Development of Methods for Detecting and Repositioning of Snug-fitting Annulus Spacers

Abstract

Annulus spacers are used in the fuel channels of the CANDU power reactor to maintain the gap, or annulus space, between the pressure tube and surrounding calandria tube. It is important that the spacers remain close to their installed locations to prevent pressure tube to calandria tube contact and subsequent hydride blister formation. There is currently no means of in-service repositioning for snug-fitting annulus spacers. In addition, it is desirable to have a means to directly detect the location of a snug-fit spacer that does not rely on secondary effects of spacer location. AECL has been working to develop the capability to directly detect and reposition snug-fitting spacers. To date, means to detect and reposition snug-fitting spacers using vibration have been successfully demonstrated in the laboratory and work is continuing towards implementing this technology for field use. This paper presents an overview of the detection and repositioning techniques.