Ludlum Measurements 2241-2, Руководство пользователя

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Model 2241-2RK Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-6 July 2012
The amount of ionizing radiation, or dose, received by a person is measured
in terms of the energy absorbed in the body tissue, and is expressed in RAD .
One rad is 0.01 joules deposited per kilogram of mass.
Equal exposure to different types of radiation expressed as RAD, do not
however, necessarily produce equal biological effects. One rad of alpha
radiation, for example, will have a greater effect than one rad of beta
radiation. When we talk about radiation effects, we therefore express the
radiation as effective dose, in a unit called the REM (Roentgen Equivalent
Man).
Regardless of the type of radiation, one rem of radiation produces the same
biological effect. (100 rem = 1 Sv)
Smaller quantities are expressed in mrem (one thousandth) or
µ
rem (one
millionth of a rem). We will use the most common unit, rem, here.
What Are The Health Risks From Ionizing
Radiation?
It has been known for many years that large doses of ionizing radiation, very
much larger than background levels, can cause a measurable increase in
cancers and leukemias (cancer of the blood) after some years delay. It must
also be assumed, because of experiments on plants and animals, that ionizing
radiation can also cause genetic mutations that affect future generations,
although there has been no evidence of radiation-induced mutation in
humans. At very high levels, radiation can cause sickness and death within
weeks of exposure (see table on next page).
But what are the chances of developing cancer from low doses of radiation?
The prevailing assumption is that any dose of radiation, no matter how
small, involves a possibility of risk to human health. However there, is no
scientific evidence of risk at doses below approximately 5 rem in a short
period of time or about 10 rem over a period of one year.
Higher accumulated doses of radiation might produce a cancer that would
only be observed several (up to 20) years after the radiation exposure. This
delay makes it impossible to say with any certainty which of many possible
agents were the cause of a particular cancer. In western countries, about a
quarter of people die from cancers, with smoking, dietary factors, genetic
factors, and strong sunlight being among the main causes. Radiation is a
weak carcinogen, but undue exposure could certainly increase health risks.