Release of C-14 and H-3 from Irradiated Graphite of the Thermal Column of VVR-S Reactor to Gas Phase

V. Fugaru, C. Postolache, G. Bubueanu, C. Tuta, M. Ioan Horia Hulubei National Institute for Reserch & Development in Physics, and Nuclear Engineering, Magurele, 077125, Romania

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14C and 3H are produced in all types of reactors, mainly through neutron-induced reactions with common isotopes of carbon, nitrogen and oxygen. They are present in the fuel, fuel cladding, coolant, moderator and structural materials of the reactor. Irradiated graphite contains wide range of activation products but, from the point of view of geological disposal, two radionuclides have to be taken into account: tritium (3H or T) and carbon-14 (14C). The release and migration of carbon 14C and 3H are critical issue for geological disposal of high/intermediate level radioactive waste. In this paper we present some results obtained regarding the release of 14C and 3H, for a relatively long time period into gas phase from intact samples of irradiated graphite which have been cut from the thermal column of the VVR-S reactor from Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH). An experimental apparatus has been designed and built to measure the release of 14C and 3H to gas phase from irradiated graphite. The experimental results regarding the release of 14C and 3H to gas phase show that only a small fraction of the initial inventory was released in a 12-month period. The result obtained should be applied with caution for a long time prediction.

DOI:10.12693/APhysPolA.135.1033 topics: irradiated graphite, release, tritium, carbon-14