Ansaldo Nuclear has designed and supplied a robot for the removal of 2000 drums of radioactive waste stored in hard-to-access areas within two temporary storage buildings at Italy's shut down Caorso nuclear power plant. Caorso, an 860 MWe boiling water reactor, was closed in 1990 after just 12 years of operation and is now being decommissioned.
The Machine Retrieval System robot developed for use at Caorso (Image: Ansaldo Nuclear)
The plant's decommissioning licence, obtained in 2014, includes the treatment and conditioning of around 860 tonnes of radioactive ion exchange resins and sludges, still contained in two on-site temporary storage buildings. This waste represents more than 90% of the contamination inventory at Caorso. The aim of the project is to transform this waste into final packages, with a volume reduction factor of 10, whilst emptying the two storage buildings in order to refurbish them.
Ansaldo Nuclear - which has been involved with the decommissioning of Caorso since 2000 - was contracted in 2015 by Società Gestione Impianti Nucleari SpA (Sogin) for the retrieval, transport, treatment and conditioning of the resins and sludges as part of a joint venture with JAVYS. This will see the firm transporting a total of 5600 200kg drums of Caorso's radioactive waste to the JAVYS waste storage facility at Jaslovské Bohunice in Slovakia, to be stabilised via incineration and finally conditioned. At the end of the process, the final products will be returned to Caorso for on-site interim storage before their eventually transfer to a national repository.
To enable the retrieval project to commence in January 2020, Ansaldo Nuclear conceptualised, designed, manufactured, installed and operated a bespoke Machine Retrieval System (MRS) robot to safely retrieve 2000 drums of radioactive waste which were stored in a variety of niches within the temporary storage facilities at Caorso. The MRS robot - which is being used to retrieve, verify, seal and pack the radioactive drums - took six months to build and install. Controlled remotely, with a double operating system in place in case of system failure, it is capable of self-recovery in the event of earthquakes or other external safety issues.
"The MRS robot used for the automatic recovery of radioactive drums at Caorso was extremely effective, having been designed from the start with safety, efficiency and adaptability as key priorities," said Francesco Orzelli, designer and structural analyst at Ansaldo Nuclear. "One of the key challenges was that we were unable to access the area to take detailed measurements, so the robot had to be constructed to be as compact as possible to allow enough clearance. In doing this, we first created a fully-functioning, 3D model, complete with all mechanical components, to allow us to develop a small machine with significant capabilities.
"We received only the boundary conditions from the customer," he noted. "This meant Ansaldo Nuclear not only had to manufacture and install an automated retrieval robot, but develop the solution as well - a process which took two years. Through proactive planning and careful implementation we were able to develop a robot with the freedom and adaptability to retrieve all the drums required, which has allowed Caorso to continue its decommissioning process on schedule."
The first of 33 scheduled transports aimed at moving the 5600 drums of radioactive resins and sludge departed from the Caorso plant on 28 January this year en route to the Bohunice plant in Slovakia. All the drums in this second phase and final phase of shipments are expected to be transported by 2022.
