The need for training licensed nuclear power plant (NPP) operators in handling novel, non-standard events was emphasised by the accident at the Fukushima Daiichi plant in 2011. A key question is how to asses transfer from this type of training, i.e., how to distil performance improvement across novel, non-standard events? The purpose of the present study was to identify a set of candidate parameters of use in assessments of training transfer of nonstandard tasks. The study is based on data collected during interviews with 12 licensed NPP operators in average 52,5 days following completion of the earliest phase of a training program directed at handling non-standard tasks. The interviews focused on actual training transfer, but also on hypothetical training transfer, i.e., transfer assessed to become manifest after three years of non-standard task training. In all, 12 candidate parameters were identified to support training transfer assessments directed at non-standard tasks. The parameters were structured using the three elements of adaptive expertise: domain-specific skills, metacognitive skills, and innovative skills. The findings suggested that training of non-standard tasks could partly transfer as safety- and competence promoting work practices, and that training transfer should be assessed based on continuous assessments over time, rather than on one or a few discrete scenarios or situations, using data from both the control-room and a training simulator.