Densification of Inert Matrix Fuels Using Naturally-occurring Material as a Sintering Additive
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1215-V09-04
Densification of Inert Matrix Fuels Using Naturally-occurring Material as a Sintering Additive S. Miwa1, M. Osaka, T. Usuki2 and T. Yano2 1 Oarai Research and Development Center, Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Higashi-ibaraki-gun, Ibaraki, 311-1393. 2 Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8550, Japan ABSTRACT We proposed a new concept for densification of inert matrix fuels containing minor actinides. In this concept, magnesium silicates which are both a naturally-occurring material and asbestos waste were used as a sintering additive which protects public health by safely disposing of the asbestos waste. In this study, the effects of magnesium silicate additives on the densification behaviors of MgO, Mo and CeO2 were experimentally investigated. The densities of MgO and CeO2 pellets increased with only 1 wt.% additives of MgSiO3 and Mg2SiO4. The densities of Mo pellets showed little change with additives. INTRODUCTION Inert matrix fuels (IMFs) with a high content of minor actinides (MAs) are currently considered as one promising option for the rapid incineration of MAs in a future fast reactor cycle system [1-5]. IMFs are a composite of MA host phase and an inert matrix (IM). Magnesium oxide (MgO) and molybdenum (Mo) are considered to be promising candidates for an IM material [1-5]. These IMs were selected based on their high manufacturability, good chemical and physical stability, high melting temperature, and relatively high thermal conductivity. We proposed a new concept for densification of IMFs with Mo and MgO by using asbestos waste as a sintering additive. This concept should contribute especially to the protection of public health (i.e. by disposing of the toxic asbestos waste through its use in the IMFs) in addition to the reduction of environmental burden (i.e. by burning the MAs). Additionally, among the MAs, americium (Am) was found to have high volatility [6], and the lowing the sintering temperature is required to prevent Am loss during sintering. In our concept, magnesium silicates such as enstatite (MgSiO3) and forsterite (Mg2SiO4) are used as sintering additive to achieve high-performance IMFs having a high density at relatively low temperature sintering. These substances are naturally-occurring materials and found to be formed by the decomposition of asbestos in a relatively low temperature heat-treatment [7]. In this study, we experimentally investigated the effects of magnesium silicate additives on densification of component materials of IMFs, i.e. host phase and inert matrix, for the purpose of establishing a sophisticated fabrication procedure for MA-containing IMF based on powder metallurgy techniques. Cerium (Ce) oxide was chosen to simulate MAs oxide host phase.
EXPERIMENTAL The fabrication procedure was based on powder metallurgy techniques. Table 1 shows the fundamental specifications of raw powders. MgSiO3 and Mg2SiO4 were milled by planetary ball-milling for 20 min at 6
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