UNITS OF RADIATION MEASUREMENT

Simple conversion from µR to µSv. You divide µR by 100 to get µSv.
Example: The Model 500VBR displays 123456 µR is the same as 1234.56 µSv.

The curie is the number of particles per second from 1 gram of Radium = 3.7 x 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 x 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.
 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.

The Sievert is a measure of biological effect.

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 uGy

Nominal background radiation absorbed dose of 100 mrad/year = 1 mGy/yr.

Nominal background radiation dose biological equivalent of 100mrem/year = 1mSv/yr.

Occupational whole body limit is 5 rem/yr = 50 mSv/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.

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