Confinement of airborne particulate radioactivity in the case of an accident

In the case of an accident, the filter elements on the inlets and exhausts of the air-cleaning systems of a nuclear facility may become a part of the remaining fission product barrier. Among others, the Project Nuclear Safety is pursuing the information necessary to insure safe operation of air-cleaning systems under accident conditions. Experimental investigations into the response of HEPA filters to differential presssures involving both dry and moist air have demonstrated the occurrence of structural failure with subsequent loss of efficiency at low values of differential pressures. Contributions are being made to the development and verification of computer codes used to calculate those fluid-dynamic and thermodynamic conditions expected to prevail in an air-cleaning system as a result of potential accident situations. With regard to further investigations, a new test facility was put into operation for the realization of superimposed challenges and a new method for testing particulate removal efficiency under high temperature or high humidity was developed. (orig./HP)