Classification of BR-1 irradiated graphite waste and the potential for thermal treatment

Neil Calder, Edouard Malambu Mbala, Frank Druyts

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The BR-1 reactor is an air-cooled, graphite-moderated and -reflected, low flux research reactor located at the SCK•CEN research centre in Mol, Belgium. With over 500 tons of irradiated graphite waste projected following the future decommissioning of BR-1, a thorough investigation into the characterization of this prospective waste stream has been conducted. Using the SCK•CEN proprietary code ALEPH, combining the computational Monte Carlo N-Particle transport code (MCNP) with a deterministic activation and depletion algorithm, the radioisotopes of most concern with regards to the disposal of BR-1 irradiated graphite (14C, 36Cl, 60Co, 3H) have been determined over the operational history and projected future life of the reactor. The specific activities of 14C and 36Cl have been assessed against the latest Belgian radioactive waste acceptance criteria (ONDRAF/NIRAS) for a future near surface disposal facility. It was found that for the full BR-1 graphite inventory, the specific activity of 36Cl following an end of operational life of 2040, exceeds the single waste package specific activity limit for this isotope for near surface disposal. Assuming a 10ppm Nitrogen concentration in the BR-1 graphite, the specific activity of 14C in 2040 exceeds the single waste package specific activity limit in 31% of the total BR-1 graphite volume. 14C has been investigated in further detail and the potential for surface concentrations of activity of this isotope has been highlighted following a literature review focusing on existing reactors with similar coolant chemistry and operational conditions to BR-1. The potential for thermal treatment to remove a significant proportion of this 14C surface activity has been highlighted from previous studies, and by applying the same reductions to the BR-1 graphite inventory, the reduction in volume of graphite failing the single waste package specific activity limit for 14C could theoretically be reduced from 31% to 11%.
Original languageEnglish
QualificationMaster of Science
Awarding Institution
  • UGA - University of Grenoble
  • Malambu Mbala, Edouard, Supervisor
  • Druyts, Frank, Supervisor
StatePublished - 23 Aug 2018

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