Developing historical technical basis for material and package classification and package test requirements of international transport safety regulations

Abstract

In a companion PATRAM 2013 paper, C. Bajwa et al. provide an overview of international level efforts that began in 2010 to develop a comprehensive and detailed Technical Basis Document (TecBasDoc) to support the current International Atomic Energy Agency (IAEA) Transport Regulations (SSR-6, 2012) and future revisions thereto. The draft TecBasDoc that has so far resulted from efforts by a large number of IAEA staff and international experts exceeds 300 pages in length using, to the greatest extent possible, historical documents dating as far back as the 1950s as reference material. The intent is to capture, for those Member States new to transport and for future generations, the scientific and technical heritage of the several decades of development that has occurred in transport safety, preserving this knowledge for future reference. The latest effort, in December 2012, involved consultants to the IAEA adapting the draft to reflect guidance from the IAEA’s Transport Safety Standards Committee and delving into the IAEA’s archives searching out many long sought, older supporting documents. This paper elaborates on Chaps. 8–10 of the TecBasDoc, dealing with respectively Classification of Materials, Classification of Packages and Package Design and Testing. Chapter 8 elaborates on the many decisions resulting in an initial nine material classifications, which focused more on the physical and not the radioactive characteristics of the materials, to the current, significantly different classifications that focus more on the material’s radioactive properties. Chapters 9 and 10 combine to provide extensive, detailed elaboration on why decisions were made concerning the various package classifications and the associated design, testing and acceptance requirements associated with each package type. Chapter 10 cites two extensive supporting appendices. These three chapters and two appendices currently cite and elaborate on >200 historical documents. Efforts are underway to make this extensive document base more complete and to make as many documents as possible available electronically. In this paper, each of these three drafted chapters and the two supportive appendices are overviewed, providing insight into key and typical findings that have been uncovered and incorporated into the draft document. The many experts who have contributed to the current draft are appropriately acknowledged.     

'Design to manufacture': journey through criticality considerations for new design fissile material transport packages

Abstract

The development of new fissile material transport packages is an increasingly complex and costly business. The IAEA regulations stipulate performance requirements for the behaviour of the package under both normal and accident conditions. The principal performance drivers are: impact/structural, thermal, shielding and criticality safety. The needs of these disciplines can often compete, with refinements becoming necessary to optimise the design of the package. Maximising the payload while achieving the required levels of safety can be time consuming and expensive. Early communication with the criticality safety analysts can frequently speed up the design process. Numerous variables are significant to criticality safety, (e.g. mass, geometry and spacing of fissile material, presence of moderators, presence of fixed poisons, potential damage to package, etc.). Small changes in the design can result in big changes in the reactivity and this may lead to a very large number of scoping calculations. Increased computing power and improved code abilities can make criticality scoping calculations much more efficient. The development of software to enable a single parameterised input to analyse multiple variations of a basic model provides significant benefits in the production of the criticality analysis and to the overall design process. Criticality analysis of a specific design and of variations in that design can now be performed more quickly and efficiently. Through frequent interaction between members of the design team, a 'fluid' design can be created, and an iterative process can then optimise the package configuration. Retaining the criticality input throughout the design, development, prototype manufacture and testing ensures that the key safety principles are progressed to the manufactured package. In turn, the time and cost of the overall project in producing an acceptable package may be much reduced. The paper presents experience from a criticality viewpoint of the development of new package designs for transport of fissile materials, emphasising the benefits of the utilisation of software/computing developments in this process, with statistics illustrating the efficiencies now achievable.     

大亚湾核电站18个月换料设计质量保证大纲的建立与实施

质量保证体系标准ISO9001-94呼国家核安全法规HAF003（91）对质量体系的要求有所差异，这是核行业质量认证组织面临的主要问题。如何才能同时满足两套标准建立体系，中国核动力研究设计院（NPIC）在大亚湾核电厂18个月换料设计论证项目上作了尝试，并建立、实施和不断完善了质量保证体系，制订并实施了专用的质量保证大纲，采取了一系列的控制、验证措施，向法马通公司（FAMATOME）和大亚湾核电厂提供满意的核设计服务产品。     

An optimization approach to establish an appropriate energy group structure for BWR pin-by-pin core analysis

An optimization approach to establish an appropriate multi-group energy structure for boiling water reactor (BWR) pin-by-pin fine mesh core analysis is proposed. In the present approach, the number of energy groups of cross sections is successively reduced or increased. In order to select an energy group boundary that is removed or added, performances of all possible candidates of energy group structures are tested in multi-assembly geometries. Then, the energy group boundary, which provides the minimum difference of the k-infinity or the pin-by-pin fission rate distribution, is finally removed or added. This procedure is repeated until the number of energy groups reaches to the target value. In order to confirm the applicability of the present approach, the accuracies of the k-infinity and the pin-by-pin fission rate distribution are investigated in various 2 × 2 multi-assembly geometries with the established energy group structure. From the verification results, the differences of the k-infinity and the pin-by-pin fission rate distribution between the reference (fine) and the established (coarse) energy group structure are small in the various 2 × 2 multi-assembly geometries. Therefore, we can conclude that the present approach is efficient to establish an appropriate energy group structure for BWR pin-by-pin fine mesh core analysis.     

