1. Characterization and Categorization of
DSRS Inventory
Presenter Name
School of Drafting Regulations for Borehole Disposal of DSRS
2016
Vienna, Austria

2. Outline of Presentation
Presentation resources
Regulatory Framework for Cat I/2 SRS
Characterization of DSRS
Categorization of DSRS
Compare and Contrast
Summary 2

3. Presentation Resources
International Atomic Energy Agency, Management of Disused Long Lived Sealed Radioactive Sources (LLSRS), IAEA-TECDOC-1357., Vienna (2003).
International Atomic Energy Agency, Code of Conduct on the Safety and Security of Radioactive Sources, IAEA, Vienna (2004).
International Atomic Energy Agency, Categorization of Radioactive Sources., Safety Guide No. RS-G-1.9, Vienna (2005). 3

4. Regulatory Framework Basis in national statues
May be based upon IAEA documents
Many countries have national regulations for controlling SRS in higher activity categories.
Protection of the public and the environment
Examples of typical regulations governing licensing:
Public dose
Worker dose – conditioning/hot cell
Training
Isotope limits due to site safety assessment
Code of Conduct limits for SRS

5. Definitions
Categorization – to provide a simple means to rank (into categories) radioactive sources with respect to their potential to cause harm to human health. The rankings/categories provide an internationally harmonized basis for risk informed decision making.
Characterization – a list of physical, chemical and radiological properties of the SRS.

6. Characterization of DSRS’s
Minimum radiological properties needed:
Isotope and radiation type
Activity with manufacture date
Status of source integrity (e.g., leaking?)
Physical properties (e.g., size, shape)
Source/device manufacturer
Model number
Serial number
Design specs
Traceability of source to documentation
IAEA’s International Catalogue of Sealed Sources

7. Characterization of DSRS’s
Additional helpful radiological properties:
Isotope half-life, energy, & dose conversion factors
Neutron flux (for neutron sources)
Non-radiological parameters:
Geometrical (e.g., long rods, spheres, strips)
Chemical & physical form (solid, liquid, or gas)
Liquid sources have a higher potential to leak

8. Characterization of DSRS’s
Common classification of SRS is by type:
Alpha
Beta
Gamma/X-ray
Neutron sources
Rule of thumb is SRS emit more than one type of radiation:
Alpha decay has a gamma with it.
Daughters are often beta emitters
Beta conversion during absorption results in Bremsstrahlung.

9. Example of DSRS Characterization
Common SRS used in industry – Cs-137
Type of source: beta – gamma
Strength: variable (e.g., 3700 GBq) w/date
Physical property: solid salt in capsule
Chemical property: CsCl is common
Radiological half-life: years
Energy: gamma energy is MeV
Source integrity: leak check of shield date
Dose conversion factor: 4.6 E-9 Sv/Bq

10. Categorization of DSRS’s
Purpose of categorizing DSRS is to provide an internationally harmonized basis for risk informed decision making.
System is based upon the concept of “dangerous sources” as measured by “D” values.
Originally derived for emergency preparedness use
D value is the radionuclide specific activity which, if not controlled, could cause severe deterministic effects for a range of scenarios creating external and/or internal exposures

11. Categorization of DSRS’s
For many isotopes, source strength can vary over several orders of magnitude. D values serve to normalize this range of activities for comparing risk.
A/D ratio is commonly used
provide initial rankings,
Rankings modified by other factors such as physical & chemical form, type of shielding or containment, supposed use, and accident case history,
Other factors are subjective and largely based on international consensus.
See Appendix I of SG No. RS-G-1.9

12. Categorization of DSRS’s
Categorization System has five categories
Cat I is the most dangerous (fatal exposure in minutes)
Cat 5 is the least dangerous (can exceed dose limits if not controlled).
Subdividing categories is NOT recommended as system is not that precise and would lead to a loss of international harmonization.
RS-G-1.9 contains list of common sources.
Can’t find your source in the listing, obtain D factor for your isotope from table in 1.9
Calculate A/D and compare to table.
Other factors may tweak result.

13. Categorization of DSRS’s
Categorization System has five categories
Cat 1 A/D≥1000
RTG’s, teletherapy, gamma knifes
Cat >A/D≥10
Industrial radiography, HD brachytherapy
Cat 3 10>A/D≥1
Fixed gages (high activity), well logging
Cat 4 1>A/D≥0.01
LD brachytherapy (except eye plagues and permanent implants), industrial gages (low activity), bone densitometers, static eliminators
Cat >A/D and A> exempt
XRF devices, electron capture, PET check sources, LD brachytherapy eye plagues and permanent implants

14. Example of DSRS Categorization
Common SRS used in industry – Cs-137
D = 0.1 TBq
Cat 1 source (food irradiator) – 1.1 E5 TBq
A/D = 1.1 E6 (> 1000)
Cat 2 (brachytherapy) – .11 TBq
A/D = 1.1, but recommended Cat 2
Cat 3 (gage) – 0.19TBq >> A/D = 1.9
Cat 4 (fixed gage) – TBq >> A/D=0.022
Cat 5 (check source) – 7400 Bq >> A/D=7E-5

15. Categorization of DSRS’s
Operational considerations
BSS and GSR-1 requirements to ensure safety and security “commensurate” to the practice and likelihood of exposures.
Short half-life sources and unsealed sources
Tc-99m and I-131 – Carefully choose “A” for A/D
Aggregation – sources in close proximity per RB
Sum isotopic activities, divide by isotope D , add A/D’s
Cat III sources may end up with a Cat II quantity
Other factors may dictate final category.
Additional labeling of high activity sources
National registry of at least Cat I or II sources
Cat III sources can also be registered

16. Categorization of DSRS’s
Operational considerations
Additional inspection protocols
Constant monitoring/restricted access
Coordination with local law enforcement
Trustworthy individuals only allowed unrestricted access
Hardened source devices

17. Compare and Contrast Characterization vs. Categorization
Similarities
Activity is critical to both
Protection of public is paramount
Physical properties dictate handling
Differences
Physical and chemical properties
License – safety requirements
High activity sources – additional security

18. Characterization and Categorization are not the same creature
Summary
Characterization and Categorization are not the same creature
Characterization specifies the physical, chemical and radiological properties of the source.
Categorization specifies the degree of safety and security needed to protect people from deterministic effects.
With multiple sources within a facility (for storage or conditioning), aggregation will be required.
Additional license conditions are required for Cat 1/2 sources.
Inspections review additional license conditions.

19. Thank you!