**UNITS OF RADIATION MEASUREMENT**

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.

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.**