An overview of Thorium Utilization in Nuclear Reactors and Fuel Cycle

The Nuclear Power Plants (NPP) constructed in the XX century, also called generation II reactors, are still in operation, most of them Light Water Reactors, but are being decommissioned. These reactors have a low burn up (~30 MWD/kg U) and utilize UO2 as nuclear fuel and are operating in a Once Through Cycle (OTC); they use a very low energy content of the natural resources (~0,5%). To overcome economic and political and partly safety issues, since the end of last century, and beginning of this century, the nuclear industry launched a new generation of evolutionary reactors, called Generation III, such as the Westinghouse AP 1000, and AREVA EPR. These reactors still use uranium as primary source but have an increased burn up (~60 MWD/Kg U), which although increasing the utilization of the natural resources (up to 1%), still are not significant to be considered sustainable: if only uranium is used in an OTC, uranium will be exhausted in this century. To increase the utilization of natural resources, recycling of uranium and plutonium is already in use in many countries and used as Mixed Oxide of U-Pu fuel (MOX) in the same thermal reactors. To turn nuclear energy sustainable, a long-term deployment of innovative reactors is underway. These reactors and their associated fuel cycle are old concepts with technological improvements and generically denominated as Generation IV, are in development and, in some cases, they are breeders, HLW burners, and efficient concepts. Another concept that although not new is constitute by the Small Modular Reactors (SMR), with power less than 300 MWe, which nowadays are deserving a lot of attention by the nuclear industry. Another option is to utilize thorium as a primary source of energy. Although not fissile at thermal energy, it produces 233U, which is one of best fissile nuclide (number of neutrons produced per neutron absorbed). Also, it is three times more abundant than uranium in the earth crust and has thermal physics properties when used as (U-Th) O2 better than UO2. Several Th/U fuel cycles, using thermal and fast reactors were proposed and are still under investigation. Although, the first reactors to utilize thorium were PWR, using (U-Th)O2, such as the Indian Point, and Shipping Port, thorium has been proposed as fuel for the molten salt reactor, the advanced heavy water reactor, High Temperature Reactors, Pebble Bed reactor, fast breeder reactors, and more recently, for the innovative accelerator driven system in a double strata fuel cycle and for the Generation IV, such as the LFTR - Liquid Fluoride Thorium Reactor, which is a self-sustainable Molten Salt Reactor, promising to turn nuclear energy by fission in a sustainable source, with a utilization of the natural resources of 100%. This paper, besides an introduction of the present time uranium fuel cycles, will give an over view of the thorium utilization in nuclear reactors and fuel cycles, with an emphasis in Advanced PWR

Conversion of Small Modular Reactors Fuel to Use Mixed (U-Th)O2 Fuel

The concept of Integral Small Modular Reactor (SMR) isn’t new but it seems that the proper time for using this idea has been coming. According to the International Atomic Energy Agency (IAEA), the reactors with electrical power lower than 300 MW have been defined as small reactors, although SMRs are categorized by this fact that more advantages and design features are attained when intentionally make reactors small. In fact, these reactors use their size as advantage to attain more design purposes. The scalability, modularity, improved safety characteristics and more important than other, lower up-front cost of the SMRs, offer great advantages over large common nuclear power plants. According to the IAEA reports there are many interests all over the world to move toward using of these kinds of reactors. There are many different type of SMRs under various stages of design, licensing and construction. Nowadays, there are many initiatives to use thorium in nuclear reactors and fuel cycles. Thorium is three times more abundance than Uranium, however, despite of several initiatives and researches on Th-232 utilization in many types of reactors, this fuel hasn’t been commercialized yet. Most of The SMRs have been designed to have long cycle, so they must use a lot of poisoning material in the beginning of the cycle. Taking in the account that Thorium can be used as a absorber in the beginning of the cycle and also be used as a fertile material during the cycle, it seems to be a good option to use mixed (U-Th)O2 as SMR’s fuel. This paper briefly is going to review the research about Thorium utilization as a nuclear fuel and the possibilities of using mixed (U-Th)O2 fuel as an alternative option for SMRs fuel. The Korean System Integrated Modular Advanced Reactor (SMART) categorized as SMR that has received its standard design approval, was chosen as reference core for our calculations. The calculations have been performed by MCNPX code as a well-known Monte Carlo code. Geometry and all materials were kept the same as the SMART core, and the only variable was the fuel pin material, in which we use several mass proportion of uranium and thorium but keeping the enrichment in U-235, lower than 5 wt%. The results confirm that it’s possible to use mixed (U-Th)O2 with lower burnable absorber at the beginning of the cycle and have a longer burnup cycle

