[en] The requirements for the structural integrity and reliability of the nuclear reactor pressure vessel (RPV) are more stringent on in-service inspection (ISI) of RPV as well as on properties of materials used in RPV. For the purpose of elimination or minimization of weld seams which are subject to ISI, demands are arising for application of seamless and integrated type of forging to the heads, petals, shells etc. of RPV which would result in easier execution and the reduction of ISI and increased availability of nuclear power stations. The bottom head of BWRPV is the most difficult area to be inspected due to very complicated contour. This paper describes the key points of manufacturing technique as well as homogeneity of material properties obtained from the bottom head which have been made of the integrated type of large scale forging (Large Size Forged Head). (author)

[en] Recent increase in energy demand due to the drastic growth of economy especially in China and reevaluation of nuclear power generation as a measure to reduce greenhouse gas have promoted construction of large capacity power plants and development of advanced power plants with the higher capacity. The components used in these power plants such as reactor pressure vessels and turbine rotor shafts tend to enlarge and some of them may require, in the future, the ingot with the weight over 600 tons for production. In order to meet the increasing order of these larger forgings and to materialize further improvement in quality, cost and productivity, investment in plant and equipment such as shop building, refining and casting facilities has been progressing. The present report introduces the outline of the investment in plant and equipment with the expected effect of the investment. (author)

[en] As a primary remedy for IGSCC of primary loop piping, especially Recirculation Loop Piping of BWR, extra low carbon stainless steel with high nitrogen content has become to be used. While, in order to make In-service Inspection easier and complete, new design of piping which decrease both number and total length of weld line has been considered. Japan Steel Works has developed the research on large size seamless forged pipe and fitting made from high nitrogen extra low carbon 316 stainless steel. This paper describes the key points of manufacturing technology as well as the material properties, especially strength and intergranular-corrosion and intergranular- stress-corrosion-cracking-resistivities of these forged pipe and fitting. (author)

[en] In recent years, the components of PWR such as a steam generator, closure head of pressure vessels and pressurizer have been replaced for the lifetime lengthening of nuclear power stations. For the closure head, we developed a head forging type integrated with flange superior to the conventional joint welding one fabricated by steel plate head and forged flange. This report described our manufacturing technology, material properties and manufacturing experience for the newly developed closure head. (author)

[en] EPR (EPR: European Pressurized Water Reactor) has been developed to achieve higher output (1,600 MW) and longer plant life (60 years), compared with the conventional unclear reactors, and the first commercial reactor was introduced in Finland no.5/Olkiluoto no.3. The integrated mono-block design was applied for nozzle shell flange instead of welded conventional flange and nozzle shell. And due to set-on type nozzles, a 600 ton ingot was required for this part. JSW successfully completed the manufacturing of first nozzle shell with integral flange 11 months after melting. This report summarizes manufacturing technology and process, and properties of nozzle shell with integral flange. (author)

[en] Mono-block low-pressure steam turbine rotor shaft forging and flange integrated nozzle shells for nuclear power plants have been produced from up to 600 metric ton ingots. With increasing generator unit capacity, there are calls for ingots larger than 600 tons. However, segregation, non-metallic inclusions, and micro porosities inevitably increase with the rise in ingot size. Making such massive ingots with high soundness is a quite difficult challenge. The Japan Steel Works has been carrying out the development of 650-ton class ingot production. In this paper, we report the result of Investigation on the internal guality of the first 650-ton ingot in the as-cast condition. (author)

[en] Due to the recent increase in world energy demand, construction of considerable number of nuclear and fossil power plant has been proceeded and is further planned. High generating capacity plant requires large forged components such as monoblock turbine rotor shafts and the dimensions of them tend to increase. Some of these components have center bore for material test, NDE and other use. In order to cope with the increase in production of these large forgings with center bores, a new trepanning machine, which exclusively bore a deep hole, was developed in JSW taking account of many accumulated experiences and know-how of experts. The machine is the world largest 400t trepanning and horning machine with numerical control and has many advantage in safety, the machining precision, machining efficiency, operability, labor-saving, and energy saving. Furthermore, transfer of the technical skill became easy through concentrated monitoring system based on numerically analysed experts' know-how. (author)

[en] From the standpoint of economy and design, mono block large forgings have become in use for nuclear steam supply system components and the minimization of weld seams has been encouraged. The SA508, C1.3 Steel is the standard material for these forgings at present and have almost the same or superior properties compared to conventional SA533, Gr. B steel plate. Until now, however, the neutron irradiation embrittlement susceptibility of this material has not been clear because of the lack of irradiation test data. In this paper, the neutron irradiation embrittlement susceptibility of SA508, Cl.3 steel are reported on the several accelerated test data using the material of actual SA508, Cl.3 large forging and compared to the susceptibility of SA533, Gr.B steel. It is proved that the neutron irradiation embrittlement susceptibility of SA508, Cl.3 steel is almost the same as that of SA533, Gr.B steel. (author)

[en] Forging components (for nuclear power plants) have become larger and larger because of decreased weld lines from a safety point of view. Consequently they have been manufactured from ingots requirement for 200 tons or more. Dehydrogenation is one of the key issues for large ingot manufacturing process. In the case of ingots of 200 tons or heavier, mold stream degassing (MSD) has been applied for dehydrogenation. Although JSW had developed mold stream degassing by argon (MSD-Ar) as a more effective dehydrogenating practice, MSD-Ar was not applied for these ingots, because conventional refractory materials of a stopper rod for the Ar blowing hole had low durability. In this study, we have developed a new type of stopper rod through modification of both refractory materials and the stopper rod construction and have successfully expanded the application range of MSD-Ar up to ingots weighting 330 tons. Compared with the conventional MSD, the hydrogen content in ingots after MSD-Ar has decreased by 24 percent due to the dehydrogenation rate of MSD-Ar increased by 34 percent. (author)

[en] Recently, with the rapid progress of the petrochemical and nuclear power industry, the demand for heavy section austenitic stainless steel forgings have been increasing to be used for elevated temperature services. When the size and thickness of the stainless steel forgings is enlarging, its mechanical and metallurgical properties should be evaluated in the view point of the criteria of elevated temperature design. In this paper, manufacturing procedures to produce the high quality heavy section stainless steel are summarized and detailed characteristics of its mechanical properties at elevated temperature are discussed based on the fundamental and practical experimental test results. (author)