Experimental investigation of clad motion in LMFBR

In a loss-of-coolant accident occurring in LMFBR fuel claddings may melt on fuel still solid. Sodium vapor is flowing upward through the subassemblies. Clad motion will then take place due to the interaction of the forces of gravity, friction, surface tension, and adhesion. The clad motion may be filmwise or, after entrainment, dropwise. This report describes experimental investigations of filmwise clad motion and investigations of the range where film motion prevails. In an annular geometry the friction of a gas flow was measured, with the central rod is covered by a liquid film. The flow conditions of the liquid film (falling, stagnant, or climbing film) are examined. The applicability of these results to melting claddings is examined by special clad melting experiments performed with the same geometry