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1. Benchmarking an AI-Guided Reasoning-Based Operator Support System on the Three Mile Island Accident Scenario

   https://doi.org/10.1115/ICONE2020-16400  

   Hanna, Botros N.; Son, Tran C.; Dinh, Nam T. (August 2020, Proceedings of the 28th Conference on Nuclear Engineering)

   null (Ed.)

   Abstract In the Nuclear Power Plant (NPP) control room, the operators’ performance in emergencies is impacted by the need to monitor many indicators on the control room boards, the limited time to interact with dynamic events, and the incompleteness of the operator’s knowledge. Recent research has been directed toward increasing the level of automation in the NPP system by employing modern AI techniques that support the operator’s decisions. In previous work, the authors have employed a novel AI-guided declarative approach (namely, Answer Set Programming (ASP)) to represent and reason with human qualitative knowledge. This represented knowledge is structured to form a reasoning-based operator support system that assists the operator and compensates for any knowledge incompleteness by performing reasoning to diagnose failures and recommend executing actions in real time. A general ASP code structure has been proposed and tested against simple scenarios, e.g., diagnosis of pump failures that result in loss of flow transients and generating the needed plans for resolving the issue of stuck valves in the secondary loop. In this work, we investigate the potential of the previously proposed ASP structure by applying ASP to a realistic case study of the Three Mile Island, Unit 2 (TMI-2) accident event sequence (in particular, the first 142 minutes). The TMI scenario presents many challenges for a reasoning system, including a large number of variables, the complexity of the scenario, and the misleading readings. The capability of the ASP-based reasoning system is tested for diagnosis and recommending actions throughout the scenario. This paper is the first work to test and demonstrate the capability of an automated reasoning system by applying it to a realistic nuclear accident scenario, such as the TMI-2 accident. 

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2. Assessing the effect of topography on Cs-137 concentrations within forested soils due to the Fukushima Daiichi Nuclear Power Plant accident, Japan

   https://doi.org/10.5194/esurf-9-861-2021  

   Yasumiishi, Misa; Nishimura, Taku; Aldstadt, Jared; Bennett, Sean J.; Bittner, Thomas (January 2021, Earth Surface Dynamics)

   Abstract. Topographic effects on Cs-137 concentrations in a forested area were quantitatively examined using 58 soil core samples collected in a village in Fukushima, Japan, which was directly impacted by the radioactive plume emitted during the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In this study, five topographic parameters and two soil properties were evaluated as controls on the soil Cs-137 concentration using generalized additive models (GAMs), a flexible statistical method for evaluating the functional dependencies of multiple parameters. GAMs employing soil dry bulk density, mass water content, and elevation explained 54 % of the observed concentrations of Cs-137 within this landscape, whereas GAMs employing elevation, slope, and upslope distance explained 47 % of the observed concentrations, which provide strong evidence of topographic effects on Cs-137 concentrations in soils. The model fit analysis confirmed that the topographic effects are strongest when multiple topographic parameters and soil properties are included. Theability of each topographic feature to predict Cs-137 concentrations wasinfluenced by the resolution of the digital elevation models. The movementof Cs-137 into the subsurface in this area near Fukushima was faster incomparison to regions affected by the Chernobyl Nuclear Power Plant accident. These results suggest that the effects of topographic parametersshould be considered carefully in the use of anthropogenic radionuclides asenvironmental tracers and in the assessment of current and futureenvironmental risks due to nuclear power plant accidents. 

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3. Priorities and Considerations in Advancing the Training of Nuclear Reactor Operators Through Mixed Reality

   Jain, Eakta; Enqvist, Andreas (January 2021, American Nuclear Society Winter Meeting and Technology Expo)

   Nuclear reactor safety is unique in that even after an incident is identified and the reactor shut down, the possibility of damage to people and environment does not stop: there is a long tail to the incident due to decay heat and potential for radiation leakage, which must also be contained properly, as exemplified in Fukushima where most radiation releases happened after initial earthquake and plant shut-down. Nuclear reactors generate close to 20% of the energy required by our nation. There is increasing interest in nuclear power as a low emissions alternative to fossil fuel-based power. Investments in the next generation of nuclear power plants include many nuclear startups such as NuScale and high-profile investments by Bill Gates’ Terra Power. Nuclear reactor operators are critical personnel who operate nuclear reactors, monitor the health of the operation, and are the first line of defense in case of an incident. Though the Nuclear Regulatory Commission creates and maintains standards and procedures for nuclear safety, their programmatic mandate involves are focused on existing technology, in the form of commercial nuclear power plants and other uses of nuclear materials through licensing, inspection and enforcement activities. This report summarizes the collected thoughts and insights from a diverse working group on the intersection of next generation technology with the training of future nuclear reactor operators. 

