[en] 1 - Description of program or function: LWRARC calculates spent fuel decay heat generation rates for standard pressurized water reactor (PWR) and boiling water reactor (BWR) fuel assembly designs for cooling times between 1 and 110 years. 2 - Method of solution: LWRARC provides an interactive menu-driven user interface to perform automated interpolations and adjustments of a data base of decay heat generation rates produced by the SAS2H analysis sequence of the SCALE-4 system. Using generic PWR and BWR assembly models, SAS2H calculations were performed with each model for six different burnups at each of three separate specific powers to produce heat rates at 20 cooling times in the range of 1 to 100 years. LWRARC uses a procedure that includes proper interpolation formulae for the tabulated heat generation rates. Adjustment formulae for the interpolated values are provided to account for differences in initial ²³⁵U enrichment and changes in the specific power of a cycle from the average value. Finally, safety factor formulae derived as a function of burnup, cooling time, and type of reactor are added. 3 - Restrictions on the complexity of the problem: Limitations include cooling times of 1 to 100 years, maximum burnups of 45 MWd/kgU for BWRs and 50 MWd/kgU for PWRs. Additional limitations and restrictions in the method are discussed in detail in the documentation accompanying the software. The code itself automatically performs checks on input data to ensure that these limits are not exceeded