FALCON-ISP1, ISP-2, fission product and aerosol transport in primary coolant system and in the containment

1 - Description of test facility: Falcon has been developed to study the transport and deposition of fission products through a complex pathway simulating to some degree a reactor environment under severe accident conditions. It consists of two negative pressure double glove boxes (one of which is mounted horizontally and the other vertically), a system of thermal gradient tubes, a stainless steel containment vessel, and a series of filters designed for use with gamma-ray spectrometers and aerosol analysis equipment. The apparatus was designed to study the transport of fission product vapours and aerosols as they pass from the high-temperature reducing conditions representative of the primary circuit to the low-temperature predominantly oxidising and condensing steam conditions simulating the containment atmosphere. Fission products are released from both simulant and trace-irradiated fuel samples heated inductively up to 3000 K in a controlled manner. The resulting species can be studied in the presence and absence of aerosols from bulk reactor materials such as the Ag-In-Cd control rod and boric acid. Such vapours and aerosols can be studied by a range of in-situ techniques including mass spectrometry, gamma-ray spectroscopy, aerosol analysis and Maypacks, together with their collection on filters and deposition foils for subsequent elemental, chemical and morphological analyses. - Thermal gradient arrangement (TG): serves study of aerosol deposition inside a tube with controlled temperature gradient supposed to simulate a primary system condition; - Containment Configuration (CT): serves to provide data related to a containment under severe accident conditions. 2 - Description of test: The FALCON experiments have been undertaken at the Winfrith Technology Centre to simulate the transport and deposition of fission products in the primary circuit and containment building of a LWR under severe accident conditions. ISP 34 were based on two Falcon experiments using simulant fuel. - FAL-ISP-1 (28 May 1992): Low relative humidity in containment (approx. 50 %) with high particle concentration (to test the impact of multicomponent aerosols involving different chemical species on different-sized particles and agglomeration models). - FAL-ISP-2 (22 July 1992): High containment relative humidity (> 90 %) and low particle concentration (to test condensation onto hygroscopic particles in the absence of agglomeration and assess the limitations of using 1-D aerosol equations).