On risk assessment of high level radioactive waste disposal

Since the first controlled chain reaction, the use of nuclear fission to produce power has grown rapidly. One of the major concerns with the continued growth of the nuclear power industry is the production of the high level radioactive wastes which are by-products of the fission process. The risks associated with the disposal of high level wastes derive from the potential for release of radioactive materials into the environment. The assessment of these risks requires a methodology for risk analysis, an identification of the radioactive sources, and a method by which to express the relative hazard of the various radionuclides that comprise the high level waste.The development of a methodology for risk analysis is carried out after a review of previous work in the area of probabilistic risk assessment. The methodology suggested involves the probabilistic analysis of a general accident consequence distribution. In this analysis, the frequency aspect of the distribution is treated separately from the normalized probability function. In the final stage of the analysis, the frequency and probability characteristics of the distribution are recombined to provide an estimate of the risk.The characterization of the radioactive source term is accomplished using the ORIGEN computer code. Calculations are carried out for various reactor types and fuel cycles, and the overall waste hazard for a projected 35 year nuclear power program is determined. An index of relative nuclide hazard appropriate to problems involving the management of high level radioactive wastes is developed in this work. As an illustration of the methodology, risk analyses are made for two proposed methods for waste management: extraterrestrial disposal and interim surface storage. The results of these analyses indicate that, within the assumptions used, the risks of these management schemes are small compared with natural background radiation doses.     

Basic concepts of reliability assessment of solid radioactive waste disposal

All-Union Scientific-Research Institute of Industrial Technology. Translated from Atomnaya Énergiya, Vol. 73, No. 1, pp. 65–69, July, 1992.     

高放废物地质处置预选区GIS中地学元数据设计

高放废物地质处置地学信息系统旨在综合管理、充分应用高放废物地质处置研究过程获取的多源地学信息,而建立及运行该系统都需要多源地学信息元数据的支持。在对高放废物地质处置预选区地学信息数据分析的基础上,应用现有的地学元数据标准,对其多源地学信息元数据的内容信息、管理模式与应用进行了设计研究。     

放射性废物处置安全若干进展

结合2005年放射性废物处置安全国际大会反映出来的放射性废物处置安全领域的最新进展,介绍了全球放射性废物安全框架、废物处置安全战略、安全方案、地质处置设施安全、近地表处置设施安全、中等深度废物处置方案和公众沟通等方面的若干新进展和新观点。     

地球化学工程学在放射性废物处置中的应用

介绍了应用地球化学工程学治理环境的基本依据,常用的放射性废物处置工程模式和工程屏障的功能,并以某放射性废物处置场地球化学工程屏障物料研究为例,说明地球化学工程学在放射性废物处置中的应用。研究结果表明,采用地球化学工程学方法来改良放射性废物处置场址的天然缺陷,可大大提高放射性废物处置的安全性。     

我国核电厂放射性废物管理进展及挑战

分析了我国核电厂放射性废物管理现状;指出了核电厂放射性废物管理面临的挑战;提出了包括进一步完善法规标准、完善放射性管理体制、加强群堆核电厂放射性废物管理、鼓励技术创新和产学研结合等加强核电厂放射性废物管理的应对措施。     

我国高放废物地质处置库场址筛选总体技术思路探讨

绿合对比瑞典、加拿大、芬兰和美国等国高放废物地质处置场址筛选技术思路,分析国外高放废物地质处置库场址筛选过程中取得的经验、教训,总结了我国处置库选址工作取得的成果和存在的问题.在综合研究基础上,分析提出我国高放废物地质处置库场址筛选总体技术思路,包括应遵循的原则、工作范围、目标和总体技术步骤等,以利于今后处置库选址工作更系统、规范和统一.     

放射性废物处置安全全过程系统分析中的指标

以往放射性废物处置的安全评价中通常使用放射性安全指标(即剂量和危险),随着放射性废物处置安全全过程系统分析这一概念的提出,辅助指标已成为评价中的一个重要组成部分。本文介绍了安全全过程系统分析中所使用指标的发展、分类和相应标准等。依评价对象不同,辅助指标通常分为安全指标和性能指标,有些组织还提出了安全功能指标;与上述指标相对应的用于比较的标准分别为参考值、指标标准和安全功能指标标准。将处置系统划分为不同库室时,指标还可分为“包容物和浓度”相关指标、“通量”相关指标和“屏障状态”相关指标三类。建议我国尽快开展放射性废物处置的安全全过程系统分析工作,建立完善的指标体系,选取适当的评价指标,并基于我国放射性废物处置的场址特性确定相应的标准,以期实现安全和防护的最优化。     

