[Wonder Warthog]

"Why do some countries still use heavy water reactors when there are light water ones? Are heavy ones the only ones which produce nuclear weapon material? If so, isn't this a hint to those people who believe that Iran is peaceful?"

Three possible reasons:

1) A heavy water reactor running on U-235 can "go critical" with natural (aka "un-enriched" uranium), and produce power and plutonium.

2) A heavy water reactor fueled with a mix of enriched U-235 and thorium will "breed" U-233 from the thorium (the U-233 is also fissionable, and can then be used to fuel for "burner" reactors). This technology is being developed by India.

3) A heavy water reactor fueled with enriched U-235 plus U-238 will breed plutonium in larger amounts.

All three have peaceful uses---but #3 points HEAVILY to the production of plutonium for use in fission explosives.

[bill1952]

Good post. Are there still many breeder reactors in the world?