1. Presentation for TRANSSC 20 meeting – June 2010
Project progress on development of system to calculate A1 and A2 and exemption values (SEAL)
Presentation for TRANSSC 20 meeting – June 2010

2. Current position - A1 and A2 values
A1 and A2 values define levels of activity for Type A packages
A1 and A2 values calculated using the Q System – described in Appendix 1 of the Advisory Material for the Transport Regulations (TS-G-1.1)
Incorporated into IAEA regulations for safe transport of Radioactive material, Safety Series No 6 (1985) for the first time and in all IAEA regulation after
These values were revised for the 1996 Edition of the IAEA Transport Regulations to be consistent with the 1990 Recommendations of ICRP (ICRP 60)

3. Course Introduction (RADSAFE)
The Q system
Q values calculated assuming accident conditions for five scenarios:
QA - External  dose (no shielding assumed)
QB - External beta dose (partial shielding assumed)
QC - Inhalation dose
QD - Skin (and ingestion) dose
QE - Submersion (immersion) dose
A1 (special form) = min(QA, QB); A2 (non-special form) = min(QA, QB, QC, QD, QE)
General assumptions
Exposure is once in a lifetime
Effective whole body dose of 50 mSv
Organ equivalent dose of 500 mSv
External exposure at 1 m for 30 minutes

4. Exposure pathways in the Q System
34575

5. Current (1996) A1 and A2 values
Calculated by 3 consultants, using separate programs and spreadsheets, for QA, QB, QC and QD (QE)
Data used in the calculations taken from:
ICRP 38 – energies and intensities of emissions
ICRP 68 – dose coefficients
Methodology based on original Q system by Goldfinch and Macdonald (CEGB), and other relevant publications

6. Course Introduction (RADSAFE)
Exemption values
IAEA BSS exemption values based on methodology given in EC RP-65 report (1993)
Did not explicitly address transport scenarios
Earlier study looked at range of transport scenarios (e.g. driver delivering packages)
Found almost all within order of magnitude of BSS values
IAEA transport regulations adopted IAEA BSS values
Exemption values for radionuclides not included in BSS but in TS-R-1 (about 100) were calculated separately
IAEA transport regulations have more radionuclides than given in BSS and where not given were calculated using RP-65 methodology 6

7. Assumptions and methodology for exemption values
Course Introduction (RADSAFE)
Course Introduction (RADSAFE)
Assumptions and methodology for exemption values
Two exemption values: exemption activities (Bq) and the exemption activity concentrations (in Bq g-1)
Three types of exposure scenario were considered:
Normal use (workplace) scenario
Exposures to the public arising are adequately covered by this scenario
Accidental (workplace) scenario for incidents occurring during the routine use of radionuclides
Disposal (public) scenario for exposures after disposal of a source
Both normal and accidental situations
IAEA transport regulations have more radionuclides than given in BSS and where not given were calculated using RP-65 methodology 7

8. Assumptions and methodology for exemption values
Course Introduction (RADSAFE)
Course Introduction (RADSAFE)
Assumptions and methodology for exemption values
Two dose criteria, applied to critical group
Annual dose of 10 µSv y-1 for normal situations
Annual dose of 1 mSv y-1 (with a probability of 0.01) for accidental situations
Annual dose of 50 mSv y-1 to the skin for deterministic effects
No collective doses
Six different waste forms (solid, liquid and gas)
Both external irradiation exposure and internal irradiation (inhalation and inadvertent ingestion) are included
IAEA transport regulations have more radionuclides than given in BSS and where not given were calculated using RP-65 methodology 8

9. Current and future ICRP developments and implications for transport regulations
New Recommendations published 2007, Publication 103
Revised data on radionuclide emissions published late 2008 – ICRP Publication 107. Nuclear Decay Data for Dosimetry Calculations. Ann. ICRP 38 (3)
Revised dose coefficients for workers to be published 2011(?), and for members of the public by 2012(?)
New dose coefficients for external exposures to be published in late 2010(?)

