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Giappone/Annunciato il riavvio dei lavori di costruzione presso la centrale di Ohma

Alla fine dell’articolo troverete una nota tecnica in italiano sull’ABWR (Advanced Boiling Water Reactor)

The Japan Electric Power Development Corp (J-Power) will resume construction of the Ohma nuclear power plant in Aomori prefecture. It will be the first Japanese nuclear construction project to restart since all such projects were suspended following the Fukushima accident.

J-Power said today that “the treatment of nuclear power plants under construction became clear” thanks to the revised energy policy announced by the Japanese government. Accordingly the company decided to resume construction of the Ohma plant, “with the understanding of the local communities.”Work to build the 1383 MWe (gross) Advanced Boiling Water Reactor (ABWR) in Aomori prefecture was 40% complete in March 2011 when a tsunami caused the accident at Tokyo Electric Power Co’s (Tepco’s) Fukushima Daiichi plant. An extended hiatus followed, during which Japan developed a new energy strategy.

The company said that it will strive to establish a safe power plant by, among other things, ensuring that reinforced safety measures are implemented that take into account the lessons learned from the Fukushima accident. J-Power will also ensure that all current and future technology standards set by the new Nuclear Regulatory Authority are met.

“As a power plant that adopts the most advanced technologies, the Ohma nuclear power plant will be a highly safe and reliable power plant that will play an instrumental role in the stable supply of electricity and the nuclear fuel cycle of Japan,” J-Power said. The company has taken various measures for reinforcing safety at the Ohma plant, including a range of anti-tsunami actions, ensuring emergency power sources and ultimate heat removal functions, and improving response to severe accidents.

J-Power plans to use all mixed oxide (MOX) uranium and plutonium nuclear fuel in the reactor core of Ohma, which necessitates some design variation from the ABWR standard. Amendments for the different reactive and thermal properties of MOX fuel include a higher-capacity liquid control injection system; additional safety valves to release steam; control rods with enhanced neutron absorption; and automatic fuel inspection devices to reduce radiation exposure to workers.

Ohma would be the first Japanese reactor built to run solely on MOX fuel incorporating recycled plutonium. It will be able to consume a quarter of all domestically-produced MOX fuel and hence make a major contribution to Japan’s “pluthermal” policy of recycling plutonium recovered from used fuel. This policy increases Japan’s self-sufficiency in energy fuels from 4% to 18% by making maximum use of imported uranium.

The start of construction of the Ohma plant was originally due in August 2007, with commercial operation planned for March 2012. However, the imposition of more stringent seismic regulations put back the start of construction May 2008 and commercial operation to November 2014. J-Power said that it has not yet scheduled a new date for the start of operation “but intends to review the matter in the future based on progress in construction.” (Source: “World Nuclear News”)

NOTA TECNICA SULL’ ABWR (Advanced Boiling Water Reactor)

L’ABWR (Advanced Boiling Water Reactor) è un reattore ad acqua bollente di III generazione.

È stato progettato dalla General Electric ed è al momento prodotto dall’alleanza fra quest’ultima ed Hitachi.

L’ABWR prevede un ciclo diretto di conversione dell’energia  utilizzando direttamente il  vapore prodotto nella caldaia nucleare per alimentare una turbina collegata ad un generatore elettrico.

Il reattore ABWR standard fornisce una potenza elettrica netta di circa 1350 MW (*),  comunque General Electric e Hitachi offrono anche un progetto con una maggiore produzione di energia. I reattori ad acqua bollente sono la seconda forma più diffusa di reattori ad acqua leggera.

L’ABWR è lo stato dell’arte attuale fra i reattori ad acqua bollente ed è il progetto di reattore di III generazione ad essere stato per primo costruito ed esercito, diversi impianti sono stati realizzati in Giappone.

Il progetto standard ABWR è certificato negli U.S.A dalla Nuclear Regulatory Commission (Autorità per la sicurezza nucleare). ABWR sono in ordine anche negli Stati Uniti, con il primo progetto approvato per nuove centrali nucleari dopo oltre un decennio (South Texas Project, con due ABWR nel 2007).

(*) l’impianto giapponese di Ohma: 1383 MWe

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