The Use of Palladium Derived from Spent Nuclear Fuel for Radionuclides Immobilization
Studies on Immobilization Technologies of Long-Lived Radionuclides with Use of "Reactor" Palladium
Tech Area / Field
- ENV-RWT/Radioactive Waste Treatment/Environment
8 Project completed
Senior Project Manager
Genisaretskaya S V
Khlopin Radium Institute, Russia, St Petersburg
- British Nuclear Fuels Ltd (BNFL) / Waste Disposal Research Group Sellafield R&D, UK, Cumbria, Seascale\nIdaho National Engineering and Environmental Laboratory, USA, ID, Idaho Falls
Project summaryThe prospects for development of nuclear power are intimately associated with solving the problem of safe management and removal from the biosphere of generated radioactive wastes. That is why one of the main objectives in radiochemical industry is to provide the safe isolation of all radionuclides generated in spent fuel.
Among the most hazardous long-lived fission products particular attention should be given to iodine-129 and transplutonium elements (TPE).
For solving the problem on immobilizing the above radionuclides one can use different methods, including the production of vitreous or ceramic materials, and transmutation process. These immobilizing methods each include stages for recovery and concentration of the nuclides, as well as operations for synthesis of compounds with high chemical and radiation stability.
Recent variants of HLW partitioning technology make it possible to solve the problem of TPE concentrate production successfully and to reduce expenses on storage of solidified products due to recovery into an inpidual small-volume fraction of the most hazardous radionuclides needed for the everlasting storage.
Partitioning principle can also be used for iodine-129 concentrate production. In this case the iodine separation into an inpidual small-volume fraction should enable to immobilize it for further disposal with the much-reduced expenses.
To synthesize the compounds suitable for manufacture of targets by radionuclide transmutation or materials for long-term storage or final disposal, it seems rather promising to use the fission products contained in spent fuel by itself.
In our opinion, as a material for immobilizing the radionuclides like iodine-129 and TPE one can use the "reactor" palladium the accumulation of which in WWER spent nuclear fuel (SNF) is about 1 kg per ton.
It is necessary to point out “reactor” palladium contains long-lived radioactive isotope 107Pd (half-life 6,5×105 years) and it will be radioactive constantly, which, naturally, restricts its application. (Despite the predicted growth of palladium consumption and its prices, the increased demand for "reactor" palladium in traditional fields of its application (catalysis, electrical engineering etc) should not be expected in the near future).
At the same time, the use of palladium in radwaste reprocessing technology (where the presence of Pd-107 is of no importance) may also play a crucial role in forming the demand for this metal.
Recovery of platinum metals before HLW vitrification will allow immediately to attain another useful aim, and namely – to simplify vitrification process, since the platinum metals group adversely affects glass-boiling operation.
The proposed Project is aimed at extensive experimental studies on synthesis of stable materials based on "reactor" palladium for I-129 or TPE immobilization.
Another objective of the work is to improve and test the HLW partitioning flowsheets with TPE concentrate separation by using actual process solutions.
The stated objective is achieved by comprehensive analysis of the available world's experience in HLW management, choice of the most promising HLW partitioning and immobilizing technology and pursuance of R&D with verification of the appropriate results by using the actual high-level solutions.
As the Project is connected with the global problem of radwaste management, the major part of the planned studies concerns the strategy related to expediency of "reactor" palladium separation and its use in the immobilization process of radionuclides being directed to transmutation and final disposal.
To attain the stated aim, the following scientific and research works will be conducted:
- Analysis of literary data and list of synthesized materials proposed for radwaste reprocessing, including I-129 and TPE. Choice of technology for preparation of iodine and TPE concentrates for subsequent immobilization.
- Experimental studies on immobilization of iodine concentrates with the use of "reactor" palladium.
- Experimental studies on choosing the most efficient HLW partitioning process from the standpoint of TPE concentrate production for further immobilization with the use of "reactor" palladium.
- Studying the conditions for synthesis of metal-ceramic compositions based on "reactor" palladium, which are suitable as targets for subsequent transmutation or final disposal of TPE fraction.
- Study of chemical stability and physico-chemical characteristics of solidified HLW forms.
Along with the results of laboratory studies, the work should permit to improve some units of facilities and setups in "hot" cells, which may be later used for other experiments, including the solution of HLW reprocessing problems.
It the case of successful implementation of the planned R&D, the optimal process parameters will be established; they should afford safe immobilization of long-lived radwastes, that, in its turn, should be a base of initial data for commercial equipment design.
It should be noted that in the case of successful immobilization of the most hazardous radionuclides with the use of "reactor" palladium, the technology of its recovery might be profitable even in the short time.
The proposed project respond to the ISTC’s objectives presented in the ISTC Statute (Article 11, Paragraph A, Section II) as a support of fundamental and applied investigations and technical developments in the field of environment protection, power production, and nuclear safety.
The authors hope that the implementation of this Project will promote multilateral cooperation in the field of waste reprocessing and environmental protection.
Besides the Russian plants involved in HLW management, the process under development is a matter of a considerable interest to the foreign partners working in this field.
As possible collaborators we can name, first of all, USA, Great Britain, France and Japan. The authors of the Project are interested in any form of cooperation with national and international organizations, research institutes, private companies and experts of the ISTC participating countries.
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