[en] A joint exchange programme on the subject of criticality data development was completed in August 1988. The programme was a cooperative effort between the U.S. Department of Energy and the Power Reactor and Nuclear Fuel Development Corporation of Japan. The primary purpose of the programme was to perform critical experiments to allow validation of computational methods used for safety analyses for facilities that recycle nuclear fuel. The experiments were performed with mixed Pu+U solutions in various geometries (cylinder, annular and slab) and various reflection conditions (bare, water and concrete). Also, critical lattices were assembled with Pu+U mixed-oxide fuel pins immersed in water, organic, Pu+U, and Pu+U+Gd solutions. The experiments spanned the range of neutron spectra from the very over-moderated condition (H/Pu ratio 22) to the very over-moderated condition (H/Pu ratio 2220). Using the criticality data provided by this programme, computational studies were performed to validate the SCALE computer code system. The good agreement between the calculational and experimental results allows the calculational method to be applied to similar plant conditions. (author)