Contribution of CFD studies to IVR assessment

Transcription

1 8 TH CONFERENCE ON SEVERE ACCIDENT RESEARCH ERMSAR 2017 Cntributin f CFD studies t IVR assessment Clémentine LE GUENNIC, EDF ; Laurent SAAS, CEA May16-18, 2017 Warsaw, Pland

2 Summary 1. Intrductin 2. Light metallic layer thermalhydraulics 1. BALI-Métal bench 2. Explratry prttypical cmputatins 3. Hmgeneus pl 4. Explratry stratified pl cmputatins 5. Cnclusins and perspectives 2

3 1. Intrductin 1 In-vessel retentin attracts significant attentin, but large incertitudes remain; demnstrating its feasibility fr high pwer reactrs is difficult. Prblems with crium pl mdelling in the current severe accident cdes: The cmmn IVR study practice [1-3] based n statinary cnfiguratins is nt bunding [4]; the transient behaviur cannt be neglected The crrelatins are derived frm steady-state experiments nt applicable t transient behaviur. Sme crrelatins may be used utside f their validity range. pssible vercnservatism, especially fr the metallic layers New fcus is needed n the transient and steady-state thermalhydraulics f crium pls t gain new margins. Pssible input f CFD studies. 3

4 1. Intrductin 2 This presentatin will deal with the fllwing phenmena: Thin metallic layer thermalhydraulics Hmgeneus xide pl behaviur Entrainment in stratified pls The CFD cdes have nt been develped fr such applicatins; a tw-step methd is suggested: Cde assessment n relevant simulant cases; Water-based tests frm the BALI-Métal [5] and BALI [6] campaigns have been chsen fr the metallic layer and xide pl respectively. Valuable data n the flw structure. Explratry prttypical cmputatins. 4

5 2.1. Metallic layer BALI-Métal bench 1/3 Tw sets f cmputatin: CEA: DNS cmputatins using TriCFD Tp bundary cnditin: cnstant temperature; Principle f the BALI-Métal test sectin N thermal dependency f the fluid prperties. EDF: RANS cmputatins using NEPTUNE_CFD Lw-Reynlds, 2 nd rder turbulence mdel; Cupling with a slid cnductin cde fr the upper bundary cnditin. P up /P dwn P lat /P dwn (P up + P lat ) / P dwn Experiment 78% 35%; *24%, **22% 113%, *102%, **100% NEPTUNE_CFD 63.3% 36.6% 99.8% TriCFD 74.4% 25.4% 99.4% Pwer repartitin Ra lat Nu lat Ra up Nu up Ra dn Nu dn Experiment Value 1.23* , *111, ** * * NEPTUNE_CFD Value 1.24* * * Errr 0.8% 3.7%, *33.9%, **64.7% 6.5% 7.3% 9.2% 1.5% TriCFD Value 5.62* * * Errr 33.4% 63.5%, *46.8%, **42.2% 64% Adimensinal numbers 112% 54.5% 86% 5

6 2.1. Metallic layer BALI-Métal bench 2/3 The temperature field is generally well-reprduced: Gd agreement f the temperature prfiles; Presence f a radial temperature gradient. Observatin f a cld strip alng the lwer plate clse t the cled lateral wall Clear need fr temperaturedependent prperties and cnductin in the upper plate t reprduce the entire phenmenlgy. NEPTUNE_CFD Temperatures alng the lwer plate NEPTUNE_CFD - Vertical temperature prfile 20cm away frm the cled lateral wall NEPTUNE_CFD Temperatures alng the upper plate 6

7 2.1. Metallic layer BALI-Métal bench 3/3 The flw structure is nt fully reprduced in 2D, as expected frm the literature [7]: The initial situatin is cmparable t classical Rayleigh-Bénard; The cnvectin cell clsest t the cld lateral wall expands twards the adiabatic wall A stable mncell is frmed; the velcities are in the expected rder f magnitude. Velcity field T bserve the alternance between mncellular and split flw, a 3D mesh is necessary. Due t the difference in Pr number and gemetrical effects, these results cannt be transpsed directly t the prttypical case. 7

8 2.2. Metallic layer Prttypical cmputatins 1/2 Setup: 0D mdel Gemetrical cnsideratins: parallelepiped, sectr? Cmpsitin and prperties: pure irn, with prperties derived frm [8] and [9]. Bundary cnditins. A first trivial cmparisn case has been perfrmed with NEPTUNE_CFD: isthermal cling n the tp and n the side at 1811 K, fr cmparisn with the standard 0D mdel used t dimensin BALI-Métal. Very favurable pwer split: nly 4.1% f the pwer is evacuated laterally. The mean temperature is 1859 K, with an average lateral heat flux f 0.33 MW/m 2. Cmpares well t the standard pint mdel predictins: average pl temperature f K, mean lateral heat flux f 0.34 MW/m 2. 8

9 2.2. Metallic layer Prttypical cmputatins 2/2 Parametrical study with TriCFD : parallelepiped gemetry, fixed physical prperties (T fu = 1658K), fr different isthermal cling n the tp, thickness, length, and bttm heating : key parameters: BC temperature T up, thickness h, high cncentratin factr. Additinal parametrical study in prgress: radiative heat transfer cling n tp the cncentratin factr tends t decrease. Thickness (tp temperature Cncentratin factr (φ lat /φ dwn ) T up =1960K) h=2.5cm 3.0 h.5cm 2.8 h=7.5cm 2.7 h=10cm 2.5 Tp bundary Cncentratin cnditin (h=2.5cm) factr T up =1658K 0.4 T up =1800K 1.5 T up =1960K 3.0 T up =2200K 5.5 T up =2460K 8.4 Radiative heat transfer 2.4 T up =2141K Temperature prfiles: isthermal tp cling radial gradient clse t the cled lateral wall Temperature prfile: radiative tp cling 9

