[en] 1 - Description of program or function: RADAC calculates the decayed radionuclide-by-radionuclide composition of the accumulated waste at preselected decay times ranging from one year to one million years after the start of accumulation. Radioactive waste is accumulated year by year. The radionuclide composition of each year's waste is known. 2 - Method of solution: RADAC differs from previous decay codes in that it uses library files of pre-calculated yield factors to determine the decayed products of actinides and long-chain fission and activation products. These files, which are part of the code package, were generated off-line by applying high-precision integer- array arithmetic to the evaluation of the Bateman equations. This two-stage (i.e., off-line and on-line) method of calculation permits the decay of long chains to be determined with unprecedented precision at both low and high decay times. Accumulation of decayed products is quickly determined by an efficient algorithm. 3 - Restrictions on the complexity of the problem: RADAC can handle up to 2 waste types (for examples, low-level waste and high-level waste) and 19 individual waste sites in a single run. Year-by-year and radionuclide-by-radionuclide results are given individually for each waste site and waste type. Problem-specific inputs are prepared by the user. The permanent nuclear data used by the code (half-lives, branching ratios, etc.) are on permanent data files supplied as part of the code package and do not have to be input by the user. The radionuclides available in the code are listed in Tables 4, 5 and 6 of the user's manual (ORNL/TM-12380) supplied with this package. Table 4 lists 62 long-lived actinides, Table 5 lists short-lived actinides, and Table 6 lists 100 fission and activation products. Time intervals less than one year are not used. Waste can be placed in storage in any year up to 60 years from the start of accumulation. Decay and accumulation are calculated by one-year steps up to 60 years from the start of accumulation, by 10-year steps up to 160 years, and by 6 discrete steps up to 1,000,000 years. These discrete steps are 300, 500, 1000, 10,000, 100,000 and 1,000,000 years. Spontaneous fission is accounted for in the decay calculations, but the products of spontaneous fission are not listed. RADAC does not make in-reactor calculations and thus cannot be used to calculate the composition of spent fuel freshly discharged from a reactor. However, given the composition of the discharged and cooled fuel, RADAC can be used for subsequent decay and accumulation calculations, provided that the cooling time has been sufficient to eliminate the short-lived nuclides not available in the code. The integer-array arithmetic package is briefly described in the user's manual (ORNL/TM-12380) but is not supplied as part of the RADAC package