Abstract
ABSTRACTThe total 14C content and its partition between inorganic and organic species were measured on irradiated Zy-4 samples from a CANDU spent fuel rod transferred from Cernavoda Nuclear Power Plant (NPP). Long-term leaching tests and accelerated corrosion tests were carried out to measure the 14C release and corrosion rate, respectively, in chemical conditions relevant to cementitious environment. Experimentally measured 14C inventory was compared to the theoretically one predicted based on the irradiation history and impurity content of Zy-4 by means of ORIGEN computations. CANDU SF claddings have a 14C content of around 2 × 104 Bq/g of Zy-4, mainly as organic compounds (more than 99%). The total 14C content measured by acid dissolution/wet oxidation method is in good agreement with the value estimated by ORIGEN simulations for an average burn-up of 7 MWd/kgU. The total 14C released as dissolved species after 18 days and 18 months of Zy-4 immersing in alkaline solution are similar, indicating that a small amount of 14C was available as instant release fraction (0.05% from the initial 14C content) followed by a very low release rate that could not be measured by liquid scintillation counting. In alkaline conditions, 14C is released predominantly (∼70%) as soluble species, but also inorganic 14C was measured as gaseous species. From the soluble 14C released during leaching test, more than 60% was found to be as organic species. Generally, corrosion rates values ranging between 46 and 130 nm/yr were measured by the linear polarization resistance method. In addition, defects and cracks were observed on the oxide layer by scanning electron microscopy (SEM) investigation.
Highlights
In Romania, two CANDU 600 (CANada Deuterium Uranium) reactors are currently in operation at the Cernavoda site and two more CANDU units are foreseen to be commenced in the future
The results show that with this analytical method, good 14C recovery and efficient purification are obtained:
∙ no gamma emitters were identified in the solutions sampled from alkaline gas washing bottles, and 14C specters were free of interferences
Summary
In Romania, two CANDU 600 (CANada Deuterium Uranium) reactors are currently in operation at the Cernavoda site and two more CANDU units are foreseen to be commenced in the future. The Romanian strategy for spent fuel and radioactive waste management foresees that the CANDU spent fuel (SF) will be disposed of together with other long-lived radioactive waste (such as non-fuel contact spent ion exchange resins, spent filters, pressure tubes and calandria tubes) in a geological disposal, foreseen to be operational in 2055. CANDU fuel assembly contains 37 elements made of sintered UO2 pellets (natural uranium) in Zy-4 tubes. CANDU units are designed such as to load and unload their fuel continuously at full power by disconnecting individual pressure tubes. In CANDU nuclear fuel, Zy-4 is used as fuel cladding, and for end-caps, end support plate, inter element spacers, and pads
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