10 3. Hmgeneus pl 1/2 BALI Temperature prfile and flw structure Temperature field RANS cmputatins with NEPTUNE_CFD: Lw Reynlds, 2 nd rder turbulence mdel 3D mesh Underestimatin f the stratified zne thickness. Mre unifrm axial temperature prfile; Higher average temperature; Higher heat flux values in the lwer part. Axial temperature prfile Lateral heat flux prfile 10

11 3. Hmgeneus pl 2/2 Velcity field The general flw structure is well-reprduced: The three znes (stratified, unstable and bundary) are clearly defined. The velcities are in the expected rder f magnitude (pssibly underestimated in the bundary zne). The thermal balances shw gd agreement. The adimensinal numbers are within 15% f the experimental data. Thermal balances P up /P int P lat /P int (P up + P lat ) / P int Experiment 43.0% 47.3% 90.3% NEPTUNE_CFD 43.3% 56.5% 99.7% Adimensinal numbers Ra i Ra e Nu up Nu dn Experiment Value 2.27* * NEPTUNE_CFD Value 2.37* * Errr 4.4% 10.1% 0.4% 13.8% 11

12 4. Explratry stratified pl cmputatins 1/2 Accident cdes cannt accunt fr thermal hydraulics interactins between several layers What happens at the interface between the metallic layer and the strngly cnvective xide pl? Is interfacial entrainment pssible? What impact (if any) n natural cnvectin in bth layers? Setup: Gemetrical cnsideratins; Layers inventry, cmpsitin and prperties: xide pl prperties derived frm [10]; Bundary cnditins: the lateral bundary cnditin pses the mst prblems withut a slidificatin mdel; Assumptins: n interfacial crust. 12

13 4. Explratry stratified pl cmputatins 2/2 First feasibility cmputatins with much higher residual pwer have been perfrmed successfully. Phenmenlgy shws resemblance t the BALI case. Sme interfacial defrmatin. Onging develpments fr mre realistic simulatins: Implementatin f a pseud-slidificatin mdel better representatin f the lateral bundary cnditin Feedback frm nging single-phase thin metallic layer cmputatins. Temperature field fr increased decay heat 13

14 5. Cnclusins and perspectives Water-based cases: Current cdes perfrm well; The results need t be cnslidated by expanding the validatin basis; Experimental results btained with water shuld nt be directly transpsed t the reactr case. Explratry prttypic cmputatins: The activity is nly starting. Obtaining enugh data t setup a cmputatin remains a prblem. Prmising perspectives fr future integral cde refinement/supprt t the dimensining f experiments. 14

15 Thank yu fr yur attentin! 15

16 References 1/2 [1] J.L. Rempe, D.L. Knudsn, C.M. Allisn, G.L. Thinnes, C.L. Atwd, M.J. Cebull, Ptential Fr AP600 In-Vessel Retentin Thrugh Ex-Vessel Flding, Tech. Reprt INNEL/EXT , [2] T.G. Thefanus, C. Liu, S. Additin, S. Angelini, O. Kymalainen, T. Salmassi, In-Vessel Clability And Retentin Of A Cre Melt, Nuclear Engineering And Design, Vl. 169, [3] H. Esmali, M Khatib-Rahbar, Analysis Of Likelihd Of Lwer Head Failure And Ex-Vessel Fuel Clant Interactin Energetics Fr Ap1000, Nuclear Engineering And Design, Vl. 235, [4] J.L. Rempe, D.L. Knudsn, M. Cebull, C.L. Atwd, Ptential fr in-vessel retentin thrugh ex-vessel flding, Prc. f the OECD/CSNI Wrk-shp n In-Vessel Cre Debris Retentin and Clability, [5] C. Villermaux, Mdélisatin physique et numérique de la cnvectin naturelle dans une cuche de fluide de faible rapprt d aspect dans le cadre des études d accidents graves de réacteurs à eau sus pressin, Ph.D. thesis, Institut Natinal Plytechnique de Grenble, France, [6] J.M. Bnnet, J.M. Seiler, Thermal hydraulic phenmena in crium pls: the BALI experiment, Prc. f 7 th Internatinal Cnference n Nuclear Engineering (ICONE 7), Tky, Japan, [7] G. Leplat, Stabilité d un éculement de cnvectin naturelle en milieu cnfiné, Ph.D. thesis, Institut Supérieur de l Aérnautique et de l Espace, France,

17 References 2/2 [8] M.J. Assael,, K. Kaksims, R.M. Banish, J. Brill, I. Egry, R. Brks, P.N. Quested, K.C. Mills, A. Nagashima, Y. Sat, W.A. Wakeham, Reference data fr the density and viscsity f liquid aluminum and liquid irn, Jurnal f Physical and Chemical Reference Data, Vl.35, [9] M.W. Chase, NIST-JANAF Thermchemical Tables, Furth Editin, Jurnal f Physical and Chemical Reference Data, Mngraph 9, [10] S.A. Smirnv, V.S. Granvsky, S.V. Bechta, V.B. Khabensky, E.V. Krushinv, A.A. Sulatsky, D.B. Lpukh, I.V. Kulagin, Direct numerical simulatin f mlten crium pl inductively heated in the cld crucible, Prc. f the MASCA-2 Seminar, Cadarache, France,