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MICROWAVE SYSTEM TO SCARIFY CONCRETE SURFACES

Objective

For the decommissioning of nuclear installations, it may be necessary to scarify masonry or concrete walls, removing at least 20-25 mm of plaster or concrete, in order to eliminate the incorporated contamination. Among the available techniques, the one based on the effect of microwaves upon the water contained in cement is very interesting; the water evaporates and the steam pressure within the pores shatters the cement in small splinters. This method is suitable for remote operation and produces no liquid effluents.

The research project concerns a microwave system consisting of a bell for the scarification and the suction of the splinters and a support structure for the bell, compatible with the remote handling systems available at the ITREC plant. The system will be manufactured, set up and tested at the ITREC plant in Trisaia on nonradioactive and on radioactive concrete surfaces.

As regards the innovative aspects of the research programme, it is intended to optimize the interconnection between the microwave generators, develop an efficient system to contain and collect the particulate, improve the efficiency of the particulate filtration and, finally, render the whole system flexible and easily operated.
For the decommissioning of nuclear installations, it may be necessary to scarify masonry or concrete walls, removing at least 20 to 25 mm of plaster or concrete, in order to eliminate the incorporated contamination. Among the available techniques, the one based on the effect of microwaves upon the water contained in cement is very interesting; the water evaporates and the steam pressure within the pores shatters the cement in small splinters. This method is suitable for remote operation and produces no liquid effluents. The research project concerns a microwave system consisting in a bell for the scarification and the suction of the splinters and in a support structure for the bell, compatible with the remote handling systems available.

The design and the construction of the prototype microwave system including the support structure and the suction unit have been carried out.

The microwave system consists of 3 5.5 kW magnetrons generating 2450 MHz microwaves. The system is equipped with rigid wave guides, irradiation heads, isolators to protect the magnetrons from reflected waves, transformers and ventilators.

The irradiation heads, which are protected by a teflon flange premeable to radiation but not to dust, are surrounded by a suction bell connected to the rigid wave guides by means of a vertically adjustable collar. The outer edge of the bell is equipped with a silicon rubber skirt that minimises the inlet of air and the dispersal of radiation. The bell is connected by means of a flexible vacuum hose to the suction system.

The different parts of the equipment described above have been assembled at the manufacture's plant and have undergone acceptance tests. The tests comprised visual inspections, dimensional checks and functional tests of the equipment. Subsequently 3 scarification tests were performed with results considered satisfactory on a preliminary basis; the surface layer of the reinforced concrete was shattered and the debris were transfered to the separation unit.
WORK PROGRAMME

1.Design and construction of a prototype microwave system
2.Design and construction of the support structure.
3.Trial operations on a nonradioactive concrete wall.
4.Testing of the prototype on a radioactively contaminated concrete surface.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Ente per le Nuove Tecnologie l'Energia e l'Ambiente (ENEA)
Address
Strada Statale Jonica 106 Km.419
75026 Rotondella Matera
Italy