1. Categorization of Radioactive Sources
Day 8 – Lecture 7

2. Objective
To understand categorization system of radioactive sources and its application in establishing the appropriate degree of regulatory control for activities relating to the safety and security of radioactive sources.

3. Contents Objective and Scope Categorization system
Implementation of the categorization system

4. Part I: Objectives and scope of categorization

5. Objectives of categorization of radioactive sources
Provides a system for ranking of sources and practices in terms of their potential to cause harm to human health.
Categorization supports international harmonization of controlling radioactive sources and their security.
Code of Conduct on the Safety and Security of Radioactive Sources
Guidance on the Import and Export of Radioactive Sources

6. Applications of categorization
Developing or refining national regulatory infrastructures;
Developing national strategies for improving control over radioactive sources;
Optimizing use resources by setting priorities for regulation;
Optimizing security measures for radioactive sources;
Emergency planning and response.

7. Scope of the RS-G-1.9 Radioactive sealed sources
Sources used in industry, medicine, agriculture, research and education;
Sources within military or defence programmes, where appropriate in the national context;
Categorization is concerned with sealed sources, however, the method can also be used to unsealed sources.
RS-G-1.9 is NOT applicable to
Radiation generating devices (x-ray machines, accelerators)
Nuclear material
Waste management of disused radioactive sources
Packages of radioactive material in transport

8. Application of the Categorization Guidance
A national categorization for establishing the appropriate degree of regulatory control should
be based on a national inventory of practices and sources
consider national circumstances and resources
Take into account also practices and sources not covered by the RS-G-1.9:
Use of unsealed sources
Use of x-ray devices and accelerators

9. Part II: Categorization system

10. Categorization System
The categorization is based on the concept of dangerous sources which are quantified in terms of D values.
The D value is the radionuclide-specific activity of a source which, if not under control, could cause severe deterministic health effects.
D values are used as normalizing factors to provide a reference for comparing risks.

11. Exposure scenarios used in deriving the D values
An unshielded source (the D1 value)
carried in the hand for one hour
carried in a pocket for 10 hours
being in a room for days to weeks
Dispersal of a source by fire, explosion or human action (the D2 value)
inhalation, ingestion and/or skin contamination
The lower value of D1 and D2 is used as the D value.

12. Examples of the D values
Radionuclide D (TBq) Am Co Cs Ir Pu Sr
Tc-99m

13. Categorization System
Initial ranking of sources:
The activity (A) of a source is divided by the corresponding radionuclide specific D value.
For commonly used sources the ratio A/D ranges from 106 to 10-6.
To obtain useful number of categories also other factors are considered:
physical and chemical form
type of shielding
circumstances of use
accident case histories

14. Categorization System (cont)
Five categories are introduced
Category Activity ratio (A/D)
1 A/D ≥ 1000
> A/D ≥ 10
> A/D ≥ 1
> A/D ≥ 0.01
> A/D
and A > exempt

15. Category 1 Sources A/D ≥ 1000 Examples
Radioisotope thermoelectric generators (RTGs)
Irradiators
Teletherapy sources
Fixed, multi-beam teletherapy (gamma-knife) sources

16. Category 2 Sources 1000 > A/D ≥ 10
Examples
Industrial gamma radiography sources
High/medium dose rate brachytherapy sources

17. Category 3 Sources 10 > A/D ≥ 1
Examples
Fixed industrial gauges that incorporate high activity sources
Well logging gauges

18. Category 4 Sources 1 > A/D ≥ 0.01
Examples
Low dose rate brachytherapy sources (except eye plagues and permanent implants)
Industrial gauges that do not incorporate high activity sources
Bone densitometers
Static eliminators

19. 0.01 >A/D and A > exempt
Category 5 Sources
0.01 >A/D and A > exempt
Examples
Low dose rate brachytherapy eye plagues and permanent implant sources
X-ray fluorescence (XRF) devices
Electron capture devices
Mossbauer spectrometry sources
Positron emission tomography (PET) sources

20. Summary of Categorization System
Activity ratio
A/D
Teletherapy sources
Irradiators
Industrial gamma radiography sources
High/medium dose rate brachytherapy sources
Industrial gauges with high activity sources
Well logging gauges
Low dose rate brachytherapy sources
Industrial gauges with moderate/low activity sources
X-ray fluorescence (XRF) devices
Electron capture devices 1 2 3 4 5
1000 10 1
0.01
exempt

21. Part III: Implementation of the categorization system

22. Use of the Categorization System
Regulatory measures
A factor to be taken into account in a graded system for notification, registration and inspections.
Assist in ensuring that allocation of resources to protection measures is commensurate with the degree of risk.
Security measures
To optimize security measures for radioactive sources, including measures directed against their possible malicious misuse.

23. Use of the Categorization System (cont)
National register of sources
To optimize decisions regarding which sources should be included and what level of detail should be used in a national register of sources.
Import/export controls
To optimize decisions regarding which sources should be subject to import and export controls, in meeting national and international standards.

24. Use of the Categorization System (cont)
Labelling of high activity sources
To guide decisions regarding which sources should be marked with an appropriate label warning of the radiation hazard.
Emergency preparedness and response
To ensure that emergency preparedness plans and response to accidents are commensurate with the hazards posed by the source.

25. Use of the Categorization System (cont)
Prioritization for regaining control over orphan sources
To inform decisions relating to how efforts should be focused to regain control over orphan sources.
Communication with the public
To provide a basis for explaining the relative hazard associated with events involving radioactive sources.

26. Use of categorization
The regulatory body should use the D and A/D values of the Safety Guide RS-G-1.9 to categorize the sources included in the national inventory of sources.
Situations where case by case considerations needed:
short half-life radionuclides
unsealed sources
aggregation of sources

27. Aggregation of sources
In situations where several sources are in close proximity to each other, the regulatory body may wish to aggregate the activity in the sources to determine a situation based categorization for the purpose of regulatory control.
In addition to activity, also other factors may need to be considered because aggregations in different situations may have different safety implications.

28. Aggregation of sources
where Ai,n = activity of each individual source i of radionuclide n Dn = D value of radionuclide n

29. National register of radioactive sources
The regulatory body should maintain a national register of radioactive sources;
The register should contain, as a minimum, Category 1 and 2 sources, but preferably also Category 3 sources;
The regulatory body should determine whether also Category 4 and 5 should be included;

30. Import and export of radioactive sources
The Code of Conduct on Safety and Security of Radioactive Sources provides general guidance for the import and export of Category 1 and 2 sources
Import/Export guidance* provides specific procedures for the import and export authorization of Category 1 and 2 sources
* Guidance on the Import and Export of Radioactive Sources IAEA, Vienna (2012)

31. Communication with the public
The Safety Guide RS-G-1.9 provides also plain language descriptions of the categories for the purpose of public information.
In summary:
Category
Risk in being close to an source 1
Extremely dangerous 2
Very dangerous 3
Dangerous 4
Unlikely to be dangerous 5
Most unlikely to be dangerous

32. References
Categorization of Radioactive Sources, Safety Guide RS-G-1.9, IAEA, Vienna (2005).
Code of Conduct on the Safety and Security of Radioactive Sources, IAEA, Vienna (2004).
Guidance on the Import and Export of Radioactive Sources IAEA, Vienna (2012).
Method for Developing Arrangements for Response to a Nuclear or Radiological Emergency: Updating IAEA-TECDOC-953, EPR-Method 2003, IAEA, Vienna (2003).

33. Exercise
A moisture/density gauge includes a 300 MBq Cs-137 source and a 1.48 GBq Am-Be source.
What is the appropriate category for such a device?