Operating Experience with Hydrological External Hazards and Their Potential Safety Significance

The nuclear accidents of Fukushima in March 2011 have indicated the significance of external hazards for nuclear installations safety. One lesson learned from post-Fukushima investigations worldwide is that the operating experience from external hazards, even if these did not pose any significant harm to the affected plant, do represent important precursors, which should be taken into account in deterministic as well as probabilistic safety assessment. This paper provides an overview on the significance of events or event combinations involving hydrological external hazards. Some more recent examples of events from hydrological external hazards and their potential safety significance for nuclear power plants are discussed

Risk analysis of external hydrological hazards with flooding potential for a German nuclear reference site

Probabilistic Safety Analyses (PSA) are a supplementary analytical tool used worldwide more and more in order to quantitatively assess the effect of hazards on the overall result regarding the safety of industrial installations, in particular nuclear power plants. In that way PSA provides a reliable basis for decisions on the necessity and the benefits of safety improvements. In the recent past, the existing methods and tools with respect to determining the site-specific risk of nuclear power plants have been comprehensively extended and further enhanced. The focus of extending the existing PSA methods was on external hydrological hazards with flooding potential. For systematically considering hydrological hazards within PSA a systematic approach has been developed. The paper demonstrates the extended approach in the example of a nuclear power plant site with different flooding risks

IL-33 controls IL-22-dependent antibacterial defense by modulating the microbiota

IL-22 plays a critical role in defending against mucosal infections, but how IL-22 production is regulated is incompletely understood. Here, we show that mice lacking IL-33 or its receptor ST2 (IL-1RL1) were more resistant to Streptococcus pneumoniae lung infection than wild-type animals and that single-nucleotide polymorphisms in IL33 and IL1RL1 were associated with pneumococcal pneumonia in humans. The effect of IL-33 on S. pneumoniae infection was mediated by negative regulation of IL-22 production in innate lymphoid cells (ILCs) but independent of ILC2s as well as IL-4 and IL-13 signaling. Moreover, IL-33's influence on IL-22-dependent antibacterial defense was dependent on housing conditions of the mice and mediated by IL-33's modulatory effect on the gut microbiota. Collectively, we provide insight into the bidirectional crosstalk between the innate immune system and the microbiota. We conclude that both genetic and environmental factors influence the gut microbiota, thereby impacting the efficacy of antibacterial immune defense and susceptibility to pneumonia