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The Cold Crucible: a world first for high-level waste

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Cold Crucible technology is now used by AREVA to maintain its technological progress in the field of vitrification whilst meeting the needs of its customers.The entry into operation of the Cold Crucible represents the end result of 25 years of research and development undertaken by the CEA in collaboration with AREVA.
This is the first time that this equipment has been used for vitrification of high-level waste.

  • Principle

    Vitrification: today the melting pot, tomorrow the cold crucible

    Schema Vitrification of wastes principle

    Vitrification of wastes principle

    Processing and recycling of spent nuclear fuel makes it possible to recover 96% of recyclable materials, which will be used again to produce electricity.
    The remaining 4% is waste. This waste is integrated into a glass matrix by the vitrification process and conditioned to be safe and stable for thousands of years in stainless steel containers.
    The radioactivity of the waste is then trapped in the glass. Until now, vitrification was performed on 6 vitrification lines fitted with melting pots.

    AREVA now uses an additional technology: the cold crucible.

    The Cold Crucible induction principle

    Schema The Cold Crucible induction principlefroid

    The Cold Crucible induction principle

    Unlike the melting pot, which heats glass by thermal conductivity from the walls of the pot to the core of the glass bath, the principle of the cold crucible is to induce electric currents directly within the glass to raise its temperature without heating the crucible.

    The cold crucible operates according to the direct induction principle :

    • The wall of the cold crucible is cooled by a water circulation system.
    • A protective layer of condensed glass then forms, called a 'self-crucible'.
    • This protects the metal crucible from the effects of high temperatures and corrosion caused by the bath of molten glass.

  • Key advantages

    What is the advantage of the cold crucible?

    Verification of fluid power cold crucible

    In comparison with the current process, the cold crucible technology has major advantages. 

    It makes it possible to:

    • increase the frequency of vitrification, thus making it possible to reach the potential of 1500 tonnes with future fuels. 
    • increase the lifetime of the equipment. The lifetime of the cold crucible is 10 times longer than that of the melting pots because its cold structure is not sensitive to corrosion, protected by the layer of solidified glass formed between the structure and the glass bath.  
    • vitrify a wider range of products and ultimately to reduce the volume of final waste. The cold crucible is 'multi-glass', i.e. it allows for vitrification of various types of waste, due to its use at a higher temperature and its cold structure that is not sensitive to corrosion.
    • In addition to the fission products that are currently vitrified by melting pots, the cold crucible allows the following:
      • conditioning of rinsing solutions from the dismantling of the UP2-400 factory, which is technically unable to be performed in a melting pot.
        Conditioning of the UP2-400 rinsing solutions requires a temperature higher than 1200°C whereas the current melting pot is designed for use at 1100°C.
        Conditioning of the solutions in glass containers will make it possible to reduce the final volume of waste produced and to simplify the final processing of the package in its transportation and storage phases.
      • conditioning of the UMo fission products from the processing of the first fuel from the graphite-moderated gas-cooled reactors at the La Hague site. As a result of their chemical characteristics (significant level of molybdenum which has a significant corrosive ability), these solutions cannot be vitrified using the current melting pots. With a cold structure, not sensitive to corrosion, and with a new glass formulation, the cold crucible makes it possible to incorporate a higher level of molybdenum.

    Thus the cold crucible is the only production tool in the world to increase frequency of vitrification and provide a solution for conditioning of a wider range of waste types.

  • Prototype

    A prototype installed at HRB

    Vitrification cell constructed at the Beaumont-Hague Research Hall (HRB)

    Vitrification cell constructed at the Beaumont-Hague Research Hall (HRB)

    A full-scale prototype of the cold crucible was brought into operation in the Beaumont-Hague Research Hall (HRB), in 2008, for preliminary validation without active materials.

    • It was installed in a reproduction of the vitrification cell and controlled from a control room exactly as in the vitrification workshop.
    • It has been used for qualification and validation of performance of the items of equipment before their installation in the workshop, but
    • It has been also used for training of the personnel who will be using this new industrial tool. A total of 120 specialist personnel (chemists, remote operators, etc.) and  managers of the Maintenance, Industrial and Quality, Safety and Security Departments were trained at HRB.

  • Installation

    Installation of Cold Crucible

    The cold crucible in one of the vitrification workshops

    The cold crucible was installed in one of the vitrification workshops on August 11th 2009.

    The cold crucible was installed in one of the vitrification workshops on August 2009.

    • Tests on the utilities were performed in September 2009,
    • followed in October 2009 by connection of the cold crucible to the area 4 equipment.  
    • The final stage, the full-scale tests, were performed by the project team and the integrated teams of the Industrial Department and Maintenance Department, with support from the CEA.
    • The first inactive casting was performed on December 17th, 2009 and the glass development tests with all equipment in operation were completed on December 23rd.
    • 3 containers were produced using solutions simulating fission products. 

  • Project

    The 'cold crucible' project

    view of glass in fusion

    glass in fusion

    Project organization

    • Commissariat à l’Energie Atomique (CEA) : Process Development.
    • AREVA :
      • AREVA provided project ownership, responsible for installation of the cold crucible on one of the 6 vitrification lines of the La Hague site, 
      • SGN, an engineering company of the AREVA group, was in charge of  managing the project, SGN, an engineering company of the AREVA group,  today part of the AREVA's Engineering & Projects organization was in charge of  managing the project.
      • Other subsidiaries of the group were called on (Mécagest, Mécachimie, etc.).
      • Fifty or so local companies and several hundred people also worked on this technology.

    More than 200 million euros were invested in Research and Development.

    The progress of the project

    2005 à 2007 : The project was launched at the end of 2004 and studies lasted 2 years.

    2007 :  At the R7 vitrification workshop in which the cold crucible will be installed, the preparatory cabling and piping work was undertaken.

    2008 : A full-scale prototype of the cold crucible was brought into operation in the Beaumont-Hague Research Hall (HRB).

    The utility installation work (electricity, cooling system) and rinsing and dismantling operations for the vitrification cell (shutdown of line on May 5th 2008) were begun.

    2009 :

    • August 11th: installation of cold crucible in one of the vitrification workshops.
    • September: tests on utilities.
    • October: connection of cold crucible to area 4 equipment.
    • October-December: full-scale tests performed with support from CEA.
    • December 17th: first inactive casting. Production of 3 containers using solutions simulating fission products.

    2010 : April 17th: production of the first container of vitrified waste using cold crucible technology.

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