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. 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. 1 rad = 1 centigray = 10 milligrays ( 1 rad = 1cGy = 10 mGy ) 1 rem = 1 centisievert = 10 millisieverts ( 1 rem = 1cSv = 10 mSv ) 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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