  The production near threshold of isoscalar pion pairs in the pd -> 3He(pi
pi)^0 reaction is estimated in a two-step model which successfully describes
the production of eta, omega and eta' mesons. A virtual pion beam, generated
through an NN -> d pi reaction on one of the nucleons in the deuteron, produces
a second pion via a pi N -> pi pi N reaction on the other nucleon. Using the
same scale factor as for heavy meson production, the model reproduces the total
pi^0 pi^0 production rate determined at an excess energy of 37 MeV. There are
some indications in the data for a suppression of events with low pi pi masses,
as in the pi^- p -> pi^0 pi^0 n reaction, and this is confirmed within the
model. The model suggests that a significant fraction of the charged pion
production in the p d -> 3He pi^+ pi^- reaction at Q=70 MeV might be associated
with isoscalar pion pairs, though this does not explain the strong dependence
observed on the pi^+ pi^- relative momentum angle.
