ITER vacuum vessel: Design review and start of procurement process

The ITER vacuum vessel (VV) is one of the most critical components in the ITER project. It is on the critical path in the construction schedule and it is also a safety important class component (SIC), providing the first confinement barrier.As a result of reviews and the latest physics analyses, design requirements have been updated (e.g. ELM/VS coils) and a few design changes have to be implemented. This paper covers the updates of the VV vertical and horizontal EM load conditions during asymmetric VDEs, the design analysis of the ELM/VS coils and their interfaces to the VV, the blanket manifold design and the preparation of the technical specification in preparation for the procurement arrangement to be signed.     

Mean annual severity: An extension of the quantitative-probabilistic approach to reactor safety analysis

The quantitative approach to reactor safety analysis introduced by F.R.Farmer is discussed and extended by continuing the analysis of each branch of an accident to a point where the probable frequency and consequent radioactivity release assigned to it are multiplied together. This product is termed Mean Annual Severity (MAS), and is useful in analysing the safeguards and accident status of a reactor. In addition to determining the severity of an accident, this approach enables any weaknesses in the overall safety design to be pin-pointed for further analysis and action.As an example, an analysis is made of a loss of coolant accident in a PWR, and the type of conclusions which can be drawn from such an analysis is demonstrated. A comparison is made between the mean annual severity and the maximum credible accident (MCA) approaches and examples demonstrating weaknesses in the MCA approach by means of MAS analysis are presented.     

Correction to: Research on tune feedback of the Hefei Light Source II based on machine learning

Nuclear Science and Techniques -     

Technological review of the HRP manufacturing process R&D activity

ENEA and Ansaldo Nucleare S.p.A. have been deeply involved in the European International Thermonuclear Experimental Reactor (ITER) R&D activities for the manufacturing of high heat flux plasma-facing components (HHFC), and in particular for the inner vertical target (IVT) of the ITER divertor.This component has to be manufactured by using both armour and structural materials whose properties are defined by ITER. Their physical properties prevent the use of standard joining techniques. The reference armour materials are tungsten and carbon/carbon fibre composite (CFC). The cooling pipe is made of copper alloy (CuCrZr-IG).During the last years ENEA and Ansaldo have jointly manufactured several actively cooled monoblock mock-ups and prototypical components of different length, geometry and materials, by using innovative processes: HRP (hot radial pressing) and PBC (pre-brazed casting).The history of the technical issues solved during the R&D phase and the improvements implemented to the assembling tools and equipments are reviewed in the paper together with the testing results.The optimization of the processes started from the successful manufacturing of both W and CFC armoured small scale mockups thermal fatigue tested in the worst ITER operating condition (20 MW/m²) through the achievement of record performances obtained from a monoblock medium scale mockup.On the base of these results ENEA-ANSALDO participated to the European programme for the qualification of the manufacturing technology to be used for the procurement of the ITER divertor IVT, according to the F4E specifications. A divertor inner vertical target prototype (400 mm total length) with three plasma facing component units, was successfully tested at ITER relevant thermal heat fluxes.Now, ANSALDO and ENEA are ready to face the challenge of the ITER inner vertical target production, transferring to an industrial production line the experience gained in the development, optimization and qualification of the PBC and HRP processes.     

中药知母有效组分——知母皂甙元“滋阴”作用的研究

本工作以~(123)I-心得静结合分析法及环核苷酸RIA法观察了知母中提取得到的知母皂甙元对甲亢模型(模拟“阴虚”)βAR-cAMP系统的作和,结果表现,知母皂甙元明显降低甲亢小鼠脑β受体的RT值,显著降低甲亢小鼠β受体-cAMP系统的反应性,重现了知母水煎剂的下调作用。体外竞争抑制实验表明,知母皂甙元和知母皂甙元半琥珀酸都不能抑制~(125)I-心得静与β受体的结合。     

Correction to: Theoretical prediction of radiation-enhanced diffusion behavior in nickel under self-ion irradiation

Nuclear Science and Techniques - 166.6-MHz quarter-wave $$\beta =1$$ superconducting cavities have been adopted for the High Energy Photon Source, a 6-GeV diffraction-limited synchrotron light...     

木材断裂过程的研究

运用同步辐射光源,对杉木和马尾松径、弦向切片在拉应力作用下的破坏过程进行了观察。结果显示：木材在径向拉伸荷载的作用下,易在早、晚材分界处出现裂纹,并向早材部分扩展,裂纹扩展路径不规则,在细胞壁处被终止;木材在弦向拉伸荷载的作用下,易在木射线处出现裂纹,并很快在其附近产生更多的裂纹,直至破坏。木材预制裂纹与木材纹理垂直,受顺纹拉伸荷载的作用时,裂纹尖端不沿预制方向扩展,而是顺纹扩展。木射线和纹孔对裂     

New developments in French transient monitoring system: SYSFAC from the experiments to the industrial process

After more than 15 years of experience with regulatory transient data collection, Electricité de France decided to design a new concept of fatigue monitoring system called SYSFAC. This new system is the result of seven years of successful experimentation with fatigue meters. This system will be connected to the on-site data acquisition system without any complementary instrumentation. The SYSFAC system has a modular structure: the mechanical transient module, the functional transient module, the fatigue meters module and the global damage computing module all have a high level of flexibility to be applied to various types of circuits. After the preliminary studies had been achieved, it was decided to undertake the industrial phase of the SYSFAC project. Specific codes on PC computers have been used to validate the basic concepts and the operator interface. Real-size coding will last one year and the first SYSFAC system will be delivered to the pilot power plant by the end of 1995.     

