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Geocement binding materials for radioactive waste immobilization

#A-1209


Development of New Types of Geocement Binding Materials Based on Natural Minerals and Technology of Conditioning of Radioactive Absorbents (Zeolites) and Sludge Immobilized in Geocement Matrix

Tech Area / Field

  • ENV-RWT/Radioactive Waste Treatment/Environment
  • OBS-NAT/Natural Resources and Earth Sciences/Other Basic Sciences

Status
3 Approved without Funding

Registration date
14.12.2004

Leading Institute
Yerevan State University, Armenia, Yerevan

Supporting institutes

  • Armenian NPP, Armenia, Metsamor\nFEI (IPPE), Russia, Kaluga reg., Obninsk

Collaborators

  • Friedrich-Schiller-Universitat / Institut fur Geowissenschaften, Germany, Jena\nStoller Ingenieurtechnik GmbH, Germany, Dresden\nEcometal S.R.L, Italy, Brescia\nUniversitat Leipzig / Wilhelm-Ostwald-Institute of Physical and Theoretical Chemistry / Adsorption Research Group, Germany, Leipzig\nFriedrich-Schiller-Universität Jena / Otto-Schott-Institute für Glaschemie, Germany, Jena\nTokyo Institute of Technology / Department of Applied Chemistry, Japan, Tokyo\nNational Nuclear Corporation, UK, Warrington\nDEKONTA, a.s., Czechia, Prague\nThe Zeopower Company, USA, MA, Chestnut Hill\nUniversité du Maine, France, Le Mans\nUniversity of Florida / Department of Geological Sciences, USA, FL, Gainesville\nUniversity of Thessaloniki / Department of Chemistry, Greece, Thessaloniki

Project summary

Recently extensive work on development of decontamination technology of liquid radioactive waste (LRW) of the Armenian Nuclear Plant was carried out at the Yerevan State University within the frame of the project ISTC A-485 (“Efficient Treatment of Radioactive Liquid Waste by Zeolites Modified through Chemical and Radiation Methods”). Clinoptilolite based natural aluminosilicate sorbents were use for this purpose. The objective of this proposal was the optimization of the sorbent preparation procedures and of the Cs and Sr removal from radioactive effluents under dynamic and static conditions. Although a high degree of LRW volume reduction (up to 400 – 600 times) was achieved, the necessity of a further management (conditioning) of used the radionuclide loaded zeolitic sorbents became obvious.In the result of mentioned technology application a demand emerges to further management (conditioning) of used zeolites containing absorbed radionuclides which in the case of large-scale usage will be accumulated abundantly at NPPs [17-25].

The proposed project is a continuation of the above-mentioned project and it will be devoted to the development of technology of conditioning of spent zeolites which may be qualified as middle-active radioactive waste (MRW). According to Russian [1] and foreign terminologies the “conditioning” means the transformation of radioactive waste into the form suitable for transportation, storage (<50 years) and disposal.

Objectives of the project:

- The development of the low resource- and energy-saving technology for the conditioning of radioactive waste by immobilization into geocement matrix materials based on readily available and inexpensive natural and technogenic materials of Armenia,


- The construction of the corresponding pilot plant and their testing at Armenian NPP.

The term “geocement” here describes the binding compounds of hydration setting which form, after solidification, stable materials.

As a feed stock may be used different natural and man-caused materials of Armenia (obsidians, perlites, tuffs, lithoide pumices, boron containing travertines, barium sulfates, as well as alkali and earth-alkali magmatic ores such as syenite, phonolite, trachyte, nepheline syenite, etc).

Different natural and man-made materials of Armenian origin (e.g. obsidians, perlites, tuffs, lithoide pumices, boron containing travertines, barium sulfates, as well as alkali and earth-alkali magmatic ores such as syenite, phonolite, trachyte, nepheline, syenite, etc) can be used as raw materials for this purpose. Both cases will be considered in this project, the common conditioning of the sorbents and sludge (oozy precipitates accumulated in tanks which can be classified as MRW) and the separate conditioning.

Several methods of conditioning the MRW such as bituminous grouting, vitrification and cementing. Then the packed blocks with immobilized radionuclides are putted into metal ore concrete tanks for subsequent storage and disposal. In the countries of former Soviet Union these works are still in the stage of development.


