Vintage radioactive wrist watches - Is Radium really nasty?

[walter b]

(01-18-2015 01:44 PM)Thomas Klemm Wrote:  ... about 340 mSv per year. Compare this to:

Quote:Maximum yearly dose permitted for US radiation workers (50 mSv).

And: Lowest one-year dose clearly linked to increased cancer risk = 100 mSv.

Watch it!

([:-(

P.S.: Radium decays emitting alpha particles. So a sheet of paper is sufficient for shielding. Once the watch hands are mounted and the cover glass is fixed, there should be no risk anymore. BUT avoid ANY direct contact of that material to your body!!

Radium is almost entirely 226Ra, decaying into 222Rn which is a gaseous alpha emitter, decaying into 218Po which is an alpha emitter again decaying into 214Pb. The lifetimes of 222Rn and 218Po are far shorter than the one of 226Ra. Since it's a noble gas, 222Rn can be inhaled, so after some days contemplating over open watch hands you have some Polonium in your lung where it must not be!!

BTW, German Wikipedia tells:

Quote:Die maximale erlaubte Jahresdosis für beruflich strahlenexponierte Personen beträgt 20 mSv, über ein Berufsleben dürfen jedoch nicht mehr als 400 mSv zusammenkommen.

(~ max. dose per year for professionals exposed to radioactivity is 20 mSv; they shall not receive more than 400 mSv in their professional life.) Compare the value stated above and you see that US radiation workers are more robust (as usual ).