Overview OF 14C release from irradiated zircaloys in geological disposal conditions. Issue 6 (28th January 2019)

• Record Type: Journal Article
• Authors: Necib, S; Bucur, C; Caes, S; Cochin, F; Cvetković, B Z; Fulger, M; Gras, J M; Herm, M; Kasprzak, L; Legand, S; Metz, V; Perrin, S; Sakuragi, T; Suzuki-Muresan, T
• Editors: Norris, Simon
• Is Part Of: Radiocarbon. Volume 60:Issue 6(2018)
• Page Start: 1757
• Page End: 1771
• Publication Date: 2019-01-28
• Subjects: activated Zircaloy, -- alkaline media, -- corrosion, -- 14C speciation, -- geological disposal; Radiocarbon dating -- Periodicals; 930.1028505
• DOI: 10.1017/RDC.2018.137
• Languages: English
• ISSNs: 0033-8222

Abstract

ABSTRACT: Carbon-14 (radiocarbon, 14 C) is a long-lived radionuclide (5730 yr) of interest regarding the safety for the management of intermediate level wastes (ILW). The present study gives an overview of the release of 14 C from irradiated Zircaloy cladding in alkaline media. 14 C is found either in the alloy part of Zircaloy cladding due to the neutron activation of 14 N impurities by 14 N(n, p) 14 C reaction, or in the oxide layer (ZrO2 ) formed at the metal surface by the neutron activation of 17 O from UO2 or (U-Pu)O2 fuel and water from the primary circuit in the reactor by 17 O(n, α) 14 C reaction. Various irradiated and unirradiated Zircaloys have been studied. The total 14 C inventory has been determined both experimentally and by calculations. The results seem to be in good agreement. Leaching experiments were conducted in alkaline media for several time durations. 14 C was mainly released as carboxylic acids. Further, corrosion measurements were performed by using both hydrogen measurements and electrochemical measurements. The corrosion rate (CR) ranges from a few nm/yr to 100 nm/yr depending on the surface conditions and the method used for measurement. From a safety assessment point of view, the instant release fraction (IRF) was determined on irradiated Zircaloy-2. The results showed that the 14 C inventory in the oxide was significantly below the 20% commonly used in safety case assessments.