Page 4 - Radiation Safety

BASIC OF IONISING RADIATION

RADIOACTIVE DECAY

PARTICULATE RADIATION PHOTON

ALPHA BETA NEUTRON GAMMA

Beta +ve γ
Alpha (Positron Neutron
particle 2 Protons ) Excess energy during
O
2 Neutron 6 C 11 = B 11 + e + γ decays of alpha and
5
+1
19
Beta –ve 9 F + α 4 = Na 22 + n 1 beta is emitted in the
2
11
0
form of gamma
4
U 235 = Th 231 + He + (Negatron
92 90 2
γ I 131 = ) Xe 131 + e + γ
O
53 54 -1
RADIOACTIVITY
Nuclides Physical ½ life
A = A e – (λ t) Rn-220 55 seconds
t
i
T = ln 2 / λ I-131 8.04 days
½
A = Current activity Ir-192 73.83 days
t
A = Initial activity T 1/2 = Half-life Co-60 5.27 years
i
Cs-137
30.23 years
t = Time Elapsed λ = Decay Constant U-238 4.47 x 9 years
λ = Decay Constant HALF-LIFE Th-232 1.40 x 10
(T ) years
A = A /2 n 1/2 T = n / t
i
t
½
A = Current activity related to Half-life is the time n = Number of Half-life
taken for a
t
A = Initial activity radionuclide to t = Time elapsed
i
n = Number of half-life reduce by half of its
initial activity.