🚀 go-pugleaf

In <FRANL.92Apr3132432@draco.centerline.com> franl@centerline.com (Fran Litterio) asks
>Isn't liquid lithium forseen as the medium used to absorbe the
>neutrons speeding away from the fusion reaction?  The
>(themodynamically) hot lithium would heat pressurized water that would
>eventually drive steam turbines to make electricity.  Over time the
>lithium becomes radioactive and needs to be replaced.  Being a liquid
>would actually make it harder to manage the storage of waste over many
>decades (in general, liquids leak, evaporate, corrode containers, etc.
>more easilly than do solids).

	Lithium is a solid at room temperatures; its m.p. is 186 deg C.
Its vapour pressure is not high at room temperatures, and it is not a
"universal solvent" in the way that water is.  Metallic lithium is extremely
reactive with oxygen and many oxygen-containing compounds, so that if
long-term storage were necessary I would expect that it would be converted to
one of its extremely stable and insoluble compounds ("lithium" comes from the
Gk for "stone").
	But why would long-term storage be necessary?  The two radioactive
isotopes of lithium have halflives of less than 1 sec; storing "radioactive
lithium" for a DAY would leave zero activity, and the lithium could then be
distilled from any contaminants, or removed chemically.
	And would there be significant quantities of radioactive
contaminants?  I am not an expert on fusion, but my understanding is that
capture by lithium of the fairly energetic neutrons involved leads to the
breakup of its nuclei into tritium (a component of the fuel, which would be
outgassed from the hot liquid lithium) and He3 or He4, which are not
radioactive.  After the lithium isotopes, the next heavier nuclides that
are unstable with long halflives are Be10 (1.6E6 yr) and C14 (5730 yr), and
I am skeptical that these could be produced in significant quantities by
neutron irradiation of lithium.

John Lewis
Physics Department
Memorial University of Newfoundland