Mike,
Check the Radiological Health Handbook, January 1970 edition, page 406.
Review the nomenclature assigned to Ra-226 progeny.
Dominic A. Versage
Radiation Safety Specialist
Laboratory & Radiation Safety Section
Department of Environmental Health & Safety
Cornell University
125 Humphryes Service Building
Ithaca, NY 14853
607 255-7397 Fax 607 255-8267 dav1@cornell.edu