Crystal chemistry of uranium (V) and plutonium (IV) in a titanate ceramic for disposition of surplus fissile material

We report X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectra for the plutonium LIII and uranium LIII edges in titanate pyrochlore ceramic. The titanate ceramics studied are of the type proposed to serve as a matrix for the immobilization of surplus fissile materials. The samples studied contain approximately 10 wt% fissile plutonium and 20 wt% natural uranium, and are representative of material within the planned production envelope. Based upon natural analogue models, it had been previously assumed that both uranium and plutonium would occupy the calcium site in the pyrochlore crystal structure. While the XANES and EXAFS signals from the plutonium LIII are consistent with this substitution into the calcium site within pyrochlore, the uranium XANES is characteristic of pentavalent uranium. Furthermore, the EXAFS signal from the uranium has a distinct oxygen coordination shell at 2.07 Å and a total oxygen coordination of about 6, which is inconsistent with the calcium site. These combined EXAFS and XANES results provide the first evidence of substantial pentavalent uranium in an octahedral site in pyrochlore. This may also explain the copious nucleation of rutile (TiO₂) precipitates commonly observed in these materials as uranium displaces titanium from the octahedral sites.     

Production management and quality assurance for the fabrication of the In-Vessel Components of the stellarator Wendelstein 7-X

The In-Vessel Components (IVC) of the stellarator Wendelstein 7-X consist of the divertor components and the first wall (FW) with their internal water cooling supply and a set of diagnostics. Due to the significant amount of different components, including many variants, a tool called Production Managing System (PMS) has been developed to organize the fabrication and the associated quality assurance. The PMS works by building a database containing the basic parts and assembly data, manufacturing and quality control plans, and available machine capacity. The creation of this database is based mainly on the parts lists, the manufacturing drawings, and details of the working flow organization. As a consequence of the learning process and technical adjustments during the design and manufacturing phase, the database needed to be permanently updated. Therefore an interface tool to optimize the data preparation has been developed. PMS has been demonstrated to be an efficient tool to support the IVC production activities providing reliable planning estimates, easily adaptable to problems encountered during the fabrication and provided a basis for the integration of quality assurance requirements.     

Spent fuel canister for geological repository: Inner material requirements and candidates evaluation

One of the key aspects in designing Spanish spent nuclear fuel canister for geological repository is selecting the inner material to be placed between the steel walls and the fuel assemblies. This material has to primarily avoid the possibility of a criticality event once the canister gets breached by corrosion and flooded by groundwater. A detailed set of requirements for a material to fulfil this role in that environment have been devised and presented in this paper. With these requirements in view, eight potentially interesting candidates were evaluated: cast iron or steel, borosilicate glass, spinel, depleted uranium, dehydrated zeolites, haematite, phosphates, and olivine. Among these, the first four materials or their families are found promising for this application.     

Historical background to the development of various requirements in the international regulations for the safe packaging and transport of radioactive material

Abstract

Questions are frequently asked regarding the source of some of the package test requirements in the Transport Regulations, the philosophy behind them and the basis for selecting them. This paper summarises the results of a review of early historical documents and elaborates on the early philosophy behind the regulatory requirements. To the extent possible, the paper compares the early philosophy with the current structure of the Transport Regulations in key topic areas with a focus on the test requirements for packages that are designed to withstand accident conditions of transport.     

我国含微量放射性物质照明产品运输和仓储环节的监管建议

根据新版《放射性物品运输安全管理条例》和《放射性物品分类和名录》(试行),将含有放射性物质的仪器或制品的例外货包纳入第三类放射性物品,需要对运输过程进行监管。作为需求量大、覆盖面广的含微量放射性物质照明产品,如果对其运输和仓储环节进行审批管理显然不利于整个照明行业的发展,也不利于审管部门的监管。目前世界多数国家在分析论证的基础上对这类照明产品的运输和仓储环节进行了豁免;本文收集和分析了我国含微量放射性物质照明产品的现状,采用相应的评价方法,对其运输和仓储环节的环境影响进行了分析,根据GB 18871—2002中的豁免准则要求,对我国含微量放射性物质照明产品运输和仓储环节的监管提出了建议。     

An ensemble approach to sensor fault detection and signal reconstruction for nuclear system control

To efficiently control a process, accurate sensor measurements must be provided of the signals used by the controller to decide which actions to actuate in order to maintain the system in the desired conditions. Noisy or faulty sensors must, then, be promptly detected and their signals corrected in order to avoid wrong control decisions. In this work, sensor diagnostics is tackled within an ensemble of Principal Component Analysis (PCA) models whose outcomes are aggregated by means of a local fusion (LF) strategy. The aggregated model thereby obtained is used for both the early detection and identification of faulty sensors, and for correcting their measured values. The fault detection decision logic is based on the Sequential Probability Ratio Test (SPRT). The proposed approach is demonstrated on a simulated case study concerning the pressure and level control in the pressurizer of a Pressurized Water Reactor (PWR). The obtained results show the possibility to achieve an adequate control of the process even when a sensor failure occurs.     

