The Mechanical Interaction of Clad and Base Metal for Molten Salt Reactor Structural Components

Cladding structural components with a corrosion resistant material may greatly extend the design life of molten salt reactor concepts. A complete design methodology for such cladded, high temperature nuclear components will require addressing many issues: fabrication, corrosion resistance, metallurgical interaction, and the mechanical interaction of the clad and base materials under load. This work focuses on the final issue: the mechanical interaction of the base and clad under creep-fatigue conditions. Depending on the relative mechanical properties of the two materials the clad may substantially influence the long-term cyclic response of the structural system or its effect might be negligible. To quantify the effect of different clad material properties we develop an efficient method for simulating pressurized cladded components in the limiting case where the section of interest is far from structural discontinuities. Using this method we evaluate the mechanics of the clad/base system and identify different regimes of mechanical response. The focus is on situations relevant to high temperature nuclear components: thermal-cyclic Bree-type problems and similar axisymmetric structures. The insights gained from these structural studies will form the basis for developing design rules for high-temperature, nuclear, cladded components.

Research and Application of Ultrasonic Guided Wave With L(0,2) Mode for Elbow Tube Defect Inspection

Ultrasonic guided wave inspection technology has been widely for long distance pipeline inspection; however, the pipe elbow’s discontinuous structure and the dispersion of L-type wave are restricting the application of this technology. This paper proposes a method of L(0,2) mode guided wave excitation based on magnetostrictive effect and explores the optimization of the magnetization sensor arrangement. Test results shows that the proposed method can detect many types of defects in the pipe elbow. This paper encourages the use of L(0,2) mode guided wave excitation based on magnetostrictive effect in pipeline site inspections.

Management of Complex Loading Histories for Use in Probabilistic Creep-Fatigue Damage Assessments

An approach is outlined for the treatment of stresses in complex three-dimensional components for the purpose of conducting probabilistic creep-fatigue lifetime assessments. For conventional deterministic assessments, the stress state in a plant component is found using thermal and mechanical (elastic) finite element (FE) models. Key inputs are typically steam temperatures and pressures, with the three principal stress components (PSCs) at the assessment location(s) being the outputs. This paper presents an approach which was developed based on application experience with a tube-plate ligament (TPL) component, for which historical data was available. Though both transient as well as steady-state conditions can have large contributions towards the creep-fatigue damage, this work is mainly concerned with the latter. In a probabilistic assessment, the aim of this approach is to replace time intensive FE runs with a predictive model to approximate stresses at various assessment locations. This is achieved by firstly modelling a wide range of typical loading conditions using FE models to obtain the desire stresses. Based on the results from these FE runs, a probability map is produced and input(s)-output(s) functions are fitted (either using a Response Surface Method or Linear Regression). These models are thereafter used to predict stresses as functions of the input parameter(s) directly. This mitigates running an FE model for every probabilistic trial (of which there typically may be more than 104), an approach which would be computationally prohibitive.

Effects of Non-Normal Input Distributions and Sampling Region on Monte Carlo Results

In order to address the risks associated with the operation of ageing pressure boundary components, many assessments incorporate probabilistic analysis tools for alleviating excessive conservatism of deterministic methodologies. In general, deterministic techniques utilize conservative bounding values for all critical parameters. Recently, various Probabilistic Fracture Mechanics (PFM) codes have been employed to identify governing parameters which could affect licensing basis margins of pressure retaining components. Moreover, these codes are used to calculate a probability of failure in order to estimate potential risks under operating and design loading conditions for the pressure retaining components experiencing plausible and active degradation mechanisms. Probabilistic approaches typically invoke the Monte-Carlo (MC) method where a set of critical input variables are randomly distributed and inserted in deterministic computer models. Estimates of results from probabilistic assessments are then compared against various assessment criteria. During the PVP-2016 conference, we investigated the assumption of normality of the Monte Carlo results utilizing a non-linear system function. In this paper, we extend the study by employing non-normal input distributions and investigating the effects of sampling region on the system function.

