EXPERIMENTAL INVESTIGATION OF AGED CONCRETE FROM UKRAINE NUCLEAR PLANT

The various forms of cement and concrete are the most common materials used in the nuclear field because they are strong, durable, inexpensive, and shield radiation well. However, the porous nature of the prepared cement and the ever-present water in them may often result in the incorporation and retention of some radioactive species, especially tritiated water, which could be subsequently released into the environment. This study is aimed to investigate the effects and threats posed to the nuclear facility and/or repository where radioactive wastes (RWs, including SNF) are and must be stored. Concrete represents the primary barrier to migration in many proposed low-level waste storage facilities. While it may retard some dissolved ions to varying extents, it is not clear to what extent tritium movement through concrete would take place over longer periods. The breaking of concrete atomic bonds is so responsible for the degradation of the concrete (i.e., modification of its structural and mechanical properties). The experimental characterization to determine the physic-chemical properties of aged concrete (samples are from the vault of Kyiv RAW facility in Ukraine exposed during almost 60 years in semi-natural conditions) was performed by means of an Electronic Scanning Microscope, X-Ray diffraction, and other novel chemical and physical methods that are available at UNIPI. The results obtained show a different water concentration confirming the filtration phenomenon the concrete took place also affecting its ultimate strength.