why we need heavy water to produce plutonium?

[saifadin]

why we need heavy water to produce plutonium?

[vanesch]

We don't.

[mgb_phys]

We don't.
;-)

To the OP - look up 'moderator'

[Astronuc]

Heavy water is one way to get a more desirable neutron energy spectrum for the production of Pu-239. There are other ways, so HW is not necessary.