4.71. Alternatives should be identified and described in sufficient detail to provide clear answers to these questions. For example, if alternative design options, such as different barrier types, are being considered, then each alternative option should be described and the potential radiological effects, costs and benefits of each alternative should be determined. The criteria and analysis of the different options should then be fully documented to support the proposed design. Further recommendations on decision making and appraisal of alternative options are provided in paras 6.79?6.89. Records should be made of the design evolution and the basis for design related decisions, and these records should be maintained throughout the evolution of the lifetime of the facility.