Radiation Quantities & Units

Question 1

What is the measurement of 1 Curie?

Answer 1

1 Curie = 37 billion atomic disintegrations per second of a radioactive substance

[eg. 1 gram of Radium will undergo 3.7 x 10¹⁰ (37 billion) disintegrations in one second]

Question 2

If 1 Ci = 37 GBq, what are the equivalent measurements of:

• 10 Ci
• 20 Ci
• 50 Ci
• 60 Ci
• 100 Ci

Answer 2

10 Ci = 370 GBq (10 x 37 GBq)

20 Ci = 740 GBq (20 x 37 GBq)

50 Ci = 1850 GBq (50 x 37 GBq)

60 Ci = 2200 GBq (60 x 37 GBq)

100 Ci = 3700 GBq (100 x 37 GBq)

Question 3

What are the decay measurements of:

• 1 Bq (becquerel)
• 1 KBq (kilobecquerel)
• 1 MBq (megabecquerel)
• 1 GBq (gigabecquerel)
• 1 TBq (terabecquerel)

Answer 3

1 Bq = 1 dps (decay per second)

1 KBq = 1,000 dps [10³]

1 MBq = 1,000,000 dps [10⁶]

1 GBq = 1,000,000,000 dps [10⁹]

1 TBq = 1,000,000,000,000 dps [10¹²]

Question 4

What new SI unit is Characteristic Intensity typically measured in?

Answer 4

Sieverts (Sv) per hour at 1 metre

*can also be seen (converted) as mSv/hr @ 1 m

Question 5

What old CGS unit is Characteristic Intensity typically measured in?

Answer 5

Roentgens (R) per hour at 1 metre

*can also be seen (converted) as mR/hr @ 1 m

Question 6

Assuming we have 37 GBq (1 Ci) of a radioactive source, what is the Characteristic Intensity and Half-Life of:

Selenium 75

Answer 6

Characteristic Intensity:

0. 20 R/hr @ 1 metre
1. 05 mSv/hr @ 1 metre

Half-Life:

120 days

Question 7

Assuming we have 37 GBq (1 Ci) of a radioactive source, what is the Characteristic Intensity and Half-Life of:

Cobalt 60

Answer 7

Characteristic Intensity:

1. 35 R/hr @ 1 metre
2. 36 mSv/hr @ 1 metre

Half-Life:

5. 3 years
   (1934. 5 days)

Question 8

Assuming we have 37 GBq (1 Ci) of a radioactive source, what is the Characteristic Intensity and Half-Life of:

Iridium 192

Answer 8

Characteristic Intensity:

0. 55 R/hr @ 1 metre
1. 15 mSv/hr @ 1 metre

Half-Life:

74 days

Question 9

Some radiation is more damaging than others because of their Quality Factor (Q) or Relative Biological Effectiveness (RBE).

What are some of the common RBE values?

(Hint: They’re found in a short chart form.)

Answer 9