We present reanalysis of the experimental data of electron capture in 7 Be embedded in Ta, which have been published by other authors. Our goal is to set upper limits on a mixture of electron neutrino with a possible right-handed heavy neutrino in the 300–750 keV mass range. In the published experiment, a 7 Li recoil energy spectrum in the 20–200 eV range was measured. In case of electron capture with emission of a heavy neutrino, the recoil spectrum should be shifted to the lower energies. We search for an additional Gauss-shaped structure with the same energy width as the main K -shell transition peak. We present the upper limits at a 95% confidence level on electron neutrino–heavy neutrino mixing element, , in the mass matrix. New upper limits are in the range of (2–4) × 10 –4 which are at least one order of magnitude lower than the existing data in 300–800 keV mass range.