Application of In-Service Temperature Lowering to Reduce Radioactivity Corrosion Product Deposition on Carbon Steel Piping of BWR Residual Heat Removal System

Assessment of plant data and experiments on deposition of ion species on carbon steel were carried out in order to develop suitable countermeasures to reduce RHR (residual heat removal) piping dose rate. It was thought that radioactivity deposits on the RHR piping were mainly from radioactive ion species in the coolant and they were enhanced by the dehydration reaction of corrosion products on the piping. From an evaluation for temperature dependence of the dehydration reaction, it was proposed to lower the start-up temperature of RHR operation as a way to reduce radioactivity deposition. Feasibility studies of improved RHR operation were conducted and test operations were carried out in the Shika Nuclear Power Station Unit 1. Application of the improved RHR operation resulted in a temperature reduction from 150°C to 110°C, and a radioactivity deposition reduction on the RHR piping to one-fifth ofthat in conventional RHR operation. The improved RHR operation has now been applied to more than fifteen Japanese BWRs and significant suppression effects of radioactivity deposition have been observed.     

Diffusion of Cesium in Stainless Steel under Condition of Oxygen Potential Controlled by Mo/MoO2 or NbO2/Nb2O5 Oxygen Buffer

The kinetic behaviors of cesium migration in SUS-316 stainless steel for a cladding material of fast breeder reactor were studied using radioactive ¹³⁴Cs as a tracer. The oxygen potential in the atmosphere surrounding the specimen was controlled by Mo/MoO₂or NbO₂/Nb₂O₅ oxygen buffer, which corresponds approximately to the one in fuel-cladding gap during irradiation. The concentration profile of Cs in the specimen was analyzed on the basis of diffusion theory. The temperature dependences of diffusion coefficients of Cs in SUS-316 stainless steel were expressed in the range of 650~800°C by the following equations:

In the oxygen potential controlled by Mo/MoO₂ oxygen buffer

D = 0.15 exp (?63,500/RT) (cm²/s).

In the oxygen potential controlled by NbO₂/Nb₂O₅ oxygen buffer

D = 9.0×10-⁵exp(?50,300/RT) (cm²/s)

where the activation energy is expressed in terms of cal/mol.     

Characterisation of 316L powder injection moulding feedstock for purpose of numerical simulation of PIM process

Abstract

Viscosity, specific heat and thermal conductivity of the standard feedstock of 316L stainless steel have been measured under the typical conditions of a real powder injection moulding (PIM) process. The viscosity was measured in a wide range of shear rates at four different temperatures. The experimental viscosity data were fitted into the Carreau-Yasuda model. Both specific heat and thermal conductivity were measured in the temperature range that overlaps the recommended processing range for the studied feedstock. It has been shown that at high cooling rates the transition temperature of the binder material is shifted towards lower temperatures. Tabulated values of thermal conductivity and specific heat for the studied feedstock are presented. The obtained data can be used for numerical simulation of the powder injection moulding process.     

Processing and properties of sinter hardened Fe–Cr–Mo steels with admixed extra-fine nickel

Abstract

The processing and properties of chromium–molybdenum, powder metallurgy steels with admixed extra-fine nickel (XF Ni) were investigated. Prealloyed Fe–1·5Cr–0·2Mo powder was blended with different quantities of XF Ni, while a hybrid steel with lower Cr content was prepared by blending Fe–1·5Cr–0·2Mo and Fe–0·5Mo prealloyed powders, with additions of XF Ni and copper powders. These steels were compacted into different part shapes in order to evaluate the effect of part thickness on sinterhardening behaviour. These parts were also subjected to different cooling rates after sintering. This study showed that additions of XF Ni improve the compressibility, densification behaviour and mechanical properties of Cr–Mo steels. Furthermore, the properties of the hybrid steel were shown to be either equal to or greater than those of the reference material. Hardenability of all steels was sufficiently high such that part thickness was seen to have negligible impact. Higher cooling rates generally resulted in improved mechanical properties.     