Evaluation and Correction of the Error due to Coarse Mesh Adjacent to Absorbing Regions in Diffusion Code Calculations

A simple correction formula is analytically derived to reduce the error due to coarse mesh adjacent to absorbing regions in diffusion code calculations. The formula is derived by equating the neutron current, obtained by the three point difference equation with a finite mesh size, with the true value corresponding to zero mesh size. The formula is numerically confirmed to be quite satisfactory in practical two dimensional critical calculations with quite coarse mesh size.

When a transitional fine mesh region is adopted to represent the geometrical heterogeneity in the vicinity of the absorber region, the error is almost entirely determined by the mesh size in the transitional region and the correction is only necessary for the mesh size therein if the region thickness is above one and a half times the diffusion length.     

Theoretical remarks on the statistics of three discriminants in Piety's automated signature analysis of PSD data

Piety (1977) proposed an automated signature analysis of PSD data. Eight statistical decision discriminants are introduced. For nearly all the discriminants, improved confidence statements can be made. In this paper, we consider the statistical characteristics of the last three discriminants which are applications of non-parametric tests.     

Call for papers to be presented at the 4th International Conference on: Structural Mechanics in Reactor Technology: San Francisco,California, USA, 15–19 August 1977

The structural response of liquid metal fast breeder reactor (LMFBR) subassemblies to local accidental events is of interest in assessing the safety of such systems. Problems to be resolved include failure propagation modes from pin to pin and from subassembly to subassembly. Factors which must be considered include: (a) the geometry of the structure, (b) uncertainty of the pressure-energy source, (c) uncertainty of materials properties under reactor operating conditions, and (d) the difficulty in performing in-pile or out-of-pile experiments which would simulate the above conditions. The main effort in evaluating the subassembly response has been centered around the development of appropriate analyses based on the finite element technique. Analysis has been extended to include not only the subassembly duct structure itself, but also the fluid environment, both within subassemblies and between them. These models and codes have been devised to cover a wide range of accident loading conditions, and can treat various materials as their properties become known. The effort described here is centered mainly around an experimental effort aimed at verifying, modifying or extending the models used in treating subassembly damage propagation.To verify the finite element codes under development, a series of out-of-pile room temperature experiments has been performed on LMFBR-type subassembly ducts under various loading conditions. The duct sections were instrumented to measure internal pressure, duct midflat strains and deflection of the mid-flat and corners. Since moderate deflections were expected, and effect influence on the radial deformation would occur over a relatively short length. Preliminary calculations and subsequent static and dynamic tests demonstrated that for the range of deformations expected in single subassembly prior to failure, a shortened duct section of only 30.48 cm in length was sufficient to provide a central section over which axially uniform conditions prevailed. As a result, with axial motion of the end plates constrained, the deformation over the uniform deflection range corresponds to two-dimensional, plane-strain conditions and a two-dimensional, finite element computer code could be applied. Tests were subsequently performed on several ducts made of type 316 stainless steel which were either annealed or 50% cold-worked. Material properties of the ducts used in the experiments were determined by testing samples obtained from each duct. Also, diamond point hardness measurements were obtained across the subassembly duct flats in order to establish that the material properties were uniform. Comparisons were then made between the code calculations and experimental results which demonstrated remarkable agreement, thus lending confidence to the code's ability to predict duct response, at least under quasi-static loading. Further preliminary work was performed on the dynamic response of hexcans to a pressure pulse designed to duplicate a postulated local event.     

基于事故进程的氟化铀酰溶液临界裂变次数估算方法

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。     

Numerical investigation on the heat transfer characteristics of a liquid-metal pool subjected to a partial solidification process

The main purpose of this paper is to investigate numerically the effects of solidification on the heat transfer characteristics of the liquid metal layer, for use in accident analyses. The situation is very similar to an overlying liquid melt pool that could be fooned in the reactor lower head during the late phase of a severe nuclear accident. Based on a computational model, MPCOOL, the numerical predictions were then assessed through a comparison with the experimental data that was obtained with various boundary temperature conditions and geometrical aspect ratios, especially for the Ra-Nu relationship. For the cases with solidification, the results of the comparison show that(a) the computational model does show a good agreement with heat transter rates inferred from the experimental data, with a few exceptions at the Ra numbers which suggest a turbulent transport; and also (b) the computational model underpredicts the heat transfer rates by about 6% than that inferred from the experimental data when it is integrally evaluated with the Ra-Nu correlation. The foregoing results are mainly due to the currently limited applicability of the computational model up to the laminar-to-turbulence transition flows and its application to the turbulence flows because it is always subjected to a model uncertainty between the laminar and turbulence. Next, an additional comparison for the cases with and without solidification was made to examine the effects of the solidification on the energy partition within the liquid metal layer and its effects on the directional heat transfer rates. The results of the comparison show that the computational model for the case without solidification predicts higher heat transfer rates by about 15% than when solidification is included, but there isn't any experimental data that directly supports this trend.