The see-saw model is the minimal framework which is able to explain the observed pattern of neutrino masses and oscillations. Righthanded neutrinos around the GeV scale are an ideal target for high-energy and high-intensity experiments. While intense experimental efforts have deeply tested this hypothesis, there remain the possibility that the origin of the neutrino sector lies in a more involved theory beyond the Standard Model, whose effect at the electroweak scale can be parametrized in terms of effective operators involving Standard Model and right-handed neutrino fields. I will discuss the associated phenomenology and show the prospects for detecting right-handed neutrinos effective interactions at present and future experimental facilities.