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[en] The paper summarises the efforts made at JRC Ispra during the last ten years on atmospheric model inter-comparison and evaluation. The scope of this activity is to provide the European Commission with an independent information on the reliability of atmospheric model results in the field of risk mitigation. The paper deals first with the activity started as a follow up of the Chernobyl accident (ATMES), and with its continuation in the frame of real-time assessment of long range atmospheric dispersion of harmful releases (ETEX and RTMOD). The paper finally deals with the assessment of circulation and dispersion models near the emission site, on which the long-range evolution of the cloud depends substantially. (author)

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[en] The pre-conceptual design phase confirmed the safety potential of the CFV cores and the CFV concept is retained for conceptual design phase. Its potential will have to be consolidated by: • characterising the core behaviour in all the operating conditions (categories 1 to 4 and severe accident prevention situations); • selecting and designing the additional safety measures in relation to prevention and mitigation situations; • reinforcing the studies related to severe accident mitigation situations

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[en] We study the impact that uncertainties on assumed relations between galaxy bias parameters have on constraints of the local PNG f_NL parameter. We focus on the relation between the linear density galaxy bias $b_1$ and local PNG bias $b_{\mathrm{\varphi <!--\; ??\; -->}}$ in an idealized forecast setup with multitracer galaxy power spectrum and bispectrum data. We consider two parametrizations of galaxy bias: 1) one inspired by the universality relation where $b_{\mathrm{\varphi <!--\; ??\; -->}}=2{\mathrm{\delta <!--\; ??\; -->}}_c(b_1-<!--\; ???\; -->p)$ and $p$ is a free parameter; and 2) another in which the product of bias parameters and f_NL, like f_NL b_φ, is directly fitted for. The constraints on the f_NL−p plane are markedly bimodal, and both the central value and width of marginalized constraints on f_NL depend sensitively on the priors on $p$. Assuming fixed $p=1$ in the constraints with a fiducial value of $p=0.55$ can bias the inferred f_NL by $0.5\mathrm{\sigma <!--\; ??\; -->}$ to $1\mathrm{\sigma <!--\; ??\; -->}$; priors $\mathrm{\Delta <!--\; ??\; -->}p\approx <!--\; ???\; -->0.5$ around this fiducial value are however sufficient in our setup to return unbiased constraints. In power spectrum analyses, parametrization 2, that makes no assumptions on $b_{\mathrm{\varphi <!--\; ??\; -->}}$, can distinguish f_NL ≠ 0 with the same significance as parametrization 1 assuming perfect knowledge of $b_{\mathrm{\varphi <!--\; ??\; -->}}$ (the value of f_NL is however left unknown). A drawback of parametrization 2 is that the addition of the bispectrum information is not as beneficial as in parametrization 1. Our results motivate strongly the incorporation of mitigation strategies for bias uncertainties in PNG constraint analyses, as well as further theoretical studies on the relations between bias parameters to better inform those strategies.

[en] This paper summarises the Westinghouse approach to Accident Management, both preventive and mitigative, and reviews the scope and some results of the VVER studies. It also identifies future work that would be needed to implement plant specific Severe accident management guidance at VVER plant (author)