Gravelines 1 shut down for crack repair

22 December 2011 Inspection work has revealed tiny cracks on a penetration at the bottom of Gravelines 1’s reactor pressure vessel. The power unit remains shut down until a repair has been made.  In France’s 900-MWe class pressurized water reactors, some 50 small tubes around 38 mm in diameter penetrate the bottoms of the reactor pressure vessels. They allow for instruments to be inserted through the vessel and into the reactor core, but their construction is important to nuclear safety because it represents part of the boundary of the pressurized cooling system. The tiny cracks were discovered within the pressure vessel in the area of welded alloy around the tube at Gravelines 1. The Nuclear Safety Authority (Autorité De Sûreté Nucléaire, ASN) said it was the first time such a defect has been found in France, although similar faults were dealt with in 2003 at the South Texas Project site in the USA. EDF owns and operates Gravelines 1 along with France’s 57 other power reactors. The company has suggested a repair method to the ASN, which is reviewing the technique in collaboration with the Institute of Radiological Protection and Nuclear Safety (Institut de Radioprotection et de Sûreté Nucléaire, IRSN). In the meantime, the reactor will remain offline, said ASN, noting that the detailed 10-year inspection that discovered the issue had required the removal of nuclear fuel. The cracks therefore have no current impact on safety. EDF has been requested by the ASN to check all its 900 MWe and 1300 MWe reactors for similar cracks – a total of 54 units. Fuente:...
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New US mine set for development

22 December 2011 Uranium Energy Corp (UEC) has now obtained all the permits needed to proceed with development of its Goliad in-situ leach (ISL) uranium project in South Texas. Having issued UEC with a draft Radioactive Materials Licence (RML) for the Goliad project in September, the Texas Commission on Environmental Quality (TCEQ) has now issued the final version. The company said that it “now has all the required permits to begin construction at the site, and the procurement of materials and initial wellfield development will commence shortly.” The Goliad project is located 64 kilometres from UEC’s Hobson uranium processing facility, which forms the basis of its regional operating strategy in the South Texas Uranium Belt and processes uranium-loaded resins from its four near-by uranium projects into yellowcake (U3O8). UEC’s Palangana ISL mine was licensed in January 2010 and is now ramping up initial production. In March 2008, UEC announced updated resource figures for Goliad, putting measured and indicated resources to 5.475 million pounds U3O8 (2100 tU). An additional 1.548 million pounds U3O8 (595 tU) has been classified as an inferred resource. All the figures are at cut-off grades of 0.05% U3O8, and are reported in accordance with Canadian National Instrument 43-101. Commenting on the issuance of the RML, Amir Adnani, UEC president and CEO, said: “Management is pleased to report the completion of this major milestone, and to initiate the early steps in the construction process.” The company noted that an aquifer exemption is still required before uranium recovery activities can be initiated at Goliad. These are issued jointly by the regional Environmental Protection Agency (EPA) and the TCEQ, and only the EPA’s approval is outstanding. ISL mines pass a leaching solution – such as oxygen with sodium carbonate – through buried sand containing uranium, dissolving it on the way. The solution is then pumped to the surface. The uranium is removed from the solution using an ion-exchange process. Usually the ion-exchange resin or solvent would undergo stripping and precipitation on-site to remove uranium. Fuente:...
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Fukushima units enter decommissioning phase

21 December 2011 A roadmap setting out the mid- to long-term activities needed for the decommissioning of the damaged Fukushima Daiichi reactors has been released. The plan envisages decommissioning activities being completed within 30 to 40 years. The roadmap – drafted by Tokyo Electric Power Company (Tepco); the Ministry of Economy, Trade and Industry’s Agency for Natural Resources and Energy; and the Nuclear and Industrial Safety Agency – received government approval today. Japanese prime minister Yoshihiko Noda announced on 16 December that the Fukushima Daiichi reactors had attained ‘cold shutdown’ conditions bringing to a close the ‘accident’ phase of events at the plant triggered by the 11 March tsunami. In announcing the decommissioning roadmap, Tepco said that it will now “shift our approach from the stabilization of the plant to the maintenance of stable condition.” The roadmap is split into three phases, the primary targets of which are: the removal of fuel from all four used fuel pools; the removal of melted fuel from the three damaged reactor cores; and finally the demolition of the reactor facilities. Work to carry out these tasks will be hampered by the amount of debris and contamination present on the site, not least that on top of units 1, 3 and 4. Tepco said that it plans to start removing the fuel from the used fuel pool at the top of the reactor building of unit 4 within the next two years, while the removal of fuel from the pool at unit 3 will begin by the end of 2014. At unit 1, the company plans to develop a used fuel removal plan based on its experience at units 3 and 4, while for unit 2 it will develop a plan once the inside of the reactor building has been decontaminated and the condition of existing used fuel handling equipment has been assessed. Tepco plans to remove all of the used fuel from the four pools within ten years, during which time it will determine what reprocessing and storage methods it will use to deal with it. With regards to fuel within the reactors themselves, its exact location and condition is still not known, but an earlier analysis suggested that most of unit 1’s fuel melted and went through the bottom of the reactor vessel, as well as about 70 centimetres of the drywell concrete below. The cores of units 2 and 3...
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New date for Olkiluoto 3

21 December 2011 August 2014 is the date that Teollisuuden Voima Oyj (TVO) expects to see power flow from its new reactor, Olkiluoto 3, according to a single-line statement issued today. The announcement brought a little more clarity to the unit’s schedule compared with TVO’s last announcement, which specified only the year 2014. The Finnish utility said it had been informed by the Areva-Siemens consortium building the unit that August 2014 was scheduled for commercial operation. Construction started in May 2005. Fuente:...
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New data on low-dose radiation

21 December 2011 Results from America’s Berkeley National Laboratory have cast doubt on the assumption that risk from radiation is always proportional to exposure – a theory that underpins most measures for radiological protection. Living cells are constantly bombarded by ionizing radiation in various forms and from various sources, all of which have the potential to damage DNA. Unless this damage is corrected by self-repair mechanisms it can result in cell malfunction or the malignancy known as cancer.   These effects have been clearly shown to be statistically likely for high radiation doses, such as those received by Japanese survivors of atomic bombs. What is less well understood and far harder to study are the effects of lower doses of radiation as received from natural sources, medical scans, or to a lesser extent nuclear power operations.   The prevailing method to deal with this area of uncertainty is to extrapolate the observable effects of high doses and assume the same relationship applies to low doses with no observable effect i.e. assume that all levels of exposure come with a commensurate health risk, no matter how small. This approach is used in practice as a basis for the management of occupational and public exposure worldwide. It is a safe assumption that the amount of DNA damage increases in line with radiation exposure, but Mina Bissell of Berkeley’s life sciences division said today: “Our data show that at lower doses of ionizing radiation, DNA repair mechanisms work much better than at higher doses.” She added that this “casts doubt on the general assumption that any amount of ionizing radiation is harmful and additive.”   The researchers used time-lapse images of cells as they responded to various radiation doses. They were able to see the repair proteins concentrate around parts of DNA that had suffered a double strand break in what are called radiation-induced foci (RIF). Over time the severed ends of DNA strands actually moved within the cell nucleus to gather in larger RIFs known as ‘repair centres’.   Sylvain Costes, who led the study, said that multiple repairs could be taking place simultaneously in the repair centres, leading to more errors in the repaired DNA. He said that at low levels of radiation, such as the natural levels humans experienced throughout evolution, it was “unlikely” that any cell would have to repair more than one double strand break at once.  ...
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