Interesting effect of the nd -> p(nn) reaction

The reaction nd -> p(nn) produce two slow neutrons in the final state instead of deuteron. In the first view we can take into account the binding energy e ~ 2.23 MeV but this approach can not explain all features which are observed in the momentum spectrum of the secondaries protons. We need to suppose that two slow neutrons in the final state form the intermediate system which has own distribution of internal Fermi momentum.