In order to reproduce the concentration of impurities in the condensate of supercritical steam during its early condensation, an experimental device was
fabricated. based on cooling of supercritical steam through rapid adiabatic expansion. The device was equipped with a trumpet-shaped tube for controlling the expanding and cooling rate of the steam. The impurities concentration in the condensate was semiquantitatively determined by several electro-conductivity cells placed in the trumpet tube.