Frontiers in data analysis methods: from causality detection to data driven experimental design

On the route to the commercial reactor, the experiments in Magnetically Confinement Nuclear Fusion have become increasingly complex and they tend to produce huge amounts of data. New analysis tools have therefore become indispensable, to fully exploit the information generated by the most relevant devices, which are nowadays very expensive to both build and operate. The paper presents a series of innovative tools to cover the main aspects of any scientific investigation. Causality detection techniques can help identifying the right causes of phenomena and can become very useful in the optimisation of synchronisation experiments, such as the pacing of sawteeth instabilities with ICRH modulation. Data driven theory is meant to go beyond traditional machine learning tools, to provide interpretable and physically meaningful models. The application to very severe problems for the Tokamak configuration, such as disruptions, could help not only in understanding the physics but also in extrapolating the solutions to the next generation of devices. A specific methodology has also been developed to support the design of new experiments, proving that the same progress in the derivation of empirical models could be achieved with a significantly reduced number of discharges.

Research on Internal Fire Ignition Frequency of Fire Probability Safety Analysis in Small Module Reactor

The equipment number of Small module reactor (SMR) is significantly less than that of commercial reactor, and accordingly, the number of fixed fire ignition sources and the ignition frequency are much less. Based on the analysis of the design characteristics of Small Module Reactor, this paper develops a preliminary research and innovation on the internal fire ignition frequency evaluation method of Small Module Reactor, and implements a sensitivity analysis on the commercial reactor ignition frequency methods. The result indicates the fire ignition frequency would increase 51% if the NUREG/CR-6850 generic ignition frequency data are adopted. However, the design characteristics of SMR can be better reflected in this innovative method, which needs more attention in the future.

The EPRI PWR Supplemental Surveillance Program (PSSP) Final Design and Implementation

There is a lack of pressurized water reactor (PWR) surveillance program transition temperature shift and upper shelf toughness decrease data due to neutron irradiation exposure especially at high fluences indicative of 60 to 80 years of plant operation. The Electric Power Research Institute (EPRI) has funded the development of a supplemental reactor pressure vessel (RPV) surveillance program to allow testing of additionally irradiated specimens in two new capsules being installed in two different commercial reactor surveillance capsule positions. The previously irradiated materials were strategically selected and will be further irradiated to give final fluence levels equal to or above those for PWRs operating up to 80 years. This paper describes the final design of the capsules and selection of the key previously irradiated RPV materials reconstituted into new Charpy-size specimens being irradiated in the two PWR Supplemental Surveillance Program (PSSP) capsules.

Performance of nitrogen removal in attached growth reactors with different carriers

Two waste materials, concrete and sponge, were used as biomass carriers in the attached growth reactor in a nitrogen wastewater treatment system. The nitrogen removal performance was compared to a control reactor using commercial carrier material. The highest nitrogen removal efficiency, 87%, was found in the sponge reactor, with the concrete reactor showing 82% efficiency ahead of the commercial reactor of 76%. A thick biofilm developed on the fiber of the sponge carrier, with the biomass increasing from 270 g-VSS/m3-carrier to 1,000 g-VSS/m3-carrier. For the concrete carrier, biomass was observed on the concrete cracks and also as a biofilm on the surface. The maximal biomass was 630 g-VSS/m3-carrier. The content of the biomass agglomerated in the commercial carrier was 310 g-VSS/m3-carrier. Nitrification and denitrification simultaneously occurred to remove nitrogen in the sponge and the commercial carrier reactor. However, in the concrete reactor, nitrification mainly occurred during the aeration phase and denitrification occurred in the non-aeration phase. These results demonstrate that the sponge was the best carrier, with high nitrogen removal efficiency, dense biomass and tolerance to shock loading. The simplicity inherent in the system design together with good performance make it suitable for use in wastewater treatment systems.

Novel Syntrophic Populations Dominate an Ammonia-Tolerant Methanogenic Microbiome

ABSTRACT The microbial production of methane or “biogas” is an attractive renewable energy technology that can recycle organic waste into biofuel. Biogas reactors operating with protein-rich substrates such as household municipal or agricultural wastes have significant industrial and societal value; however, they are highly unstable and frequently collapse due to the accumulation of ammonia. We report the discovery of a novel uncultured phylotype (unFirm_1) that is highly detectable in metaproteomic data generated from an ammonia-tolerant commercial reactor. Importantly, unFirm_1 is proposed to perform a key metabolic step in biogas microbiomes, whereby it syntrophically oxidizes acetate to hydrogen and carbon dioxide, which methanogens then covert to methane. Only very few culturable syntrophic acetate-oxidizing bacteria have been described, and all were detected at low in situ levels compared to unFirm_1. Broader comparisons produced the hypothesis that unFirm_1 is a key mediator toward the successful long-term stable operation of biogas production using protein-rich substrates. Biogas reactors operating with protein-rich substrates have high methane potential and industrial value; however, they are highly susceptible to process failure because of the accumulation of ammonia. High ammonia levels cause a decline in acetate-utilizing methanogens and instead promote the conversion of acetate via a two-step mechanism involving syntrophic acetate oxidation (SAO) to H2 and CO2, followed by hydrogenotrophic methanogenesis. Despite the key role of syntrophic acetate-oxidizing bacteria (SAOB), only a few culturable representatives have been characterized. Here we show that the microbiome of a commercial, ammonia-tolerant biogas reactor harbors a deeply branched, uncultured phylotype (unFirm_1) accounting for approximately 5% of the 16S rRNA gene inventory and sharing 88% 16S rRNA gene identity with its closest characterized relative. Reconstructed genome and quantitative metaproteomic analyses imply unFirm_1’s metabolic dominance and SAO capabilities, whereby the key enzymes required for acetate oxidation are among the most highly detected in the reactor microbiome. While culturable SAOB were identified in genomic analyses of the reactor, their limited proteomic representation suggests that unFirm_1 plays an important role in channeling acetate toward methane. Notably, unFirm_1-like populations were found in other high-ammonia biogas installations, conjecturing a broader importance for this novel clade of SAOB in anaerobic fermentations. IMPORTANCE The microbial production of methane or “biogas” is an attractive renewable energy technology that can recycle organic waste into biofuel. Biogas reactors operating with protein-rich substrates such as household municipal or agricultural wastes have significant industrial and societal value; however, they are highly unstable and frequently collapse due to the accumulation of ammonia. We report the discovery of a novel uncultured phylotype (unFirm_1) that is highly detectable in metaproteomic data generated from an ammonia-tolerant commercial reactor. Importantly, unFirm_1 is proposed to perform a key metabolic step in biogas microbiomes, whereby it syntrophically oxidizes acetate to hydrogen and carbon dioxide, which methanogens then covert to methane. Only very few culturable syntrophic acetate-oxidizing bacteria have been described, and all were detected at low in situ levels compared to unFirm_1. Broader comparisons produced the hypothesis that unFirm_1 is a key mediator toward the successful long-term stable operation of biogas production using protein-rich substrates.