10. Project on A1 and A2 and exemption values
Develop a system consisting of a computer program + databases
Calculates values using current methodology and data. Revised data that reflect the new ICRP data, when published can be included
Can be used to provide values for radionuclides not listed in the regulations, using current data
Accompanying report also gives a review of the methodology used and an indication of areas where methodology can be improved
A general comparison of values with those in relevant publications

11. Project progress
A prototype of the system called SEAL (System to calculate Exemption and A1 and A2 Levels) has been developed
SEAL output has been compared for about 400 radionuclides with
TS-G-1.1 values for Q, A1 and A2 values
TS-R-1 values for exemption values

12. Comparison of Q values - QA and QB values
QA and QB values (external dose due to photons and betas) were calculated using method developed by Benassai and Bologna (1994)
Method could not be exactly replicated. Two main issues:
Interpolation
Contribution from progeny

13. QA and QB values - interpolation
Interpolation required for:
The air mass energy absorption coefficient, mass attenuation factor, build up factor and air exposure to dose conversion factor (QA values) and dimensionless dose and continuous slowing down approximation range (QB values) given for specified energies
Benassai and Bologna gives equations and parameters to generate values for other energies. It has not been possible to use these equations
However HPA has developed interpolation methods which give results within 10% of those published in Benassai and Bologna report (this applies to single radionuclides i.e. not including contribution from progeny)

14. QA and QB values – treatment of progeny
Benassai and Bologna gives method to include contribution from progeny for QA and QB values. HPA found that values calculated are different to those in TS-G-1.1 for a number of radionuclides. HPA also investigated using secular and transient equilibrium methods for calculating values.

15. QA values - problem radionuclides
Parent radionuclide
QA value (TBq)
Ratio of QA for TS-G-1.1 to alternative methods
TS-G-1.1
HPA calculation method
Secular
B & B
Transient
131Ba
1.6
2.1
5.3
0.8
1.0
0.3
47Ca
2.7
0.9
0.81
2.3
3.0
3.3
1.2
166Dy 34 15 13 26
2.6
1.3
225Ra 12
4.3
1.5 10
2.8
8.0
189Re 32 16
2.0
91Sr
0.84
0.72
1.4
1.8
1.1
Red text indicates a factor of 2 or greater difference between TS-G-1.1 and calculations from other methods.

16. QB values – problem radionuclides
Parent radionuclide
QB value TBq
Ratio of QB for TS-G1.1 to alternative methods
HPA calculation
TS-G1.1
Secular
B & B
Transient
47Ca* 37
0.8
0.79
1.8
46.3
46.8
20.6
225Ra
0.22
0.82
0.26
0.3
0.1
* The Benassai and Bologna report gives a value of 3.7; TS-G-1.1 gives 37. It is thought that this is a transcript error

17. Summary – progeny for QA and QB values
Transient equilibrium method gives closer results to TS-G-1.1 particularly for QA values
SEAL can currently include contribution from progeny using Benassai and Bologna and transient equilibrium method so that two methods can be compared
In addition we think there is mistake for 26Al – TS-G-1.1 value ten times less than value HPA has calculated

18. Qc inhalation dose coefficients
TS-G-1.1 recommends use of inhalation dose coefficients from IAEA BSS and ICRP 68. However do not match up in all cases.
Differences found in isotopes of tritium, carbon, mercury, iodine, nickel, lead, thorium and curium.
SEAL uses values given in ICRP 68

19. Rounding of A1 and A2 values
In TS-G-1.1 Q values are displayed to 2 significant figures and A1 and A2 values to 1 significant figure. However the A values displayed are not rounded from given Q values but from the calculations.
This process can for certain results cause a slight difference in the calculated number for Q (eg 1.49 and 1.51) which becomes a large difference in the A1 and A2 value. There are currently 13 radionuclides with this problem (108mAg, 211At, 133mBa, 60Co, 150sEu, 150lEu, 172Hf, 32P, 191Pt, 222Rn, 121mSn, 85mSr and 200Tl)

20. Exemption values
Differences between TS-R-1 and SEAL output found for 16 radionuclides
Differences have been investigated and all discrepancies resolved. Only outstanding difference is for 139Ce where value should be 10 times less restrictive than value given in TS-R-1
Appendix added to methodology which details amendments to RP-65 on which TS-R-1 values are based

21. Timescales
Report documenting methodology – original deadline was summer of However we have continued to add to this document during development of prototype.
Prototype for DfT to test – April 2010
Next timescale is revision of methodology and final version of system – March 2011