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Zirconolite is recognized as one of the most durable waste matrices for the disposal of high-level radioactive wastes (HLWs). In this study, HfO2 was employed as the surrogate of tetravalent actinides. Hf-bearing zirconolite-based composite waste forms (CaZr1-xHfxTi2O7) were rapidly prepared by combustion synthesis (CS) using CuO as the oxidant, where quick pressing (QP) was introduced to obtain densified samples. Similar as solid state reaction process, the Zr site of zirconolite can be totally occupied by Hf (x = 1.0) under the CS reaction. The original 2M zirconolite structure was maintained and a small amount of perovskite impurity phase was generated in the final products. The aqueous durability of representative sample (Cu-Hf-0.6) was tested, where the 42-day normalized leaching rates (LRi) of Ca, Cu, and Hf are 0.25, 3.10×10-2, and 1.11×10-8 g·m-2·d-1.


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Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Show Author's information Kuibao ZHANGa,b( )Dan YINaZongsheng HEaBaozhu LUOaHaibin ZHANGc
State Key Laboratory of Environment-friendly Energy Materials, Southwest University of Science and Technology, Mianyang 621010, China
National Defense Key Discipline Lab of Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang 621010, China
Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China

Abstract

Zirconolite is recognized as one of the most durable waste matrices for the disposal of high-level radioactive wastes (HLWs). In this study, HfO2 was employed as the surrogate of tetravalent actinides. Hf-bearing zirconolite-based composite waste forms (CaZr1-xHfxTi2O7) were rapidly prepared by combustion synthesis (CS) using CuO as the oxidant, where quick pressing (QP) was introduced to obtain densified samples. Similar as solid state reaction process, the Zr site of zirconolite can be totally occupied by Hf (x = 1.0) under the CS reaction. The original 2M zirconolite structure was maintained and a small amount of perovskite impurity phase was generated in the final products. The aqueous durability of representative sample (Cu-Hf-0.6) was tested, where the 42-day normalized leaching rates (LRi) of Ca, Cu, and Hf are 0.25, 3.10×10-2, and 1.11×10-8 g·m-2·d-1.

Keywords: combustion synthesis (CS), nuclear waste, HfO2, zirconolite, aqueous durability

References(45)

