Internal Dose Conversion Factors for Serial Decay

["Falo, Gerald A Dr HMJF" <Jerry.Falo@us.army.mil>]

Hi all,

 

I've managed to work myself into a state of confusion concerning dose

conversion for series decay such as Ra-226 and progeny. I know the dose

conversion factors from the ICRP assume an intake of a pure radionuclide and

account for ingrowth in the body. I assume that FGR No. 11 follows the same

method. I also know how to apply the mixture rule and can derive a DCF in

terms of a parent when I know that the progeny isn't included in the DCF. 

 

What I'd like to know is if there is a rule of thumb for assuming that

ingrowth in the body is essentially equal to an intake of a radionuclide.

For example, with Ra-226, neglecting the possible escape of radon from

inhaled material, the Pb/Bi progeny grow-in with an effective half life of

about half an hour so an intake of pure Ra-226 or Ra-226 in secular

equilibrium would seem to have essentially the same DCF. But what about

Po-210? It seems to me that 138 days is too long of a half-life to neglect

and I should explicitly include the Po-210 activity when I calculate a

"natural radium-226" DCF?

 

Any clarification would be greatly appreciated.

 

Thanks,

Jerry Falo

 

The statements and opinions expressed herein are my responsibility; no one

else (certainly not my employer) is responsible, but I still reserve the

right to make mistakes.

 

Check core temperature: yes./no? Yes! - Homer Simpson

 

Gerald A. Falo, Ph.D., CHP

Henry M. Jackson Foundation for the Advancement of Military Medicine

U.S. Army Center for Health Promotion and Preventive Medicine

jerry.falo@us.army.mil <mailto:jerry.falo@us.army.mil> 

410-436-4852