Abstract
ABSTRACT Ion-specific media (ISM) have played an integral role in the clean-up and remediation efforts at the Fukushima Dai-ichi disaster site, through the processing of contaminated wastewaters. The use of these materials generates a secondary nuclear waste stream, presenting its own series of engineering problems arising from stringent handling and long-term storage requirements. A reactive spark plasma sintering (SPS) method was investigated for conditioning of the spent cesium exchanged zeolite, chabazite. A natural form of the zeolite was used as an analogue to the engineered ISM used at the Fukushima NPP site. Simulant wasteforms were sintered using different temperature and pressure parameters followed by analysis of phase assemblage, density, and durability (using the product consistency test (PCT)). The results indicated that zeolite structure had collapsed completely, with the exchanged cesium partitioned primarily into a durable feldspar to assure stability of the sintered material for passively safe storage or geological disposal.
Highlights
The March 2011 earthquake and tsunami led to a series of serious coolant loss incidents at the Fukushima Daiichi nuclear power plant (NPP) [1]
The results indicated that zeolite structure had collapsed completely, with the exchanged cesium partitioned primarily into a durable feldspar to assure stability of the sintered material for passively safe storage or geological disposal
Microstructural characterisation and phase assemblage revealed the diverse mineral composition of a natural chabazite source used as a simulant for spent ion exchange media arising on the Fukushima NPP site
Summary
The March 2011 earthquake and tsunami led to a series of serious coolant loss incidents at the Fukushima Daiichi nuclear power plant (NPP) [1]. One method of effluent treatment is the use of ion exchange materials, such as zeolites. These microporous aluminosilicates are available commercially as mineral or synthetic materials, finding common usage in ion exchange as adsorbents. The individually unique structures of these media result in both high selectivity and specificity for ion exchange. To facilitate Cs removal from the contaminated coolant water, one of the main effluent treatment facilities installed on the Fukushima Daiichi NPP site is the KURION ion exchange plant, using engineered Na-chabazite as an exchange medium [2]. The high porosity of this material, based on a ~3.8 Å diameter “8-ring” framework structure, provides a large surface area for exchange with high selectivity for Cs [3,4]. As of October 2018, this facility has treated a cumulative Cs-contaminated water volume of
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