Healthy Environment, Healthy Community, Healthy Business

Environment Protection Authority

Environmental Issues

Managing radiation in NSW

Categorisation of sealed radioactive sources

The initial step in determining whether the requirements for security-enhanced sources apply to a source is for the licensee to categorise sealed radioactive sources for which they are responsible, in accordance with the Security Code.

The category of a source is determined by the ratio of the activity of the source to the dangerousness (D-value) of the radionuclide. Depending on that ratio, the source is categorised from 1 to 5.

Schedule B of the Security Code sets out D-values for radionuclides and details the methodology for categorising sources; some of the common radionuclides are listed in the table below.

Categorisation thresholds of common radionuclides

These thresholds apply to sources or aggregations of the same radionuclide. Those responsible for sources should apply the formula in Schedule B of the Code to aggregate sources of different radionuclides.

Radionuclide

Category 1 (TBq)

Category 2 (GBq)

Category 3 (GBq)

Category 4 (GBq)

Category 5 exemption levels (MBq)

Am-241

60

600

60

0.6

0.01

Am-241/Be

60

600

60

0.6

0.01

Cs-137

100

1000

100

1

0.01

Cf-252

20

200

20

0.2

0.01

Co-60

30

300

30

0.3

0.1

Cm-244

50

500

50

0.5

0.01

Ir-192

80

800

80

0.8

0.01

P-32

10,000

100,000

10,000

100

0.1

Pu-238

60

600

60

0.6

0.01

Po-210

60

600

60

0.6

0.01

Ra-226

40

400

40

0.4

0.01

Se-75

200

2000

200

2

1

Sr-90

1000

10,000

1000

10

0.01

Page last updated: 28 June 2013