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NEW BUILD A POLAR CRANE, with a carrying capacity of 390 tonnes, has been installed at unit 2 of Russia’s Kursk-II NPP. Specialists of JSC Energy Special Installation (ESI) lifted and installed the polar crane bridge on rail tracks at around 38.18 metres using a heavy tracked Liebherr crane with a lifting capacity of 1350 tons.
FINNISH POWER COMPANY Teollisuuden Voima Oyj, owner-operator of the Olkiluoto NPP, has said that the investigation into the damage at Olkiluoto 3’s feedwater pumps will continue for some weeks, and its impact on the schedule cannot be estimated. Regular electricity production is not now expected to begin before the end of January 2023.
INSTALLATION OF THE metal structures of the outer containment dome for the reactor building of unit 1 at the Rooppur NPP in Bangladesh, has been completed, the Engineering Division of Rosatom (ASE) reported. The upper part of the dome, which weighs 100 tons with a diameter 34.4 metres, was mounted in the design position at a height of 57.140 metres.
THE UK CHANCELLOR Jeremy Hunt has confirmed the government’s support for construction of the Sizewell C NPP subject to final agreement. In his Autumn Statement, he said the nuclear power station would create thousands of jobs and represented the biggest step in the UK’s journey to energy independence.
ROSATOM DIRECTOR GENERAL of Alexei Likhachev has confirmed the decision to build BN-1200 sodium-cooled fast neutron reactor at unit 5 of the Beloyarsk NPP. The BN-1200 will have a 60-year service life, a 60-month construction period from first concrete to the reactor start-up.
PLANT OPERATION ATTILA STEINER, SECRETARY of State for Energy at Hungary’s Ministry of Technology and Industry at a meeting of the state assembly (unicameral parliament) has introduced a bill proposing that the Paks NPP should be authorised to operate for an additional 20 years.
LAWMAKERS IN THE German Bundestag (parliament) have voted to keep Germany’s three remaining NPPs in operation until April. The three plants are Isar 2 in the southern state of Bavaria, Emsland in northwestern Germany and Neckarwestheim 2 in the southwestern Baden-Württemberg state.
impact schedule ITER repairs
This chlorine reaction had generated stress corrosion cracking and, over time, cracks up to 2.2 millimetres deep had developed. “The risk is too high, and the consequences of
Above: The thermal shield at ITER must be removed to affect repairs. This will impact the schedule
Two-and-a-half years into its machine assembly phase, defects have been identified in two key components at ITER – the thermal shields and the vacuum vessel sectors. The vacuum vessel thermal shields and the
cryostat thermal shields are actively cooled silver-plated elements, 20 and 10 millimetres thick respectively, that contribute to thermal insulation for the superconducting magnet system operating at 4°K, or minus 269°C. In each of the nine vacuum vessel modules – one of which is already installed in the machine assembly pit – thermal shield panels are positioned in the narrow gap between the vacuum vessel sector and the two associated toroidal field coils. A circular thermal shield, approximately 20 metres in diameter, also lines the inner wall of the cryostat to complete the heat barrier protecting the superconducting magnetic system. The lower section of the cryostat thermal shield was positioned inside the pit in January 2021. “In November 2021, helium tests detected
leaks on an element of the vacuum vessel thermal shield that had been delivered a year and a half earlier,” ITER said in a statement. “Working groups with experts from different ITER partners were rapidly established to investigate, and they were able to identify the root cause for the leaks.” They concluded that stress caused by the bending and welding of the cooling fluid pipes to the thermal shield panels, compounded by a slow chemical reaction due to the presence of chlorine residues in some small areas near the pipe welds, was responsible.
6 | December 2022 |
www.neimagazine.com
a leaking thermal shield panel during operation are too dire. We must assume the problem is extensive,” said ITER Director-General Pietro Barabaschi. “Dealing with it in the pit on the module that has already been assembled would be enormously difficult. This means we have to lift out the installed module and disassemble it in order to proceed.” Whereas this thermal shield issue is now thought to be essentially due to a weakness in the design of the cooling pipe attachment, which made it impossible to fully wash away the chlorine residue, vacuum vessel sector issues stem from a more common industrial fabrication difficulty: the distortion that invariably occurs in welding processes, compounded by the overall complexity of the ITER vacuum vessel sectors. A total of approximately 23 km of piping are welded to the surface of the thermal shield. Deviations during the welding process of the
vacuum vessel sectors led to dimensional ‘non- conformities’ on the outer shells, affecting the geometry of the field joints where the sectors are to be welded together. In the case of the three vacuum vessel
sectors that have already been delivered, the welding of the component’s four segments caused deviations that were more substantial than the specified limit. Despite ongoing coactivity in the assembly
pit’s restricted space and particle contamination risks, solutions were initially contemplated that would see repairs executed in situ, without extracting the vacuum vessel module from its present position. “The thermal shield issue has now changed the perspective,” said Barabaschi. As repair strategies for both components are
being refined, schedule scenarios established, and costs estimated, the present sequence of vacuum vessel assembly is now on hold. “We know what we need to do, we know ways to do it, and we are of course very much aware of the consequences as far as schedule and cost are concerned – and they will not be insignificant.” In order to deal efficiently with both thermal shield piping and vacuum vessel issues, the decision was taken to lift the module already installed in the machine pit and disassemble it in order to proceed with the repairs. “If there is one ‘good thing’ about this situation,” said Barabaschi, “it is that it is happening at a moment we can fix it. It is in ITER’s nature and mission, as a unique and ambitious research infrastructure, to go through a whole range of challenges and setbacks during construction. ■
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