Encapsulation of Cs/Sr contaminated clinoptilolite in geopolymers produced from metakaolin

The encapsulation of caesium (Cs) and strontium (Sr) contaminated clinoptilolite in Na and K based metakaolin geopolymers is reported. When Cs or Sr loaded clinoptilolite is mixed with a metakaolin geopolymer paste, the high pH of the activating solution and the high concentration of ions in solution cause ion exchange reactions and dissolution of clinoptilolite with release of Cs and Sr into the geopolymer matrix. The leaching of Cs and Sr from metakaolin-based geopolymer has therefore been investigated. It was found that Na-based geopolymers reduce leaching of Cs compared to K-based geopolymers and the results are in agreement with the hard and soft acids and bases (HSAB) theory. Cs ions are weak Lewis acids and aluminates are a weak Lewis base. During the formation of the geopolymer matrix Cs ions are preferentially bound to aluminate phases and replace Na in the geopolymer structure. Sr uptake by Na-geopolymers is limited to 0.4 mol Sr per mole of Al and any additional Sr is immobilised by the high pH which causes precipitation of Sr as low solubility hydroxide and carbonate phases. There was no evidence of any other phases being formed when Sr or Cs are added to metakaolin geopolymers

Following the electroreduction of uranium dioxide to uranium in LiCl-KCl eutectic in situ using synchrotron radiation

The electrochemical reduction of uranium dioxide to metallic uranium has been investigated in lithium chloride–potassium chloride eutectic molten salt. Laboratory based electrochemical studies have been coupled with in situ energy dispersive X-ray diffraction, for the first time, to deduce the reduction pathway. No intermediate phases were identified using the X-ray diffraction before, during or after electroreduction to form α-uranium. This suggests that the electrochemical reduction occurs via a single, 4-electron-step, process. The rate of formation of α-uranium is seen to decrease during electrolysis and could be a result of a build-up of oxygen anions in the molten salt. Slow transport of O2− ions away from the UO2 working electrode could impede the electrochemical reduction

The future implications of shale gas developments and LNG exports from Australia

In recent years, LNG markets have become more competitive. Growing energy demand in Asia coupled with the loss of electricty from nuclear power generation in Japan after the Fukushima disaster have led to a thriving LNG market, currently headed by Australia but projected to include new supplies from the U.S., Canada and, potentially, Africa by 2020. Long-term oil-linked price contracts have so far benefited the Australian gas export industry. However, most of the new gas supplies will be based on spot-market prices. This study forecasts an increase of at least 6% by volume of Henry Hub based LNG into the Asian market by 2017 and for spot pricing to make up to 40% of the market. It is estimated that LNG exports from the U.S., based on current Henry Hub prices of less than $7/GJ, will be priced in the range of$12-14/GJ for the Asian market, making it more attractive to importers compared to prices likely in excess of $15/GJ from Australia. The disparity is largely due to the much higher operating and labour costs of the Australian LNG industry and it will put increasing pressure on the industry to change its business models and reduce its prices. In addition, increasing LNG exports from Australia have led to constraints on domestic gas supplies, leading to increases in the price of domestic gas as a result of the exposure to international markets. The development of unconventional gas resources and of conventional offshore gas resources with FLNG is perceived as a viable means to increase gas availability not only to the domestic market but also for export to the Asian market, thereby maintaining contracted obligations on supply. However, the potential of FLNG is not certain, with the “Prelude Project” predicted to come online only in 2017, and the success of unconventional gas is currently limited only to coal seam gas, despite a high level of controversy in relation to environmental impact and public protest. Australian shale gas faces many barriers, mainly due to the unique geology, high development costs, a lack of infrastructure and services, and community concerns. Therefore, there is a degree of uncertainty as to whether shale gas will ever become a significant component of Australian LNG exports. This study reviews the global LNG markets, in particular those in Asia, and makes some conclusions on the LNG export outlook for Australia