[ RadSafe ] Check out Story - Bomb Test Exposed CivilianstoRadiation

[NIXON, Grant]

The rule-of-thumb that is more widely-known is the 7:10 rule:
For each 7 fold increase in time after detonation, there is a ten-fold
decrease in the fallout activity/dose rate.

Grant I. Nixon, Ph.D., P.Phys.
Science Specialist (Physics)
Radiation Applications Development Team
Engineering, Development & Compliance
MDS Nordion
447 March Road
Ottawa, ON  K2K 1X8
Canada
 
Tel: +1 613 592 3400 ext. 2869
Fax: +1 613 591 7423

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Brennan, Mike (DOH)
Sent: Wednesday, July 18, 2007 12:35 PM
To: radsafe at radlab.nl
Subject: RE: [ RadSafe ] Check out Story - Bomb Test Exposed
CivilianstoRadiation

"Around nearby ranches, exposure rates around 15 Roentgen per hour were
measured just three hours after detonation."

>I wonder what isotopes were being measured at the 15 R per hour rate,
and how quickly the rate dropped back to background.

A rule of thumb I came across years ago is that the half-life of fallout
from a nuclear blast is roughly equal to the time since the blast.
Using that, and ignoring other factors (and there would be a number of
other factors), the rate would fall below 1 R/hr in a couple days and
below 2 mR in around 100 days.  

As to "back to background", it depends on your definition.  We still
find Cs137 in almost samples of sediment or soil that we look at.  On
the other hand, the levels that we find are usually lower activity than
one or more naturally occurring isotopes in the same sample.

I personally am not a rad-a-phobe, but if someone asked me if we should
have people stay in the situation described in the article, I'd have
said, "no."
_______________________________________________
You are currently subscribed to the RadSafe mailing list

Before posting a message to RadSafe be sure to have read and understood
the RadSafe rules. These can be found at:
http://radlab.nl/radsafe/radsaferules.html

For information on how to subscribe or unsubscribe and other settings
visit: http://radlab.nl/radsafe/


This email and any files transmitted with it may contain privileged or confidential information and may be read or used only by the intended recipient.  If you are not the intended recipient of the email or any of its attachments, please be advised that you have received this email in error and any use, dissemination, distribution, forwarding, printing or copying of this email or any attached files is strictly prohibited.  If you have received this email in error, please immediately purge it and all attachments and notify the sender by reply email or contact the sender at the number listed.