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Introduction

Basics of Radiation

Detection

Measurement

Safety Around Radiation Sources

Types of Radiation Exposure

Managing Radiation Emergencies

Procedure Demonstration

Measurement

Activity: How Much Is Present?

The size or weight of a container or shipment does not indicate how much radioactivity is in it.

The amount of radioactivity in a quantity of material can be determined by noting how many curies of the material are present. This information should be found on labels and/or shipping papers.

More curies = a greater amount of radioactivity

A large amount of material can have a very small amount of radioactivity; a very small amount of material can have a lot of radioactivity.

Image example: A large amount of material can have a very small amount of radioactivity; a very small amount of material can have a lot of radioactivity.

For example, uranium-238 has 0.00015 curies of radioactivity per pound (0.15 millicuries), while cobalt-60 has nearly 518,000 curies per pound.

In the International System of units (SI), the becquerel (Bq) is the unit of radioactivity. One Bq is 1 disintegration per second (dps). One curie is 37 billion Bq. Since the Bq represents such a small amount, you are likely to see a prefix used with Bq, as shown below:

  • 1 MBq (27 microcuries)

  • 1 GBq (27 millicuries)

  • 37 GBq (1 curie)

  • 1 TBq (27 curies)

 

SI Units and Prefixes
The International System of Units has been given official status and recommended for universal use by the General Conference on Weights and Measures.

Radiation Measurements

  Radioactivity Absorbed Dose Dose Equivalent Exposure
Common Units curie (Ci) rad rem roentgen (R)
SI Units becquerel (Bq) gray (Gy) sievert (Sv) coulomb/kilogram (C/kg)

Following is a list of prefixes and their meanings that are often used in conjunction with SI units:

Multiple Prefix Symbol
1012 tera T
109 giga G
106 mega M
103 kilo k
10-2 centi c
10-3 milli m
10-6 micro Á
10-9 nano n

Conversions

Conversion Equivalence

1 curie = 3.7 x 1010
disintegrations per second
1 becquerel =
1 disintegration per second
1 millicurie (mCi) = 37 megabecquerels (MBq)
1 rad = 0.01 gray (Gy)
1 rem = 0.01 sievert (Sv)
1 roentgen (R) = 0.000258 coulomb/kilogram (C/kg)
1 megabecquerel (MBq) = 0.027 millicuries (mCi)
1 gray (Gy) = 100 rad
1 sievert (Sv) = 100 rem
1 coulomb/kilogram (C/kg) = 3,880 roentgens

Conversion Factors

To convert from To Multiply by
Curies (Ci) becquerels (Bq) 3.7 x 1010
millicuries (mCi) megabecquerels (MBq) 37
microcuries (ÁCi) megabecquerels (MBq) 0.037
millirads (mrad) milligrays (mGy) 0.01
millirems (mrem) microsieverts (ÁSv) 10
milliroentgens (mR) microcoulombs/kilogram (ÁC/kg) 0.258
 
becquerels (Bq) curies (Ci) 2.7 x 10-11
megabecquerels (MBq) millicuries (mCi) 0.027
megabecquerels (MBq) microcuries (ÁCi) 27
milligrays (mGy) millirads (mrad) 100
microsieverts (ÁSv) millrems (mrem) 0.1
microcoulombs/kilogram (ÁC/kg) milliroentgens (mR) 3.88

 

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