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DEFENCE IN DEPTH
Defence in depth: sources

GUIDANCE FOR CATEGORIZATION

 

Another situation is that where an orphan source is found with  no identification markings.

There are two options 

1

Estimate activity from isotope and dose rate measurements and determine A/D ratio

Estimate the activity based on identifying the isotope and measuring the dose rate. If  you know these two parameters, you can estimate the activity using, for example the weblink here:

http://www.radprocalculator.com/Gamma.aspx

2

Identify the source category by its common practice

Category A/D ratio Common practices (examples)

1

A/D > 1000 Radioisotope thermoelectric generators
Irradiators
Teletherapy
Fixed multi-beam teletherapy
2 10 ≤ A/D < 1000 Industrial gamma radiography
High/medium dose rate brachytherapy
3 1 ≤ A/D < 10 Fixed industrial gauges
Well logging gauges
4 0.01 ≤ A/D < 1 Low dose rate brachytherapy
Thickness gauges
Portable gauges
Bone densitometers
Static eliminators

If you know where the source has come from, you may be able to estimate the category based on what the source is being used for. We have already seen the table above.

Appendix IV gives examples of the different uses of sources and their likely category.

References:

  • Categorization of Radioactive Sources, No. RS-G-1.9 Safety Guide

Appendix IV

RADIOACTIVE SOURCE CATEGORIZATION BASED ON COMMON PRACTICE
Information taken from the IAEA’s Categorization of Radioactive Sources*.

TABLE 23. CATEGORIZATION OF COMMON PRACTICES

Category

Categorization of common practices

Typical isotopes

1

Radioisotope thermoelectric
generators (RTGs)
Irradiators
Teletherapy
Fixed, multi-beam teletherapy
(gamma knife)

Sr-90, Pu-238

Co-60, Cs-137
Co-60, Cs-137
Co-60

2

Industrial gamma radiography

High/medium dose rate brachytherapy

Co-60, Se-75, Ir-192,Yb-169,
Tm-170
Co-60, Cs-137, Ir-192

3

Fixed industrial gauges:
- Level gauges
- Dredger gauges
- Conveyor gauges containing high
activity radioactive sources
- Spinning pipe gauges
- Well logging gauges

Co-60, Cs-137
Co-60, Cs-137
Cs-137, Cf-252

Cs-137
Am-241/Be, Cs-137, Cf-252

4

Low dose rate brachytherapy
(except eye plaques and permanent
implant sources)
Thickness/fill-level gauges

Portable gauges
(e.g. moisture/density gauges)
Bone densitometers
Static eliminators

I-125, Cs-137, Ir-192, Au-198,
Ra-226, Cf-252

Kr-85, Sr-90, Cs-137, Am-241,
Pm-147, Cm-244
Cs-137, Ra-226, Am-241/Be
Cf-252
Cd-109, I-125, Gd-153, Am-241
Po-210, Am-241

5

Low dose rate brachytherapy eye
plaques and permanent implant
sources
X ray fluorescence devices
Electron capture devices
Mossbauer spectrometry
Positron emission tomography (PET)
Check sources

Sr-90, Ru/Rh-106, Pd-103

Fe-55, Cd-109, Co-57
Ni-63, H-3
Co-57
Ge-68

* INTERNATIONAL ATOMIC ENERGY AGENCY, Categorization of Radioactive Sources, IAEA Safety Standards Series No. RS-G-1.9, IAEA, Vienna (2005)