Early age behaviour of concrete supercontainers for radioactive waste disposal

Various types of radioactive waste were and are produced in Belgium. This waste originates from different producers: nuclear power plants, medical applications, industry, research centre, etc. During the past 25 years several preliminary repository designs were proposed. Today, the cylindrical supercontainer is considered to be the most promising Belgian design on the matter of enclosing the vitrified high level radioactive waste (HLW) and the spent fuel assemblies and is based on the use of an integrated waste package composed of a carbon steel overpack surrounded by an Ordinary Portland Cement buffer. For the choice of this cementious buffer two compositions, a self-compacting concrete (SCC) and a traditional vibrated concrete (TVC), are being considered, tested and compared by means of an intensive laboratory characterization program. Through-going cracks in the concrete buffer should, at all times, be avoided because they will considerably ease the transport mechanisms inside the supercontainer. Therefore, finite element simulations are performed, using a 2.5-D thermal and crack modelling program, to predict the mechanical and thermal behaviour of the concrete buffer at any time during hardening. Looking at the finite element simulation results of the first stage of manufacturing of the supercontainer (cast in one), and the emplacement of the heat-emitting waste canister (second stage), we experience no early age cracking of the concrete buffer. The impact of environmental conditions and shrinkage and creep behaviour on the simulation results are noticeable.     

高放废物处置库场址北山预选区新构造运动分区与中、强地震分布特征

根据高放废物处置库场址北山预选区的新构造运动特征,将其分为祁连山强烈隆升区、河西走廊差异沉降区、安西差异沉降区和北山弱隆升区。预选区内中、强地震集中分布于祁连山强烈隆升区和河西走廊差异沉降区,其中,5.0级以上地震的发生均与区内主要大型断裂带的活动有关。中、强地震的分布与新构造运动的活跃程度相关。新生代以来,青藏高原的NE向扩展、挤压和缩短是形成以上新构造运动格局及地震分布的动力来源。     

核电站低放废物集中减容处理技术探讨

本文简述了国内核电站放射性废物的管理现状及对废物高效减容的迫切需求。针对放射性废物减容的需求,对国内外高效减容工艺技术开展调研,分析各种工艺的技术特征,对兼顾经济与环保效益的放射性废物集中减容处理技术进行探索,发现等离子体处理技术具备明显优势,提出了一种组合减容技术路线,为国内放射性废物管理工作提供参考。     

Development of methodology of probabilistic safety assessment for radioactive waste disposal in consideration of epistemic uncertainty and aleatory uncertainty

Probabilistic safety assessment has not been performed for radioactive waste disposal owing to the difficulty of dealing with the probability distributions of the parameters included in the long-term safety assessment of radioactive waste disposal. In this study, we develop a methodology of probabilistic safety assessment in consideration of both epistemic uncertainty and aleatory uncertainty, in which the probability density function (PDF) and cumulative distribution function (CDF) of the maximum annual dose can be calculated. We also propose an approach to demonstrating dose assessment results in compliance with the stepwise target annual doses of likely and less-likely scenarios according to the occurrence probability of the scenario without classifying the probabilities of parameters involved prior to the safety assessment. For the likely scenario, we can employ the larger of the modal value of the PDF and the 50th percentile of the CDF to meet the target annual dose (10 µSv y^-1). For the less-likely scenario, we can adopt the 95th percentile of the CDF as the assessment result for comparison with the target annual dose (300 µSv y^-1).     

Development of a grout database for geological disposal of high-level radioactive waste

Japan Atomic Energy Agency (JAEA) has developed a grout database (GDB) comprising the latest technical data of grout materials relevant to the geological disposal of high-level radioactive waste (HLW). Currently, only newly developed grout materials of low pH cements, superfine spherical silica and colloidal silica, which are expected to provide a target pH ≤ 11 leachate, are included in the GDB. Case examples from on-site works and laboratory-based tests that have been published in the literature have been used to add construction and material details to the GDB. The GDB is available online (https://groutdb.jaea.go.jp/grout/ [in Japanese]) for registered users to obtain and provide data of grout technology. Furthermore, the GDB can be used to correlate requirements of mechanical, physical, and/or chemical properties of a grout material to specifically address concerns over safety assessment, material and injection method development, and/or prediction of grout penetration.     

某近地表处置场废物处置码放工艺优化研究

针对我国西南某近地表处置场原设计码放方案在实际应用中存在诸如处置单元容积利用率降低等相关问题,本文对原设计码放方案进行了介绍并提出了新的码放设计方案,又从施工成本、码放耗时、辐射剂量和国外同类处置场码放方式四个方面对优化后的码放方案进行了效果分析和对比。分析对比结果表明,经优化后的码放方案较原设计方案更切合实际处置需求,处置单元容积利用率得到显著提高,个别优化码放方案已获得成功实践应用,并取得预期设计效果。     

放射性废物近地表处置设施的应急管理研究北大核心CSCD

放射性废物近地表处置设施是放射性废物处置设施的一种。根据核安全法,该类设施内发生的放射性事故属于核事故范畴,考虑到该类事故具有辐射事故特征,建议其场内应急预案参照核设施核事故应急预案进行编制,其中应急体系按照核设施核事故进行管理,如应急组织体系、应急报告制度、应急设施等,但在事故分级上采用辐射事故分级原则。