Re: China Capacitors are Radioactive

hmm, yeah other places agree, I wonder how I got that idea, I had the impression that 39 and 41 were just much less radioactive.

I always wondered how the term "Radio Active" came to be....

It has nothing to do with a Radio. If it did, everytime I turned on a radio, it would be radio active, because when it's playing, it's active.

I sort of figure the "RAD" has to do with radiation, but why did the word "radio" come to be used?

It derives from the latin 'radiare': 'to shine'. 'Radio' is the first person present tense: "I shine".

Jeroen Belleman

K is about the hottest stuff commonly around. Two others are old red (uranium colored) bricks, and thoriated Coleman lantern mantles.

Bismuth (one of my favorite elements) is just barely radioactive. ~10^19 years according to wiki.

George H.

Europium is also very mildly radioactive--half of it is Eu 151, which has a half life of (5 +- 10)E18 years, i.e.

Ten years or so ago, I needed to put down some europium films to make fancy tunnel junctions, and I couldn't because the thin film folks at Watson weren't allowed to use radioactive materials. :(

A one-gram evaporator target would emit one alpha particle on average in a time

t = 1/(6.02e23 atoms/mol * 1g/ 151g/mol * ln(2) / (5e18 y * 3.16e7 s/y))

= 57175 seconds, i.e. about one every 16 hours.

Sigh.

Cheers

Phil Hobbs

Antique stores sometimes have old radium-dial clocks. Once you are dark adapted, if you look at them up close, there is a cool alpha-shot dancing pattern. You can see single alpha events.

They make nice pulses into a PMT too. I made it to the National Science Fair doing that. Baltimore that year. Ugh.

And I thought it was only state institutions that had silly radioactivity laws/ rules.

George H.

Yeah, it did. For the most part. But from stage 4 to what they now think is cured is pretty good. Required more than radiation but the radiation part was at least interesting. Eric

Long may it wave. ;)

Cheers

Phil Hobbs