Closing the Nuclear Fuel Cycle with a Simplified Minor Actinide Lanthanide Separation Process (ALSEP) and Additive Manufacturing

Expanded low-carbon baseload power production through the use of nuclear fission can be enabled by recycling long-lived actinide isotopes within the nuclear fuel cycle. This approach provides the benefits of (a) more completely utilizing the energy potential of mined uranium, (b) reducing the footprint of nuclear geological repositories, and (c) reducing the time required for the radiotoxicity of the disposed waste to decrease to the level of uranium ore from one hundred thousand years to a few hundred years. A key step in achieving this goal is the separation of long-lived isotopes of americium (Am) and curium (Cm) for recycle into fast reactors. To achieve this goal, a novel process was successfully demonstrated on a laboratory scale using a bank of 1.25-cm centrifugal contactors, fabricated by additive manufacturing, and a simulant containing the major fission product elements. Americium and Cm were separated from the lanthanides with over 99.9% completion. The sum of the impurities of the Am/Cm product stream using the simulated raffinate was found to be 3.2 × 10−3 g/L. The process performance was validated using a genuine high burnup used nuclear fuel raffinate in a batch regime. Separation factors of nearly 100 for 154Eu over 241Am were achieved. All these results indicate the process scalability to an engineering scale

A review of acid recovery from acidic mining waste solutions using solvent extraction

This is the peer reviewed version of the following article: Uchenna Kesieme, Andreas Chrysanthou, Maurizio Catulli, and Chu Yong Cheng, ‘A review of acid recovery from acidic mining waste solutions using solvent extraction’, Journal of Chemical Technology and Biotechnology, (2018), which has been published in final form at https://doi.org/10.1002/jctb.5728. Under embargo until 1 July 2019. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The minerals industry is increasingly being forced by regulatory and cost pressures to reduce the amount of liquid acidic waste they produce. This requires a strong focus on waste reduction by recycling, regeneration and reuse. Four mineral acids were examined for recovery from waste acidic solutions including H 2SO 4, HNO 3, HCl, and H 3PO 4. The selection of the optimal extractant for acid recovery was based on extraction, stripping and scrubbing efficiencies. The extractants suitable for the recovery of H 2SO 4 and HCl are in the order of TEHA > Cyanex 923 > TBP > Alamine 336. TEHA has the highest degree of acid extraction and stripping compared with Cyanex 923 and almost 99% of the acid can be stripped. Alamine 336 can extract higher acid (for H 2SO 4 and HCl systems) than Cyanex 923 and TBP. However loaded acid for Alamine 336 system cannot be stripped using water at 60°C. For the recovery of nitric and phosphoric acids from acidic waste effluents, TBP was the best option. This work clearly demonstrates that extractant suitable for acid extraction may not be suitable for its recovery. However such extractant may be applied for the removal of acid from any waste acidic solution sacrificing the back extraction of the loaded acid. The effective implementation of options for acid recovery was examined to improve sustainability in the mineral industry.Peer reviewe

Combined material flow analysis and life cycle assessment as a support tool for solid waste management decision making

AbstractMaterial flow analysis (MFA) and life cycle assessment (LCA) have both widely been applied to support solid waste management (SWM) decision making. However, they are often applied independently rather than conjointly. This paper presents an approach that combines the MFA and LCA methodologies to evaluate large and complex SWM systems from an environmental perspective. The approach was applied to evaluate the environmental performance, focusing on greenhouse gas (GHG) emissions, of a local authority SWM system and to compare it with alternative systems to assess the potential effectiveness of different waste policy measures. The MFA results suggest that national recycling targets are unlikely to be met even if the assessed policies are implemented optimally. It is likely that for the targets to be met, investigated policies would need to be combined with additional policies that target reductions in waste arisings. The LCA results found landfilling of residual waste to be the dominant source of GHG burdens for the existing system, whilst material reprocessing was found to result in GHG benefits. Overall, each of the alternative systems investigated were found to result in lower GHG impacts compared to the existing system, with the diversion of food waste from the residual waste stream found to be potentially the most effective strategy to reduce GHG emissions. The results of this study demonstrate that the complementary methodologies of MFA and LCA can be used in combination to provide policy and decision makers with valuable information about the environmental performance of SWM systems

Separation of Fluoride Residue Arising from Fluoride Volatility Recovery of Uranium from Spent Nuclear Fuel