The authors of proposed project suggest to use the technology of energy-saving and environmentally sound (in contrast to vitrification or sintering which result in radioactive gas emission) and safe compacting of radionuclide loaded zeolites by means of geocements prepared on the base inexpensive natural or man-made materials. For satisfying the requirements of good insulation from environment during long-term storage the obtained blocks must be very water-resistant for preventing radioactive ions desorption from matrix material containing used zeolite, they must have high mechanical strength and be stable to the residual radioactive radiation. It is proposed to study the properties of various geocement compounds by using of water-resistant and radiation-resistant technogenic and natural minerals, volcanic rocks and crushed stone.
The literature review showed that there is a close relation of our proposal to the technology for the treatment of LRW of middle activity by the use of natural absorbents presented in ref. [2]. This method consists of absorption of radionuclides by natural zeolites from aqueous solutions of pH values between 8 and 12. Then the obtained zeolites with immobilized radioactive ions are cemented by the use of binding system containing furnace slag and clay mixed with the solution of sodium silicate. In the result a water-resistant and mechanically strong stone is formed. The disadvantage of this technique is the restriction of availability of the main man-made glassy slag material. The other glassy materials proposed in our project will expand considerably the possibilities of application of geocement binding materials.

Competence of the project participants
The participants who will work on the project are the specialists (4 – doctors of sciences, 15– candidates, 5 - scientific the employee and 24 - engineers) experienced in the last 10-15 years in the field of:
· development of the methods of purification of LRW from radionuclides by using different absorbents, including natural minerals of Armenia,
· study of aluminosilicate binding materials and other systems for formation of geocement matrices containing analogs of rockforming minerals,
· immobilization of LRW into different cement matrices,
· manufacturing of the equipment for mixing of powdered minerals and viscous mediums for cement preparation,
· study of the properties, composition and structure of minerals and rocks with reference to their application for insulation of radionuclides from environment,
· study of the mechanical strength, radiation stability, water permeability and chemical properties of solid materials applicable to their use for the isolation of biologically significant radionuclides from biosphere.
In the process of fulfillment of the proposed project, scientists from:
- Vernadsky Institute of Geochemistry and Analytic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Institute of the Problems of Development of Atomic Energy, Russian Academy of Sciences, Moscow, Russia
will also be involved.

Expected results and their application
As result of the project implementation a new technology of conditioning of middle active radioactive waste loaded absorbents (zeolites) and sludges will be developed. An experimental pilot plant for the testing of technological regimes of radioactive absorbents cementing will be constructed. This plant will contribute to the increase of radiation safety at Armenian NPP as well as at NPPs in other countries.
Solidification processes will be developed, which could also be applied to the conditioning of non-radioactive hazardous heavy metal containing wastes.

Meeting ISTC Goals and Objectives

The project completely satisfies the ISTC goals and objectives. The project will give an opportunity of employment in civilian R&D efforts to scientists and specialists of Armenia and Russia that were formerly engaged in defense programs. During the implementation of project the business contacts with foreign researchers will be established that will help the members of our staff to be integrated in the international science community.

The project will largely contribute to basic and applied research and development of technologies in the fields of environment protection, and nuclear safety. It will considerably contribute to the solution of problems related to the radioactive wastes management, that are actual not only in Armenia, but also in other countries of the world.

The project will contribute to the solution of regional and international problems and will promote the transfer to the market economy responsible for civil needs.

The project will contribute to the solution of regional and international problems related with the nuclear waste management, will promote the know-how transfer from other countries and develop technology which can also be applied to the solution of other conventional environmental problems (e.g. hazardous conventional industrial waste management).

Scope of Activities



Development of technology of radioactive absorbents conditioning and creating of experimental pilot plant need the implementation of the following work:

- study of the properties of natural minerals, rocks and their modifications for their utilization as binding materials,
- optimization of technical parameters and optimal formulation of binding systems for immobilization of granulated radioactive absorbents,
- optimization of technical parameters and optimal formulation of binding systems for the immobilization of sludge,
- study of mechanical, structural and physical chemical properties of various geocement matrices,
- study of the leaching rate of radionuclides from geocement matrix,
- development of the methods of accelerated ageing of geocement materials and investigation of their stability

Role of foreign collaborators

- participation in the development of project proposal and work plan;
- exchange of information during project implementation;
- mutual review of technical reports;
- joint seminars, workshops, meetings, consultations;
- verification of results using independent methods and /or equipment;

- joint or parallel investigations.


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