i-Nuclear Update: New inspections confirm cracking in Belgium's Doel-3 reactor pressure vessel

i-NUCLEAR

New inspections confirm cracking in Belgium’s Doel-3 reactor pressure vessel by I-Nuclear Supplementary inspections of Electrabel’s Doel-3 reactor pressure vessel have confirmed the presence of a large number of cracks, initially indicated by inspections in June and July, according to an official report issued September 3. The confirmation of a large amount of cracking raises the bar significantly for Electrabel to prove the 30-year-old reactor is safe to return to service. A spokeswoman for the Belgian Federal Authority for Nuclear Control (FANC) said September 4 that Doel-3 could not return to service before October at the earliest. Studies are currently under way to confirm the structural integrity of the vessel and a pressurised thermal shock (PTS) study will be required to see how the vessel would respond to an overcooling, high-pressure event, according to the report. For the time being it is believed that the cracks did not evolve during plant operation as a result of irradiation or other mechanisms, but have been present since fabrication of the reactor vessel by the now-defunct Dutch company Rotterdam Dry Dock (Rotterdamsche Droogdok Maatschappij) or RDM. RDM was accredited with a nuclear stamp from the American Society of Mechanical Engineers (ASME N-stamp). The reactor pressure vessel contains the nuclear fuel core and is typically made of thick steel forgings and plates welded together. In the case of Doel-3, the raw materials for the reactor shells was supplied by Krupp, the forging by RDM, the cladding and assembling by Cockerill for the lower part (two core shells, transition ring and bottom plate) and by Framatome (now Areva NP) for the upper part comprising the RPV head, nozzle shell, and the final assembly. The 1,006-MW Doel-3 is owned by France’s GDF Suez and operated by Belgium’s Electrabel. The confirmation of reactor vessel cracks at Doel-3 also threatens the operation of the Electrabel’s 1,055-MW Tihange-2 reactor, currently in an outage, because parts of its vessel were manufactured by RDM under the same contract. According to Nuclear Energy Agency, 21 reactors worldwide had parts of their reactor vessels manufactured by RDM. In addition to Doel-3 and Tihange, the other European reactors potentially affected are the permanently shutdown Brunsbuettel and Philippsburg-1 in Germany; Borssele and Dodewaard (permanently shut) in the Netherlands; Garoña and Cofrentes in Spain; Ringhals-2 in Sweden and Leibstadt and Mühleberg in Switzerland. In the US, the reactors with parts of their reactor pressure vessels manufactured by RDM are: Catawba-1, McGuire-2, North Anna-1 and -2, Quad Cities-2, Sequoyah-1, and-2, Surry-1 and -2, Watts Bar-1, according to the NEA. In its report released September 3, the FANC said the preliminary results of the supplementary inspections on Doel-3 “confirmed the presence of a large amount of quasi-laminar indications in the upper and lower shell rings” of the reactor vessel. The FANC report said the core lower shell ring was the most affected at Doel-3 with a total of 7,776 crack indications, with 931 in the core upper shell. The bulk of the crack indications are located in the base material, outside the weld regions, throughout a zone extending from about 30 mm from the inner wall surface to one-half of the thickness of the vessel wall, the FANC report said.—David Stellfox I-Nuclear | September 4, 2012 at 8:10 pm | Categories: Belgium, France, GDF Suez, Regulation | URL: http://wp.me/p22dAl-nF