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4. Out of Sight, Out of Mind: Widespread Nuclear and Plastid-Nuclear Discordance in the Flowering Plant Genus Polemonium (Polemoniaceae) Suggests Widespread Historical Gene Flow Despite Limited Nuclear Signal

   https://doi.org/10.1093/sysbio/syaa049  

   Rose, Jeffrey P; Toledo, Cassio A; Lemmon, Emily Moriarty; Lemmon, Alan R; Sytsma, Kenneth J; Carstens, Bryan (July 2020, Systematic Biology)

   Abstract Phylogenomic data from a rapidly increasing number of studies provide new evidence for resolving relationships in recently radiated clades, but they also pose new challenges for inferring evolutionary histories. Most existing methods for reconstructing phylogenetic hypotheses rely solely on algorithms that only consider incomplete lineage sorting (ILS) as a cause of intra- or intergenomic discordance. Here, we utilize a variety of methods, including those to infer phylogenetic networks, to account for both ILS and introgression as a cause for nuclear and cytoplasmic-nuclear discordance using phylogenomic data from the recently radiated flowering plant genus Polemonium (Polemoniaceae), an ecologically diverse genus in Western North America with known and suspected gene flow between species. We find evidence for widespread discordance among nuclear loci that can be explained by both ILS and reticulate evolution in the evolutionary history of Polemonium. Furthermore, the histories of organellar genomes show strong discordance with the inferred species tree from the nuclear genome. Discordance between the nuclear and plastid genome is not completely explained by ILS, and only one case of discordance is explained by detected introgression events. Our results suggest that multiple processes have been involved in the evolutionary history of Polemonium and that the plastid genome does not accurately reflect species relationships. We discuss several potential causes for this cytoplasmic-nuclear discordance, which emerging evidence suggests is more widespread across the Tree of Life than previously thought. [Cyto-nuclear discordance, genomic discordance, phylogenetic networks, plastid capture, Polemoniaceae, Polemonium, reticulations.] 

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5. Spatial chloroplast-to-nucleus signalling involving plastid–nuclear complexes and stromules

   https://doi.org/10.1098/rstb.2019.0405  

   Mullineaux, Philip M.; Exposito-Rodriguez, Marino; Laissue, Pierre Philippe; Smirnoff, Nicholas; Park, Eunsook (June 2020, Philosophical Transactions of the Royal Society B: Biological Sciences)

   null (Ed.)

   Communication between chloroplasts and the nucleus in response to various environmental cues may be mediated by various small molecules. Signalling specificity could be enhanced if the physical contact between these organelles facilitates direct transfer and prevents interference from other subcellular sources of the same molecules. Plant cells have plastid–nuclear complexes, which provide close physical contact between these organelles. Plastid-nuclear complexes have been proposed to facilitate transfer of photosynthesis-derived H 2 O 2 to the nucleus in high light. Stromules (stroma filled tubular plastid extensions) may provide an additional conduit for transfer of a wider range of signalling molecules, including proteins. However, plastid–nuclear complexes and stromules have been hitherto treated as distinct phenomena. We suggest that plastid–nuclear complexes and stromules work in a coordinated manner so that, according to environmental conditions or developmental state, the two modes of connection contribute to varying extents. We hypothesize that this association is dynamic and that there may be a link between plastid–nuclear complexes and the development of stromules. Furthermore, the changes in contact could alter signalling specificity by allowing an extended or different range of signalling molecules to be delivered to the nucleus. This article is part of the theme issue ‘Retrograde signalling from endosymbiotic organelles’. 

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