Search

The increasing deployment of renewable energy sources and greater electrification of demand is requiring more frequent use of load following in pressurised water reactors (PWRs) . A limiting aspect with respect to load following is the thermo-mechanical behaviour of the fuel. Hence a greater use of best-estimate multi-physics tools that can more accurately capture such behaviour during load following manoeuvres – in particular, extended reduced power operation (ERPO) – has become important in recent years. To this end, we have developed a coupled, whole-core analysis framework and demonstrated it with a new generic PWR model. The demonstration is for uncontrolled RCCA bank withdrawal at power (URWAP) faults following a period of ERPO, since such scenarios are often limiting with respect to fuel integrity. The coupled, whole-core analysis framework that was developed consists of the PARCS neutronics code, the RELAP and CTF thermal–hydraulics codes, the ENIGMA fuel performance code, and the NEXUS platform for whole-core fuel performance. The generic PWR model constructed is for a 1240 MWe plant with a modern core design (maximum assembly burnup of 51.0 GWd/tHM, cycle length of 16 months, and an average fuel residence time of 2.3 cycles per assembly). Previous work in the literature on URWAP faults has focused on coupled neutronics and thermal–hydraulics analysis, with fuel performance assessment and the effects of load following neglected. These shortcomings are therefore addressed here. From a fuel performance perspective no fuel was predicted to fail due to pellet-clad interaction (PCI). Of the remaining failure indicators, margin to clad yield stress was most limiting, although no failure was predicted in all cases under the scenarios considered.

Additional file 8:.

Additional file 2:.

Additional file 4:.

Table describing final models used for phylogenetic analysis. (PDF 14 kb)

Full D27 phylogenies. See figure legends within. (PDF 702 kb)

Table describing final alignments used for phylogenetic analysis. (PDF 9 kb)

CCD phylogeny. See figure legends within. (PDF 138 kb)

Full MAX1 phylogenies. See figure legends within. (PDF 439 kb)

Full LBO phylogenies. See figure legends within. (PDF 585 kb)

Full CCD7 phylogenies. See figure legends within. (PDF 417 kb)

Full CCD8 phylogenies. See figure legends within. (PDF 506 kb)

Comparison of SWISSMODEL- and I-TASSER-generated homology models. Root-mean-square deviation (RMSD) values were calculated for 10 representative sequences modelled in I-TASSER compared to their SWISSMODEL counterpart. *The sequence of A. thaliana KAI2, for which there are several crystal structures, was also submitted to the I-TASSER server. The I-TASSER model of A. thaliana KAI2 was compared with the A. thaliana KAI2 crystal structure 4JYM (Guo et al. [50]), the SWISSMODEL template used in this study, as a control. (DOCX 12Â kb)

Cavity volumes of KAI2 and D14 crystal structures and homology models. Cavity volumes of KAI2 (Protein Data Bank (PDB) codes 4JYM, 4JYP (Guo et al. [50]), 5DNU, 5DNV (Xu et al. [73])) and D14 (PDB codes 4DNP (Hamiaux et al. [12]), 4IH4 (Zhou et al. [17]), 3WIO (Nakamura et al. [14])) and homology models were calculated using the Computed Atlas of Surface Topography of proteins (CASTp) server (Dundas et al. [68]). (DOCX 20Â kb)

Sampling of D14/KAI2 family members. Table showing D14/KAI2 family sampling rates across the plant kingdom. The primary taxonomic divisions are shown at the left; lycophytes (L), monilophytes (M), gymnosperms (G) and angiosperms (A) are further broken down into major sub-groups. The number of species (unshaded) and the number of sequences (shaded) obtained from each taxon are shown. Numbers for the Poaceae are shown separately from other Poales, which are in turn shown separately from other commelinids. (DOCX 16Â kb)

Sampling of MAX2 family members. Table showing MAX2 family sampling rates across the plant kingdom. The primary taxonomic divisions are shown at the left; lycophytes (L), monilophytes (M), gymnosperms (G) and angiosperms (A) are further broken down into major sub-groups. The number of species (unshaded) and the number of sequences (shaded) obtained from each taxon are shown. (DOCX 16Â kb)

MAX2-interacting residues. The residues in the leftmost column are those identified by Yao et al. [9] as playing a role in the interaction of Arabidopsis D14 with D3 (=MAX2) from rice. Numbers in the first column are relative positions with the AtD14 protein; these are corrected to our unified system in the second column. The consensus amino acids at those positions in the whole family, eu-D14 and eu-KAI2 clades are given in the next three columns. Shading indicates the degree of conservation at the position (pale blue >50%, light blue >70%, mid-blue >90%, dark blue >99%, purple 100%). The final column indicates clades in which these residues are not conserved. (DOCX 17Â kb)

The plant hormone auxin is a conserved regulator of development which has been implicated in the generation of morphological novelty. PIN-FORMED1 (PIN) auxin efflux carriers are central to auxin function by regulating its distribution. PIN family members have divergent structures and cellular localizations, but the origin and evolutionary significance of this variation is unresolved. To characterize PIN family evolution, we have undertaken phylogenetic and structural analyses with a massive increase in taxon sampling over previous studies. Our phylogeny shows that following the divergence of the bryophyte and lycophyte lineages, two deep duplication events gave rise to three distinct lineages of PIN proteins in euphyllophytes. Subsequent independent radiations within each of these lineages were taxonomically asymmetric, giving rise to at least 21 clades of PIN proteins, of which 15 are revealed here for the first time. Although most PIN protein clades share a conserved canonical structure with a modular central loop domain, a small number of noncanonical clades dispersed across the phylogeny have highly divergent protein structure. We propose that PIN proteins underwent sub- and neofunctionalization with substantial modification to protein structure throughout plant evolution. Our results have important implications for plant evolution as they suggest that structurally divergent PIN proteins that arose in paralogous radiations contributed to the convergent evolution of organ systems in different land plant lineages.

Funder: National Institute for Basic Biology (NIBB) Collaborative Research Program (13-710), Funder: The Forschungskredit of the University of Zurich The University Research Priority Program “Evolution in Action” of the University of Zurich The Georges and Antoine Claraz Foundation (Switzerland), Funder: Spanish Ministry of Science, Innovation and Universities (BFU2016-80621-P), Funder: The Georges and Antoine Claraz Foundation (Switzerland) The Research Priority Program “Evolution in Action” of the University of Zurich, Funder: Foundation of German Business (sdw), Georges and Antoine Claraz Foundation, URPP Evolution in Action of the University of Zurich, Funder: Special Grant for Innovation in Research Program of the Technical University of Dresden (Germany)., Hornworts comprise a bryophyte lineage that diverged from other extant land plants >400 million years ago and bears unique biological features, including a distinct sporophyte architecture, cyanobacterial symbiosis and a pyrenoid-based carbon-concentrating mechanism (CCM). Here, we provide three high-quality genomes of Anthoceros hornworts. Phylogenomic analyses place hornworts as a sister clade to liverworts plus mosses with high support. The Anthoceros genomes lack repeat-dense centromeres as well as whole-genome duplication, and contain a limited transcription factor repertoire. Several genes involved in angiosperm meristem and stomatal function are conserved in Anthoceros and upregulated during sporophyte development, suggesting possible homologies at the genetic level. We identified candidate genes involved in cyanobacterial symbiosis and found that LCIB, a Chlamydomonas CCM gene, is present in hornworts but absent in other plant lineages, implying a possible conserved role in CCM function. We anticipate that these hornwort genomes will serve as essential references for future hornwort research and comparative studies across land plants.