Detection device for the position of failed fuels

Purpose: To enable to maintain the temperature uniformly for the activated carbon adsorbents in a activated carbon adsorbing bed through which reactor cover gases are passed, thereby catch tag gases without escaping them and concentrating the same. Constitution: An activated carbon adsorption bed is contained within a cooling tower through which cover gases are passed, and tag gases contained in the cover gases are adsorbed thereon. Liquid nitrogen is supplied from a cooling system to the activated carbon adsorption bed to cool the same. The activated carbon adsorption bed is then heated to release the adsorbed tag gases, which are then analyzed. If failures are resulted in fuel rods, leaked nuclear fission products and tag gases are incorporated into the cover gases. The cover gases containing the tag gases are caused to flow into a failed fuel position detector, and the tag gases are adsorbed on the activated carbon adsorbents. Since the axial temperature gradient in the activated carbon adsorption bed can be eliminated, the tag gases can be caught with no escape and the length of the adsorption bed can be shortened to render the configuration compact. (Moriyama, K.)