Apparatus for testing He leakage through flange gaskets at elevated pressure and temperature

Abstract

The study focuses on the measurement of He leakage from the cooling circuits of the helium-cooled GFR (gas-cooled fast reactor). It is necessary to measure two phenomena, namely losses of He from the pipeline circuit through flange joints and the contamination of helium inside the pipeline by the diffusion of permanent gases from the external environment (i.e. against the pressure gradient). Methods for determining the tightness of flange joints according to current standards are not fully suitable for these purposes. For this reason, a self-designed apparatus was constructed in order to measure both effects at pressures up to 20 MPa and temperatures within the range from ambient values up to 400 °C. Gas chromatography with a PDHID detector was used to determine the rate of diffusion of nitrogen and other permanent gases through the flange into pure He. On the other hand, the He leakage through the piping flange joint into the external environment was measured using a gas chromatograph with a high sensitivity TCD. The issues of heat distribution within the high-pressure measuring vessel are discussed as well.