General rules for bosonic bunching in multimode interferometers

We perform a comprehensive set of experiments that characterize bosonic bunching of up to 3 photons in interferometers of up to 16 modes. Our experiments verify two rules that govern bosonic bunching. The first rule, obtained recently in [1,2], predicts the average behavior of the bunching probability and is known as the bosonic birthday paradox. The second rule is new, and establishes a n!-factor quantum enhancement for the probability that all n bosons bunch in a single output mode, with respect to the case of distinguishable bosons. Besides its fundamental importance in phenomena such as Bose-Einstein condensation, bosonic bunching can be exploited in applications such as linear optical quantum computing and quantum-enhanced metrology.Comment: 6 pages, 4 figures, and supplementary material (4 pages, 1 figure

Long-Term Efficacy of Intensive Zoledronate Therapy and Predictors of Retreatment in Paget’s Disease of Bone

Despite the current debate on the best therapeutic approach, i.e. symptomatic vs intensive strategy, one zoledronate (Zol) infusion is effective in most patients with Paget’s disease of bone (PDB), whereas few need retreatment, whose predictors are not well established. We aimed to evaluate long-term efficacy of intensive Zol therapy and predictors of retreatment in PDB. Pagetic complications, clinical and biochemical response to Zol together with frequency of retreatment were retrospectively assessed in forty-seven PDB patients (age, mean ± SD: 72.5 ± 8.9 years, M/F: 24/23; symptomatic/asymptomatic: 16/31). Statistical analysis for retreatment prediction were based on Mann–Whitney U test, Pearson’s Χ2 and ROC curve analysis. During seven-year follow-up, all patients achieved pain relief and only one underwent arthroplasty. Bone alkaline phosphatase (BAP) detected three non-responder (6%) and six relapsing (13%) patients needing retreatment. Retreated patients had less old age (66.1 ± 11.2 vs 74.0 ± 7.7 years), higher frequency of polyostotic disease (78% vs 40%) and higher baseline (96.5 ± 24.8 vs 44.9 ± 27.7 mcg/l) and post-Zol nadir BAP levels (24.7 ± 24.1 vs 8.1 ± 4.1 mcg/l) than patients treated once (p < 0.05 for all comparisons). In multivariate analysis both serum baseline and post-Zol nadir BAP significantly predicted retreatment (OR 1.09, 95%CI 1.01–1.17 and 1.29, 1.03–1.62, respectively), with ROC curve analysis showing the greatest accuracies for threshold values of 75.6 and 9.9 mcg/l (sensitivity 88 and 90%, specificity 94 and 86%, AUC 0.92 and 0.93, respectively). Our data in mostly asymptomatic, metabolically active PDB patients treated with intensive Zol therapy show a negligible incidence of pagetic complications and long-term optimal disease control, with BAP being the best predictor of retreatment

Expanded Total Equivalent Warming Impact analysis on experimental standalone fresh-food refrigerator

The stand-alone refrigerators for fresh food storage represent a large part of supermarket refrigeration equip-ment. In these devices, the usage of refrigerants with low Global Warming Potential allows the mitigation of the direct emissions due to refrigerant leakages. In contrast, the indirect emissions in these components are highly dependent on the refrigerant charge, leakage, and equivalent emission factors related to the electricity pro-duction mix. The most used index to evaluate the environmental impact of refrigerators is the Total Equivalent Warming Impact. Despite that this index presents limits on the fixed evaluation of many parameters such as refrigerant charge, electricity consumption and, electricity emission factor. Otherwise in this study, an accurate evaluation of refrigerators emissions has been realised by using the innovative Expanded Total Equivalent Warming Impact method to an experimental stand-alone refrigerator by using a dynamic approach to evaluate direct and indirect contributions. The environmental analysis considers four different refrigerants and four different countries of location. The results show that the indirect emissions due to electricity consumption cover the highest share of emissions. In addition, the operating years affected by low refrigerant charges are respon-sible for emissions by greater than 25% compared to other ones. The hourly equivalent emissions due to elec-tricity consumption in countries characterized by an electricity generation mix mainly based on renewable and/ or nuclear plants show an indirect environmental impact up to 5 times lower than countries with a natural gas -based electricity production mix. The study also defines new strategies to reduce the environmental impact of the stand-alone refrigerator such as the use of photovoltaic systems combined with this technology or earlier maintenance processes that could determine an equivalent emission saving of up to 38%

Small modular reactor full scope core optimization using Cuckoo Optimization Algorithm

