THE IMPORTANCE OF CHEMICAL PHENOMENA IN THE FORMATION AND TRANSPORT OF NUCLEAR AEROSOLS

The perceived consequences of nuclear reactor accidents are dependent on the magnitude and composition of the radioactive aerosol generated in the damaged plant. Various important chemical phenomena are described in this review with respect to their impact on such accidents and incorporation in the necessary safety assessments. For example, pressurised water reactors contain over 3000 kg low-melting Ag-In-Cd alloy clad in 304L stainless steel to control the neutron flux, boric acid is used as a soluble neutron absorber in the coolant, and core structures contain volatile components (eg. tin in the Zircaloy cladding of the fuel, and manganese in stainless steel). These constituents would vaporise at high, uncontrolled temperatures and condense to form aerosols that may interact with labile fission-product vapours as such mixtures are transported through the damaged coolant system into the containment building.