Indústrias Nucleares do Brasil (INB) says it has completed the first stage of demolition of buildings at the Unit for Decommissioning of Caldas (UDC) in southern Minas Gerais, which is currently undertaking clean-up of a former uranium mine. Altogether 12 buildings were demolished at the industrial plant comprising 1,900 square metres of disused structures. The cooling tower was the last structure demolished in early September. According to INB, the area where the buildings were located will be restructured using local soil.
Uranium exploration by the Brazilian National Research Council i began in 1952 leading to the discovery of the first uranium deposits in Poços de Caldas and Jacobina. The Poços de Caldas Industrial Complex (CIPC) was the first uranium mining and milling unit to be installed in Brazil. Initially activities depended on foreign know including from the USA, France and Germany among others. Exploration was continued by the National Energy Commission (CNEN - Comissào National de Energia Nuclear), formed in 1962 and by Nuclebras set up in 1974.
In the Osamu Utsumi mine area, extensive prospecting began in 1971 and, six years later, open-pit mining began. Processing of uranium into yellow cake started in 1982. Following the reorganisation of the Brazilian nuclear programme in 1988, uranium activities were delegated INB subsidiary Urânio do Brasil. From 1990-92 uranium production was in stand-by status. Production restarted in 1993 but stopped again in 1995.
Ore extraction was from an open pit. Of the material removed, aside from that extracted for uranium, some was used on-site for road construction and building embankments while the remainder was disposed of onto two major rock piles. There are a number of potential historical and current environmental impacts to groundwater as a consequence of discharges into streams which then flow off site, according to the International Atomic Energy Agency (IAEA).
The former open pit currently forms an acidic lake of 1200 metres diameter and 180 metres depth. The complex comprises the disused uranium mill, the uranium mill tailings basin, and deposits of radioactive materials including some transferred from other sites
In 2012, INB presented its Plan for Recovery of Degraded Areas following a two-year study addressing hydrogeological, geochemical, and radiological situation. The programme provides for the recovery of the environment of the area comprising the mine, industrial facilities and tailings dam. The work was expected to extend over nearly two decades.
The recent demolition activity started in May and cost BRL645,000 ($130,675). The work also includes the processing of waste generated by the demolitions, which will continue until 13 October, according to the contract established with the company providing the service. Management of tailings, which can be used in civil construction, will be done by INB, which can use them to rebuild internal roads and surrounding areas. Materials such as wood, plastic, ceramics and tiles have already been used for properly licensed landfills. Steel and metals will be stored inside the unit for a sale that is expected to take place in 2024.
INB says the demolition of buildings, among other actions in the UDC's deactivated industrial plant, has made it possible to advance the dismantling of simpler structures, while decommissioning solutions for more complex structures will be defined by the hydrogeological, hydrogeophysical and geotechnical characterisations already underway.
Among the demolished structures were old changing rooms, office, warehouse, the Caldeira Command House, the Machinery Command Centre, the Command House of the Water Treatment Station and the old Water Treatment Station. As part of the decommissioning process, in 2022 INB sold about 500 tonnes of scrap to the UDC. The process of discarding items started in September 2019. The sale included various goods and materials, vehicles and equipment, as well as electronics and information technology not used by the company.
INB also reported that it had completed remediation of Pie II packages at UDC. The activity, supervised by CNEN, consisted of overpacking the Pie II packages with new metal drums and replacing the pallets that support the stacking of the drums.
The drums contain Torta II, a residue from the chemical treatment of monazite. It is a low radioactivity waste that needs to be stored according to established safety standards. Monazite was processed between the 1940s and 1990s in São Paulo to produce rare earth compounds, used in ceramics, composition of electronic materials, superconductors, permanent magnets and special metal alloys.
The first phase of the work took place from January to May 2022, and resulted in the overpacking and replacement of pallets of 3,500 metal drums. The second phase of the activity started in September 2022 with the goal of remediating 16,100 metallic drums.
UDC covers an area of 1,360 hectares in the municipality of Caldas. Currently, the control of the remaining materials from uranium mining and beneficiation is carried out through acid water treatment, waste and solid tailings management, dam safety management, environmental management of the area, including vegetation recomposition, worker safety management and radiological and environmental monitoring of the region.
INB says that, simultaneously with the control of the installation, UDC has been carrying out several decommissioning actions, such as the dismantling and demolition of industrial areas, environmental recovery of areas currently used in the treatment of acidic waters, as well as identifying the best decommissioning solutions for the mine shaft, dams and piles of mining waste. These solutions will be described in an environmental Decommissioning Plan under the environmental regulations and in an abandonment plan under the nuclear regulations.