[ RadSafe ] Fukushima beta radiation burns

Lachapelle, Edward B Edward_B_Lachapelle at RL.gov
Thu Mar 24 16:24:12 CDT 2011

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
Subject: [ RadSafe ] Fukushima beta radiation burns

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?)?  


Rick Strickert
Austin, TX
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