  We compute the real-radiation corrections to Higgs boson pair production at
  next-to-next-to-leading order in QCD, in an expansion for large top quark
mass. We
  concentrate on the radiative corrections to the interference contribution
  from the next-to-leading order one-particle reducible and the leading order
  amplitudes. This is a well defined and gauge invariant subset of the full
  real-virtual corrections to the inclusive cross section. We obtain analytic
  results for all phase-space master integrals both as an expansion around the
  threshold and in an exact manner in terms of Goncharov polylogarithms.
