Heat-treatment device for prolonging the life of a pressure vessel such as a reactor pressure vessel especially

Claim 1

Heat-treating device for prolonging the life of a pressure vessel formed of thermally resistant material subject to time-dependent structural changes due to neutron fluence comprising an heating device positionable within a pressure vessel adjacent to a wall portion thereof which is to be heat-treated; a mounting support for said heating device including a substantially cylindrical, heat-insulating holding member insertable into and removable from the pressure vessel through an opening in the pressure vessel; supply lines for an energy carrier supplying the heat; insulating means for keeping the heat away from heat-sensitive parts of the pressure vessel which are not to be heat-treated and for reducing heat losses during the heat treatment; a hollow substantially cylindrical thermal shield disposed in the pressure vessel and, with the inner peripheral surface of the pressure vessel, defining an annular gap; and a reactor chamber wherein at least part of the pressure vessel is located, said reactor chamber being otherwise empty during the heat treatment and having ceiling slabs disposed thereon for shielding said reactor chamber from the outside, said holding member being receivable in the pressure vessel in a location whereat it defines, with the inner peripheral surface of said thermal shield, a convection space communicating at upper and lower ends thereof with said annular gap, said heating device comprising a heating source and being secured to said holding member so that, with the heating device received in the pressure vessel, a flow of heating gas is traversible from said heating source through said convection space to an upper deflection space and, from the latter, downwardly through said annular gap to a lower deflection space and, from the latter, back to said heating source, in a closed circuit, the pressure vessel being formed with an annular shoulder at the opening thereof and having a spherical bottom, and said holding member being formed as a hollow member having a first annular flange at an upper end thereof and a second annular flange at a lower end thereof, said annular flanges being sealingly engageable, respectively, with said annular shoulder and the inner peripheral surface of said spherical bottom, a plurality of convection shafts formed by a plurality of prismatic hollow conduction members being distributed about the outer periphery of said holding member and extending parallel to the axis of the pressure vessel.