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?

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?

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,

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 

3. Steps on the way to a new model

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

Package Type Parameter

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

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

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

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.

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

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

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

4. Discussion and Conclusions Sample results dose criteria 6 mSv/a 2 mSv/a contamination Bq/cm² Bq/cm² Co-60 324 108 Cs-137 849 283 Sr-90 648 216 Ra-226 6,6 2,2 Pu-239 1,2 0,4 Fe-55 56 000 19 000 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 2 700 Bq/cm² for Co-60.

Optimum

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

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!

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

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

However……..

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