Characterization of colloidal species formed in cooling water at accelerator facilities


At high-energy accelerator facilities, various radionuclides are produced in the cooling water by nuclear reactions caused by radiations originated in beam-loss points. Further, metal-related particle species (m-scale) and colloidal species (nm-scale) are produced by corrosion of metal components in water. These particle and colloidal species may cause various troubles in water circulation systems, not only clogging of the filters and strainers but also flowing of the radionuclides in water systems. Radionuclides are adsorbed on colloidal species and flow in the circulating water. In order to secure stable and safety operations of accelerator facilities, it is important to understand the formation processes, properties and behaviors of colloidal species in the cooling water.

Various analytical techniques have been applied for chemical analyses of colloidal and particle species existing in the cooling waters. For example, in the cooling water for electromagnets, chemical forms of particle species were found to be two kinds of copper oxides, Cu2O and CuO, by using X-ray diffraction analyses. ICP-AES elemental analyses also demonstrated that nm-scaled metal oxide colloids exist in the cooling waters. Furthermore, characterization of colloidal species in sampled and model cooling-waters are in progress by using various instrumental techniques which can evaluate size distribution and electrical charge of colloidal species in water.