Radioactive Waste Disposal Using Microspheres
Immobilisation and Disposal of Radioactive Wastes Using Modified Microspheres of Natural Silicates
Tech Area / Field
- CHE-RAD/Photo and Radiation Chemistry/Chemistry
- ENV-RWT/Radioactive Waste Treatment/Environment
- ENV-WDS/Waste Disposal/Environment
- MAN-MAT/Engineering Materials/Manufacturing Technology
8 Project completed
Senior Project Manager
Novozhilov V V
VNIIEF, Russia, N. Novgorod reg., Sarov
- Institute of Organic Chemistry, Russia, Moscow
- Los-Alamos National Laboratory, USA, NM, Los-Alamos\nPennwood Technology Inc., USA, New York
Project summaryDevelopment of activities in nuclear power engineering has resulted in formation of great masses of radioactive wastes. In coming 10-20 years this tendency will gain strength because of decomissioning of atomic reactors put into operation in early 80-s. These circumstances necessitate to provide efficient and economically proved methods for disposing of piled up and newly produced radioactive wastes. One way to solve this problem is to develop the ion-exchange material capable of binding heavy metals forming the basis of radioactive wastes and providing their subsequent isolation under long-term storage conditions.
The main project objective is to study applicability of natural silicate microspheres (microspheres from fly ashes of power stations) having surfaces modified by various ion-exchange reagents to produce materials capable of sorbing toxic metals, uranium fission products and actinide elements, as well as to look into the methods of compacting microspheres-sorbents used for isolation of radioactive wastes in their long-term storage.
Scientific and practical significance of this work consists in the possibility to produce a new rather inexpensive ion-exchange material having a wide range of effects, which would provide an optimum application of sorbents in a thin surface layer and have a physical and chemical stability of a natural silicate material. Such a material will make it possible to solve the problems of immobilization and isolation of radioactive wastes. In this case an effective ecological problem solution, that is application of available and large-scale wastes of the fuel and energy complex for disposal of atomic- industry wastes will be realized.
Technical approach and methodology
When burning coals in boiler furnaces, aluminosilicate microspheres in the form of a light loose finely pided powder consisting of separate strong, hollow, spherical particles are produced from mineral impurities. In 1996 through 1998 VNIIEF having financial support of the ISTC (project № 214) carried out a technical monitoring of ash microspheres taken from power stations of the Russian Federation. The obtained data on formation of microspheres in fly ashes show that they can very well serve as a practicable large-capacity commercial product. Due to the combination of technical properties, microspheres may be used as a carrier of sorbents that is formed on microsphere surfaces in the form of a thin layer. A chemical surface modification can be provided using organic or inorganic reagents (8-hydroxyquinoline, iminoacetic acid, ferrocyanides and phosphates of heavy metals) and binding a sorbent by one of the following known methods: covalent graft, impregnation, adsorption, formation of hydrogen links. The ion-exchange material structure of this kind provides an effective sorbent application and at the same time it has a low hydraulic resistance, which allows its use both under static and dynamic sorption conditions. Physical and chemical characteristics of microspheres-sorbents will be studied including their stability in various aggressive media, kinetic sorption parameters with respect to uranium fission products (137Cs, 90Sr, etc.), actinide elements (Am, Np, Cm) and toxic metals (Hg, Pb, Cu, Cd, etc.). General principles of using ion exchangers based on modified microspheres have been developed for decontamination of liquid radioactive wastes.
An aluminosilicate composition of microsphere materials provides their high physical and chemical stability, which can be favourably used in disposal of radioactive wastes. It is planned to study various methods of compacting microspheres by sintering (melting) and using binders of organic and inorganic nature such as cements, ceramics, fly ashes, glass. The basic physical-chemical and thermal properties of such composite materials will be specified. Their stability will be studied under conditions simulating a long-term storage such as leaching processes, a-radiation effects.
To create barrier layers preventing in a long-term storage from spread of radioactive elements under subsoil water effects, the possibility of immobilizing heavy metals with a silicate matrix using sol-gel technology principles will be examined.
The project also proposes to work through the technical concept of fly ash microspheres recovery, which is based on picking microspheres from surfaces of power station water basins.
During activities both conventional and up-to-date investigation methods are proposed to be used. These are high-resolution electron microscopy, x-ray microdiffractometry, microelement and chromatographic analyses, a-and g-spectrometry, various methods of mechanical and thermal tests.
RFNG-VNIIEF and IOKh RAS associates are experienced in modifying microsphere surfaces, studying their properties and producing composite materials using microspheres. The available preliminary results on sorption of heavy metals point to the chosen approach efficiency and a successful combination of technical capabilities and practical expertise of specialists, which will allow the tasks stated in the project to be fulfilled successfully.
Potential role of foreign collaborators
The project orientation towards solution of topical problems may contribute into establishing of business relations with foreign partners. Of interest is collaboration in exchange of information related to the subjects touched upon in the project. Cooperation in the form of discussions, seminars, joint studies of material samples may be beneficial for improving the project plans and implementation of its results.