[1]
International Atomic Energy Agency. Design and operation of high level waste. Vitrification and storage facility. Technical Report Series No. 176. IAEA, Vienna, 1977.
[2]
MI Ojovan, WE Lee. Principles of nuclear waste management. In: An Introduction to Nuclear Waste Immobilisation. Elsevier, 2005: 71-79.
DOI
[3]
WJ Weber, A Navrotsky, S Stefanovsky, et al. Materials science of high-level nuclear waste immobilization. MRS Bull 2009, 34: 46-53.
[4]
AE Ringwood, SE Kesson, NG Ware, et al. Immobilisation of high level nuclear reactor wastes in SYNROC. Nature 1979, 278: 219-223.
[5]
HJ Matzke, ILF Ray, BW Seatonberry, et al. Incorporation of transuranic elements in titanate nuclear waste ceramics. J Am Ceram Soc 1990, 73: 370-378.
[6]
WE Lee, M Gilbert, ST Murphy, et al. Opportunities for advanced ceramics and composites in the nuclear sector. J Am Ceram Soc 2013, 96: 2005-2030.
[7]
ER Vance, CJ Ball, RA Day, et al. Actinide and rare earth incorporation into zirconolite. J Alloys Compd 1994, 213-214: 406-409.
[8]
RC Ewing, WJ Weber, J Lian. Nuclear waste disposal-Pyrochlore (A2B2O7): Nuclear waste form for the immobilization of plutonium and “minor” actinides. J Appl Phys 2004, 95: 5949-5971.
[9]
KB Zhang, GJ Wen, HB Zhang, et al. Self-propagating high-temperature synthesis of Y2Ti2O7 pyrochlore and its aqueous durability. J Nucl Mater 2015, 465: 1-5.
[10]
L Peng, KB Zhang, ZS He, et al. Self-propagating high-temperature synthesis of ZrO2 incorporated Gd2Ti2O7 pyrochlore. J Adv Ceram 2018, 7: 41-49.
[11]
KB Zhang, ZS He, L Peng, et al. Self-propagating synthesis of Y2-xNdxTi2O7 pyrochlore and its aqueous durability as nuclear waste form. Scripta Mater 2018, 146: 300-303.
[12]
KB Zhang, ZS He, JL Xue, et al. Self-propagating synthesis of Y2-xNdxTi2O7 pyrochlores using CuO as the oxidant and its characterizations as waste form. J Nucl Mater 2018, 507: 93-100.
[13]
DM Strachan, RD Scheele, EC Buck, et al. Radiation damage effects in candidate titanates for Pu disposition: Zirconolite. J Nucl Mater 2008, 372: 16-31.
[14]
RW Cheary. Zirconolite CaZr0.92Ti2.08O7 from 294 to 1173 K. J Solid State Chem 1992, 98: 323-329.
[15]
TJ White. The microstructure and microchemistry of synthetic zirconolite, zirkelite and related phases. Am Mineral 1984, 69: 1156-1172.
[16]
AA Coelho, RW Cheary, KL Smith. Analysis and structural determination of Nd-substituted zirconolite-4M. J Solid State Chem 1997, 129: 346-359.
[17]
GR Lumpkin. Alpha-decay damage and aqueous durability of actinide host phases in natural systems. J Nucl Mater 2001, 289: 136-166.
[18]
RC Ewing. Nuclear waste forms for actinides. P Natl Acad Sci USA 1999, 96: 3432-3439.
[19]
ER Vance. Synroc: A suitable waste form for actinides. MRS Bull 1994, 19: 28-32.
[20]
M Jafar, P Sengupta, SN Achary, et al. Phase evolution and microstructural studies in CaZrTi2O7-Nd2Ti2O7 system. J Am Ceram Soc 2014, 97: 609-616.
[21]
YC Teng, SL Wang, Y Huang, et al. Low-temperature reactive hot-pressing of cerium-doped titanate composite ceramics and their aqueous stability. J Eur Ceram Soc 2014, 34: 985-990.
[22]
Y Zhang, MWA Stewart, H Li, et al. Zirconolite-rich titanate ceramics for immobilisation of actinides—Waste form/HIP can interactions and chemical durability. J Nucl Mater 2009, 395: 69-74.
[23]
SK Sun, MC Stennett, CL Corkhill, et al. Reactive spark plasma synthesis of CaZrTi2O7 zirconolite ceramics for plutonium disposition. J Nucl Mater 2018, 500: 11-14.
[24]
M Muthuraman, KC Patil, S Senbagaraman, et al. Sintering, microstructural and dilatometric studies of combustion synthesized synroc phases. Mater Res Bull 1996, 31: 1375-1381.
[25]
TV Barinova, IP Borovinskaya, VI Ratnikov, et al. SHS immobilization of radioactive wastes. Key Eng Mater 2001, 217: 193-200.
[26]
G Cao, R Orrù. Self-propagating reactions for environmental protection: State of the art and future directions. Chem Eng J 2002, 87: 239-249.
