EVITA Extended Final Report (Part 1)

  • Gert Sdouz (Autor)

    Aktivität: Vortrag ohne Tagungsband / VorlesungPräsentation auf einer wissenschaftlichen Konferenz / Workshop


    5 WP4: ASTEC VO vaI against experiments 5.1 WECHSL validation Author: Gert Sdouz (ARCS) 5.1.1 Introduction The aim of this specific work is the vahdation of WECHSL against experiments. The WECHSL code [ is a mechanistic code developed for the analysis of the thermal and chemical interaction of initially molten reactor materials with the concrete basemat in a twa- dimensional as weil as in a one-dimensional, axisymmetrical cavity (its name is derived from "Wechselwirkung" - that is interaction - between corium and concrete). The caiculation starts from the initial contact of a hat malten pool over the onset of solidification processes until lang basemat erosion up ta several days. 5.1.2 Validation ofWECHSL In the past a number of experimental programs have been dedicated ta investigate the Malten Care-Cancrete lnteractian (MCCI) particularly in FZK (Germany), SNL (USA) and ANL (USA). In all three facilities the decay heat is simulated by electrical heating thraugh inductian. The main parameters studied in these experiments were: geametry af the crucible, carium campasitian and physical state, concrete campasitian, and presence of water at the tap af the corium. Three typical tests far the validation af this comprehensive database were selected: . BETA Test VI .8 (FZK): high power input carresponding ta early shart-term interactian in a Severe Accident, . SURC 4 (SNL) [ Zr addition ta stainless steel pool t investigate effects af the Zr oxidatian an MCCI, . MACE MO (ANL) [ investigatian af caalability of the melt by water addition after onset of MCCI. The WECHSL 3.5 validatian (in the farm af an exe-file far PC-calculatians) was perfarmed with comparisan ta twa ather versians of the code: . WECHSL 3.3 stand-alane version (as it was delivered as part af the ESTER package), . WEX 2.2 (this version was supplied by GRS and impraved during the validatian pracess). 5.1.3 Results Only the results with the version WECHSL 3.5 are discussed. For each experiment ane typical result will be shawn. The test BETA VI .8 simulated the early short-term interactian in a core melt accident with a high pawer input. During 220 s the pawer was kept at 1 800 kW and then decreased slawly ta 670 kW. One of the test results is that the propagatian of the melt was predaminantly dawnwarci (mare than 40 cm) with very limited sidewall erosion. The metal temperatures started at abaut 2000 K and decreased ta abaut 1600 K. Gas release was mainly compased af steam and hydragen. H was the dominant species because the concrete was siliceaus. The erosion behaviaur can be simulated pretty weIl. Only the erosion in the z-axis is slightly overpredicted. In additian the malar flaw of gas releases are predicted weil. Deviatians between experiment and calculatian occur in the corium temperatures (Fig. 1). E TA 1na Reoo June 2003 48 D - 3AV In the SURC-4 test the initial melt was composed of metals and the basemat consis of basaltic concrete. 1 05,4 min after the start the initiaflon of the corlum-concrete interaction occurr `i 3 min later 20 kg ot Zr ware added to the met ne test was conducted wi a net Input power of 6o kW over a period of 160 min except during a 7 min time interval. The measured ablatlon r dld increase shortly after Zr addition. This was caused by die Zr-oxidation because at mis time vier. was no input power available. The gas w greatly reduced by the metallic malt. Thd measurect malt temperatures started at about 1750 K followed by a sudden increase up to 1920 K aft Zr was added to the malt The erosion of the concrete at the center of the cavfty was about 23 cm. The erosion could be simulated quite weil by the code. However the changes in the behSour due to ha Zr-addiöon could not be calculated especially Uie dse of Die codum temp Thera is a delay 01 almost 1 000 s in the increase of the molar flow of the gases (Fig. 2). The MACE Scophig Test MO was conducted to assess the coolabilfty of die matt The corlum was heated up due to an electric power of almost 100 kW, man the power dropped. Water was introduced into the test section at 4 min after onset of concrete ablation causing an additlonal drop in power. The test continued until the water supply tank was emptled ei 235,5 mIn. 25 min later the residual water in fiie test section was boiled ot As a result an upper bridge crust formed. The crust remained at die elevation where it initially formed, and Vic MCCI r its downward migration. As can be seen in Fig. 3 tue cavity shape is predicted very weil by the code. The crust thickSss was calculated too smaL * The calculated corium temperatures however showed. a different behaviour than Hie experiment. In summary WECHSL 3.5 predicts reasonable tue cavity shape and tue molar flow of gas release. However t are deviations between experiment and ca for tue corlum temperatures. 5.1 .4 References [ * J.J.Foit, M.Reimann, B.Adroguer, G.Cenerino, S.Stiefel: The WECHSL-Mod3 Code: A Computer Program for the lnteraction of a Core Melt wi Concrete lncluding the Long Term Behaviour, FZKA 5522, February 1995 [ M.Lee, R.A.Bari:ISP-24: SURC-24 Experiment on core-concrete interactions, CSNI-report 1 55, Volume 1 ` December 198 [ M.T.Farmer, B.W.Spencer, D.J.Kilsdonk, R.W.Aeschlimann: Resu of MACE Core Coolability Experiments MO and Mib; Proceedings of ICONE 8 - 8" Intemational Conference on Nuclear Engineering, April24, 2000, Battirnore, MD USA [ B.W.Spencer, M.Fischer, M.T.Farmer, D.R.Amistrong: MACE Scoping Test Data Report, MACE-TR-D03, June 1991
    Zeitraum16 Juni 200318 Juni 2003
    Ereignistitel6. EVITA Progress Meeting

    Research Field

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