Glass - Back to the Future!

Presenting Author:

article posted 11 April 2016

Jae-Young Pyo 2015 POSTECH (M. S. candidate Nuclear Engineering)
2013 2015 Samsung Electro-Mechanics (Associate Research Engineer)
2006 2013 Hanyang Univ. (B. S. Materials Science and Engineering)

Tellurite glasses for immobilization of Tc-99 from pyro-processing technology

Jae-Young Pyo1*, Jae-Hwan Yang2, Hwan-Seo Park2, Jong Heo1
1Division of Advanced Nuclear Engineering and Department of Materials Science and Engineering, Pohang University of Science and Technology(POSTECH), 77 Cheongam-Ro. Nam-Gu. Pohang. Gyeongbuk, 790-784, Republic of Korea
2Korea Atomic Energy Research Institute, 1045 Daedukdaero, Yuseong, Daejeon 305-353, Republic of Korea

Pyro-processing is one of the nuclear reprocessing methods to reuse radioactive uranium and trans-uranium elements from the spent fuels. Tc-99 is the fission product existing in the spent fuels and needs to be firmly immobilized due to its high mobility and a long half-life [1]. In the off-gas treatment of the pyro-processing, Tc-99 is captured by calcium based filter and becomes Ca(TcO4)2 or Ca5Tc2O12 [2]. Vitrification of Tc-containing wastes is challenging because technetium is easily volatilized during the high temperature melting process [3]..

We investigated tellurite glasses as potential hosts for Tc-99 due to their low melting temperatures. The nominal composition (mass%) of the tellurite glass frit was 79.06TeO2 8.68Al2O3 5.39B2O3 3.84Na2O 3.04CaO. 20g batches were first melted in alumina crucibles for 30min at 800oC and these glass frits together with different amount of Ca(ReO4)2, a nonradioactive surrogate for Ca(TcO4)2, were mixed to form (100-x)[Glass frit powder]-xCa(ReO4)2 where x=3, 6, 9 and 12mass%. Total batches of 12g in weight were melted at 730oC for 20min and cooled by pouring on the brass mold at room temperature. (Fig. 1)

Compositions of glasses were analysed using ICP-AES. Re retention (= measured rhenium concentration in the fabricated glass divided by rhenium concentration in the nominal composition) reached to approximately 95%, that is considerably high compared to the retention of other rhenium-containing glass wastefoms [4]. Chemical durability test using 7days-product consistency test (PCT) showed good resistance against the attack of water. Up to 9mass% of Ca(ReO4)2 added, the normalized elemental releases values were within U.S requirement, 2g/m2. (Fig. 2)

Fig. 3 shows the Raman spectra of the tellurite glasses. Intensities of the 334, 900, 966 cm-1 peak increased as concentration of Ca(ReO4)2 increased. It suggests that Re ions in tellurite glass exist ReO4- ion state. Oxidation state and fine structure of Re ions analysed by X-ray absorption spectroscopy (XAS).

REFERENCES [1] K.V. Kotegov, O.N. Pavlov, V.P. Shvedov, Adv. Inorg. Chem. 11 (1968) 190.
[2] S. Frank, W. Ebert, B. Riley, H.S. Park, Y.Z. Cho, C.H. Lee, M.K. Jeon, J.H. Yang, H.C. Eun, INL/EXT-14-34014
[3] Ian L. Pegg, J. Radioanal. Nucl. Chem. 305:287-292,2015
[4] John S. McCloy, Environ. Sci. Technol. 2012, 46, 12616-12622