Behaviour of fission products and fuel in LMFBR power plants

For economic reasons, future LMFBR power plants will have to operate with a certain number of defective fuel pins. Fission products and fuel will be released to the coolant and will cause contamination of the inner surfaces of the primary loop components. Prediction and knowledge of this contamination are important for the design of new reactors and for maintenance and repair work. The Kernforschungszentrum Karlsruhe and its associates have a number of programmes for the study of the behaviour of radioactive fission product elements and radionuclides and of fuel in sodium systems. The paper reports mainly about two of these activities. Experiments were performed with the Power Reactor and Nuclear Fuel Development Corporation, Tokyo, and Toshiba Corporation, Kawasaki, who built the Fission Product Loop 2 (FPL-2) on the TTR reactor in Kawasaki. First results on the FPL-2 experiment have been published previously. The paper gives a more general description of the radionuclide behaviour. The evaluation of the experiments will be completed in 1986. All kinds of fission product elements can be measured, and some indications of the behaviour of uranium dioxide fuel in an isothermal system are expected to be obtained from the study after dismantling of the loop. All results from the experimental programmes will be used as input into a new computer code, called CONTAMINATION. With this code, the radionuclide distribution in experimental facilities and in the primary systems of sodium-cooled fast reactors will be calculated. CONTAMINATION is a dynamic code which will be able to describe the buildup and decay of deposited radioactivity on selected positions of reactor systems. (author)