Development of nondestructive techniques for fuel cladding evaluation in hot cell

In nuclear light water reactors (LWR), an effective heat transfer from the fuel through the fuel cladding to the water in the reactor is essential. Furthermore, the cladding should prevent the radionuclides in the fuel from contaminating the reactor circuit. During service the cladding suffers from damage by corrosion, microstructural changes, hydrogen pick-up, creep etc. Regular nondestructive evaluation in a hot cell is a relatively new complement to laborious destructive evaluation of in-service degradation of irradiated material. In this work the possibilities of laser ultrasonics and eddy current techniques in hot cells are presented. The main emphasis is on oxide thickness measurements and on detection of cracks and delaminations for oxide layers of tubular or planar fuel cladding materials. The detectability of hydrogen concentration in the cladding wall is also discussed.