Abstract
In water cooled and water moderated reactors (H2O in boiling water reactors/pressurised water reactors, D2O in pressurised heavy water reactors) during normal operation, radiolysis is a source of production of hydrogen/deuterium and oxygen. During the progress of a nuclear accident, while there are other important sources of hydrogen/deuterium, the oxygen availability can occur only through radiolysis or direct contact with air. In air saturated with water vapour at room temperature and pressure when H2/D2 concentration exceeds 4 vol % (a conservative estimate), a combustible mixture with oxygen can be formed. It is proposed to examine the basic principles of water radiolysis as far as they pertain to generation of H2/D2 and O2 and try to apply these concepts to reactors both under operating conditions and in accident situations. It is concluded that the possibility of an accident taking place through radiolysis is highly unlikely.