How many neutrons can a gram of hafnium-172 absorb and remain stable?

Question

What would be a good use for hafnium?

lol. Ok, hf-174 then.

Answer 1

Hf-172 is an unstable isotope with a half-life of just under 2 years, so adding neutrons will only 'help' make it stable.

Going up the line, Hf-174 is for all practical purposes stable (~trillion year half-life) but Hf-176 is absolutely stable, so I'll go with the Hf-176.

So, that's 4 neutrons added to the 172. One gram of Hf-172 is 5.814 milli-mols (1/172), so it would take 3.50E21 neutrons to change 1 gram of Hf-172 into Hf-176 (that's 0.005814 * 6.023E23).

Hafnium alloys are used to make control rods for nuclear reactors because it absorbs neutrons (just what you wanted) and has a very high melting point.

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