[ RadSafe ] A novel use of I-131

[Syd H. Levine]

I believe this account of how I-131 has been used in Florida to prove 
mechanical integrity of municipal disposal wells is a bit confused.  EPA, 
and the well logging licenses issued by NRC or agreement states never allow 
the introduction of radioactive tracer material into a potable water supply 
well.  In fact, I am aware of jobs in Florida that have been run with 
Gold-198 where EPA was afraid the tracer material MIGHT get into the water 
supply aquifer.  Further, I am aware of no municipal water supply well where 
the same well bore is used for disposal (it is possible such a critter 
exists, but I cannot imagine the UIC permit writers at EPA Region IV in 
Atlanta issuing such a permit).

Syd H. Levine
AnaLog Services, Inc.
Phone:  270-276-5671
Telefax:  270-276-5588
E-mail:  analog at logwell.com
URL:  www.logwell.com

----- Original Message ----- 
From: "Geo>K0FF" <GEOelectronics at netscape.com>
To: <radsafe at radlab.nl>
Sent: Monday, July 16, 2007 11:05 AM
Subject: [ RadSafe ] A novel use of I-131


Info per a client:
Municipal water well drilling in Florida has changed in the last decades. 
Once a well would only need to be a
few hundred feet deep.
Now that the population has grown, naturally the water table has dropped 
from overuse.
Today a well will go down 1500 feet, and be of 36 inch diameter.
The actual hole is much deeper than that, at least 2000 feet deep.

Water pumped from the well is still saline, but not as salty as the 
ocean.Desalination plants process the
water into drinking water and brine.Instead of pumping the waste brine into 
the ocean for disposal, it is pumped back down the
well, all the way to the bottom of the hole. By doing so, the water table is 
maintained at a higher level. Being much denser than
the source water, the brine is supposed to stay at the bottom of the hole.

During the well proofing process, that is after construction but before 
turning it over to the end users, a radioactive
I-131 tracer  is metered into the brine flow down into the well. 
Simultaneously a 25 foot long tool containing  7 scintillator
gamma detectors is lowered into the well, monitoring any leaks of high 
pressure brine into the supply pipeline, and the relative position that the 
brine takes up in the water table.

A normal medical dose of I-131 in liquid form is used, from Cardinal Health 
Services.

I-131 has a radiological half life of 8.040 days and decays to stable Xe-131 
(NUDAT 2) with a 1.2% branch to radioactive Xe-131m, T/2 11.840 days (C. 
Hacker)
I-131 beta minus  decays 100% with an 81% probability of a 364.5 gamma ray 
(and others at lower %).

After 7 half-lives, any isotope is reduced to only 1% of the original dose.
http://web.ead.anl.gov/marssim/doc/docs/Radiation_Basics.pdf


After each 5 years of use, the above tests are repeated.

Such uses or radioactive materials are numerous and are excellent examples 
of the risk/benefit ratio theory.


George DowellNLNLNew London Nucleonics Lab56791 Rivere Au Sel Pl.New London, 
MO 63459GEOelectronics at Netscape.com573-221-3418
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