The overall objective of this study was to support an alternative hybrid process to meet Advanced Fuel Cycle Initiative (AFCI) goals, using fluorination and aqueous processing techniques, for treatment of spent nuclear fuel (SNF). The specific goal was to develop a simple aqueous dissolution process to separate two high-heat fission products, cesium and strontium, from SNF fluoride residues. This separation study was based on solubility differences examined by modeling using the HSC Chemistry 5.0 and OLI Stream Analyzer 1.2 programs. HSC automatically utilizes an extensive thermochemical database, which contains enthalpy (H), entropy (S), and heat capacity (Cp) data for more than 17,000 chemical compounds. The OLI Stream Analyzer 1.2 program is the result of over 30 years of effort and represents the state-of-the-art technology in aqueous solution simulation. The work focused on the fluoride residues from the voloxidation and fluorination steps of the fluoride volatility process and was limited to SNF from commercial light-water reactors. Material balances were used to estimate the quantity of residue. A representative SNF was considered to be one with a burnup of 33,000 megawatt days per metric tonne initial heavy metal (MWd/MTIHM) after a 10-year cooling period, from a pressurized-water reactor (PWR). The dry fluorination method was used for uranium removal. The work described in this paper was based solely on computer modeling, which may serve as the basis for any necessary follow-on laboratory validation experiments. Observations from this study showed that the separation of fluoride residues by a simplified, alternative aqueous process is practical. The simulated process could be carried out at 1 atm and 30-50oC. The OLI model showed separation of cesium and strontium was possible with only one dissolution with water, whereas the HSC model indicated two dissolutions would be required. Plutonium and Np were removed together, which would maintain proliferation resistance. Because this research was based on computer modeling, follow-on laboratory experiments are necessary to validate the results and to improve the process flow diagram. Further development of the process flow diagram, with equipment design and cost estimation, is also recommended

Supply chain challenges for sustainability: the case of waste textiles as raw materials

Purpose: This paper addresses the growing problem of textile waste in the rapidly developing cities of subSaharan Africa and examines, from a supply chain perspective, the potential for waste textile materials to be transformed into the raw materials for new consumer products. Research Approach: The paper reflects on the outcomes of a field trip to Dar es Salaam in which stakeholders in a hypothesised textile waste supply chain were interviewed and waste textile materials were analysed in order to determine their content and appropriateness for reuse. Findings from the field study have been compared with current literature on logistics and market creation, waste generation, management and recycling in sub-Saharan Africa. Findings and Originality: The findings show that a rudimentary system has been in place for many years to collect and recycle textiles in Dar es Salaam. However, at the same time as textile waste is projected to increase in the city, collection rates are falling. The chief reasons for the falling rates are failures in the ‘modernised mixture’ approach to waste collection employed by Dar es Salaam City Council and market failure for the collected materials. Alternative combinations of ‘modernised mixtures’, incorporating community-based organisations, are likely to increase textile yields from unplanned urban areas but previous high-profile failures in such systems within Dar es Salaam mean there is caution on both sides in entering into such a relationship. The more pressing problem is to identify appropriate end markets for the textile materials, since in a country where recycling is entirely market-driven, failure to do so will undermine any attempt to improve the collection system. Whilst many studies have considered general recycling practices in sub-Saharan Africa, there are few investigations into textile waste. Furthermore, those existing studies do not consider the importance of understanding fibre composition of the materials in order to determine the most appropriate end markets. Research Impact: The research contributes to the growing body of knowledge on ‘bottom of the pyramid’ approaches to sustainable futures. Practical Impact: The work presented considers supply chain problems and offers approaches to tackling the increasing waste management issues of Dar es Salaam and proposes a mechanism for doing so which has the potential to provide income for the poorest sectors of the urban society

Process intensification applied to spent nuclear fuel reprocessing: An alternative flowsheet using small channels

Commercial plants for spent nuclear fuel reprocessing rely on the Plutonium Uranium Extraction (PUREX) process, based on traditional liquid–liquid extraction technologies. In this paper, an alternative flowsheet for spent nuclear fuel reprocessing is proposed, based on small-scale extractors to overcome some of the issues related to the conventional technologies, such as solvent degradation, size and nuclear criticality control. The main goal of the process is to preclude the risk of nuclear proliferation, hence a mixed uranium/plutonium oxide is produced instead of pure plutonium. A superstructure optimisation based framework has been used to identify a process with several benefits over the conventional process. Novel flow configurations and organic solvent composition have been investigated. A large number of components and chemical reactions are included in the framework. The resulting model is a mixed integer nonlinear optimisation problem, implemented in the General Algebraic Modeling System (GAMS). The most promising flowsheet identified is more cost effective than the conventional one. Furthermore, advantages in terms of safety and separation efficiency have been achieved. It was found that increasing the inner diameter of the small channels up to 2.5 mm, as well as increasing the tributyl phosphate fraction in the organic solvent, are advantageous

Parametric study of prospective early commercial MHD power plants (PSPEC). General Electric Company, task 1: Parametric analysis

The performance and cost of moderate technology coal-fired open cycle MHD/steam power plant designs which can be expected to require a shorter development time and have a lower development cost than previously considered mature OCMHD/steam plants were determined. Three base cases were considered: an indirectly-fired high temperature air heater (HTAH) subsystem delivering air at 2700 F, fired by a state of the art atmospheric pressure gasifier, and the HTAH subsystem was deleted and oxygen enrichment was used to obtain requisite MHD combustion temperature. Coal pile to bus bar efficiencies in ease case 1 ranged from 41.4% to 42.9%, and cost of electricity (COE) was highest of the three base cases. For base case 2 the efficiency range was 42.0% to 45.6%, and COE was lowest. For base case 3 the efficiency range was 42.9% to 44.4%, and COE was intermediate. The best parametric cases in bases cases 2 and 3 are recommended for conceptual design. Eventual choice between these approaches is dependent on further evaluation of the tradeoffs among HTAH development risk, O2 plant integration, and further refinements of comparative costs