共查询到18条相似文献,搜索用时 156 毫秒
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建立了基于蒙特卡罗(MCNP)程序建模的铀加工与燃料制造设施核临界事故工况下瞬发剂量的计算方法,并将该计算方法与EJ/T 988—96规定的计算方法进行了比较分析。以我国某核燃料元件研发厂址为例,采用MCNP程序建模计算了该厂址核临界事故对厂界公众所致的瞬发剂量。结果表明,EJ/T 988—96的计算方法过于保守的估计了核临界事故工况下的瞬发剂量;基于MCNP程序建模的计算方法,因其求解算法的科学性和模型对屏蔽介质的准确描述,以及结果误差的可控性,使得计算结果更准确。因此,建议采用基于MCNP程序建模的方法计算铀加工与燃料制造设施核临界事故下的瞬发剂量。 相似文献
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次临界核系统的瞬发中子衰减常数α与反应性有着重要联系。采用252Cf随机脉冲源法测量了一柱形金属次临界系统的瞬发中子衰减常数。为对源中子的影响进行分析,借助蒙特卡罗模拟方法建立模型进行了模拟,对源直穿中子和核系统瞬发中子时间分布特性进行了比较,分析了源中子对瞬发中子衰减曲线的影响。模拟结果表明,对该柱形金属铀系统,源中子注入100 ns后源直穿中子对核系统瞬发中子的影响可忽略。根据分析结果选取了合理起始道,对实验数据进行单指数最小二乘拟合,得到该次临界系统的α为15.5μs-1。 相似文献
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瞬发中子衰减常数α是反应堆的重要动态参数,由次临界和临界状态下的瞬发中子衰减常数可以刻度出反应堆的次临界深度。在瞬发中子衰减常数的测量中,脉冲中子源方法是经常使用的非常成熟的方法。本文叙述另一种方法——核噪声方法测量瞬发中子衰减常数,这种方法使用中子探测器,探测堆内中子水平的涨落,通过对中子涨落信号的分析处理,导出瞬发中子衰减常数α。与脉冲中子源方法相比,核噪声方法的优点是测量方法简单,只需在反射层内放置中 相似文献
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据美国核管理委员会国际项目办公室发出的情况通报报道,阿根廷原子能委员会所属的RA-2零功率临界装置,于1983年9月23日下午4时10分发生瞬发临界事故。此装置是一个轻水慢化的试验和培训用反应堆,采用材料试验堆型元件,铀-235的浓缩度为90%。一名操作员在该试 相似文献
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在没有中子源或中子源强度很弱的核系统中,由于意外发生的临界事故(核闪变)释放的能量远大于反应堆动力学的预估值,为了给反应堆运行启动程序的制定和减小临界事故规模提供参考,本文建立了核闪变能量释放模型.在引发第一个持续裂变链的时间分布的基础上,从理论上推导出核闪变峰内能量释放与中子源强度.反应性加入速度的关系.结果表明:中子源强度越小,反应性加入速度越大,事故规模越大. 相似文献
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基于蒙特卡罗均匀化理论与有限体积方法,建立了适用于瞬发临界事故分析的三维扩散时空动力学模型。将三维扩散时空动力学模型与非稳态传热模型、辐照裂解气泡模型耦合,对计算程序GETAC-S进行了升级,使其具备了对溶液系统任意几何与材料条件下的瞬态分析能力。使用国际上已有的瞬态装置TRACY的实验数据对GETAC-S进行了验证,结果符合良好。使用GETAC-S对日本的JCO临界事故进行了事故进程反演,证明GETAC-S具备了对复杂溶液系统下的临界事故后果进行评价与反演的能力,为核临界事故的预防、评估和屏蔽提供了理论支持。 相似文献
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氟化铀酰溶液临界事故是核燃料循环设施潜在的一种临界事故,需要做好其相应的事故应急评价,为应急响应提供辅助决策支持。临界裂变次数是核临界事故应急评价的重要内容,也是技术难点之一。它反映了核临界事故的大小和规模,直接影响事故应急防护行动决策。裂变次数估算有多种方法,有各自的适用条件。随着事故发生的时间推移,获取的信息越丰富,选择的评价方法也随之优化。因此提出了基于事故进程的氟化铀酰溶液临界裂变次数估算方法,该方法解决了临界事故应急评价实际应用问题及技术人员选择何种评价方法的困难问题。 相似文献
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根据国外的事故统计资料,介绍了各种交通工具的概率以及放射性物质运输事故的情景和辐射后果。可以认为,放射性装运事故的概率较低,事故中放射性物质从货包中泄漏的概率更小。 相似文献
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AbstractAs a regulatory authority for the transportation of spent nuclear fuel (SNF) in the USA, the Nuclear Regulatory Commission requires that SNF transportation packages be designed to endure a fully engulfing fire with an average temperature of 800°C (1475°F) for 30 min, as prescribed in Title 10 of the Code of Federal Regulations Part 71. The work described in this paper was performed to support the Nuclear Regulatory Commission in determining the types of accident parameters that could produce a severe fire with the potential to fully engulf an SNF transportation package. This paper describes the process that was used to characterise the important features of rail accidents that would potentially lead to an SNF transport package being involved in a severe fire. Historical rail accidents involving all hazardous material (i.e. all nine classes of hazardous material) and long duration fires in the USA have been analysed using data from the Federal Railroad Administration and the Pipeline and Hazardous Materials Safety Administration. Parameters that were evaluated from these data include, but were not limited