Carbon Materials for Nuclear Waste Storage and Transmutation
Development of the Methods for Encapsulation of Long-lived Nuclear Waste in the Carbon Matrixes for Storage and Transmutation
Tech Area / Field
- ENV-RWT/Radioactive Waste Treatment/Environment
- CHE-RAD/Photo and Radiation Chemistry/Chemistry
- MAT-SYN/Materials Synthesis and Processing/Materials
- PHY-ANU/Atomic and Nuclear Physics/Physics
8 Project completed
Senior Project Manager
Genisaretskaya S V
Nuclear Physics Institute, Russia, Leningrad reg., Gatchina
- Institute of Macromolecular Compounds, Russia, St Petersburg\nKhlopin Radium Institute, Russia, St Petersburg
- European Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe\nRWE NUKEM Limited, UK, Chesire, Risley Warrington\nJAERI / Tokai Research Establishment, Japan, Tokai Mura\nEnergiewerke Nord GmbH, Germany, Lubmin\nKinectrics Inc., Canada, ON, Toronto
Project summaryThe goal of the Project is the development of the methods for encapsulation of long-lived radionuclides 99Tc, 129I and 241Am in carbon matrixes and the investigation of properties of the synthesized samples with the aim to use such type materials for the nuclear waste storage and transmutation.
These radionuclides are a part of the spent nuclear fuel. 99Tc and 129I are the most long-lived fission products and because of some properties represent the greatest danger for the biosphere.
According to the concept of the double-strata nuclear fuel cycle the waste management includes the extraction of radionuclides from spent nuclear fuel into separate fractions, a storage them under control for some time and the transmutation into stable or short-lived isotopes which are radiologically safe. An encapsulation of 99Tc, 129I and 241Am into inert carbon matrixes will allow to store them and to fabricate the appropriate targets for a long term irradiation aiming the transmutation of these radionuclides.
Nuclide 241Am together with other minor actinides will be present as an impurity in the eliminated fractions of 99Tc and 129I. In this respect 241Am could be considered as a model nuclide for the study of the actinide behavior in the process of their transmutation.
The choice of carbon materials as a basis for the target fabrication is made because of an unique combination of the carbon properties, namely:
– carbon is a widespread chemical element in Nature, available in various chemical forms;
– there are four allotrophic carbon forms with the different crystalline structure and various types of the chemical bonds between atoms. Numerous amorphous and semicrystalline transition forms of carbon are well known in addition to crystalline one. Some carbon forms, such as fullerens, nanotubes etc. have a cage-like structure and the atoms of any alien element can be confined inside these cages;
– carbon is a moderator of neutrons but it is more transparent than most of other fuel and target materials: the capture cross-sections for the stable isotopes 12C and 13C are, respectively, 3.53 and 1.37 mb for thermal neutrons;
– many forms of carbon are chemically and thermally stable and can be unchangable for a long (geological) time even in a very hard conditions.
The properties of carbon mentioned above provide the basis for the use of various carbon materials for encapsulation and strong retention of radionuclides. As an illustration of such type possibility we can refer to the results of study of the target material produced by pyrolysis of some organometallic compounds. It has been shown by PNPI (Gatchina) group that the retention almost of all radioactive atoms (including even heavy noble gases) formed in the pyrolyzed carbon matrix MeCx irradiated by 1 GeV proton beam, is close to 100 percents under high vacuum conditions and temperatures up to 1,000 °C.
Our plans are as follows:
– to develop methods of synthesis of waste-bearing carbon materials;
– to synthesize samples of various carbon matrixes which are different both in the structure and in the content of encapsulated radionuclides (99Tc, 129I, 241Am);
– to test thermal and chemical stability of these samples;
– to study the retention of the transmutation products in these materials after neutron irradiation.
To implement the goals of Project we propose to use the following methods:
– the RFA method, the Rutherford backscattering of protons, gamma-spectrometry, the thermal analysis and the NMR spectroscopy – all these listed methods will be used for composition, stability and structure analysis;
– the retention of atoms after neutron capture and induced fission will be analyzed by the gamma- and X-ray-spectrometry.
An attractive side of the Project can be its impact to the industrial development of nuclear waste storage and transmutation because the methods proposed deal with the physically and chemically stable carbon materials which are cheap in production.
The participation in the project of scientists working in the military science and defence problems will promote the reorientation of their activity on the solution of peaceful problems in which a problem of neutralization of nuclear waste is of a great importance.
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