Abstract
The aim of this study is applying fuzzy set theory to analysis dependence level of human reliability at nuclear power plant. Traditionally, the evaluation of dependence of human reliability analysis is based on THERP. In this study, crisp set of dependence model has been expanded to fuzzy set. Expert's opinions have been collected by using questionnaires. The questionnaire has been evaluated with fuzzy mathematical techniques and joint human error probability. According to the responsibility and interaction among operators, the questionnaire contained five questions which were the main factors on evaluating dependence level of the specific item. In addition, computer software on PC has been developed in evaluating dependence relation and calculating joint human error probability. In this computer model, the result has been also compared with the traditional method.