to, class of track where the accident occurred, class of hazardous material that was being transported and number of railcars involved in the fire. The data analysis revealed that in the past 34 years of rail transport, roughly 1800 accidents have led to the release of hazardous materials, resulting in a frequency of roughly one accident per 10 million freight train miles (Because all of the data were obtained in the USA, which still uses distance measured in miles, and the primary source is an extensive database from the Federal Railroad Administration that is also in reported in miles, the data in this paper are reported in miles rather than kilometres. Conversion of miles to kilometres is by multiplication of 1·61.). In the last 12 years, there have only been 20 accidents involving multiple car hazardous material releases that led to a fire. This results in an accident rate of 0·003 accidents per million freight train miles that involved multiple car releases and a fire. Out of all the accidents analysed, only one involved a railcar carrying class 7 (i.e. radioactive) hazardous material. 相似文献
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AbstractThe increase in the use of radioactive materials worldwide requires that these materials be moved from production sites to the end user, or in the case of radioactive waste, from the waste generator to the repository. Tens of millions of packages containing radioactive material are consigned for transport each year throughout the world. The amount of radioactive material in these packages varies from negligible quantities in shipments of consumer products to very large quantities in shipments of irradiated nuclear fuel. Transport is the main way in which the radioactive materials being moved get into the public domain. The public is generally unaware of the lurking danger when transporting these hazardous goods. Thus radiation protection programmes are important to assure the public of the certainty of their safety during conveyance of these materials. Radioactive material is transported by land (road and rail), inland waterways, sea/ocean and air. These modes of transport are regulated by international 'modal' regulations. The international community has formulated controls to reduce the number of accidents and mitigate their consequences should they happen. When accidents involving the transport of radioactive material occur, it could result in injury, loss of life and pollution of the environment. In order to ensure the safety of people, property and the environment, national and international transport regulations have been developed. The appropriate authorities in each state utilise them to control the transport of radioactive material. Stringent measures are required in these regulations to ensure adequate containment, shielding and the prevention of criticality in all spheres of transport, i.e.routine, minor incidents and accident conditions. Despite the extensive application of these stringent safety controls, transport accidents involving packages containing radioactive material have occurred and will continue to occur. When a transport accident occurs, it is unlikely to result in a significant release of radioactive material, loss of shielding or loss of criticality control. 相似文献