Application of Systems Usability Case in an Integrated System Validation of Control Room

The Systems Usability Case (SUC) approach enables a requirement-based human factors (HF) evaluation of complex technical systems that may cover the entire verification and validation process. SUC is based on the Safety Case approach and on the Systems Usability (SU) construct. One of the main aims of establishing a Safety Case is to bring the arguments and evidence for safety to the front in such a way that the reasoning supports the work of a regulator or licensing organization. In the end, the approach enables evaluating the SU 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 [i.e., identified human engineering discrepancies (HEDs)] to approve or reject the claim concerning the quality of the system. The paper presents an application of SUC to real data from an integrated system validation of the modernized control room (CR) of the Loviisa nuclear power plant. The results of the validation are discussed from the point of view of how the SUC approach enables forming a statement about the acceptance of the CR. Moreover, practical examples are given to demonstrate the identified HF issues and how they were handled in the validation process. The paper provides a general framework for handling of HEDs and for their resolution that can be used in the consolidation of validation test results in a real-world validation project.