The programme proposes to develop a technique using a chemical agent dispersed as fog for the decommissioning of nuclear installations, finalized towards the decontamination of the thermosyphon evaporator used for the concentration of the end product (enriched uranium and plutonium solutions) of ENEA's pilot reprocessing plant EUREX at Saluggia.
The programme includes:
a theoretical study of the processes that the inside walls of the evaporator have undergone in contact with the uranium-plutonium solution, in order to obtain valid hypotheses on the behaviour of the contaminants during their attack and removal during decontamination;
cold and hot laboratory tests to determine the characteristics of a class of chemical compounds (acids, specific complexing agents for actinides) with a great affinity for the contaminants to be removed and capable of operating in an aqueous phase, possibly together with inert carriers such as micelle aggregates;
cold tests on a mock-up of the evaporator provided with a pneumatic circulation system, in order to optimize the transport and attack procedures of the selected chemical agents;
a feasibility study of the actual hot tests to be carried out at the plant, in order to test the technology developed during the previous phases;
hot decontamination tests of the evaporator, if feasible and subject to licensing authorization.
This research programme aims at obtaining consistent information on a novel approach towards the decontamination of components of nuclear installations: decontamination by means of high affinity chemical reagents, in an aqueous medium for a good surface contact, using the equipment for the circulation and atomizing of the solution already existing at the installation.
The programme proposes to develop a technique using a chemical agent dispersed as fog for the decommissioning of nuclear installations, finalised towards the decontamination of the thermosyphon evaporator used for the concentration of the end product (enriched uranium and plutonium solutions) of Ente per le Nuove Technologie, l'Energia e l'Ambiente (ENEA)'s pilot reprocessing plant EUREX at Saluggia.
An extensive bibliographic research on decommissioning, namely on chemical decontamination requirements, has allowed the state of the art in this field to be defined. On this basis and using historical data collected during the operations of the evaporator plant, some hypotheses on the characteristics of the contamination layer were determined, in order to define the details of the experimental work to be performed. A cold mock-up reproducing the main characteristics of the actual EUREX evaporator was designed; it has been completely assembled and located in an area of the EUREX plant in order to simulate as far as possible the real situation, utilising the same instrumentation. The main characeristics of the contamination were investigated running cold and hot laboratory tests with specimens.
1. Theoretical studies
1.1. Literature review
1.2. Theoretical investigation
2. Laboratory tests
3. Mock-up tests
3.1. Design and manufacture of a mock-up
3.2. Simulation tests
4. Plant tests
4.1. Decontamination tests
5.Evaluation of results