Actinide samples irradiated in the Dounreay Prototype Fast Reactor for 492 effective full-power days were analyzed at Japan Atomic Energy Research Institute by radiochemical methods to measure the isotopic compositions of the fission products (molybdenum, zirconium, and neodymium isotopes) and of the actinides (uranium, neptunium, plutonium, americium, curium, and californium isotopes). In this first of two companion papers, procedures used for chemical analyses and the analyzed data are presented. There is good agreement between the current results and previous results obtained at Oak Ridge National Laboratory. Therefore, these analytical results could serve as a benchmark for future calculations and validation of nuclear data libraries. Such a validation is attempted in the companion paper.