Reply To: turn heat into electricity

[jamesr]

delt0r wrote: I didn’t read it all in detail since he misses a pretty serious detail with D+D fusion. That is he claims D+D fusion gives 4He, which it does not. A 10sec wiki search would have told him that.

Yes, he’s a little misleading on that – although it is what happens eventually, as in the Sun. On Earth we have to deal with the intermediate products
The initial reactions (with a 50/50 split) are of course:
D + D -> He-3 + n
D + D -> T + p

but then you get all the other combinations
D + T -> He-4 +n
D + He-3 -> He-4 +p
He-3 +He-3 -> He-4 + 2p
He-3 + T -> He-4 + p + n
He-3 + T -> He-4 + D
n + p -> D

Which all end in He-4. Given D+T much larger cross section than DD, in a DD reactor most of the tritium gets burnt up instantly rather than causing a legacy problem. Although there is still enough that precautions need to be taken. Another important aspect is that the neutrons from the DD primary reaction are only 2.45MeV not 14.1MeV so need slightly less stopping power in the shielding/blanket.

On the whole I found the article well written, and the subsequent posts I wouldn’t term biased – I’d say they had a pretty healthy scepticism.