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Analysis of water absorption onto ceria and thoria thin films by direst mass and contact angle measurements: 14th International Nuclear Fuel Cycle Conference, GLOBAL 2019 and Light Water Reactor Fuel Performance Conference, TOP FUEL 2019

Research output: Contribution to conference - Without ISBN/ISSN Conference paperpeer-review

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Publication date26/09/2019
Number of pages7
Pages145-151
<mark>Original language</mark>English
Event14th International Nuclear Fuel Cycle Conference, GLOBAL 2019 and Light Water Reactor Fuel Performance Conference, TOP FUEL 2019 - The Westin Seattle, Seattle, United States
Duration: 22/09/201926/09/2019
http://globaltopfuel.ans.org/

Conference

Conference14th International Nuclear Fuel Cycle Conference, GLOBAL 2019 and Light Water Reactor Fuel Performance Conference, TOP FUEL 2019
CountryUnited States
CitySeattle
Period22/09/1926/09/19
Internet address

Abstract

Plutonium oxide (PuO2) is one of the most highly radioactive products of the nuclear fuel cycle and its storage poses particular challenges due to the high temperatures produced by its decay and the production of gases from, inter alia, surface adsorbed water entrained with the PuO2 during the packaging process. Its high radiotoxicity necessitates the use of actinide oxides in similar oxidation states, such as CeO2 and ThO2, as model systems to allow the comprehensive study of its interaction with water under storage conditions. We have developed a method which enables direct gravimetric measurement of the adsorption of microgram amounts of water onto CeO2 and ThO2 thin films, also with masses in the microgram range. Additionally sessile contact angles of water droplets deposited onto the same films have been measured to provide a correlating measure of the affinity of the oxide surface with water. Porous CeO2 and ThO2 films were deposited from a surfactant based precursor solution onto thin GaPO4 crystal and glass substrates. The absorption of water onto the CeO2 or ThO2 coating at different relative humidities was then studied in a closed reactor using crystal nanobalance gravimetry, wherein changes in crystal resonant frequency due to absorbed mass are directly and linearly related to mass changes occurring at the crystal surface. Using this method, we have determined the enthalpy of absorption of water onto CeO2 to be 49.7 kJmol-1 and onto ThO2 to be 54.6 kJmol-1 at 75°C, 11 and 15 kJmol-1 greater than the enthalpy of evaporation. Sessile contact angle measurements on the same films provide values for CeO2 and ThO2 of 56° and 27° respectively - indicating that water shows a greater affinity for the ThO2 surface than CeO2, an observation consistent with the hierarchy of water adsorption enthalpies derived here These enthalpies are within the range predicted for the reversible absorption of water onto PuO2, confirming this method allows for the investigation of water absorption onto plutonia using microgram samples. The significantly higher enthalpy of water absorption for thoria over ceria, and the correspondingly smaller water droplet contact angles indicates a high variation in water-absorbing properties of commonly used plutonia analogues, further emphasizing the need for studies on active PuO2 samples. Copyright © GLOBAL 2019 - International Nuclear Fuel Cycle Conference and TOP FUEL 2019 - Light Water Reactor Fuel Performance Conference.All rights reserved.

Bibliographic note

Conference code: 157481 Export Date: 19 March 2020 Funding details: G0025 Funding details: Engineering and Physical Sciences Research Council, EPSRC, EP/S01019X/1, EP/L014041/1 Funding details: Nuclear Decommissioning Authority, NDA, 1006049 Funding text 1: The authors would like to acknowledge the EPSRC (Award Nos. EP/L014041/1 and EP/S01019X/1), The National Nuclear Laboratory and Nuclear Decommissioning Authority (Agreement No. 1006049) and the Lloyd’s Register Foundation (Award number G0025) for funding. The Lloyds Register Foundation is an independent charity that supports the advancement of engineering-related education, and funds research and development that enhances safety of life at sea, on land and in the air. References: (1999) IAEA Annual Report for 1998, pp. 99-1041. , International Atomic Energy Agency; Stakebake, J.L., McClard, J., Szempruch, R.W., Stabilization and packaging of plutonium oxide for 50-year storage (2000) Abstracts of Papers of the American Chemical Society, 219, p. U70; Hyatt, N.C., Plutonium management policy in the United Kingdom: The need for a dual track strategy (2017) Energy Policy, 101, p. 303; (1994) Assessment of Plutonium Storage Safety Issues at Department of Energy Facilities, , U. S. D. o. Energy DOE/DP-0123T; Montagne, X., Lynch, J., Freund, E., Lamotte, J., Lavalley, J.C., A study of the adsorption sites on thoria by scanning transmission electron microscopy and fourier-transform infrared spectroscopy. Adsorption and desorption of water and methanol (1987) Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 83, p. 1417; Stakebake, J.L., Thermal desorption study of surface interactions between water and plutonium dioxide (1973) Journal of Physical Chemistry, 77, p. 581; Stakebake, J.L., Steward, L.M., Water vapor adsorption on plutonium dioxide (1973) Journal of Colloid and Interface Science, 42, p. 328; Paffett, M.T., Kelly, D., Joyce, S.A., Morris, J., Veirs, K., A critical examination of the thermodynamics of water adsorption on actinide oxide surfaces (2003) Journal of Nuclear Materials, 322, p. 45; Haschke, J.M., Allen, T.H., Stakebake, J.L., Reaction kinetics of plutonium with oxygen, water and humid air: Moisture enhancement of the corrosion rate (1996) Journal of Alloys and Compounds, 243, p. 23; Murphy, P., Boxall, C., Taylor, R., Woodhead, D., Investigation of water adsorption on metal oxide surfaces under conditions representative of PuO2 storage containers (2013) ECS Trans, 53 (81), p. 14; Jayaraman, A., Kourouklis, G.A., Vanuitert, L.G., A high-pressure Raman-study of ThO2 to 40 GPa and pressure-induced phase-transition from fluorite structure (1988) Pramana, 30, p. 225; Zhao, R., Wang, L., Chai, Z.F., Shi, W.Q., Synthesis of ThO2 nanostructures through a hydrothermal approach (2014) Rsc Advances, 4, p. 52209; Jakab, S., Picart, S., Tribollet, B., Rousseau, P., Perrot, H., Gabrielli, C., Study of the dissolution of thin films of cerium oxide by using a GaPO4 crystal microbalance (2009) Analytical Chemistry, 81, p. 5139; Patnaik, P., (2003) Handbook of Inorganic Chemicals, , McGraw-Hill; Dollimore, D., Spooner, P., Turner, A., The bet method of analysis of gas adsorption data and its relevance to the calculation of surface areas (1976) Surface Technology, 4, p. 121; Nottbohm, C.T., Hess, C., (2012) Catalysis Communications, 22, pp. 39-42; Hayun, S., Shvareva, T.Y., Navrotsky, A., Nanoceria - Energetics of surfaces, interfaces and water adsorption (2011) J. Am. Ceram. Soc., 94, p. 3992