Procedure to test HEPA-filter efficiency under simulated accident conditions of high temperature and high humidity

In the framework of investigations into air cleaning within nuclear power facilities during accident conditions, a method has been developed to measure the removal efficiency of HEPA filters at high humidity and elevated temperature or at high temperature alone. Tests were performed with condensation aerosols of TiO2 or MoO3 generated with the aid of an argon plasma torch. Efficiency measurements were accomplished by the collection of test-aerosol samples onto Nuclepore filters and subsequent atomic absorption analysis. The sensitivity of the method allows decontamination factors as high as 104 to be determined. Comparison tests with two different standard procedures at room-air conditions proved the reliability of the newly developed method