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| February 3, 2005 No.1040 | ||
| MHI Performs World's First PWR Reactor Internals Replacement Work Using New All-in-One Extraction Method -- No Splitting or Cutting Necessary -- |
| Tokyo, February 3, 2005 - Mitsubishi Heavy Industries, Ltd. (MHI) today has completed replacement work on the upper and lower reactor internals of the 566 MW (megawatt) Ikata Nuclear Power Station Unit No.1 of Shikoku Electric Power Co., Inc. The event marks the world's first all-in-one-piece extraction and replacement work of its kind in pressurized water reactors (PWR). |
Replacement of the reactor internals with a structure of the newest design was executed with two objectives: (a) to accommodate additional control rods in line with the planned adoption of advanced fuel for high burn-up*; and (b) to prevent damage of baffle-former bolts, of the kind reported overseas, caused by stress corrosion cracking (SCC). MHI developed a new method that enables extraction of existing reactor internals in one piece in air, without splitting or cutting. The new method shortened the required work period and also greatly reduced workers' radiation exposure. The replacement work was conducted as part of periodical inspection work on the Ikata Station Unit No.1. The replaced internals consist of a lower structure that houses fuel assemblies and an upper structure that supports them from above; the combined structure, made entirely of stainless steel, measures 8 meters in length and 2.8 meters in inner diameter and weighs 100 metric tons. Since the work had to be performed without workers coming in close contact due to the presence of strong radiation dose, both of the upper and lower reactor internals were directly removed as one piece in air from the reactor vessel, without being split or cut into pieces. The removed materials were hoisted by a specially installed crane and stored in a special steel container cask. The total weight of the cask after housing the removed reactor internals reached some 450 tons. When the new reactor internals were installed in the water-filled reactor vessel, extremely high accuracy was demanded: about 0.4 millimeter at the narrowest clearance, equal to the requirement during initial construction. To fulfill that requirement, MHI newly developed a high-precision remote-controlled measurement system for underwater applications. Prior to actually executing the work on-site, a series of elaborate verifications were performed and rigorous training in the new work method was conducted to ensure full satisfaction of the project's stringent work requirements. The Shikoku Electric Power is now planning to carry out the same reactor internals replacement work during the next periodical inspection of the Ikata Station Unit No. 2 , which will be scheduled from September this year. MHI will use the leverage of its experience and technology applied at the Ikata power plant to continue its active pursuit of preventive maintenance for nuclear reactors, as a way of supporting the safe operation of nuclear power plants everywhere. *Note:Advanced fuel for high burn-up is a nuclear fuel that can be used for a longer time in the reactor. This is achieved through use of higher enriched uranium (U235). # # #
About Mitsubishi Heavy Industries Mitsubishi Heavy Industries, Ltd. (MHI), headquartered in Tokyo, Japan, is one of the world's leading heavy machinery manufacturers, with consolidated sales of 2,373 billion yen in fiscal 2003 (year ended March 31, 2004). MHI's diverse lineup of products and services encompasses shipbuilding, steel structures, power plants, chemical plants, steel plants, environmental equipment, industrial and general machinery, aircraft, space rocketry and air-conditioning systems. For more information, please visit the MHI website (http://www.mhi.co.jp). PRESS CONTACT: Hideo Ikuno: h.ikuno@daiya-pr.co.jp Tel: +813-6716-5277, Fax: +813-6716-5929 Daiya PR (in charge of public relations for Mitsubishi Heavy Industries, Ltd.) |
