MELTING OF RADIOACTIVE METAL SCRAP FROM NUCLEAR INSTALLATIONS.

Objetivo

THIS RESEARCH IS BASED ON THE RESULTS AND EXPERIENCE OF WORK CARRIED OUT AT SIEMPELKAMP IN THE FRAMEWORK OF THE FIRST FIVE-YEAR (1979-83) PROGRAMME (REF. : EUR 10021). THE PRECEDING RESEARCH WORK PROVED THAT IT IS POSSIBLE TO MELT DOWN CONTAMINATED SCRAP BY MEANS OF A MODIFIED INDUSTRIAL FURNACE DEVICE IN COMPLIANCE WITH THE LEGAL LIMITS AND REGULATIONS.

THIS RESEARCH WORK, THEREFORE, AIMS MAINLY AT THE BEHAVIOUR OF RADIONUCLIDES DURING THE MELTING PROCEDURE, WITH REGARD TO VARIOUS MATERIAL QUALITIES AND THE HARMLESS RECYCLING OF MELTED-DOWN METAL PARTS COMING FROM REFURBISHING AND DECOMMISSIONING OF NUCLEAR INSTALLATIONS.
To date, approximately 3500 tonnes of very low level contaminated steel components from the refurbishing and dismantling of various nuclear installations in Germany have been treated by melting. 95% of the radioactivity was due to cobalt-60 and caesium-137 with an average ratio of 60:40. After melting, caesium was found in the slag and filter dust, whereas cobalt-60 mainly remained in the ingot (90-99%).
A special melting facility has been constructed to treat components which have been contaminated up to a level of 200 Bq/g in a controlled area. Approximately 2000 tonnes of steel components have been melted, so far, in this facility and to a large extent it has been recycled for nuclear purposes such as for transport and disposal containers and biological shieldings.
One of the most important problems was to quantify the amount of secondary waste produced during melting (eg slag, filterdust).

Melting of radioactive waste metal from the dismantling or refurbishing of nuclear installations has been assessed with respect to recycling (eg type A and type B containers for transport and/or final disposal, and shieldings). Long term tests showed that the radiation exposure of workers and the environment can easily be maintained below the admissible limits. The radioactivity distribution within the melt product is homogeneous and its activity can be measured precisely. Steel, copper, brass and graphite were treated.
In the melted copper, it was possible to meet the limits for unrestricted reuse, whereas for brass the limit for conditional industrial reuse was attained. Radioactive carbon can only be bound in cast iron as small graphite lamellas or nodules and has therefore to be crushed prior to adding to the melt.
B.1. PLANNING AND DESIGN OF THE MELT DEVICE TAKING INTO ACCOUNT AN EXISTING FURNACE.
B.2. CONSTRUCTION OF THE NEEDED MELT DEVICE COMPONENTS.
B.3. MELT WORK USING AS SCRAP CONTAMINATED CARBON STEEL, STAINLESS STEEL AND ITS MIXTURE.
B.4. EVALUATION OF MELT RESULTS.
B.5. TECHNICAL, ECONOMICAL AND RADIOLOGICAL CONSEQUENCES.
B.6. EXTRAPOLATION ECONOMICAL AND RADIOLOGICAL CONSEQUENCES.TO LARGE NUCLEAR POWER PLANT AND COMPARISON WITH ALTERNATIVE MODES WITH A VIEW TO THE ECONOMICAL AND ENVIRONMENTAL ASPECTS.
B.7. MELTING OF CONTAMINATED GALVANISED SHEET MATERIAL.
B.8. MELTING OF NON-FERROUS METAL (E.G. COPPER AND BRASS) TO INVESTIGATE THE BEHAVIOUR OF RELEVANT RADIONUCLIDES (E.G. CO-60, CS-137) DURING THE MELTING PROCESS.
B.9. INVESTIGATION ON ADDING RADIOACTIVE CARBON TO THE STEEL MELT PROCESS TO OBTAIN CAST IRON OF SUITABLE QUALITY FOR E.G. DISPOSAL CONTAINERS.
B.10. INVESTIGATION ON THE LONG-TERM BEHAVIOUR OF THE FURNACE LINER, THE CHARGING DEVICE AND THE FILTER SYSTEM AFTER MELTING OF ABOUT 500 T OF CONTAMINED STEEL WASTE (OVER TWO YEARS) WITH PARTICULAR VIEW TO ACTIVITY CONCENTRATION IN THE DIFFERENT PARTS OF THE MELTING PLANT.

Ámbito científico

Programa(s)

FP1-DECOM 2C - Research programme (Euratom) concerning the decommissioning of nuclear installations, 1984-1988

Tema(s)

Data not available

Convocatoria de propuestas

Data not available

Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

SIEMPELKAMP NUKLEAR- UND UMWELTTECHNIK GMBH & CO.

Aportación de la UE

Sin datos

Dirección

45,Siempelkampstra?e 45
47803 Krefeld
Alemania

Coste total