Search for dissertations about: "Sevostian Bechta"

Showing result 1 - 5 of 6 swedish dissertations containing the words Sevostian Bechta.

  2. 1. CFD Study of Molten Pool Convection in a Reactor Vessel during a Severe Accident

    Author : Boshen Bian; Walter Villanueva; Sevostian Bechta; Weimin Ma; Shuisheng He; KTH; []
    Keywords : Severe accident; Corium; Natural convection; Turbulence; Scalability; Direct numerical simulation DNS .; Svåra haverier; härdsmälta; naturlig konvektion; turbulens; skalbarhet; direkt numerisk simulering DNS .; Physics; Fysik;

    Abstract : During severe accidents in nuclear reactors, the core and internal structures can melt down and relocate into the reactor pressure vessel (RPV) lower head (LH) forming there a stratified molten corium pool. The pool generally consists of superheated oxidic and metallic liquid layers imposing thermo-mechanical loads on the RPV wall. READ MORE

  4. 2. Experimental Study on Steam Explosions in Chemical Solutions and Seawater

    Author : Yucheng Deng; Weimin Ma; Sevostian Bechta; Andrei Komlev; Renaud Meignen; KTH; []
    Keywords : Severe accident; fuel coolant interactions; steam explosion; chemical additives; seawater; Svåra haverier; bränsle-kylmedelsinteraktioner; ångexplosion; kemiska tillsatser; havsvatten; Kärnenergiteknik; Nuclear Engineering;

    Abstract : Steam explosions may be encountered in severe accidents of light water reactors (LWRs), which are thermal detonations caused by rapid and intense vaporization of the coolant upon its direct contact with the core melt (corium). Motivated by the interest in understanding and mitigation of severe accident progression, many studies have been conducted to investigate the steam explosion phenomena during severe accidents. READ MORE

  5. 3. Thermo-mechanical Assessment of Reactor Pressure Vessels of Light Water Reactors During Severe Accidents

    Author : Hongdi Wang; Walter Villanueva; Sevostian Bechta; Weimin Ma; Artem Kulachenko; Michael Fitzpatrick; KTH; []
    Keywords : Severe accident scenario; reactor pressure vessel; in-vessel melt retention; failure analysis; finite element analysis; validations; Scenario för svåra haverier; reaktortank; in-vessel retention; feleffektsanalys; Finite Element Analyser; validering; Physics; Fysik;

    Abstract : The reactor pressure vessel (RPV) is one of the crucial safety barriers designed to isolate the reactor core, safeguarding against potential radioactive releases into the environment during a severe accident. The assessment of RPV behaviour and its failure is necessary to predict the characteristics of melt release into the reactor pit and succeeding ex-vessel accident progression. READ MORE

  6. 4. Study on Metallic Melt Coolant Interactions and Debris Bed Formation in a Water Pool

    Author : Yan Xiang; Weimin Ma; Sevostian Bechta; Andrei A. Komlev; Michael Buck; KTH; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Severe accident; fuel coolant interactions; metallic melt; jet fragmentation; debris bed; CLSVOF.; Svåra haverier; interaktioner mellan bränsle och kylmedel; metallsmälta; jetfragmentering; grusbädd; CLSVOF; Kärnenergiteknik; Nuclear Engineering;

    Abstract : To assess corium coolability during severe accidents of LWR, significant number of studies have been conducted previously to investigate the characteristics of debris beds formed from FCI due to fragmentation of molten corium and settlement of the fragments in a water pool. However, their focus has been placed on the oxidic component (UO2/ZrO2) of corium, while little attention has been paid to the debris bed formation due to FCI of the metallic component (Zr/Fe) of corium. READ MORE

  7. 5. Modelling and Simulation of Reactor Pressure Vessel Failure during Severe Accidents

    Author : Peng Yu; Weimin Ma; Walter Villanueva; Sevostian Bechta; Florian Fichot; KTH; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; RPV failure; thermo-fluid-structure coupling; creep modelling; melt pool heat transfer; severe accident; CFD; FEA; transIVR;

    Abstract : This thesis aims at the development of new coupling approaches and new models for the thermo-fluid-structure coupling problem of reactor pressure vessel (RPV) failure during severe accidents and related physical phenomena. The thesis work consists of five parts: (i) development of a three-stage creep model for RPV steel 16MND5, (ii) development of a thermo-fluid-structure coupling approach for RPV failure analysis, (iii) performance comparison of the new approach that uses volume loads mapping (VLM) for data transfer with the previous approach that uses surface loads mapping (SLM), (iv) development of a lumped-parameter code for quick estimate of transient melt pool heat transfer, and (v) development of a hybrid coupling approach for efficient analysis of RPV failure. READ MORE