The underlying large-scale investigation into melting of alpha-contaminated steel from nuclear facilities aims at demonstrating the feasibility of the unrestricted reuse of such radwaste within legal limits.
The work programme will be based on the results and experience obtained on melting of radwaste in former research contracts within the second EC programme on Decommissioning (1984-88), especially contract FI1D0044 with Siemens AG and contract FI1D0016 with Siempelkamp Giesserei GmbH.
Start with laboratory-scale melts to identify the most suitable crucible material and slag, then large-scale melts with subsequent detailed analysis of the prevailing alpha-distribution in and between steel, slag and filter dust.
Based on the foregoing results, large-scale melts with about 100 t of uranium and plutonium contaminated material from Siemens fuel fabrication will be carried out and finally, using 2 large-scale melts of plutonium and thorium contaminated steel waste (5 t), it will be assessed how these alpha-emitters behave.
It is anticipated that extensive testing and radiological measurements will enable the assessment that alpha-contaminated steel can be conditioned by melting for safe unrestricted reuse and that the melting plant can be operated safely also with respect to radiation protection of workers and the environment of the foundry, with special consideration of the arising slag and filter dust. In particular, the generation of specific data on costs, working hours and job doses as well as on the amount of created secondary waste is considered as an important objective of this project.
The specific contamination of the treated radwaste is estimated to be in the range of up to 200 Bq/g (alpha/beta) and the anticipated fission product inventory for large-scale melting is estimated at about 200 g of uranium-235 and 1 g of plutonium. Expected dose rates in the controlled melting area are in the order of magnitude of up to 0.1 mGy/h.
Work will be executed in close co-operation between Siemens AG, KWU Erlangen (Siemens) acting as coordinator and Siempelkamp Giesserei (SG).
The large scale investigation into melting of alpha contaminated steel from nuclear facilities aims at demonstrating the feasibility of the unrestricted reuse of such radwaste within legal limits.
Laboratory scale melts aimed at identifying the most suitable crucible material and slag former will be followed by large scale melts with subsequent detailed analysis of the prevailing alpha distribution between steel, slag and filter dust.
The delivery of 100 t of material for the melting campaign has been completed. The melting approval has been given but the permit for the handling of the radioactive substances for the residual materials due to nuclear fuel concentration has not yet been obtained from the authorities. The test programme for the performance of the trials has been elaborated and must still be coordinated with the authorities. The experimental equipment for the melting of steel scrap was installed and tested. The main components are the electrical power supply unit and the inductively heated furnace.
1. Identification of appropriate materials for crucible and slag formers and procurement of U, Th and Pu containing radwaste samples (SG)
2. Installation of an induction-heated laboratory furnace and execution of reference tests with non-radioactive materials (Siemens)
3. Laboratory-scale melting tests with uranium, thorium and plutonium contaminated steel (selection of materials for crucible lining and slag formers) (Siemens)
4. Procurement of uranium and plutonium contaminated material (Siemens) and thorium contaminated material (KEMA)
5. Pilot melting tests aimed at determining the uranium (alpha)-content in ingot, slag and filter system (SG, Siemens)
6. Main melting programme of about 100 t of uranium and plutonium contaminated radwaste with subsequent alpha-content determination in each ingot, slag and filter dust (SG)
7. Execution of two large-scale melts with Pu and Th-contaminated steel (SG)
8. Determination of the alpha-distribution in the crucible material (Siemens)
9. Generation of specific data on costs, radioactive job doses, working time and secondary waste arisings, derived from the execution of items 2 and 6.
Funding SchemeCSC - Cost-sharing contracts