🚀 go-pugleaf

In article <1993Jan7.144516.20330@cam-orl.co.uk>, dg@cam-orl.co.uk (Dave Garnett) writes:
> Peering at a cut-away drawing of the Lunar Module the other day
> I noticed what appears to be a Radioisotope Thermal Generator
> mounted on the outside low down.
> 
> Was this intended to power some experiment - I don't think
> that they generate very much power (order 80 watts ?)

Yup.  They powered the Apollo Lunar Science Experiment Packages
(ALSEP), various experiments left behind on the Moon, such as heat
flow measurements and seismographs.

> What are the radiation hazards (to the crew) associated
> with such a thing, as I understand that they comprise an
> unshielded lump of plutonium ?

Fairly negligible.  Escaping radiation is probably some gamma rays,
but the bulk of the radiation is alpha particles which are stopped
very quickly in the casing of the RTG.  The RTGs were probably fairly
far from the astronauts with considerable material intervening for
shielding.  With care, handling them to set up the experiments was
probably not very dangerous.  My guess is they are really plutonium
dioxide, which is chemically quite inert (insoluble in water and very
weakly soluble in acid, so pretty resistant to corrosion).  Anybody
got more facts?

For lots more detail on plutonium see the references given in the
sci.space FAQ.  They deal mostly with the Galileo and Ulysses RTGs but
there is a good general rundown on Pu toxicity: "Hazards from
Plutonium Toxicity", by Bernard L. Cohen, *Health Physics*, Vol 32
(may) 1977, page 359-379.

A relevant quote from the FAQ:

   Two interesting data points are (1) The May 1968 loss of two SNAP
   19B2 RTGs, which landed intact in the Pacific Ocean after a Nimbus
   B weather satellite failed to reach orbit. The fuel was recovered
   after 5 months with no release of plutonium. (2) In April 1970, the
   Apollo 13 lunar module reentered the atmosphere and its SNAP 27 RTG
   heat source, which was jettisoned, fell intact into the 20,000 feet
   deep Tonga Trench in the Pacific Ocean. The corrosion resistant
   materials of the RTG are expected to prevent release of the fuel
   for a period of time equal to 10 half-lives of the Pu-238 fuel or
   about 870 years.

-- 
     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     HIGGINS@FNAL.BITNET
   -   -       Internet:  HIGGINS@FNAL.FNAL.GOV
     ~         SPAN/Hepnet:      43011::HIGGINS