1. International ISOE Workshop Lyon 2004
Recent International Developments on Contamination Limits on Packages J. Hesse, RWE Power, Germany; B.Lorenz, GNS, Germany
Introduction Reasons for a new model
Faibairne Model valid as basis of the contamination limits since 1961
New Model IAEA Coordinated Research Project
Discussion and Conclusions are the old contamination limits appropriate?

2. The Outcome of the Contamination Affair
Loss of trust in the nuclear industry, no transport of spent fuel in Europe for a certain time, in Germany from 1998 until 2001.
However, none of the contamination findings led to any remarkable dose
Are the actual contamination limits really appropriate?

3. IAEA CRP on Radiological Aspects of Package and Conveyance Non-Fixed Contamination
B.Lorenz, GNS GmbH J. Hesse, RWE Power AG, M. Holl, Kernkraftwerk Mülheim-Kärlich, RWE Power AG W. Schwarz,Kernkraftwerke Isar, E.ON Kernkraft GmbH S. Thierfeldt, Brenk Systemplanung GmbH,

4. 2. The Fairbairne Model Basis of our actual limits of 4 Bq/cm² and 0
2. The Fairbairne Model Basis of our actual limits of 4 Bq/cm² and 0.4 Bq/cm² (alpha emitters); developed in 1961
How had the actual limits been derived?
“most hazardous radioisotopes in common use”: Pu 239, Ra 226, Sr 90.
“very dusty operations” with a resuspension factor of 410‑5 m‑1
2000 hours per year working in that “dusty” atmosphere
taking into account skin contamination and inhalation only
50 mSv/a as basis for deriving the contamination limits
no considerations of the doses of members of the public 

5. 3. Steps on the way to a new model

6. General Modelling Requirements
world wide transport in all countries
all kinds of packages
realistic, representative, conservative
direct modelling
objective: derived limits

7. Package Type Parameter

8. Transport Steps and Workers assigned to Tasks (1)
Main Step
Action
Persons
involved
Workers SM SR LR FF
1. Final Inspection of Package
1.1 Visual inspection
Personnel A
1.2 Dose rate meas.
1.3 Contamination measurement (final meas.)
1.4 Labelling of package
2. Loading onto conveyance
2.1 Transfer from site to conveyance C BC B
2.2 Fastening, loading, lifting and fixing
2.3 Dose rate meas. at conveyance AC
2.4 Contamination meas. of conveyance
2.5 Placarding of conveyance
3. Movement phase
3.1 Movement (with packages)
3.2 Unforeseen interruptions
3.1a Movement, public, road/rail
Public no
3.1b Movement, public, air
3.1c Movement, public, sea
3.3 Regular stops

9. Transport Steps and Workers assigned to Tasks (2)
Main Step
Action
Persons
involved
Workers SM SR LR FF
4. Transfers during transport
4.1 Unloading (incl. sub-steps) from conv. #1
4.1.1 dose rate & contam. meas.
Personnel
Public no F H
4.1.2 unfixing, fastening, lifting FG
4.2 Loading (incl. sub-steps) on conv. #2
4.2.1 transfer, loading, fixing
4.2.2 dose rate meas. at conveyance
4.2.3 contamination meas. of coveyance
4.2.4 placarding of conveyance
4.3 Regular stops
5. Receiving inspection and unloading
5.1 Visual inspection of load T
5.2 Dose rate meas. conveyance
5.3 Unfixing, fastening, lifting, unloading C CU U
5.4 Transfer from conveyance to consignee
5.5 Dose rate measurement package
5.6 Contamination meas. package
5.7 Contamination meas. empty conveyance

10. The Model - Personnel (1) General Parameters
Enveloping conditions used
high percentage of workday spent with packages
large number of packages

11. Exposure Pathways External irradiation
from the removable surface contamination
not by the contents of the package
Inhalation of radioactive aerosols
re-suspended from the contaminated surface
Ingestion
via a hand-to-mouth pathway
Skin contamination
resulting from direct skin contact with the contaminated surface.

12. Detailed Parameters
Example workers: Step 1.1
Example public: Step 3

13. Results - Example of Spreadsheet Calculation - Co 60
Nuclide
name
model steps
results for external exp.
results for inhalation
results for ground shine
summation
workers involved
working time
other dose contributions
grand total on dose
person
total on work time
time correct-ed dose
derived transport level

14. Results (2) Overview Doses are determined by worker scenarios
Contamination levels derived from 2mSv/a for workers, 0.3 mSv/a for general public
Doses are determined by worker scenarios
Leading scenarios for package types are SM, SR

15. 4. Discussion and Conclusions
Sample results
dose criteria 6 mSv/a 2 mSv/a
contamination Bq/cm² Bq/cm² Co Cs Sr
Ra ,6 2,2
Pu ,2 0,4 Fe
Überblick über weltweit angewandte Techniken und praktische Anwendung der Zwischenlagerung zu geben
Konzentration auf Trockenlagerung
The results depend strongly on the radionuclide
Even derived from a constraint of 2 mSv/a we get values much higher than 4 Bq/cm² for radionuclides of importance in practice
Note: Fairbairne derived the actual limit from 50 mSv/a. This would mean Bq/cm² for Co-60.

16. Optimum

17. Annual doses due to 4Bq/cm²
the most exposed workers
Small manual
Small remote
Large remote
Fuel Flask
Co-60
73 µSv/a
74 µSv/a
33 µSv/a
25 µSv/a
Cs-137
28 µSv/a
18 µSv/a
16 µSv/a
a member of the public
Small manual
Small remote
Large remote
Fuel flask
Co-60
0,011 µSv/a
0,092 µSv/a
0,375 µSv/a
0,197. µSv/a
Cs-137
0,003 µSv/a
0,024 µSv/a
0,048 µSv/a
calculated with the assumption that the entire surface of all packages is contaminated up to 4 Bq/cm²

18. Comparision of doses for fuel flasks
Potential dose due to contamination of 4Bq/cm²
assumed 125 flasks/a
4 Bq/cm²
25 µSv/a
0.2 µSv/flask
Real doses due to the measures to ensure compliance with 4 Bq/cm²:
~ 1mSv/(flask*person) German NPPs
This is no optimum!

19. New Limits ???
When setting new limits also other arguments have to be taken into account:
• A reached level of cleanliness should not be given up without reason.
• The dose due to contamination should be only a part of the dose for the whole process.
• The contamination limits for transports should be in compliance with the contamination limits in the receiving facilities.
• New contamination limits must be justifiable also in a political debate with the public

20. Final conclusion The new international model of the IAEA CRP suggests
• to chose the new model as basis for the contamination limits.
• to change to a radionuclidspecific limitation
• to use an appropriate constraint (e.g. 2mSv/a) for the derivation of the limits

21. However……..

22. Life could be so beautiful
...if everybody had the same opinion.
Überblick über weltweit angewandte Techniken und praktische Anwendung der Zwischenlagerung zu geben
Konzentration auf Trockenlagerung