Abstract
ABSTRACTLeaching tests were carried out in aerobic and anaerobic conditions to assess the 14C released from TRIGA irradiated graphite. Both total 14C and inorganic and organic fractions in the leachant solutions were measured. The experimental results obtained from the leaching tests confirm the low 14C release rate in alkaline environment. Less than 2% of the total 14C inventory in the specimens subject to the leaching tests was released as dissolved species. Both inorganic and organic 14C species are released in alkaline conditions, with more inorganic 14C release under aerobic conditions (around 68% of the total 14C released was released as inorganic dissolved species), and more organic 14C species in anaerobic conditions (around 65% of the total 14C released was released as organic dissolved species). Both for anaerobic and aerobic conditions, the leaching rates are high in the first days of immersion and decrease after that, indicating a two stage process: an initial quick release (less than 9 × 10–02 % of inventory/day for the first 48 days) followed by a slower release rate (around 4 × 10–03 % of inventory/day).
Highlights
Irradiated graphite is one of the radioactive waste categories that will be generated after decommissioning of the TRIGA research reactor, a reactor in operation at the Institute for Nuclear Research
Both for anaerobic and aerobic conditions, the leaching rates are high in the first days of immersion and decrease after that, indicating a two stage process: an initial quick release followed by a slower release rate
Two cylindrical bars originating from a brick extracted and dismantled in 2000 from the thermal column of TRIGA reactor were available for the experimental program carried out in RATEN ICN under CAST WP5: one cylinder with a diameter of 50 mm and length of 200 mm, and the second one with diameter of 60 mm and length of 250 mm
Summary
Irradiated graphite is one of the radioactive waste categories that will be generated after decommissioning of the TRIGA research reactor, a reactor in operation at the Institute for Nuclear Research. The thermal column of the TRIGA Reactor is a graphite block (1716 × 1144 × 710 mm) made up of 98 rectangular graphite cells (12 rows × 8 bricks) in aluminum cladding, which is placed into the reactor pool on the north side of the steady-state core. It was built up in 1985, using sintered graphite blocks with a density of 1.72 g/cm and various geometries
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