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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.
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Decimal
| Scientific
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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
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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.
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Multiplier
| Prefix
| Symbol
| Multiplier
| Prefix
| Symbol
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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
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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.
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Symbol
| Term
| Symbol
| Term
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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
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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.
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Quantity
| Old unit
| Symbol
| New unit
| Symbol
| Relationship
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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
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