Ludlum Measurements 2241-2, Руководство пользователя

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Model 2241-2RK Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-7 July 2012
On the other hand, large doses of radiation directed specifically at a tumor
are used in radiation therapy to kill cancerous cells, and thereby often save
lives (usually in conjunction with chemotherapy or surgery). Much larger
doses are used to kill harmful bacteria in food, and to sterilize bandages and
other medical equipment. Radiation has become a valuable tool in our
modern world.
How Much Ionizing Radiation is Dangerous?
Radiation levels and their effects
The following table gives an indication of the likely effects of a range of
whole body radiation doses and dose rates to individuals:
1000 rem as a short-term and whole-body dose would cause immediate
illness, such as nausea, decreased white blood cell count, and
subsequent death within a few weeks.
Between 200 and 1000 rem in a short-term dose would cause severe
radiation sickness with increasing likelihood that this would be fatal.
100 rem in a short-term dose is about the threshold for causing
immediate radiation sickness in a person of average physical attributes,
but would be unlikely to cause death. Above 100 rem, severity of illness
increases with dose.
If doses greater than 100 rem occur over a long period, they are less
likely to have early health effects, but they create a definite risk that
cancer will develop many years later.
Above about
10 rem , the probability of cancer (rather than the severity
of illness) increases with dose. The estimated risk of fatal cancer is 5 of
every 100 persons exposed to a dose of 100 rem (i.e. if the normal
incidence of fatal cancer were 25%, this dose would increase it to 30%).
5 rem
is conservatively the lowest dose at which there is any evidence
of cancer being caused in adults. It is also the highest dose which is
allowed by regulation in any one year of occupational exposure. Dose
rates greater than 5 rem/yr arise from natural background levels in
several parts of the world but do not cause any discernible harm to local
populations.