Ludlum Measurements 2241-2, Manual

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Model 2241-2RK Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-8 July 2012
2 rem/yr
averaged over 5 years is the limit for radiological personnel
such as employees in the nuclear industry, uranium or mineral sands
miners, and hospital workers (who are all closely monitored).
1 rem/yr is the maximum actual dose rate received by any Australian
uranium miner.
300-500 mrem/yr is the typical dose rate (above background) received
by uranium miners in Australia and Canada.
300 mrem/yr
(approx) is the typical background radiation from natural
sources in North America, including an average of almost 200 mrem/yr
from radon in air.
200 mrem/yr (approx) is the typical background radiation from natural
sources, including an average of 70 mrem/yr from radon in air. This is
close to the minimum dose received by all humans anywhere on Earth.
30-60 mrem/yr
is a typical range of dose rates from artificial sources of
radiation, mostly medical.
5 mrem/yr , a very small fraction of natural background radiation, is the
design target for maximum radiation at the perimeter fence of a nuclear
electricity generating station. In practice, the actual dose is less.
What is the risk estimate?
According to the Biological Effects of Ionizing Radiation Committee V
(BEIR V), the risk of cancer death is 0.08% per rem for doses received
rapidly (acute) and might be 2-4 times (0.04% per rem) less than that for
doses received over a long period of time (chronic). These risk estimates are
an average for all ages, males and females, and all forms of cancer. There is a
great deal of uncertainty associated with the estimate.
Risk from radiation exposure has been estimated by other scientific groups.
The other estimates are not the exact same as the BEIR V estimates, due to
differing methods of risk and assumptions used in the calculations, but all
are close.
Risk comparison
The real question is, “How much will radiation exposure increase my
chances of cancer death over my lifetime?”
To answer this, we need to make a few general statements of understanding.
One is that in the US, the current death rate from cancer is approximately 20
%, so out of any group of 10,000 United States citizens, about 2000 of them
will die of cancer. Second, the contracting cancer is a random process,