People are prone to use various kinds of cognitive heuristics to simplify decision making especially in demanding situations. Sometimes, these heuristics expose them to failures in judgement, which may lead to errors. Even though these kind of failures are also possible in process industries, there is little research on the effect of cognitive biases on process control and maintenance work. In the present paper, we provide suggestions of how heuristics and biases may appear in these tasks in nuclear domain. Overall, our observations suggest that operative and maintenance personnel may be prone to commit biases also in nuclear domain. We have reviewed existing literature on the effect of cognitive biases in NPP incidents and accidents, and we describe some of the most well-known biases and give examples of their application for decision making in nuclear domain. We have also analyzed failures and problem situations in a simulator study conducted in a Finnish NPP. A small set of failures of judgement could be identified in which some forms of cognitive biases may have manifested themselves. The present paper is one of the first systematic reviews on effects of cognitive heuristics and biases among operative and maintenance personnel in NPPs and ways to prevent them. Our next step would be to analyze more systematically a set of cognitive errors specific to operative and maintenance activities in nuclear domain in order to identify occurrences of cognitive biases and illusions in them.