OPERATIONS & MAINTENANCE | RPV WELDING REPAIRS
Atucha II novel reactor repair
Discovery of a support that had moved out of position due to a failure of its fixation and located on a lower plenum within the
reactor pressure vessel of Atucha II prompted the development of new remotely operated manipulators, welding, and other tools. The result was a rapid return to service at a fraction of the estimated cost
Marcelo Bercellini, SM&S Business Unit Manager, CONUAR SA and Gustavo Rozadas, Business Development Manager, CONUAR SA
IN OCTOBER 2022, ARGENTINA’S NUCLEAR utility Nucleoeléctrica Argentina S.A. (NA-SA) contacted CONUAR SA to develop remotely controlled tools to solve a mechanical issue located inside the Atucha II Pressurised Heavy water Reactor (PHWR). The mechanical issue identified related to one of the four supports located in the lower plenum of the Reactor that had become released from its fixation and moved from its position. The Atucha Nuclear Power Plant is located in Lima, about 100 kilometres from Buenos Aires on the Parana de Las Palmas River. Construction of the second unit at the site first began in 1982, stopped between 1994-2006 and commercial operations ultimately began in June 2014. The reactor has a gross nameplate capacity of 745 MWe. By the time of the contract award CONUAR, a company owned by Comisión Nacional de Energía Atómica and Perez Companc, already had extensive experience in manufacturing tooling for working inside the moderator tank located within the reactor pressure vessel. CONUAR offers remotely controlled tools for working and welding parts and components inside operating reactors, with the first set of tools supplied to NA-SA in 1990 for unit 1 at Atucha. Those tools included a cutting tool, a flattening tool and a gripping tool. NA-SA still continues to use improved versions of those tools, which are also supplied by CONUAR.
However, the lower plenum is an area of the reactor
pressure vessel that has much more limited space in comparison with the moderator tank. It is therefore far more difficult to access and no work or intervention had been carried out in the lower plenum previously. By that time, NA-SA had also already assessed that
with radioactive fuel elements in place it would take approximately six years to disassemble all the relevant components and fuels to provide clear access to the problem area, remove the loose separator, and then reassemble all components and reload the fuels. This assessment was based on the three years NA-SA had required for assembly of the reactor internals and the first core loading. NA-SA thus concluded that such a long-term operation would have been unaffordable. Facing that scenario, NA-SA formed several working groups and decided to manufacture tailor-made tools.
Expediting welding repairs CONUAR was subsequently contracted for the manufacture of one those sets of tooling that consisted of: a mechanical- gripping tool and a vacuum-gripping tool both of which had been designed by NA-SA. The plant owner/operator also delegated the design and manufacture of two welding tools to CONUAR. All of the tools were to be remotely controlled.
Above: Repairs to Argentina’s Atucha II NPP required special tools and a life-size training facility 28 | September 2024 |
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