Radiation detector for monitoring high temperature incinerator

The device of the present invention shields heat from a high temperature sample box and enables the use of devices including a radiation detector usable only by compulsorily cooling by air at a room temperature. Namely, high temperature portions are covered except for particular portions by a heat insulation material equipped with a reflection material to minimize heat dissipation area in order to suppress heat dissipation as much as possible from exhaust gases at a high temperature (heat source) in a sample box. The sample box at least at a surface opposed to the detector is covered with an outer enclosure made of an electrically conductive thin plate in a non-close contact manner to suppress dissipation of radiation heat. In addition, the radiation detector is surrounded by an outer enclosure made of an electrically conductive thin plate in order to suppress entrance of heat to the radiation detector to reduce the amount of radiation heat transferred to the detector. (I.S.)