It also poses the question to which extent the wholesale electricity market is still the relevant instrument for matching demand and supply and for co-ordinating investment decisions. Independently of social preferences for one technology over another, the current trend of superposing market outcomes with different layers of policy instruments to achieve certain outcomes poses serious questions concerning the transparency and ultimately the sustainability of electricity sectors in OECD countries. Nuclear energy does indeed create a number of specific system effects, in particular with respect to siting and to the specific requirements that it demands in terms of transmission infrastructure and grid access. Both issues are ultimately linked to the need to ensure continuous cooling of the reactor core. Nuclear power plants thus need to be located close to sufficiently large water sources that can provide continuous cooling.