In a briquet stove-type reactor in which the loading and unloading are carried out intermittently. The pressure from loading applied to the surface of core container is limited because the area of section is increased from bottom to top or by means of a bottom board with sunken holes in the no-core area. The sunken holes on the bottom board are arranged spherically. The level distance between two neighbouring spheres is 1%-8% the diameter of the sphere.