Unit conversion formula
UNITS OF RADIATION MEASUREMENT
The curie is the number of particles per second from 1 gram of
Radium = 3.7
×
10 E10 counts/second = 37 billion cps = 37
Billion Becquerel.
1 Becquerel (Bq) = 1 count per second = 1 event per second
1 microcurie = 1 uCi = 37,000 Bq = 37,000 cps.
1 microcurie = 2.22
×
10E6 disintegrations / minute = 2,220,000
Cpm.
1 nanocurie = 1 billionth of a curie = 2,220 disintegrations /
Minute.
1 picocurie = 2.2 disintegrations / min.
Dosage units:
Gray (Gy) = 1 Joule/kg
Sievert (Sv) = Gray x QF, where QF is a "quality factor" based on the type
Of particle. The Sievert is a measure of biological effect.
QF for electrons, positrons, and xrays = 1 QF = 3 to 10 for
Neutrons,
Protons dependent upon the energy transferred by these heavier
Particles.
QF = 20 for alpha particles and fission fragments.
Converting older units:
1 rad = 1 centigray = 10 milligrays ( 1 rad = 1cGy = 10 mGy )
1 rem = 1 centisievert = 10 millisieverts ( 1 rem = 1cSv = 10 mSv )
1 mrad = 10 μGy
Nominal background radiation absorbed dose of 100 mrad/year =1 mGy/yr.
Nominal background radiation dose biological equivalent of
1mrem/year = 10usv/yr.
Occupational whole body limit is 5 rem/yr = 50 μsv/yr.
( Recently proposed that levels be reduced to 2 rem/yr.)
2.5 mrem/hr or 25 uSv/hr is maximum average working level in
Industry.
Exposure rate from Naturally Occurring Radioactive Material
(NORM) ; an
Empirically derived conversion factor for Ra-226 decay series:
1.82 microR/hour = 1 picoCurie/gram.
mR/h=10μSv/h
mR=10μSv
Sievert
Meaning
:
In physics, we already know three kinds of rays.
α
,
β
,
γ (Χ
Ray is low energy
β
Ray range
)
They not only have different physical characteristics, but also have different effects on the human body. In order for the three rays to be compared when applied to the human body, a value is established which is based on the effect of the radiation on the organism.
Sievert
Sivert
(
symbol
Sv,
Dose equivalent unit
, 1 Sv=100 rem)
Rem
(
Roentgen equivalent man
)
Rem
,
Human roentgen equivalent
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