Meter Movement Magnet Activity: 600-800 CPM

[dlgoff]

The other day I used my Ludlum survey meter to check out if any of my old junk electrical part may show any traces of radioactivity. I was rather surprised to find an old meter movement magnet showed some activity. Today I took some pictures while determining just how much activity there was. With the Ludlum meter can't tell what type of radioactivity it is, but since I had to have the detector really close, I guessing either beta or alpha. It turned out that the activity was coming from a rivet that's holding the laminates together. I'm getting somewhere between 600 and 800 Counts/minute. Any comments welcome.

The magnet laminates showing the rivet:

Activity on the X0.1 scale:

Activity on the X1 scale:

 

[Bystander]

my old junk electrical part

How "old?"

 

[dlgoff]

How "old?"

I don't know. Maybe in the '50s, but that's just a guess.

 

[Bystander]

'50s, but that's just a guess.

Looking at the plating, lack of rust/corrosion, ink color, I'd agree, '50s to '70s.

 

[jim hardy]

Is that rivet copper plated?

Copper, Vanadium and Uranium ores run together in US southwest. When i visited the Phelps-Dodge Morenci mine about 1969 they used electrolytic refining and made mighty pure copper. I don't know how they did it in late 40's, early 50's though .

So my guess would be trace uranium in the vanadium alloy rivet steel and/or its copper plating. Just a GUESS with no real basis.

Guys down at Wolf Creek could identify the isotope but at that activity, even though it's a miniscule 600 cpm, they might not be able to give it back to you..
Know any HP techs there?

Hmmm 50's was the decade of atmospheric weapons testing.

old jim

 

[dlgoff]

Is that rivet copper plated?

It's doesn't look like copper and it appears that whatever it was "plated"(?) with was done on both the rivet and the laminates. Here's a couple of other close up pics.

Depending on the angle of the light source you can get "coppery" hues on all of it.

 

[OmCheeto]

A sheet or two of paper should shield alpha particles.
A thin sheet of glass or metal should shield beta particles.
[ref]

It may not identify the source element/isotope, but at least we'd know what the emitted particles are.

 

[jim hardy]

My first thought was cobalt in the magnetic steel , but why would it be only in the rivet? Unless the rivet factory got a bar of contaminated steel...
Probably there was some Co60 floating around in the 50's.

 

[Tom.G]

That coating looks suspiciously like shellac. Or, maybe, some sort of chemical passivation.

 

[jim hardy]

Unknown to me,

. A round 1918 "Standard Alloy Company" tried alloying uranium with steel , they claimed success in their book "Uranium in Steel"
https://books.google.com/books?id=Q...H#v=onepage&q=uranium traces in steel&f=false

only to be challenged by another author early in 1921, writing in "Iron Trade Review"
https://books.google.com/books?id=8...J#v=onepage&q=uranium traces in steel&f=false

Could your rivet date back to 1920's ?

old jim

 

[dlgoff]

A sheet or two of paper should shield alpha particles.
A thin sheet of glass or metal should shield beta particles.

Yes I know. That's why I said, "I had to have the detector really close, I guessing either beta or alpha". It appeared that the air was shielding particles as I couldn't detect one six inches away. I'm thinking, not only either alpha or beta particles but low energy ones at that. I'm no expert but I have worked a lot with ¹⁴C and Tritium.

 

[dlgoff]

"... Standard Alloy Company" tried alloying uranium with steel , they claimed success in their book "Uranium in Steel"

How cool you finding this.

Could your rivet date back to 1920's ?

I haven't looked into when/what year panel meters of this size we were being used. I got this when I was a kid; probably in the late '50, early '60s. So maybe it does date to the 1920's. Here's a picture of the coil assembly I removed before testing if that sheds any light on it's year.

 

[jim hardy]

Well, this is a definite digression but Wikipedia has a section on Ferro-Uranium. They say post war Ferro-Uranium is made with depleted U.
https://en.wikipedia.org/wiki/Ferrouranium

FerroUranium was still around at beginning of Manhattan project. The Russians bought around 400 pounds of Uranium salts allegedly for research into alloying it with steel. General Groves also approved a Russian export request for twenty five pounds of Uranium metal . He only did it to find out if there was anybody in US able to fill the order. His project was quietly buying up all the Uranium they could find.
https://books.google.com/books?id=e...nepage&q=how to identify ferrouranium&f=false

It wouldn't surprise me at all if during the war there was a bin of Ferro-Uranium rivets in a meter factory. A WW2 surplus meter would have been only twenty years old when you got that one.

So it's plausible.Thanks Don for an interesting diversion !

old jim