No abstract available

[en] The effect of frequency or hold-time on the low-cycle fatigue strength of AISI 316 stainless steel and SCM 3 Cr-Mo steel for fuel cladding, piping and other structural members of LMFBR is investigated under high temperature conditions. Push-pull fatigue tests are conducted in air under conditions of fully reversed axial strain-control with a tensile strain hold-time ranging from 0 to 120 min for AISI 316, and with a tensile and an equal compressive strain hold-time ranging from 0 to 995 s for SCM 3. In these tests, a considerable decrease of fatigue life is observed as the hold-time is increased. An empirical formula is presented which can predict well the effect of hold-time on high temperature low-cycle fatigue life in terms of frequency. The formula is a little different from those in the literature. (author)

[en] The effect of frequency or hold-time on the low-cycle fatigue strength of AISI 316 stainless steel and SCM 3 Cr--Mo steel for fuel cladding, piping, and other structural members of LMFBR is investigated under high temperature conditions. Push-pull fatigue tests are conducted in air under conditions of fully reversed axial strain-control with a tensile strain hold-time ranging fromm 0 to 120 min for AISI 316, and with a tensile and an equal compressive strain hold-time ranging from 0 to 995 s for SCM 3. In these tests, a decrease of fatigue life is observed as the hold-time is increased. An empirical formula is presented which can predict well the effect of hold-time on high temperature low-cycle fatigue life in terms of frequency. The formula is a little different from those in the literature

[en] Research and development work done recently in connection with high temperature projects in Japan are briefly reviewed. The subjects discussed are: development of high temperature resisting superalloys; creep rupture strength of welded joints; environmental effects on materials in elevated temperature service; effect of cold work on creep strength; elastic follow-up; criterion for high temperature allowable stress; and estimation of creep damage. (author)

[en] A study was made to develop a method for evaluation of the local strain in a cladding tube of the Advanced Thermal Reactor due to radial cracking of a UO₂ fuel pellet. Effects of the number of cracks, initial crack width and the friction coefficient of a pellet-clad interface on behaviors of the local strain in a cladding tube were evaluated with a modelized experiment. A Zircaloy-2 ring specimen with inner diameter of 95 mm, height of 25 mm and wall thickness of 5 mm was expanded at room temperature with equally divided peripheral dice of a tool steel set in a specimen. The dice were divided into 8, 12 or 16 pieces. For each dividing number, two dice edge geometries were prepared, that is, not chamfered and chamfered by 2 mm. Strains of an external surface of the specimen were measured with 28 wire strain gages with gage length of 0.3 mm. The friction coefficient on the pellet-clad contact surface was not measured, but two friction conditions were prepared. One was metal-metal contact and the other was a contact surface coated with teflon film. The estimated friction coefficient was 0.1 for the former and 0.05 for the latter. An elastic-plastic analysis was carried out in order to evaluate the membrane hoop strain in the cladding tube. The analysis was made under two conditions. One was a plane stress condition of a radial and hoop stress which resembled the state of stress-strain developed in the ring specimen. The other was a plane strain condition of a radial and hoop strain which approximated the stress-strain state in a cladding tube

[en] Steady and cyclic creep tests with internal pressure were performed at temperatures of 800 to 1000⁰C on Hastelloy X cylinders with and without a circumferential Tungsten Inert Gas (TIG) welding technique. The creep rupture strength of the TIG welded cylinders was much lower than that of the non-welded cylinders whilst creep rupture strength reduction by the TIG technique was not observed in uniaxial creep tests. The reason for the low creep strength of welded cylinders is discussed and it is noted that the creep ductility of weld metal plays an essentially important role. In order to improve the creep strength of the TIG welded cylinder, various welding procedures with assorted weld metals were investigated. Some improvements were obtained by using welding techniques which had either Incoloy 800 or a modified Hastelloy X material as the filler metal. (U.K.)

[en] In order to improve the creep strength of the TIG welded cylinder, welding procedure with miscellaneous weld metals was investigated. An improvement was obtained by Incoloy 800 and the modified-Hastelloy X as the filler metal. The creep rupture strength and ductility of the welded cylinders with these filler metals became higher to a certain extent than that of the conventional TIG welded cylinder. As another attempt to the improvement, electron beam welding was applied to the Hastelloy X cylinder. The result was so good that the creep rupture strength and ductility at 1000⁰C were almost equal to those of the non-welded cylinder. (orig.)

No abstract available

[en] A study was made to develop a method for evaluation of the local strain in a cladding tube of the Advanced Thermal Reactor due to radial cracking to a UO₂ fuel pellet. Effects of the number of cracks, initial crack width and the friction coefficient of a pellet-clad interface on behaviors of the local strain in a cladding tube were evaluated with a modelized experiment. Analytical evaluation of a membrane strain was also carried out on the basis of a procedure similar to that proposed by J. H. Gittus, Nuclear Engineering and Design 18 (1972) 69-82, in order to follow the experimental results and to extend the model experiment to cladding tube. A Zircaloy-2 ring specimen with inner diameter of 95 mm, height of 25 mm and wall thickness of 5 mm was expanded at room temperature with equally divided peripheral dice of a tool steel set in a specimen. Strains on an external surface of the specimen were measured with 28 wire strain gages with gage length of 0.3 mm. An elastic-plastic analysis was carried out in order to evaluate the membrane hoop strain in the cladding tube on the basis of a simple procedure similar to that proposed by Gittus. The results of analysis showed that the maximum hoop strain occured at a location apart from the dice edge. This was caused by unloading in the crack opening portion. The strain concentration factor obtained from analysis is greater than that obtained from experiment. The difference of concentration factors between analysis and experiment is due to the bending strain. Therefore, the strain concentration factor at the inner surface is evaluated from the experimental concentration factor at the external surface and the analytical concentration factor of a membrane strain. (Auth.)

[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.)