Small Modular Reactors (SMRs) with their excellent safety and economic features will be in high demand in the near future. Most SMR designs have longer burn-up cycle length with more fuel enrichment and smaller core size in comparison to the large conventional nuclear reactors. The small size of these reactors causes more neutron leakage (less core radius results in a higher area to volume ratio and more relative leakage). This feature of SMRs causes high values of maximum Power Peaking Factors (PPFs) through the core, so optimizing the safety parameters is of high necessity. Also, long burn-up cycle length needs a high initial excess reactivity, which results into use of some materials and methods to control this high excess reactivity. One of these methods is using a high number of Integral Fuel Burnable Absorber (IFBA) rods.In the present designs of IFBA rods, usually some amounts of fuel with lower enrichment are used at the top and bottom parts of the IFBA rods (known as cutback fuel) to flatten the axial PPFs. The small size of the SMRs (using a lower number of FAs) helps to have much less possible radial loading patterns (in comparison to the large reactors) and provides the possibility to optimize the axial variations in amounts of cutback fuel in IFBA rods simultaneously. Accordingly, the best axial and radial loading pattern according to the objective functions could be achieved. At the present work, the main goal is to optimize radial core loading pattern and axial variations of cutback fuel lengths at the IFBA rods of an SMR simultaneously using a multi-objective neutronic and thermal-hydraulic fitness function. The multi-objective fitness function includes burn-up cycle length, Minimum Departure from Nucleate Boiling (MDNBR), maximum and average radial and axial PPFs during the entire cycle lengths. The Cuckoo Optimization Algorithm (COA) as a new robust metaheuristic algorithm with high convergence speed and global optima achievement has been used. For the thermo-neutronic calculation, DRPACO package consists of the coupling system of DRAGON/ PARCS/COBRA codes have been used. Finally, the results of SMR core axial and radial loading pattern optimization using COA presents a core configuration with improvement in the core safety and economic parameters in comparison to the reference SMR cor

Phospholipid hydroperoxide glutathione peroxidase is the 18-kDa selenoprotein expressed in human tumor cell lines.

Human tumor cell lines cultured in 75Se-containing media demonstrate four major 75Se-labeled cellular proteins (57, 22, 18, and 12 kDa) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Among these selenoproteins, an enzymatic activity is known only for the 22-kDa protein, since this protein has been identified as the monomer of glutathione peroxidase. However, all tested cell lines also contained a peroxidase activity with phospholipid hydroperoxides that is completely accounted for by the other selenoenzyme, phospholipid hydroperoxide glutathione peroxidase (PHGPX) (Ursini, F., Maiorino, M., and Gregolin, C. (1985) Biochim. Biophys. Acta 839, 62-70). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography of 75Se-labeled proteins separated by gel permeation chromatography supported the identification of PHGPX as the monomeric protein matching the 18 kDa band. This paper is the first report on the identification of PHGPX in human cells

A Comprehensive Energy Model for an Optimal Design of a Hybrid Refrigerated Van

The path towards decarbonization requires a progressive adaptation of all refrigeration systems, but only stationary ones have been intensely studied to improve their environmental performance. However, refrigerated transport is vital in the cold chain and must be considered in the green transition. In this paper, we propose a model for a hybrid refrigerated van that includes photovoltaic panels and electric batteries to decrease total greenhouse gas emissions from the engine. Thermal, electrical, and battery sub-models are considered and integrated into the comprehensive hybrid solar-powered refrigerated van model. Different technologies are compared, including lithium and lead-acid batteries and three different types of photovoltaic panels. The model was validated regarding van fuel consumption, showing a 4% deviation. Single and multiple delivery scenarios are considered to assess the energy, economic, and environmental benefits. Monthly CO2,e emissions could be reduced by 20% compared to a standard refrigerated van. Despite the environmental benefits provided by this sustainable solution, the payback period is still too long (above 20 years) because of the necessary investment to adapt the vehicle and considering fuel and electricity prices currently

IL4 induces IL6-producing M2 macrophages associated to inhibition of neuroinflammation in vitro and in vivo

Background: Myeloid cells, such as macrophages and microglia, play a crucial role in neuroinflammation and have been recently identified as a novel therapeutic target, especially for chronic forms. The general aim would be to change the phenotype of myeloid cells from pro- to anti-inflammatory, favoring their tissue-trophic and regenerative functions. Myeloid cells, however, display a number of functional phenotypes, not immediately identifiable as pro- or anti-inflammatory, and associated to ambiguous markers. Methods: We employed in vitro assays to study macrophage polarization/differentiation in the presence of classical polarizing stimuli such as IFNγ (pro-inflammatory) and IL4 (anti-inflammatory). We induced neuroinflammation in mice by immunization with a myelin antigen and treated diseased mice with intracisternal delivery of an IL4-expressing lentiviral vector. We analyzed clinical, pathological, and immunological outcomes with a focus on myeloid cells. Results: We found that IL6, usually considered a pro-inflammatory cytokine, was released in vitro by macrophages treated with the anti-inflammatory cytokine IL4. We show the existence of macrophages expressing IL6 along with classical anti-inflammatory markers such as CD206 and demonstrate that these cells are immunosuppressive in vitro. In neuroinflamed mice, we show that IL4 delivery in the central nervous system (CNS) is associated with clinical and pathological protection from disease, associated with increased IL6 expression in infiltrating macrophages. Conclusions: IL6 is known to mediate both pro- and anti-inflammatory effects, having two distinct ways to induce cell-signaling: either through the membrane bound receptor (anti-inflammatory) or through trans-signaling (pro-inflammatory). We show here that IL6-expressing macrophages are associated to protection from neuroinflammation, suggesting that IL6 anti-inflammatory properties prevail in the CNS, and calling for a general reconsideration of IL6 in macrophage polarization