RE: report find radium raises risk of bone cancer in men

["Dukelow, James S Jr" <jim.dukelow@PNL.GOV>]

Gerald Nichols and Jim Dukelow wrote:

-----Original Message-----

From: Gerald Nicholls [mailto:Gerald.Nicholls@dep.state.nj.us]

Sent: Wednesday, September 24, 2003 10:32 AM

To: radsafe@list.vanderbilt.edu; Dukelow, James S Jr; sjd@swcp.com

Subject: RE: report find radium raises risk of bone cancer in men



    <snip>



James Dukelow wrote:



>Regarding the greater concern about private wells:



I need to ask a naive question here.  If there is any Ra-224 (3.6 day

half-life) in any water system, there has to be a source of that Ra-224.

 For Ra-224, that source appears to be Th-228 (1.91 year half-life).  If

the source and the progeny are in equilibrium, then decay of Th-228 will

be replacing those Ra-224 atoms as rapidly as they decay away.  Why

should community water systems be any different from private wells with

respect to Ra-224 activity?



Response:

The Ra-224 in the water obtained from the Kirkwood-Cohansey aquifer is

not in equiblibrium with Ra-228.  The ratio of Ra-224 to Ra-228 is

between 1 and 2, with an average around 1.4.  The "unsupported fraction"

of Ra-224 is believed to be due to the "alpha recoil effect" and the

relatively low pH of the aquifer (typically 3.5 to 5.5).



The water company serving most of the area operates wells in three

aquifers and the water from the wells is mixed in the distribution

system.  Radioactivity levels in the other two aquifers are lower than

in the Kirkwood-Cohansey so both dilution and time for decay reduce the

concentration of radium in water system.  Virtually all the private

wells are in the Kirkwood-Cohansey and, given the shorter time between

pumping and use, and since no dilution is available, the concentrations

of radium in private wells are generally higher than in the water

company's distribution system.  The distribution system is quite

complicated and involves 21 wells and several storage locations.



   <snip>



Regards,



Gerry



===============



Except with respect to the issue of mixing waters of different radium content, this doesn't seem to be responsive to my question.



Ra-224 would not be expected to be in equilibrium with Ra-228.  They are on the same decay chain, which would suggest equilibrium, but Ra-224 is also on a separate decay chain that does not include Ra-228.  At any rate, on both decay chains, the immediate parent of Ra-224 is Th-228 and given the half-lives it is difficult to see why Ra-224 and Th-228 should not be in equilibrium or why a few days decay time should make any difference.



I am aware of alpha recoil and its interesting child, alpha-recoil spalling, but I haven't been able to imagine how alpha recoil could have any impact on the "unsupported fraction" of Ra-224.  I would appreciate a more detailed explanation.



Also, I have a difficult time understanding the paper's computation of Ra-228 equivalent, given that Ra-228 has a weak beta decay.  Again, perhaps someone can explain those numbers to me.



Best regards,



Jim Dukelow

Pacific Northwest National Laboratory

Richland, WA

jim.dukelow@pnl.gov



These comments are mine and have not been reviewed and/or approved by my management or by the U.S. Department of Energy.

************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.

You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/