14 C content in candu spent ion exchange resins and its release under alkaline conditions

Abstract

The total 14 C content and its speciation (inorganic/organic) were measured in spent ion exchange resins (SIERs) received from Cernavoda Nuclear Power Plant (NPP). Also, 14 C release from SIERs was investigated by desorption tests carried out in alkaline solution relevant for cementitious environment disposal. The method used for total 14 C measurement consists of combustion in oxygen-rich atmosphere, while for speciation measurements, both in SIERs and in desorption solutions, an analytical method based on acid stripping and wet oxidation was applied. Around 97% from the total 14 C inventory measured on the Cernavoda SIERs (33.7 kBq/g) was found to be in inorganic form and only 7% as organic 14 C. Under alkaline conditions, 14 C could be released both as gaseous and as soluble species: from the total 14 C present in the SIERs samples around 7% was released as inorganic 14 C in the gas phase and 79% as dissolved species (mainly as inorganic 14 C). These percentages were obtained for unconditioned SIERs in NaOH solution. The SIERs will be immobilized in a suitable matrix for disposal, and the presence of Ca ions dissolved in cement pore water favor precipitation of 14 C and consequently the amount of 14 C released from disposal area should be lower.