[en] A design guide for high-temperature gas-cooled reactor components is proposed and applied to the design and construction of the 1.5-MW (thermal) helium heat exchanger test loop for nuclear steelmaking. To assure that the design method covers all conceivable failure modes and has a large enough safety margin, a series of lifetime tests of partial model may be needed. For this project, three types of model tests are performed. A lifetime test of an in-scale model of the center manifold pipe and eight heat exchanger tubes is described. Applied load is the combination of the simulated thermal expansion stress (deformation controlled quantity) and primary stress by internal pressure of tubes. The level of both loads is much higher than the corresponding values in the actual plant, which causes failure of the model in a shorter time. The eight tubes are arranged so that each is subjected to different damage conditions. The lifetime tests ran for 48 days, and six tubes out of eight failed during the test at the highest stressed stub tubes. Other parts of the components were found to be sound after the test. A damage criterion with a set of material constants and a simplified method for stress-strain analysis for a stub tube under a three-dimensional load are newly developed and used to predict the lives of each tube. The predicted lives are compared with the experimental lives and good agreement is found. The lifetime test model is evaluated according to the proposed design guide, and it is found that the guide has a safety factor of about 200 in life for this particular model

[en] The authors propose a simplified method for elastic follow-up analysis of elevated temperature piping systems composed of straight pipes and pipe bends. Here, the elastic follow-up is considered as a relaxation phenomenon of the overall structure, and, for statically determinate structures, relaxation characteristic function is explicitly given for Norton's creep law by an approximation method based on the complementary virtual work theorem. The authors define a global reference stress (G.R.S.) to obtain a relaxation characteristic function for general creep law other than Norton's, where G.R.S. is expressed as a function of initial section forces and the local reference stress (L.R.S.) which represents fundamental creep responses of the piping components concerned. It is clarified analytically that the degree of concentrated deformation by elastic follow-up depends largely on the ratio L.R.S./G.R.S. To obtain L.R.S. and other coefficients for the proposed method, parametric numerical calculations are performed using ISTRAN/3D, a general purpose three-dimensional structure analysis program, on pipe bends subjected to in-plane and out-of-plane bending moments. A computer program for the present simplified elastic follow-up analysis is developed for piping systems comprising pipe bends with the pipe factor lambda ranging from 0.05 to 0.57. The results of analyses performed on two- and three-dimensional piping models agree well with the numerical analyses by ISTRAN/3D or by SINAP-II, a program which takes flexibility factors into account. (orig./HP)

[en] There is the ASME B and PV code for design criteria of high temperature heat exchanger and these design codes cannot be applied to the 1.5 Mwt Heat Exchanger System because the codes applying range are limited up to 815⁰C, while the new heat exchanger system is supposed to be operated at the temperatures upto 1000⁰C. Because this heat exchanger is a test loop for nuclear direct steal making plant, its design and construction requires as much safety assurance as the nuclear power plant. In order to satisfy safety requirement, a new design code specifying heat exchanger components operable at a maximum allowable temperature of 1,000⁰C was proposed. (orig.)

[en] This paper reports the structural integrity study of 1.5 Mwt helium gas intermediate heat exchanger performed as a part of 'Research and Development of Direct Steel Making Technology Utilizing High Temperature Reducing Gas' which is one of the National Research and Development Programs by Agency of Industrial Science and Technology, Ministry of International Trade and Industry, Japan. The normal operation temperature of the heat exchanger exceeds 1000⁰C which is beyond the scope covered by the existing design code, e.g. ASME Code Case 1592. Therefore, a special analytical and experimental procedure should be developed to establish design rules of unprecedented components operating at extremely high temperature. (orig.)