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Paul Robinson explains why 85 per cent of the radioactivity in the ore remains in the tailings

Submitted by Marilyn Crawford

I asked Paul Robinson* to explain why 85 per cent of the radioactivity in the ore remains in the tailings. He gives permission to quote the following explanation.

“Uranium typically occurs in nature as combination of three isotopes, U-238 - 99.3%, U-235 -0.7% and U-234 -<0.01%. Each typically occurs in nature in association with its series of radioactive decay products. For U-238, these decay products include Thorium-230, Radium-226, Radon-222 among isotopes.

As uranium mill processes only remove the uranium, most of the decay products, which constitute most - about 85% - of the radioactivity in the ore, remains in the tailings along with almost all of the heavy metals typically found in association with the ore. The U-238 decay products mentioned are more hazardous than U-238.

You can find statements for citation that presents a similar conclusion but not the basis for the conclusion at

1) p. 3-29 of in a report called Technologically Enhanced Naturally Occurring Radioactive Materials From Uranium Mining Volume 1: Mining and Reclamation Background [EPA 402-R-05-007] Revised June and

2) Uranium Mining and Milling - A Primer on the web site at, among other sources.”

*Paul Robinson
Research Director
Southwest Research and Information Center
PO Box 4524
Albuquerque, NM USA 87196-4524
phone: 505-262-1862 fax: 505-262-1864
web site:

MISSION: Southwest Research and Information Center is a multi-cultural organization working to promote the health of people and communities, protect natural resources, ensure citizen participation, and secure environmental and social justice now and for future generations.