| 1. |
- Journeau, C., et al.
(författare)
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European Research on the Corium issues within the SARNET network of excellence
- 2008
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Ingår i: International Conference on Advances in Nuclear Power Plants, ICAPP 2008. - 9781605607870 ; , s. 1172-1181
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Konferensbidrag (refereegranskat)abstract
- Within SARNET, the corium topic covers all the behaviors of corium from early phase of core degradation to in or ex-vessel corium recovery with the exception of corium interaction with water, direct containment heating and fission product release. The corium topic regroups in three work packages the critical mass of competence required to improve significantly the corium behavior knowledge. The spirit of the SARNET networking is to share the knowledge, the facilities and the simulation tools for severe accidents, so to reach a better efficiency and to rationalize the R&D effort at European level. Extensive benchmarking has been launched in most of the areas of research. These benchmarks were mainly dedicated to the recalculation of experiments, while, in the next periods, a larger focus will be given to integral experiments or reactor applications. Eventually, all the knowledge will be accumulated in the ASTEC severe accident simulation code through physical model improvements and extension of validation database. This paper summarizes the progress that has been achieved in the frame of the networking activities. A special focus is placed on the melt pool and debris coolability and corium-concrete interaction, in which, the effects due to multidimensional geometries and heterogeneities has been shown, during SARNET, to play a crucial role and for which further research is still needed.
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| 2. |
- Hartmann, N., et al.
(författare)
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Attosecond time-energy structure of X-ray free-electron laser pulses
- 2018
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 12:4, s. 215-220
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Tidskriftsartikel (refereegranskat)abstract
- The time-energy information of ultrashort X-ray free-electron laser pulses generated by the Linac Coherent Light Source is measured with attosecond resolution via angular streaking of neon 1s photoelectrons. The X-ray pulses promote electrons from the neon core level into an ionization continuum, where they are dressed with the electric field of a circularly polarized infrared laser. This induces characteristic modulations of the resulting photoelectron energy and angular distribution. From these modulations we recover the single-shot attosecond intensity structure and chirp of arbitrary X-ray pulses based on self-amplified spontaneous emission, which have eluded direct measurement so far. We characterize individual attosecond pulses, including their instantaneous frequency, and identify double pulses with well-defined delays and spectral properties, thus paving the way for X-ray pump/X-ray probe attosecond free-electron laser science. © 2018 The Author(s).
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| 3. |
- Pohlner, G., et al.
(författare)
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Analyses on ex-vessel debris formation and coolability in SARNET frame
- 2014
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 74, s. 50-57
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Tidskriftsartikel (refereegranskat)abstract
- The major aim of work in the SARNET2 European project on ex-vessel debris formation and coolability was to get an overall perspective on coolability of melt released from a failed reactor pressure vessel and falling into a water-filled cavity. Especially, accident management concepts for BWRs, dealing with deep water pools below the reactor vessel, are addressed, but also shallower pools in existing PWRs, with questions about partial cooling and time delay of molten corium concrete interaction. The subject can be divided into three main topics: (i) Debris bed formation by breakup of melt, (ii) Coolability of debris and (iii) Coupled treatment of the processes. Accompanied by joint collaborations of the partners, the performed work comprises theoretical, experimental and modelling activities. Theoretical work was done by KTH on the melt outflow conditions from a RPV and on the quantification of the probability of yielding a non-coolable ex-vessel bed by use of probabilistic assessment. IKE introduced a theoretical concept to improve debris bed coolability. A large amount of experimental work was done by partners (KTH, VTT, IKE) on the coolability of debris beds using different bed geometries, particles, heating methods and water feeds, yielding a valuable base for code validation. Modelling work was mainly done by IKE, IRSN, RSE and VTT concerning jet breakup and/or debris bed formation and cooling in 2D and 3D geometries. A benchmark for the DEFOR-A experiment of KTH was performed. Important progress was reached for several tasks and aspects and important insights are given, enabling to focus the view on possible key aspects of future activities.
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| 4. |
- Van Dorsselaere, J.P., et al.
(författare)
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ASTEC extension to other reactor types than Generation II PWR
- 2008
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Ingår i: Proc. of ERMSAR 2008.
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Konferensbidrag (refereegranskat)abstract
- The initial IRSN-GRS requirements for the development of the ASTEC European integral codecovered all present and future PWR, VVER and BWR. After 4 years and a half of SARNET activities, theASTEC V1 code is fully applicable to all severe accident scenarios, at power operation, in Gen.II PWR andVVER. Partners performed substantial code assessment tasks on both VVER-440 and 1000 with good resultson validation (such as PACTEL) and benchmarking with other codes on plant sequences.In the frame of preparation of the new series of ASTEC V2 versions that will account for the needs ofevolution expressed by the SARNET partners, the extension to Gen.III PWR is under way. The 1stversionV2.0, planned for march 09, will be applicable to the EPR, in particular its external core-catcher and to newPWR designs with In-Vessel Melt Retention (IVMR), the latter thanks to CEA work. IVS calculations onVVER-440/V213 showed the ASTEC V1 capabilities to evaluate the IVMR possibilities: these capabilitieswill be improved in the future through a coupled analysis of in-vessel corium and cavity cooling circuit.For BWR applications, the KTH ranking of needs of model adaptations was reviewed by GRS. Theseadaptations mainly concern the Reactor Cooling System (RCS) thermal-hydraulics (internal pumps, drier,separator...) and the core degradation (canisters, control rod guide tubes, penetrations in lower head...). Forcore degradation, the scoping application test on the CORA-18 experiment using the current ASTEC V1models (for adaptation to absorber blades and canisters) showed promising results. The GRS benchmark withthe COCOSYS GRS code showed the applicability of the CPA containment module. For ex-vesselphenomena, the only missing model is the formation of a debris bed during corium slump from lower headinto a flooded cavity after lower head failure and its coolability/erosion behaviour with core concreteinteraction under flooded conditions. All other current V1 models can be used, sometimes with minoradaptations or further need of validation, as for iodine behaviour in containment at temperatures up to 1000Kand the possible decomposition of metal iodides to gaseous iodine at these high temperatures in atmosphere.Detailed specifications will be written soon to prepare the development and validation task planned inSARNET2 with the same partners.For CANDU reactors applications, the priority concerns the core degradation due to the peculiarity ofthe vessel geometry (horizontal core, pressure tubes, calandria...). The exploratory plant applications haveshown that all other current models can be used but tests are still necessary to conclude on models of PHT(Primary Heat Transfer) thermal-hydraulics. INR work takes benefit of the AECL knowledge of MAAP4-CANDU models. A significant benefit is foreseen from the BARC (India) work on core degradation modelsin the frame of IRSN-BARC bilateral collaboration.
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