单位转换公式

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 onthe 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

的含义

：

在物理学上，我们已经知道三种射线

α

、

β

、

γ （Χ

射线属于低能

β

射线范围

）

，它们不但有不同的物理特性，而且作用于人体的效果也不一样。为了让这三种射线在作用于人体时可以比较，一个数值被建立起来，这个数值基于射线作用于生物体的效果。