241 (²⁴¹Am), and capture reactions of ²³⁷Np. Subcritical irradiation of ²³⁷Np and ²⁴¹Am foils is conducted in a hard spectrum core with the use of the back-to-back fission chamber that obtains simultaneously two signals from specially installed test (²³⁷Np or ²⁴¹Am) and reference (uranium-235) foils. The first nuclear transmutation of ²³⁷Np and ²⁴¹Am by ADS soundly implemented by combining the subcritical core and the 100 MeV proton accelerator, and the use of a lead-bismuth target, is conclusively demonstrated through the experimental results of fission and capture reaction events.     

Formation of radioactive cesium microparticles originating from the Fukushima Daiichi Nuclear Power Plant accident: characteristics and perspectives

ABSTRACT

Following identification of radioactive Cs microparticles (CsMPs) in aerosol samples from the Fukushima Daiichi Nuclear Power Plant (FDNPP), numerous reports on CsMPs have been published. This paper reviews recent progress in the measurement and characterization of CsMPs by advanced analytical techniques, including advanced transmission electron microscopy (TEM) and synchrotron X-ray analysis. These analyses revealed that the CsMPs contained Si, Fe, Zn, Cs, and minor quantities of U together with some fission products. Uranium in the CsMPs was identified as being in the form of uraninite and (U,Zr)O₂. Detailed advanced TEM analysis has clarified some of the processes resulting in the alteration of constituents of the nuclear fuels and containment vessel materials during this severe accident. In addition, a detailed report on the elemental compositions and structures of the fuel debris fragments collected inside and outside of the primary containment vessel²⁵ highlighted the fact that the fuel debris fragments contained nanoparticles with the U and Zr components having similar structures to that of the CsMPs. This similarity in structures has stimulated further research on the structure and elemental constituents, especially for U and Zr in the CsMPs, and has opened up new avenues for studying the chemical characteristics of the fuel debris.