Application of systems usability case in an integrated system validation of control room

We present an application of Systems Usability Case (SUC) as an overall human factors validation approach in a nuclear power plant control room modernization project. SUC enables a requirement-based human factors evaluation of complex technical systems that may cover the entire verification and validation process. The SUC is based on the Safety Case approach and on the Systems Usability construct. One of the main aims of establishing a Safety Case is to bring to the front the arguments and evidence for safety in such a way that the reasoning supports the work of a regulator or licensing organization. In the end, the SUC enables evaluating the Systems Usability of a system and making a reasonable solid argument about the acceptance of the system for use. The question is how the conclusions are reached through a reasoning process, in which the arguments are made about the evidence to approve or reject the claim concerning the quality of the system. The paper presents an application of the SUC to real data from an integrated system validation of the modernized main control room of Loviisa nuclear power plant. The results of the validation are discussed from the point of view of how the SUC approach enabled forming a statement about the acceptance of the control room. Moreover, some examples are given to demonstrate the learnings (e.g., strengths and weaknesses) as well as the development needs of the SUC approach.