Device for studying changes in gaseous fission product pressure inside a fuel can

A device for in-core studying the changes in gaseous fission product pressure inside a fuel can is described. The device comprises a bellows hermetically connected with the can cavity near the gas collector. The free side of the bellows is equipped with a disk on which thermobimetallic spring with a microcutter on the free side is fixed. The cutter tonches the surface of the plate set at the side of the fuel can. When the reactor is brought to assigned power level a fuel element temperature grows and therefore, gas temperature and pressure inside the fuel can and that of the bimetallic spring grow as well. Thus,the mobile side of the bellows replaces over the fuel element axis and the bimetallic spring is bent so that the microcutter scratches the initial groove perpendicularly to the fuel elemet axis. The mobile end of the bellows slifts over this axis at accumulation of gaseous fission products and gas pressure growth in the fuel element. Benol of the bimetallic plate changes during artificial cycles and longitudinal trace of the cutter is broken by transverse grooves. Trace on the plate after its extraction can be decoded knowing calibration