Appendix B : Symbols and Units

Appendix B. Symbols and Units
Scientific notation
It is often more convenient to express the numbers encountered in radiological protection in scientific, rather than decimal notation because of their magnitude. This involves the use of significant figures within desired limits and multiplication by the appropriate power of ten. Examples are shown.
Decimal Scientific 1230000 100000 3531 15.6 0.239 0.001 0.000087 1.23 x 106 105 3.53 x 103a 1.56 x 101 2.4 x 10-1b 10-3 8.7 x 10-5
Prefixes
Some powers of ten have special names and symbols. These may be prefixed to units of measurement: thus kilogram, symbol kg, for 103 gram; millimetre, symbol mm, for 10-3 metre. A table of prefixes follows.
Multiplier Prefix Symbol Multiplier Prefix Symbol 101 102 103 106 109 1012 1015 1018 1021 1024 deca hector Kilo Mega Giga tera peta exa zeta yotta da h k M G T P E Z Y 10-1 10-2 10-3 10-6 10-9 10-12 10-15 10-18 10-21 10-24 deci centi milli micro nano pico femto atto zepto yocto d c m µ n p f a z y
Symbols
Symbols are used extensively in radiological protection. The elements are usu­ally represented by symbols, for example, C for carbon, Ba for barium, and Pb for lead. It is usual to indicate the mass number and atomic number of a par­ticular nuclide by a superscript 'and subscript. The atomic number is frequently omitted . A table of common symbols follows. When the symbol for a unit is shown with a superscript of -1 on its right, it signifies that the quantity is being used in a fractional context or to represent rate. Thus, for example, sievert per hour can be written either as Sv h-1 or as Sv/h.
Symbol Term Symbol Term α β γ e p n z alpha particle beta particle gamma ray electron proton neutron atomic number A eV Bq Gy Sv Man Sv t½ mass number electron volt Becquerel Gray Sievert man sievert half-life
Units
Some time ago, the units for the main ionizing radiation quantities were changed to those used in this text. Readers may come across old units: this table shows how to convert them to the new units.
Quantity Old unit Symbol New unit Symbol Relationship Activity Absorbed dose Equivalent dosea curie rad rem Ci rad rem becquerel gray sievert Bq Gy Sv 1 Ci = 3.7 x 1010 Bq 1 rad = 0.01 Gy 1 rem = 0.01 Sv