Development of geometry measurement technique for complicated flow channel based on optical visualization image

Kobayashi, Jun ; Sato, Hiroyuki; Hayashi, Kenji; Kamide, Hideki 

High burn-up core in a sodium cooled fast reactor may result in fuel pin deformation due to irradiation, e.g., swelling and bowing. Such deformation will influence thermal hydraulics in a core fuel subassembly, i.e., the highest temperature. Thus it is significant to estimate pin deformation effects. A water experiment was carried out to measure velocity field in a deformed pin bundle by using transparent resin and refractive index matching technique. In the experiment, the deformed pin geometry should be measured as a boundary condition. Here an optical measurement technique of pin bundle geometry was developed. An image of a horizontal cross section of the pin bundle was captured by a camera set on an inclined line to the pin bundle axis. This image was converted to a straight image to the pin bundle axis by taking accounts of refraction at the wall. The positions of deformed pins were well estimated by this method.