The UK Government has said that energy companies can invest in new nuclear power stations. As part of this, the safety, security and environmental regulators (the Nuclear Directorate of the Health and Safety Executive and the Environment Agency in England and Wales) are engaged in a process known as generic design assessment (GDA) that was proposed by UK Government to improve the process of consulting on and approving new nuclear power stations. The GDA process is expected to take about 3½ years to complete. From an environmental perspective, the Environment Agency is interested in assessing whether the proposed reactor designs represent the 'best available techniques' (BAT) with regard to environmental discharges. This paper describes a project that has been assessing BAT for radioactive discharges for analogues (i.e. the previous generation) of four reactor designs on which assessment work started in 2007. Where possible data on environmental discharges has been collated for individual radionuclides for a number of reactor analogues and the discharge performance has been normalized with respect to thermal and electrical outputs to allow trends in the data to be determined. Where possible, explanations for any trends have been identified.