First-principles studies of hydrogen behavior interacting with oxygen-enriched nanostructured particles in the ODS steels

Through first-principles calculations, we systematically investigated the hydrogen interactions with the oxygen-vacancy (O:V) pairs complex in bcc Fe matrix (mimic oxygen-enriched nanoclusters (NCs) of ODS steels) in comparison with the vacancy-alone defects. The results uncovered that the presence of the (O:V) pairs in oxygen-enriched NCs play a crucial role in prohibiting the growth and swelling of the hydrogen cluster but strongly trap a few hydrogen atoms around each cluster of vacancies. As accompanied with a high density of dispersed NCs in ODS steels, this fact significantly elevates the tolerance of the critical hydrogen concentration of ODS steels as compared with traditional steels. The underlying mechanism to pin the growth of hydrogen cluster has been elucidated to be strongly correlated with the viable charges transfer from the nearby Fe atoms around vacancies. This is the key to determine the trapped concentration and the distribution of hydrogen atoms in ODS steels.     

Metal-adhesive bonded systems: Adhesion measurement using a three point flexure test

Single metallic adherend-adhesive bonded specimens are subjected to a three point flexure test in order to investigate the effects of adherend surface conditioning and adhesive curing conditions on the mechanical properties of the substrate-adhesive interfacial region. The main advantage of this test over more conventional ones (i.e. peel, tensile, shear tests) is to induce stress concentration which is responsible for a failure locus within the interfacial region and consequently its ability to provide data representative of practical adhesion in an adhering system. The results obtained are shown to be independent of adherend thickness, adhesive layer thickness, width of the bonded area and displacement speed used during testing. Data presented here are relative to Ti-6Al-4V titanium alloy/epoxy systems. They demonstrate the high sensitivity of the flexure test to the effects of prebonding treatments (chemical etching, anodization) and of adhesive curing conditions on practical adhesion.     

Characterization and Rockwell-C adhesion properties of chromium-based borided steels

In this study, adhesion properties of boride layers formed on the surface of AISI 52100, AISI 5140, AISI 440C, AISI 420 and AISI 304 steels were investigated. Boronizing treatment was carried out in Ekabor-II powders at the temperatures of 850 and 950 °C for 4 h. The properties of boride layers were evaluated by optical microscopy, SEM, X-ray diffraction and micro-Vickers hardness tester. The Daimler-Benz Rockwell-C adhesion test was used to assess the adhesion of boride layers. Test result showed that adhesion of boride layers depended on the dual-phase structure. The stresses at the FeB/Fe₂B interphase caused delamination failure and poor interphase adhesion with increase in the depth of hard and brittle FeB-based layer.     

Abrasive erosive wear of powder steels and cermets

Composite materials produced by powder metallurgy provide solutions to many engineering applications that require materials with high abrasive wear resistance. The actual wear behaviour of a material is associated with many external factors (abrasive particle size, velocity and angularity) and intrinsic material properties of wear (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of wear resistant materials are highly dependent on the content of the reinforcing phase, its size and on the mechanical properties of the constituent phase. This study is focused on the analysis of the (AEW) abrasive erosive wear (solid particle erosion) using different wear devices and abrasives. Powder materials (steels, cermets and hardmetals) were studied. Wear resistance of materials and wear mechanisms were studied and compared with those of commercial steels. Based on the results of wear studies, surface degradation mechanisms are proposed. The following parameters characterizing the materials were found necessary in materials creation and selection: hardness (preferably in scale comparable with impact), type of structure (preferably hardmetal type) and wear parameters characterizing material removal at plastic deformation.     

超高速度生产优质线材的TMB(R)先进技术

在生产特殊钢线材轧机上应用达涅利摩加沙玛公司的一项新技术,即双模块机组（TMB）,生产能力平均提高10%,最终产品具有更好的技术性能。     

厚板钢材在钢结构工程中的应用及其材性选用

近年来厚板钢材在钢结构工程中的应用日益广泛 ,为此 ,详细地介绍了 2 0世纪 5 0年代至今不同时期的厚板应用、设计与材料标准及材料性能特点等 ,同时对当前工程中选用厚板材性的难点与问题进行了评述 ,并提出了合理选材的建议 ,可供设计参考。