Lachapelle, Edward B Edward_B_Lachapelle at RL.gov
Fri Mar 25 08:57:22 CDT 2011

```Whoops.  Dropped a decimal point.  More like 0.1 mCi/sq. cm.

Ed Lachapelle

-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu [mailto:radsafe-bounces at agni.phys.iit.edu] On Behalf Of Lachapelle, Edward B
Sent: Friday, March 25, 2011 6:38 AM
To: 'The International Radiation Protection (Health Physics) Mailing List'

Good point about the Sr-90/Y-90 equilibrium.  (Sometimes you miss the obvious.)

Given the same assumptions, I got a dose to curie factor of 1.6E-6 Gy/hr per Bq/sq. cm.

That resulted in a Y-90 concentration of 0.08 Ci/L.

And for a 600/hr rads of beta dose, I got .01 mCi/sq. cm.  You're within the bounds of RadCon math.

Ed Lachapelle

-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu [mailto:radsafe-bounces at agni.phys.iit.edu] On Behalf Of Glenn R. Marshall
Sent: Friday, March 25, 2011 6:18 AM
To: The International Radiation Protection (Health Physics) Mailing List

Assuming Sr-90 is the culprit, the beta dose is from Y-90 with a 0.934 MeV average energy.  A "very quick" calculation shows a dose of about 600 rad/hour from skin contamination of 1 mCi/cm2.  Disclaimer: I only had a minute to do this and don't have time to check my math.....

But if that's true, they have a problem.

Glenn Marshall, CHP

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Lachapelle, Edward B
Sent: Thursday, March 24, 2011 5:24 PM
To: 'The International Radiation Protection (Health Physics) Mailing List'

Here are my thoughts:

If you assume that the dose was on the order of 500 Rads, and they were exposed for 10 hours, that would be 50 Rads/hr, or 0.5 Gy/hr.

If you also assume that the dose was from beta radiation from Sr-90, (average beta energy of 0.196 MeV), and using a skin dose calculation from Cember's "Introduction to Health Physics," you get a conversion of 4.9E-7 Gy/hr per Bq/sq. cm.

If you assume that there was about 0.1 cm of thickness of water over the area, that would result in a Sr-90 concentration of 0.3 Ci/L.

Ed Lachapelle, M.S., CHP

-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu [mailto:radsafe-bounces at agni.phys.iit.edu] On Behalf Of Strickert, Rick
Sent: Thursday, March 24, 2011 1:51 PM
To: The International Radiation Protection (Health Physics) Mailing List

Below are a couple of links on reports that three workers at the Fukushima No. 3 reactor got beta-radiation burns on their feet when they were laying electrical cables while standing in radioactively-contaminated water.  One report stated: "TEPCO said radioactive water may have seeped through the workers' radiation protective gear, causing radioactive materials in the water to stick to their skin."

The workers also received radiation doses of 17 to 18 rem while working from 10 AM to 12:10 PM (suggesting a 1.2 - 1.3 rem/h average dose rate).  It's not clear whether the workers were standing in water the entire 14 hours.

Can one estimate (or WAG) the solution concentrations of beta-emitters (Ci/L) that would have to be in the water for the workers to get radiation burns from the water that seeped through the workers' radiation protective gear (e.g. Tyvex booties over work shoes?)?

http://e.nikkei.com/e/fr/tnks/Nni20110324D24JF855.htm

Rick Strickert
Austin, TX
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