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Conditioning Middle-Active Liquid Wastes into Matrix

#3031


Development of Resource Saving Alternative Technology of Conditioning Nuclear Power Plant Middle-Active Liquid Wastes with High Salt Content into Water Stable Mechanically Strong Isolating Matrix

Tech Area / Field

  • ENV-RWT/Radioactive Waste Treatment/Environment

Status
8 Project completed

Registration date
25.03.2004

Completion date
14.05.2009

Senior Project Manager
Mitina L M

Leading Institute
FEI (IPPE), Russia, Kaluga reg., Obninsk

Collaborators

  • Nuclear Safety Solutions Limited, Canada, ON, Toronto\nUniversitat Leipzig / Wilhelm-Ostwald-Institute of Physical and Theoretical Chemistry / Adsorption Research Group, Germany, Leipzig\nEcometal S.R.L, Italy, Brescia\nStoller Ingenieurtechnik GmbH, Germany, Dresden\nUniversity of Thessaloniki / Department of Chemistry, Greece, Thessaloniki\nFriedrich-Schiller-Universitat / Institut fur Geowissenschaften, Germany, Jena

Project summary

Purpose

Development of resource-saving alternative technology and creation of demonstration facility model for processing concentrated liquid middle-active wastes (CLRW) from NPP and nuclear submarine into waterproof durable isolating matrix.

State of the art in the field

Concentrated liquid intermediate-level wastes (CLRW) are produced in the works for minimizing the large volumes of liquid radioactive wastes from NPPs and nuclear centers by means of evaporation. This technological process is used both in Russia, and in many countries – USA, Sweden, Germany, France, Japan, Ukraine, Kazakhstan.

Concentrated radioactive solutions are dispatched to interim storage in special reservoirs because of a potential hazard of loosing tightness due to the structural materials corrosion with radioactive contamination of the environment. The final stage of LRW reprocessing is to solidify the liquid concentrates for subsequent long-term storage or disposal.

Among the CLRW conditioning methods by hardening (cementation, bituminization, deep evaporation), preference is given to cementation nowadays.

The simplest method of direct CLRW cementation (traditional technology) is based on mixing liquid wastes with inorganic binders – various cements and slags. In order to improve the properties of cement stone (first of all, its water stability), different additives (mineral ones and others) are employed.

The main disadvantage of the direct CLRW cementation technology is the low water resistance of cement compounds, which requires a reliable hydro-isolation of storage facilities; a reduced strength of compounds with increased salt content in CLRW, and a significant enlargement of the volumes of solid RAW produced. In general, this considerably raises the cost of storage (burial) of solidified concentrated liquid wastes.

To eliminate the abovementioned shortcomings, a technology is proposed, which combines the two most important factors: waste volume reduction through the use a substantially simplified technology of CLRW reprocessing into solid state.

The technology is based on the sorption-crystallization method, which makes it possible to fix the entire sum of inorganic and organic substances present in CLRW as a result of sorption and heterogenous crystallization on sorbent together with the radionuclides; thereafter the sorbent with concentrate (sorption-crystallization concentrate, SCC) is fixed as a durable mineral-like matrix material typified by a high water resistance, durability, and mechanical strength.

The new technological method will provide the volume reduction of high salt CLRW with high content of organic substances at the cost of their solidification by cementation due to the fact that the capacity of the geocement matrix by filling-up with radionuclides, inorganic and organic substances (CLRW components) increases.

Competence of Project participants

Specialists that have been involved in the following areas for at least 10-15 years are to participate in the project:


- development of sorption methods for decontamination of liquid media;
- designing the heat exchange and mass exchange apparatuses;
- operation of the evaporation installations;
- development of the system for separation and decontamination of dispersed media;
- solidification of LRW by the cementation method;
- management and disposition of radioactive wastes.

Expected results and their application

The activities under this project are to result in the development of a new alternative technology for CLRW conditioning and construction of a demonstration model facility for the upgrading of technological parameters of the waste reprocessing process.

The proposed resource saving technology of conditioning middle- active NPP and nuclear submarine wastes can be applied in CLRW reprocessing centers of other countries.

Such technology can be used also in other branches of industry (for example, chemical) in handling wastes like high salt water solutions containing toxic and harmful chemical materials as well as with the object to solidify them into water resistant compounds convenient for long-term storage at industrial waste storage plants, whereby the potential risk of the environmental pollution by noxious chemical substances will be avoided, and the storage cost will be reduced.

Fulfillment of ISTC targets and tasks

This project is in a complete agreement with the fulfillment of ISTC principal targets and tasks:

- it offers the possibility for scientists and experts of Russian Federation whose activity was related to weapons and especially those who have knowledge and experience in the field of mass distraction weapons and missile delivery systems to use their abilities for the peaceful activity;

- it supports fundamental and applied investigations and technology development in peaceful purposes especially in the field of environment protection, energy generation and safety assurance in nuclear power;

- it helps to solve national and international technical problems (besides those indicated above);

- it supports the conversion to market economy, which meets social needs.

Scope of work

To develop the technology and construct the demonstration model, the following scope of work should be done:

- experimental investigation of the optimal parameters of sorption-crystallizational extraction of 137Cs and 90Sr radionuclides mainly contributing to the CLRW radioactivity, and also inorganic and organic substances, using available cheap natural and technogenic materials suitable for subsequent cementation;

- experimental investigation of the condensate produced from CLRAW evaporation on sorbent;

- development technological parameters and of an optimum formula of the binding system for immobilizing dry materials sorbent with concentrates (SCC) into stable geocement stones;

- studies on the development of ultramembrane filter for cleaning condensate from microparticles of sorbent;

- development of technological design, construction of small-size demonstration model for CLRW reprocessing (up to 10 l volume).

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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