Massive sterile neutrinos in single and double beta decays

Nuclear beta and double beta decay experiments are intensively exploring the neutrino parameter space. In this talk, we will see how these experiments could through light not only to the active neutrino sector, but also to the sterile one. During the first part, we will revisit the potential of single beta decay experiment to search for keV sterile neutrinos, highlighting its complementarity with neutrinoless double beta decay searches. In the second part, we will discuss a new method to search for sterile neutrinos in the two neutrino double beta decay process, which could probe the MeV mass hypothesis beyond current limits.