[27]
XH Mao, ZG Qin, XN Yuan, et al. Immobilization of simulated radioactive soil waste containing cerium by self-propagating high-temperature synthesis. J Nucl Mater 2013, 443: 428-431.
[28]
KB Zhang, D Yin, PW Han, et al. Two-step synthesis of zirconolite-rich ceramic waste matrice and its physicochemical properties. Int J Appl Ceram Technol 2018, 15: 171-178.
[29]
KB Zhang, GJ Wen, HB Zhang, et al. Self-propagating high-temperature synthesis of CeO2 incorporated zirconolite-rich waste forms and the aqueous durability. J Eur Ceram Soc 2015, 35: 3085-3093.
[30]
KB Zhang, D Yin, L Peng, et al. Self-propagating synthesis and CeO2 immobilization of zirconolite-rich composites using CuO as the oxidant. Ceram Int 2017, 43: 1415-1423.
[31]
J Szajman, RSC Smart, S Myhra. X-ray photoelectron spectroscopy studies of valence states of cerium and uranium in SYNROC C. Surf Coat Technol 1987, 30: 333-342.
[32]
JP Holgado, R Alvarez, G Munuera. Study of CeO2 XPS spectra by factor analysis: Reduction of CeO2. Appl Surf Sci 2000, 161: 301-315.
[33]
JN Cachia, X Deschanels, C den Auwer, et al. Enhancing cerium and plutonium solubility by reduction in borosilicate glass. J Nucl Mater 2006, 352: 182-189.
[34]
E Curti, D Grolimund, CN Borca. A micro-XAS/XRF and thermodynamic study of CeIII/IV speciation after long-term aqueous alteration of simulated nuclear waste glass: Relevance for predicting Pu behavior? Appl Geochem 2012, 27: 56-63.
[35]
J Emsley. The Elements. Oxford: Clarendon Press, 1992.
[36]
DS Perera, MWA Stewart, HJ Li, et al. Tentative phase relationships in the system CaHfTi2O7-Gd2Ti2O7 with up to 15 mol% additions of Al2TiO5 and MgTi2O5. J Am Ceram Soc 2004, 85: 2919-2924.
[37]
RD Shannon. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst 1976, A32: 751-767.
[38]
ASTM C1220-98. Standard test method for static leaching of monolithic waste forms for disposal of radioactive waste. West Conshohocken, PA, USA, 1998.
[39]
D Caurant, P Loiseau, I Bardez. Structural characterization of Nd-doped Hf-zirconolite Ca1-xNdxHfTi2-xAlxO7 ceramics. J Nucl Mater 2010, 407: 88-99.
[40]
KL Smith, GR Lumpkin, MG Blackford, et al. The durability of synroc. J Nucl Mater 1992, 190: 287-294.
[41]
C Guittonneau, S Gin, N Godon, et al. A 25-year laboratory experiment on French SON68 nuclear glass leached in a granitic environment—First investigations. J Nucl Mater 2011, 408: 73-89.
[42]
YC Teng, SL Wang, Y Huang, et al. Low-temperature reactive hot-pressing of cerium-doped titanate composite ceramics and their aqueous stability. J Eur Ceram Soc 2014, 34: 985-990.
[43]
X Cai, YC Teng, L Wu, et al. The synthesis and chemical durability of Nd-doped single-phase zirconolite solid solutions. J Nucl Mater 2016, 479: 455-460.
[44]
ZS He, KB Zhang, L Peng, et al. Self-propagating plus quick pressing synthesis and characterizations of Gd2-xNdxTi1.3Zr0.7O7 (0 ≤ x ≤ 1.4) pyrochlores. J Nucl Mater 2018, 504: 61-67.
[45]
ZS He, KB Zhang, JL Xue, et al. Self-propagating chemical furnace synthesis of nanograin Gd2Zr2O7 ceramic and its aqueous durability. J Nucl Mater 2018, 512: 385-390.
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Publication history

Received: 22 January 2019
Revised: 23 April 2019
Accepted: 03 May 2019
Published: 31 July 2019
Issue date: September 2019

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© The author(s) 2019

Acknowledgements

We sincerely appreciate the projects supported by the National Natural Science Foundation of China (Nos. 51202203 and 51672228), the Project of State Key Laboratory of Environment-friendly Energy Materials (Nos. 16kffk05 and 17FKSY0104, Southwest University of Science and Technology), and Science Development Foundation of China Academy of Engineering Physics.

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