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| The containers have a metal insert with a sorbent. Photo credit: EKSORB press-service |
Ural specialists have developed and tested a technology for conditioning (conversion from liquid to solid state) of liquid radioactive waste. The traditional scheme involves mixing sorbent enriched with radioactive isotopes of cesium-134 and 137 and cobalt-60 during the purification of liquid radioactive waste with cement mortar and placing it in special concrete protective containers. However, this requires a large number of containers, which increases the cost of processing and the volume of storage facilities to place the containers. Composite inorganic sorbents have been gaining popularity lately because they concentrate radionuclides very well from a large volume of liquid with a small volume of the sorbents themselves.
Scientists have developed a technology that makes it possible to condition liquid radioactive waste and then safely store the resulting solid waste. The technology is being developed by the EKSORB Scientific Production Enterprise (Ekaterinburg) with the support of the Foundation for Assistance to Innovations and in cooperation with the Ural Federal University.
The specialists tested the technology on a pilot plant. It was used to clean more than three cubic meters of liquid radioactive waste of BN-350 Reactor. As a result, the activity of cesium-137 decreased from 78 million Bq/L to 20 Bq/L, cobalt-60 - from 10 thousand Bq/L to less than 400 Bq/L. The clean concrete product was obtained from the cleaned solutions. After cleaning, the resulting solid waste can be stored safely, the developers assure.
"The advanced container consists of three compartments. The outer side is 15 cm thick and is made of concrete, followed by a space that can be filled with various fillers for additional shielding. In the center of the container there is a cylindrical metal insert 0.5 to 3 cm thick, which contains a sorbent enriched with cesium and cobalt isotopes," explains Oleg Tashlykov, Associate Professor at the Department of Nuclear Power Plants and Renewable Energy Sources at UrFU.
Scientists are now conducting computational and experimental studies by deciding how to optimize additional shielding of containers with different options for placement of solidified liquid radioactive waste by selecting materials for the capsule liner and the filler.
Reference
All radioactive waste generated during nuclear power plant operation and decommissioning must be processed and brought into compliance with the eligibility criteria for final containment. Depending on the aggregate state, radioactive waste is divided into solid, liquid and gaseous. All radioactive waste is cleaned at nuclear power plants or is further processed at special facilities. The main task of liquid radioactive waste management is the final isolation of conditioned radioactive waste.
Source/Credit: Ural Federal University
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