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Absorption-Electrochemical Surface Decontamination

#2686


Development of a Comprehensive Decontamination Database and an Absorption-Electrochemical Metal Surface Decontamination Technique Combining Chemical and Electrochemical Process

Tech Area / Field

  • ENV-RED/Remediation and Decontamination/Environment

Status
3 Approved without Funding

Registration date
29.01.2003

Leading Institute
All-Russian Scientific Research Institute of Non-Organic Materials named after A. Bochvar, Russia, Moscow

Collaborators

  • Los Alamos National Laboratory, USA, NM, Los-Alamos\nBritish Nuclear Fuels Ltd (BNFL) / Waste Disposal Research Group Sellafield R&D, UK, Cumbria, Seascale\nIdaho National Engineering and Environmental Laboratory, USA, ID, Idaho Falls\nCEA/DEN/DPA/Saclay, France, Gif-sur-Yvette Cedex\nUniversity of Sheffield / Department of Engineering Materials / Immobilisation Science Laboratory, UK, Shiffield\nBritish Nuclear Fuels Ltd (BNFL) / Nuclear Sciences and Technology Services, UK, Warrington

Project summary

1. The chemical and electrochemical decontaminations are extensively used in nuclear engineering. The grave trouble with these techniques is secondary radioactive waste (radwaste) aroused in significant amounts. “Dry” decontamination by easily strippable polymeric coatings generates no liquid radwaste. But the existing dry methods remove only non-fixed and loose contaminants but no tightly adhering (fixed) deposits. An absorption-electrochemical technique to be realized under the present Project is highly suitable for removing all kinds of radioactive deposits and produces a minimum of secondary radwaste. An objective of the Project is to develop an absorption-electrochemical technique using high-conductive strippable polymeric coatings, and a prototype device for covering metal surfaces with a polymeric coating to be further stripped. The technique is distinguished for its unique approaches like: a) first of all, an electric potential imposed; b) special reagents added to polymeric formulations to improve their desorbing power and conductivity for better removal of fixed radioactive deposits; c) a special electrode-tool. The scope of work involves the following stages:

– specifying polymeric coating compositions;


– identifying optimum process parameters (current density, treatment time and temperature, etc.);
– identifying conditions for stripping polymeric coatings;
– developing and constructing a device for applying a minimum of polymeric formulation;
– developing a tool for stripping and collecting secondary radwaste;
– testing a variety of additives to improve the existing polymeric formulations.

There is a number of tasks to be done during the stages (problems to be solved):

– specify optimum high-conductive easily-strippable formulations;


– identify optimum electrolysis parameters;
– prepare a conceptual design of an electrode-tool;
– manufacture a decontamination facility;
– develop a procedure for applying coatings by the electrode-tool;
– decontaminate radioactivity-contaminated specimens;

The expected results are as follows:

– coating-forming formulations for absorption-electrochemical decontamination;


– process parameters recommended;
– complete documentation on a conceptual design of an absorption-electrochemical facility;
– facility prototype;
– process flow sheet.

VNIINM has developed an approach to the removal of fixed contaminants from stainless steel surface without liquid polymeric formulations or the process are selected. Work on specifying optimum electrochemical parameters (current density, time, temperature, specific material removal) for effective removal of fixed contaminants is in progress. Our research has progressed to a high decontamination of surfaces artificially-contaminated with various radionuclides. A conceptual design for an electrode-tool is under development. Producing no liquid radwaste, the method is useful for decontaminating the metal surfaces of radiochemical facilities and nuclear power stations under normal and abnormal operation. Its industrial implementation will considerably reduce radwaste management costs, the decontamination process being highly effective.

2. The Database is created for technical examination and an optimum choice of techniques for cleaning radionuclides-contaminated surfaces. The DB consist of records which of them keep information concerning the properties of material to be decontaminated, contamination composition and conditions, decontamination techniques and results. The amount of records to be stored is assumed to be more 20,000. Different treatment stages may be illustrated by photos, figures, diagrams, tables. Subpisions of each “flow sheet card” cover the following data on a specific technology: properties of materials being decontaminated; contamination parameters; characteristics, shape and size of a contaminated surface; contaminant type and application; exposure time, initial radioactive level; isotopic composition of contaminants; composition and concentration of detergents and their components; properties of reagents used as detergents; decontamination variables: V/S, time, temperature, stress mode, capacity (for a radionuclide); a number of treatments, etc.; decontamination factor; corrosion effects; an average corrosion rate; describes pitting, intergranular defects, corrosion cracking; describes pictures and documents demonstrating initial state, process course, final results. The DB data presentation makes possible the realization of a record selection algorithm and some expertise for a non-skilled user to make the best decision on a specific decontamination technique.

The Database asks user some questions and the user's answers will be in full the better decision one will has.

Therefore we are going to create a Comprehensive (Full-Scale) Decontamination Method Database, which must include:

– liquid decontamination method for different surfaces;


– non-chemical decontamination techniques (laser, mechanical, biological, remelting);
– high-temperature water-free methods (using melts, thermal reduction, gas phases);
– decontamination facilities (designs, features);
– decontamination of soils, buildings, hydrogeological structures;
– facilities and methods for decontaminating liquid radwaste; etc.

We are going to include to DB separated subpision about decontamination techniques, which were used during decommission of real object in Russia.

VNIINM’s experience of long duration provides a high level of research and engineering.

In line with the ISTC’s objectives the project will redirect the knowledge and skills of weapon scientists and engineers to peaceful conversion activities. Besides, the findings will be presented to the international community.


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