Comparison of Wall-Temperatures of Two Types of Large Capacity Cylinders for Tube Trailers During CNG Loading Processes

Tube trailers with large capacity gas cylinders have been widely used to deliver compressed natural gas (CNG) in China in recent years. Most of the large capacity cylinders are full steel cylinders (Type CNG-1), and the tube trailers with large capacity glass fiber hoop-wrapped composite cylinders with steel liners (Type CNG-2) have entered into Chinese market since 2011. The tube trailers with CNG-2 cylinders can carry more gases than those with CNG-1 cylinders, but need more loading and cooling time to control their wall-temperatures according to the experiences of on-site operators in gas stations. In this paper, the wall-temperatures of those two types of large capacity cylinders on two tube trailers have been tested using a thermal infrared imaging camera during CNG loading processes in two natural gas stations in China. And numerical simulation on the CNG loading processes has been carried out to investigate the temperature changes of the gases and the shells of the cylinders. The results show that CNG-2 cylinders can have less maximum temperatures of the gases and the shells and less wall-temperature increments at the cost of lower loading rate and longer loading time.

Comparisons of Testing Methods for High-Pressure Hydrogen Storage Container Under the Law and Regulation System of UN and EU

Hydrogen energy as the cleanest fuel to replace gasoline has been accepted by society, hydrogen fuel could be promoted based on the safety of hydrogen-fuel storage containers. For risk-controlling of hydrogen storage containers, there are many laws and regulations in UN and EU set the strict technical requirements on high pressure hydrogen storage systems and require a lot of rigorous experimental verification should be performed before mass production. Frame of GTR No.13, ECER No.134 and EU No406/2010 and the content relevant with high-pressure hydrogen storage container would be discussed emphatically in this paper. Rigorous testing methods in regulations and standards are compared and comments on hydrogen storage container performance testing are provided, besides, some important testing items are discussed.

Development of Small Diameter and Thin-Walled Tube Docking Girth Joint Ultrasonic Testing Probe and Block

Due to the Small diameter and thin walled tube docking girth joint ultrasonic testing has the problems of: dead zone is often greater than the wall thickness; large curvature of the pipeline causes ultrasonic scattering, greatly reduces the sensitivity; pipe weld root’s is not welded and so on. In this paper, the prepared small-bore and sheet steel tube docking girth joint ultrasonic testing probe has sufficient sensitivity, is less than 2.5mm of initial pulse width, short front (≤ 5mm), high resolution, less clutter, less surface wave components, At the same time, the test block was designed and used for the testing of probe’s related technical indicators, the test block can meet the focus probe’s performance and scanning sensitivity calibration. Combined with the field detection and compared with the radiographic testing, the ultrasonic testing obtain good result. It is suitable for the ultrasonic quantitative testing of the joint ring weld of thin wall pipe.

Fracture Failure Analysis of 304 Stainless Steel Elbow

A cracking incident of a 304 stainless steel elbow serving in the synthesis gas purification device occurred during running. In order to get an understanding of the failure mechanism, a failure analysis was performed on the cracked elbow in this paper. The chemical composition, mechanical properties of strength, toughness and hardness, hydrogen content were identified and determined. The metallographical structure was observed and analyzed by optical microscope (OM) and X-Ray Diffraction (XRD), while the fracture morphology was observed by scanning electron microscope (SEM). The results showed that the chemical composition of the cracked elbow meet the requirements for China standard, while comparing with GB/T 14976-2012 standards, the strength and elongation of the leaked elbow are higher and lower respectively, and the hardness of the leaked elbow was higher than quality certificate documents that of HB ⩽ 187. Large quantities of martensite and δ-ferrite were observed in elbow, which indicated that the elbow was not well solid solution heat treated required by specification (1050°C,30min). The fracture morphology presents typical brittle fracture. The hydrogen content of cracked elbow was significant higher than that of other 304 stainless steel elbow serving in the environment without hydrogen. It is acknowledged that martensite showed higher sensitivity of hydrogen embrittlement compared with austenite. Furthermore, the operating temperature of cracked elbow was in the range of high hydrogen embrittlement sensitivity. Depending on the metallographical structure, strength, service environment, hydrogen content and fracture morphology, it can be concluded that hydrogen induced delayed cracking was the dominant mechanism of the failure.

RCC-M Code: Main Evolutions From the 2016 to 2018 Editions

The paper will cover the general approach followed by nuclear code RCC-M [1] of AFCEN, the French Society for Design, Construction and In-Service Inspection Rules for Nuclear Island Components, in codes and standards setting, from the technical and organizational points of view. After reminding the main modifications introduced in the 2016 & 2017 editions, the main evolutions expected in the 2018 edition of RCC-M code will be explained and commented, as well as the main new topics of activity of RCC-M subcommittee. The presentation highlights how the industrial experience is currently integrated into the RCC-M code. It also develops how the substantial effort carried out by AFCEN for the last three years, to demonstrate the conformity with European and French regulatory requirements, led not only to the development of dedicated guides and modifications in regulatory appendices of the code, but also to improvements in the main parts of the code.