An integrated approach to source term uncertainty and sensitivity analyses for nuclear reactor severe accidents

Large-scale computer programs simulate severe accident phenomena and often have a moderate-to-large number of models and input variables. Analytical solutions to uncertainty distributions of interested source terms are impractical, and influential inputs on outputs are hard to discover. Runs of such integral codes for complex severe accidents are generally time-consuming and hence computationally expensive. This article presents an integrated approach to uncertainty and sensitivity analyses for nuclear reactor severe accident source terms, with an example which simulates an accident sequence similar to that occurred at Unit 2 of the Fukushima Daiichi Nuclear Power Plant using an integral code, MELCOR. Monte-Carlo-based uncertainty analysis has been elaborated to investigate the released fractions of representative radionuclides, Cs and CsI. In order to estimate the sensitivity of inputs, which have a substantial influence on the core melt progression and the transportation process of radionuclides, a variance decomposition method is applied. Stochastic process, specifically a Dirichlet process, is applied to construct a surrogate model in sensitivity analysis as a substitute of the code. The surrogate model is cross-validated by comparing with corresponding results of MELCOR. The analysis with the simpler model avoids laborious computational cost/load, so that the importance measures for input factors are obtained successfully.     

Optimal ion beam,target type and size for accelerator driven systems: Implications to the associated accelerator power

In interactions of different energetic ions with extended targets hydrogen isotopes are the most effective projectiles for the production of spallation neutrons. It is shown that for every target material and incident ion type and energy there is an optimal target size which results in the escape of a maximum number of spallation neutrons from the target. Calculations show that in an ADS, combination of a beam of 1.5 GeV deuteron projectiles and a uranium target results in the highest neutron production rate and therefore highest energy gain. For fast 1.5 GeV d + ²³⁸U ADS with lead or lead–bismuth eutectic moderator, the required ion beam current is only 38% of that for 1 GeV proton projectiles on lead target. It is shown that for a modular ADS with uranium target and output power of 550 MW_th a 1.5 GeV deuteron beam of current 1.8 mA is required, which is easily achievable with today’s technology. For an ADS with k_eff = 0.98 and output power of 2.2 GW_th, the required beam currents for (a) 1 GeV p + Pb and (b) 1.5 GeV d + U systems are 18.5 and 7.1 mA, respectively.     

IAEA《放射性物质安全运输条例》(2018版)主要变化内容与修订GB11806的适用性研究

现行国标《放射性物质安全运输规程》(GB 11806—2004)等同采用了IAEA《放射性物质安全运输条例》(以下简称“IAEA《条例》”)(2003年版),技术内容完全相同。其后,IAEA多次修订了《条例》,其中2012和2018年修订版的技术内容变化较大,部分变化内容对相关行业实施放射性物品运输产生了重大影响。本文扼要阐述了IAEA《条例》(2018版)的重要变化内容,结合我国实践,进行剖析及适用性例证,以期更好地修订和理解GB 11806。     

A novel approach to regulate cell membrane permeability for ATP and NADH formation in Saccharomyces cerevisiae induced by air cold plasma

Air cold plasma has been used as a novel method for enhancing microbial fermentation.The aim of this work was to explore the effect of plasma on membrane permeability and the formation of ATP and NADH in Saccharomyces cerevisiae,so as to provide valuable information for largescale application of plasma in the fermentation industry.Suspensions of S.cerevisiae cells were exposed to air cold plasma for 0,1,2,3,4 and 5 min,and then subjected to various analyses prior to fermentation(0h) and at the 9 and 21 h stages of fermentation.Compared with nonexposed cells,cells exposed to plasma for 1 min exhibited a marked increase in cytoplasmic free Ca~(2+) concentration as a result of the significant increase in membrane potential prior to fermentation.At the same time,the ATP level in the cell suspension decreased by about 40%,resulting in a reduction of about 60%in NADH prior to culturing.However,the levels of ATP and NADH in the culture at the 9 and 21 h fermentation stages were different from the level at0 h.Taken together,the results indicated that exposure of S.cerevisiae to air cold plasma could increase its cytoplasmic free Ca~(2+) concentration by improving the cell membrane potential,consequently leading to changes in ATP and NADH levels.