[ RadSafe ] Uranium grinding wheels

Thu Jun 11 17:26:53 CDT 2009

Neil, 

I can report from direct evidence that some current grinding wheels do indeed contain naturally occurring radioactive materials as part of the aluminum oxides, silicon carbides, magnesium compounds and bauxite ores that compose resin and phenolic based abrasive wheels/grinding discs.

Surface dose rates from bulk shipments have been measured from these industrial wheels that approach 20 microR/h and are readily detectable above background with handheld instruments used for screening cargo.  Gamma spectrum analysis indicates that Ra-226, U-235, U-238 and Th-232 in the range of 2-4 picoCi/g are predominantly present but in overall concentrations that are half of the US Federal limit of 500 ppm which necessitate regulation.  

If the debris from dry grinding operations are collected (as most are to prevent dust inhalation hazards), the fines in the first stage are the primary source of the elevated radiation readings.  Second stage fines have not been shown to be contaminated in our evaluations, which suggests the particles involved are much greater than 5 microns in size.

Although until recently the US was the largest producer of grinding materials and compounds, China is now the primary source of these items.  These shipments are routinely detected at the US ports of entry.

Daren Perrero
The opinions expressed are mine, all mine....
I'm with the government, I'm here to help you.
Daren.Perrero(a)Illinois.gov

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf Of Franz Schönhofer
Sent: Wednesday, June 10, 2009 3:07 PM
To: 'John R Johnson'; 'Brennan, Mike (DOH)'; radsafe at radlab.nl
Subject: AW: [ RadSafe ] Uranium grinding wheels

John,

I agree with you, but though not really being an expert in grinding
equipment I think that the old days, when natural materials were used for
this purpose are long gone. Granite was obviously not used, because it was
to hard to be put into the necessary shape. Sandstone seems to have been the
preferred material. New materials like synthetic carbides and oxides have
since long replaced the old ones (like different sandstones). I see it
whenever I have to sharpen my excellent and beautiful Japanese knives.
------ I interrupted writing, because I got interrested in the radioactivity
of my sharpening and grinding stones! Here are the results: none of the six
of them showed any elevated radioactivity. Unfortunately (!) I do not have a
HPGe gammaspectrometry unit at home, but I think that the primitive dose
rate meter I have indicates the lack of excessive radiation as well. 

This sounds like fun, but to be honest I wonder how the obviously
governmental and official HSS can issue such an unfounded opinion!

Franz

Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA

-----Ursprüngliche Nachricht-----
Von: John R Johnson [mailto:idias at interchange.ubc.ca] 
Gesendet: Mittwoch, 10. Juni 2009 20:55
An: Franz Schönhofer; 'Brennan, Mike (DOH)'; radsafe at radlab.nl
Betreff: Re: [ RadSafe ] Uranium grinding wheels

Franz

I don't think that uranium is used for grinding but can be present in the 
material, such as granite, that is.

John
***************
John R Johnson, PhD
CEO, IDIAS, Inc.
4535 West 9th Ave
604-676-3556
Vancouver, B. C.
V6R 2E2, Canada
idias at interchange.ubc.ca

----- Original Message ----- 
From: "Franz Schönhofer" <franz.schoenhofer at chello.at>
To: "'Brennan, Mike (DOH)'" <Mike.Brennan at DOH.WA.GOV>; <radsafe at radlab.nl>
Sent: Wednesday, June 10, 2009 11:17 AM
Subject: AW: [ RadSafe ] Uranium grinding wheels

RADSAFErs,

Looking on Wikipedia, which I really do not esteem because of the very poor
performance (also on uranium!) I find that "uranium is slightly softer than
steel". So why should it be used for grinding????? Maybe uranium oxide or
uranium carbide would be better suited, but no such compounds have been
mentioned! So what is really behind that "urban myth" that uranium is
present in grinding wheels? This is really not positive for the "HSS"!

Franz

Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA

-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im Auftrag
von Brennan, Mike (DOH)
Gesendet: Mittwoch, 10. Juni 2009 18:40
An: radsafe at radlab.nl
Betreff: RE: [ RadSafe ] Uranium grinding wheels

I would think that the issue here is with breathing the dust, and while I
agree with Franz about the radioactive isotopes that are likely in the dust,
I am skeptical as to whether they are likely to be the biggest health risk.
It is entirely possible that silica and/or asbestoses are in the grinding
wheel, and there are bound to be fine particles of whatever is being ground.
None of these go well with lung tissue.

The US Navy some time ago instituted dust control procedures for health
protection reasons (and there was a lot of complaining by the "old hands").
They found that such procedures actually saved a lot of money in decreasing
cleanup time and cost, and preventing damage to equipment from the dust.
Doing things right often costs less in the long run than doing them without
worrying about the consequences.

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf
Of Franz Schönhofer
Sent: Wednesday, June 10, 2009 5:09 AM
To: neildm at id.doe.gov; radsafe at radlab.nl
Subject: AW: [ RadSafe ] Uranium grinding wheels

Dave,

There is not the slightest doubt that grinding wheels contain uranium,
thorium, K-40 and decay products. Your body as well as mine and foodstuff
contains all these long-lived radionuclides and additionally shorter lived
ones like C-14 and tritium, not to talk about more exotic ones - of natural
origin.

Abrasives may contain naturally occurring radioactive material (NORM),
depending on their origin. Best known are the zirconium containing sands.
Those compounds are mostly used because they are very hard, very resistant
to mechanical wear, and last extremely long before having to be replaced.

You do not specify what "HSS" means, further I miss a description of what
substances are ground - dry or wet operation. In the latter case the air
borne particles would really play no role. In the first case: Do you eat
grinding wheels dust?

Best regards,

Franz

Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA

-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im Auftrag
von neildm at id.doe.gov
Gesendet: Dienstag, 09. Juni 2009 23:51
An: radsafe at radlab.nl
Betreff: [ RadSafe ] Uranium grinding wheels

There is an HSS bulletin out about grinding wheels containing uranium
potentially causing surface contamination and/or airborne particles.

I had never heard of this, nor can I find any reference to uranium
containing abrasives on the internet.  Undoubtedly, it is present as a trace
material, but this would not seem to me to be of any concern at all.

Does anyone have better information?

Thank you,
Dave Neil