Norio Yokoyama

Ductile fracture behavior of circumferentially cracked type 304 stainless steel piping under bending load

Abstract A ductile pipe fracture test program has been conducted in Japan Atomic Energy Research Institute (JAERI) to investigate the ductile fracture behavior of circumferentially cracked pipes and to demonstrate the validity of the leak before break concept in LWR pipings. In the paper are described the scope of the pipe test program and current test results for 6-inch diameter type 304 stainless steel pipes. Test pipes with a through-wall or a part-through crack in the circumferential direction were bent under low or high compliance condition, and stable or unstable pipe fracture behavior was investigated. J based tearing instability criterion and the net section collapse criterion are compared with the pipe test results, and the validity of these fracture criteria is discussed. Furthermore, geometries of acceptable flaws in pipes are evaluated considering the leak before break condition.

Present status of Data-Free-Way (distributed database system for advanced nuclear materials)

Abstract The National Research Institute for Metals (NRIM), the Japan Atomic Energy Research Institute (JAERI), the Power Reactor and Nuclear Fuel Development Corporation (PNC), and the Japan Science and Technology Corporation are jointly developing a distributed database for advanced nuclear materials named Data-Free-Way. The main objective of the development is to share fresh and stimulating information as well as accumulated information for the development of advanced nuclear materials, for the design of structural components, etc. This paper describes the present status of the system and examples of utilization of the system. From such examples, it is demonstrated that the present distributed database system is attractive to evaluate materials performance in the fusion environment.

A Distributed Database System for Mutual Usage of Materials Information (Data-Free-Way)

A distributed database system named ``Data-Free-Way`` for advanced nuclear materials has been developed by the National Research Institute for Metals (NRIM), the Japan Atomic Energy Research Institute (JAERI), and the Power Reactor and Nuclear Fuel Development Corporation (PNC) under a cooperative agreement. In this paper, features and functions of the system, including input data, are described together with a method to share the database among the three organizations as well as examples of the easy accessible search of material properties provided by the system. Results of an analysis of tensile and creep properties data on Type 316 stainless steel collected by the different organizations and stored in the present system are introduced as an example of attractive utilization of the system. Moreover, in order to known how to use the system, some trails of the WWW server of several sites in Data-Free-Way to supply the information on nuclear materials are introduced.

System design of pilot data-free-way (Distributed database for advanced nuclear materials)

Abstract The pilot system on the distributed database for advanced nuclear materials is named “Data-Free-Way”. The project started in April 1990, and the material database including metals, ceramics and composites will be established within five years under the cooperation of the National Research Institute for Metals (NRIM), Japan Atomic Energy Research Institute (JAERI) and Power Reactor and Nuclear Fuel Development Corporation (PNC). For the pilot system, the method of sharing data, data structure and examples of the easily accessible search of materials properties are shown. Furthermore, the future trials of attractive/sophisticated utilization focused on the issues relating to fusion materials are described.

Present status of Data-Free-Way — Distributed database for advanced nuclear materials

Abstract This paper describes the status of the pilot system on the distributed database for advanced nuclear materials named Data-Free-Way. Trials of utilization of the system focused on the issues relating to fusion materials are mentioned. A relational database management system was utilized to unify useful data of material properties into the distributed database. The other software such as operating system, network utilities, etc. were also incorporated. To make retrieval rationally and promptly, a menu for selecting data items was expanded for the system. High-temperature tensile properties of type 316 stainless steel irradiated in various reactors were analyzed. The results indicated that correlation between postirradiation total elongation versus amounts of displacement damage was better than that between postirradiation total elongation versus helium accumulation in the alloys. Furthermore, correlation coefficients of the data between those two variables were better at higher temperature ranges.

Fatigue and fracture behavior of straight pipe with flaws in inner surface

Abstract Fatigue and fracture tests of piping models with flaws in the inner surface were carried out to investigate the fatigue crack growth, coalescence of multiple cracks and fracture behavior. Two straight test pipes with and without weldment in the test section of AISI type 304L stainless steel were tested under almost the same test conditions by imposing moment loads. Three artificial defects were machined in the inner surface of the test section of the test pipes and the fatigue test was performed until the cracks coalesced and grew through the thickness. Subsequently, a static load was imposed on the test pipe which contained a large crack in the test section. The fatigue test results are compared with an analytical crack growth behavior predicted by the method described in the Section XI of ASME Code, and show slower crack growth than that of the prediction. From the fracture test results, it is found that the test pipes can endure considerably high load.

Development of "Data-Free-Way" Distributed Database System for Advanced Nuclear Materials

A distributed database system named “Data-Free-Way (DFW)” is under development by a cooperation among three Japanese national research organizations to support the creation of advanced nuclear materials. The development of DFW started in 1990 as a five-year program with a support from Science and Technology Agency of Japan. Before starting the program, a preliminary survey of both domestic and foreign databases of nuclear materials had been made for two years. Then, subjects for the construction of DFW were extracted. To meet the subjects, the development and construction programs were established. The DFW is constructed on the computer network which connects engineering workstations in the separate organizations. A relational database management system is used, a distributed material database is equipped on the hardware with specially designed common data structure. Data storage has been carried out continuously in each organization. The equipment of useful user-interface systems, such as retrieval, data...

Development of Comprehensive Material Performance Database for Nuclear Applications.

Computer technology has remarkably improved recently, especially the World Wide Web (WWW), which has become the predominant method for accessing the Internet. As the result, it is possible to extract attractive and sophisticated information easily and timely through massive and quick communication of complex materials data. At Japan Atomic Energy Research Institute (JAERI), the JAERI Material Performance Database (JMPD) has been developed to utilize various kinds of characteristic data about nuclear metallic materials efficiently. The data entry supporting system is developed to reduce the data input task. Retrieval and graphic presentation are carried out through the WWW. Based on the stored data, analyses are performed.

Statistical analyses of variability/reproducibility of environmentally-assisted cyclic crack growth rate data relative to ΔK control modes

Abstract Statistical analyses were conducted by using the cyclic crack growth rate data for pressure vessel steels stored in the JAERI Material Performance Database (JMPD), and comparisons were made on variability and/or reproducibility of the data between obtained by Δ K -increasing and by Δ K -constant type tests. Based on the results of the statistical analyses, it was concluded that Δ K -constant type tests are generally superior to the commonly used Δ K -increasing type tests from the viewpoint of variability and/or reproducibility of the data. Such a tendency was more pronounced in the tests conducted in simulated LWR primary coolants than those in air.

Fatigue behavior of pipes containing multiple flaws in inner surface

Abstract In this work was studied the growth behavior of multiple cracks in the inner surface of pipes. The fatigue tests were performed using two kinds of test pipes, i.e., the straight pipes and bend pipes of AISI Type 304L stainless steel, having 320 mm in outer diameter and 35 mm in thickness approximately. The crack growth curves obtained by the fatigue tests were compared with the analytical curves of two kinds of crack growth prediction methods. One method is based on the ASME Boiler and Pressure Vessel Code, Sec. XI. Another method is based on the procedure in which the crack growth formula is applied to both the surface and thickness directions. The analytical crack growth curves predicted by the ASME Code are conservative for the test results of the straight and bend pipes. However the results of bend pipe test suggest that the procedure of the ASME Code may give an unconservative fatigue life under the certain condition. On the other hand, the test results of the straight pipes can be evaluated reasonably and those of the bend pipes can be evaluated conservatively by the latter method.