D-Cinnabar : Stabilisation of contaminated metallic mercury

Stabilisation of metallic mercury from nuclear facilities by dry process

• The Challenge

  At room temperature, mercury is a liquid metal, toxic by ingestion or by inhalation of vapors. In France, several tons of contaminated metallic mercury are stored in nuclear facilities: Waste from research and development (CEA). Waste from processes: mercury cathode electrolysis in the fuel cycle (CEA), valve plugs from the Superphénix RNR reactor (EDF). Waste from instruments used in facilities (e.g., pressure sensors) or laboratories (all producers). Contaminated mercury was considered until recently as a waste without a channel in the National Plan for the Management of Radioactive Materials and Waste (PNGMDR). However, it is possible to stabilize it into a non-polluting product, which can be accepted by Andra's storage centers. How can such waste be stabilized for final disposal ?

• The Solution

  D-CINNABAR is a process designed by Orano DS to stabilise metallic mercury contaminated with sulphur flower in an industrial reactor. It allows :

  The recovery of untreated metallic mercury stocks.

  Contaminated water present with metallic mercury, by evaporation.

  The process is executed dry in a specific equipment under controlled pressure and temperature conditions.

  The final form of mercury after treatment is stable, insoluble in water and acceptable by Andra's storage centres.

• Key Features

  The process is based on the following chemical reaction : Hg + S → HgS

  
  

  The industrial solution is constituted by a reactor that can treat a batch of 6 kg of mercury metal (that is 1 batch) on a shift of approximately 7.5 hours, including inbound and outbound logistics.

  The reactor is sealed and operates under vacuum (of the order of a few tens of mbar) and at moderate temperature (< 90°C).

  The reaction is carried out with a slight excess of sulphur (molar ratio S/Hg > 1) to ensure complete transformation of mercury as a liquid into solid mercury sulphide. Contaminated metallic mercury is currently treated by the Orano DS Triade ICPE in a dedicated cell specially equipped for mercury risk management. Once stabilised, the waste is evacuated to the CIRES Andra.

• Expertise & Experiences

  The pilot process (capacity 1 kg/batch of treatment) was implemented in 2016 at the Orano Triade site to stabilise 5.3 kg of metallic mercury contaminated with uranium. The contaminated mercury sulphide (HgS) and the waste resulting from the construction area were all accepted and evacuated to the CIRES Andra.

  The industrial process was qualified in October 2021 to process unit batches of 6 kg of metallic mercury.

  Orano DS experts provide you with their expertise for the implementation of this process in your facilities :

  Definition and installation of the working environment.

  Handling and processing of metallic mercury.

  Assistance in transporting metallic mercury to processing facilities.

• Your Benefits at a glance

  A single equipment, space-saving, mobile for supernatant separation and mercury stabilisation.

  
  

  Once stabilised, the waste is insoluble in water, chemically stable and accepted in Andra's* waste storage centres.

  
  

  The conversion rate is close to 100%, proven by chemical analysis and pollutant potential tests.

  
  

  The risks of toxicity to operators and the environment from mercury vapours are controlled.

  
  

  This solution makes it possible to dispose of a previously non-disposable waste, thus improving the safety and security of waste storage facilities.

• Links