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Table 14.2

Properties of radioisotopes commonly used in the biological sciences

Property

3 H

14

C

35

S

32

P

33

P

125

I

131

I

t1/2

12.3 years

5730 years

87.4 days

14.3 days

25.4 days

59.6 days

8.04 days

Mode of decay

bbbbb

X (EC) and Augerelectrons

g

and

b

Max

b

energy (MeV)

0.019

0.156

0.167

1.709

0.249

Augerelectrons 0.035

0.806

ALI

a

480 (Mbq)

b

34 (Mbq)

15 (Mbq)

6.3 (Mbq)

14 (Mbq)

1.3 (Mbq)

c

0.9 (Mbq)

c

Maximum range in air

6 mm

24 cm

26 cm

790 cm

49 cm

>

10 m

>

10 cm

Shielding required

None

1 cm acrylic

1 cm acrylic

1 cm acrylic

1 cm acrylic

Lead 0.25 m orlead-impregnatedacrylic

Lead 13 mm

g

dose rate (

mSv h

-1

from 1 GBq at 1 m)

–––(

b

dose rate

760

mSv, 10 cm

from 1 MBq)

–41 51

ˇCerenkov counting

• 
  


• 
  


• 
  

Yes

• 
  


• 
  


• 
  

Notes:

aAnnual limit on intake, based on a dose limit of 20 mSv using the most restrictive dose coefficients for inhalation or ingestion.

bBound

3 H.

cBased on dose equivalent limit of 500 mSv to thyroid.