Author(s)

Gitender Singh^1*, Prashal M. Khot², Pradeep Kumar³, Chetan Baghra¹, Raj Bhushan Bhatt¹, Praveen G. Behere¹

¹Advanced Fuel Fabrication Facility (AFFF), Bhabha Atomic Research Centre, Tarapur, India.
²Radio-Metallurgy Division, Bhabha Atomic Research Centre, Mumbai, India.
³Homi Bhabha National Institute (HBNI) and Integrated Fuel Fabrication Facility (IFFF), Bhabha Atomic Research Centre, Mumbai, India.

This paper presents a study on the process engineering aspects of relevance to the industrial implementation of ThO₂ and (Th, U)O₂ mixed oxide (MOX) pellet type fuel manufacturing. The paper in particular focuses on the recycling of thoria based fuel production scrap which is an economically important component in the fuel manufacturing process. The thoria based fuels are envisaged for Advanced Heavy Water Reactor (AHWR) and other reactors important to the Indian Nuclear Power Programme. A process was developed for recycling the chemically clean, off-specification and defective sintered ThO₂ and (Th, U)O₂ MOX nuclear fuel pellets. ThO₂ doesn’t undergo oxidation or reduction and thus, more traditional methods of recycling are impractical. The integrated process was developed by combining three basic approaches of recycling namely mechanical micronisation, air oxidation (for MOX) and microwave dissolution-denitration. A thorough investigation of the influence of several variables as heating method, UO₂ content, fluoride and polyvinyl alcohol (PVA) addition during microwave dissolution-denitration was recorded on the product characteristics. The suitability evaluation of the recycled powder for re-fabrication of the fuel was carried out by analyzing the particle size, BET specific surface area, phase using XRD, bulk density and impurities. The physical and chemical properties of recycled powder obtained from the sintered (Th_1-y, Uy)O₂ (y; 0 - 30 wt%) pellets advocate 100% utilisation for fuel re-fabrication. Recycled ThO₂ by integrated process showed distinctly high sinterability compared to standard powder evaluated in terms of surface area and particle size.

ThO₂, MOX, (Th, U)O₂, AHWR, Recycling, Microwave, Denitration

Singh, G. , Khot, P. , Kumar, P. , Baghra, C. , Bhatt, R. and Behere, P. (2017) An Integrated Process for Recycling of ThO₂ Based Mixed Oxide Rejected Nuclear Fuel Pellets. World Journal of Nuclear Science and Technology, 7, 309-330. doi: 10.4236/wjnst.2017.74024.