The synthesis of graphite–glass composites intended for the immobilisation of waste irradiated graphite

Graphite immobilisation in iron phosphate glass composite materials produced by microwave and conventional sintering routes

“…Graphite peaks can be seen in all of the XRD patterns. For all of the microwaved samples, mixtures of Fe 2 (P 2 O 7 ), Fe(PO 3 ) 3 and FeP 2 O 6 phases were identified, in addition traces of Fe 2 O 3 , NH 4 H 2 PO 4 and Fe 3 O 4 were also identified in samples microwaved for 1-3 min. This agrees with the mass loss data that suggest decomposition of the raw materials occurs on this time scale.…”

“…The use of graphite as a moderator, reflector and fuel matrix in various types of reactors such as the UK Magnox and Russian RBMK reactors has resulted in approximately 250 000 tonnes of irradiated graphite waste worldwide [1][2][3]. This waste still requires an appropriate waste management strategy for its long-term treatment and disposal.…”

“…The main radionuclides in irradiated graphite are 3 H, 14 C and 36 Cl along with some minor contamination by fission products.…”

“…Irradiated graphite is classified as intermediate level waste and although it is reasonably stable to the environment the inventory of radioisotopes means that many irradiated graphites need pre-treatment before disposal [7]; for example release of 3 H, 14 C (in formation of CO and/or CO 2 ), organic 14 C [8], 36 Cl and contaminated radionuclides to groundwater are possible, which makes near surface disposal challenging. Furthermore, the vulnerability of the irradiated graphite to oxidation and the ability to store Wigner energy make the immobilisation of the waste more problematic [9,10].…”

“…However, the use of conventional melting and/or heating in glass processing is potentially problematic due to oxidation of the graphite. Recently, graphite-glass composites prepared by viscous glass sintering have shown some potential for the encapsulation of irradiated graphite waste [3]. These authors examined three different base glass compositions and, of the ones studied, they found that soda-lime-silica based glass compositions appeared to be the most promising.…”