[en] An apprehension for the safety of the geological disposal system was analyzed and identified as a scenario. Such scenario development has become the general term used to describe the marshalling and syntheses of the scientific and technical information requirements necessary to the assessment. Recently, it is widely recognized that scenario development may have functions such as the demonstration of comprehensiveness of assessment, the presentation of importance of FEP and scenario, the demonstration of traceability and transparency of assessment, the improvement of understandability of assessment. Based on such recognition, the examination for the improvement of the scenario development method has been carried out and the functions relating to the comprehensiveness, traceability and transparency of assessment have been improved. However, the examination relating to the presentation of the importance and the improvement of the understandability has been not necessarily enough. In this study, the presentation of the importance and the improvement of the understandability were recognized as unsolved issues. Therefore, a new concept of the scenario development method to be able to represent the importance of a scenario on geological disposal of HLW in an understandable way was examined with considering the versatility that the method can address the various scenarios universally. As a result, a new concept of the scenario development method has been developed. This method consists of several approaches such as the represent of prerequisite, the arrangement of apprehensions, the identification of discussion points for quantitative discussion of the influence relating to the change of the various conditions, the rearrangement of the information according to the discussion point, the identification of the importance of the apprehension by using data classification and influence properties of parameters obtained from sensitivity analysis and the representation of plain scenario. Furthermore, the example of systematic relationship diagram including the assessment field, which this method can be applied versatility such as the study on the impact of the natural phenomena, has been shown. By carrying out the scenario development using this method, the information relation to the confidence building such as 'why is the scenario important', 'why can the assessment according to the scenario ensure completely the safety' would be represented in the easy-understand format. Furthermore, the useful information for total performance assessment of geological disposal would be given with the role of each study and the relationship between the studies in the assessment. (author)