Re: Radioactive decay and long-term preservation

Spike Jones (
Sat, 23 Oct 1999 00:46:36 -0700

> > How would the waste isotopes be safely removed from the object?
> >Robert J. Bradbury wrote:
> The simplest way for the nanobot to "weigh" the molecule and compare
> it to the molecular weights from a table of perfect nonradioactive
> molecules.

Ja, but I fear that figuring out how to weigh an atom would be profoundly difficult. It is a mystery to me how any nanobot could tell a 14C from a 12C.

> ...Your house nano-filtration systems can probably
> purify the air & water of 14C, radon and other isotopes.

Hmmm. Radon, yes, but carbon 14? How?

> Isotopically pure materials do have interesting properties.
> I've got one conference note that isotopically pure 12C has
> thermal conductivity 45% greater than natural diamond (but I would
> want to check the reference to make sure).

OK, but natural diamond is pure 12C, is it not? I need more information here. Do you mean isotopically pure graphite? As for thermal conductivity, the presence or absence of 14C would make no difference that I can see.

> ...the difference must be due to the ~1% abundance of 13C.
> This would probably make sense since slight distortions in the
> crystal lattice should distort heat flow, perhaps electron
> conductivity as well....

Objection Your Honor! The presence of 13C would not cause distortions in the crystal lattice. 12C, 13C, 14C are all the same size. Can anyone here provide counterevidence? Website?

> I seem to recall that there is a company
> providing isotopically pure Si for use in semiconductors.

32Si has a shortish halflife of 108 yrs, so if one makes anything really small with it, one would like to not have any 32 present.

> ...If we get the costs of
> producing the isotopes low enough it seems to make sense
> to build your air-car using nuclear power. Some of our rocket
> engineers might want to comment on the tradeoffs due to shielding
> requirements. It might not buy you much if anything.

I ha' me doots. However, we are getting to where it is possible to achieve power to weight ratios sufficient for vertical takeoff and landing using internal combustion engines. Wayne Handley crashed one example of such an aircraft at an airshow three weeks ago. It could hang on the propeller, then accelerate vertically. Kewalllll. {8^D Too bad about Wayne tho. He broke a couple vertebrae.

I suspect a more reasonable approach is using small gas turbines. The first practical personal VTOL will surely be done with 2-stroke gasoline powered motors, like that two-ducted-fans arrangement those guys from Santa Clara are building. Whaddya think?

Robert, I was on a camping trip during the radioactivity-impact- on-protoplasm-due-to-nearby-exploding-star discussion that went on the week before Extro4. Ill hafta dig thru the archives. {8-] spike