Online measurement device and method for fission gas release pressure of fuel element

The invention discloses an online measuring device and method for fission gas release pressure of a fuel element. The online measuring device comprises a fission gas measuring tool arranged in a pressure container and a gas adjusting device arranged outside the pressure container. The fission gas measuring tool comprises an outer sleeve; a pressure-bearing sleeve and a linear displacement sensor are sequentially fixed on the inner side of the outer sleeve from one end to the other end; a corrugated pipe is fixed in the pressure-bearing sleeve, an adjusting gas chamber and a measuring gas chamber are respectively arranged in the pressure-bearing sleeve at two ends of the corrugated pipe, and the fuel pellet is communicated with the inside of the corrugated pipe; a magnetic iron core rod is fixed at the other end of the corrugated pipe; the gas adjusting device is used for conveying inert gas to the adjusting gas chamber and the measuring gas chamber. The displacement sensor is combined with the corrugated pipe