[en] From 1981 through 1983 the Pacific Northwest Laboratory has been developing a computer model named RECON to calculate repository costs from parametric data input. The objective of the program has been to develop the capability to evalute the effect on costs of changes in repository design parameters and operating scenario assumptions. This report documents the development of the model through March of 1983. Included in the report are: (1) descriptions of model development and the underlying equations, assumptions and definitions; (2) descriptions of data input either using card images or an interactive data input program; and (3) detailed listings of the program and definitions of program variables. Cost estimates generated using the model have been verified against independent estimates and good agreement has been obtained