KIT TOWN OFFICE OSTENDORFHAUS Karlsruhe, 21 st November 2012 CIRTEN Consorzio universitario per la ricerca tecnologica nucleare Antonio Cammi, Stefano Lorenzi LEADER WP2 LEADER WP2 Task 2.3 CIRTEN/POLIMI Contribution CFD Assessment of ALFRED Fuel Assembly: A one-twelfth model LEADER meeting, KIT Town Office Ostendorfhaus, Nov OUTLINE Introduction Goals CFD Model Geometry & BC conditions Power input data Other input data Results Case 1: Reference geometry Case 2: Reference geometry & gagging scheme Case 4: Modified geometry & gamma heating Conclusions LEADER meeting, KIT Town Office Ostendorfhaus, Nov INTRODUCTION A preliminary thermal-hydraulic analysis of one-twelfth of central Fuel Assembly (FA) has been carried out using computational fluid dynamics (CFD). LEADER meeting, KIT Town Office Ostendorfhaus, Nov GOALS Evaluation of the temperature field in the FA: the respect of the limit on cladding temperature in nominal conditions (< 550 C); Evaluation of the non-uniformity circumferential cladding temperature distribution in nominal condition; Comparison with T/H analyses of the task 2.3, giving additional information on T/H behaviour (FAST, ANTEO-LFR); LEADER meeting, KIT Town Office Ostendorfhaus, Nov CFD MODEL Shear Stress Transport (SST) k- model; 4.810 6 Computational volumes; y + ~ 1 10; 60 cm of active length 60 cm of inactive entrance channel; No spacer grids; No fuel pellets. LEADER meeting, KIT Town Office Ostendorfhaus, Nov CFD MODEL: GEOMETRY&BC Symmetry B.C. Wall B.C. Corner subchannel Wall subchannel Central subchannels LEADER meeting, KIT Town Office Ostendorfhaus, Nov CFD MODEL: POWER INPUT DATA Power distribution according to different zones FuelCladWrapperFA Pb InsulatorBypassDummiesCRSRExt. PbExteriorTotal Reactor [%]93.06%0.48%0.86%2.85%0.32%0.40%0.95%0.57%0.17%0.09%0.26%100% Reactor [MW] /12 Central FA [%]93.06%0.48%0.43%2.85% 96.82% 1/12 Central FA [kW] C. Petrovich, G. Grasso. D07 - Definition of the ETDR core and neutronic characterization. ENEA LEADER meeting, KIT Town Office Ostendorfhaus, Nov CFD MODEL: INPUT DATA OECD/NEA. Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Materials Compatibility, Thermal-hydraulics and Technologies, ParameterCorrelation (function of 450 CUnits Density= T10504kg m -3 Thermal conductivityk= T16.15W m -1 K -1 Heat capacityC p = 10 -2 T+8.34110 -6 T J kg -1 K -1 Dynamic viscosity=4.5510 -4 e 1069/(T ) 210 -3 Pa s Outlet pressure condition at upper boundary; Inlet constant velocity and temperature (400 C) at lower boundary LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS The simulation cases are: 1.Reference FA geometry, no gagging, only fuel power, no bypass; 2.Reference FA geometry, gagging, only fuel power, no bypass; 3.Reference FA geometry, no gagging, only fuel power released in the FA, bypass; 4.Modified FA geometry, no gagging, fuel power and gamma heating, no bypass; 5.Modified FA geometry, no gagging, fuel power and gamma heating, bypass. Bypass simulation work in progress LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: CASE 1 Total power released 179 kW; Lead mass flow rate is kg s -1 ; Inlet constant velocity of 1.31 m s -1. Outlet averaged bulk temperature 501 C. LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: VELOCITY CONTOURS, CASE 1 Velocity in the corner reduced due to the small gap between the last row of the fuel rods and the 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: TEMP CONTOURS, CASE 1 581C Temperature in the corner very high! T max = 581C > 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: WALL TEMP CONTOURS, CASE 1 80C Circumferential temperature different in the pin corner T = 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: PRESSURE DROP, CASE bar Pressure drop between inlet (0 mm) and outlet (1200 mm) is bar Coherent with other similar analyses [Schikorr, Magugliani, Di Piazza] LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: CASE 2 (GAGGING) Total power released 179 kW; Lead mass flow rate is kg s -1 ; 1.52 Inlet constant velocity of 1.52 m s -1. Outlet averaged bulk temperature 486 C. LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: VELOCITY CONTOURS, CASE 2 Velocity increases a little bit but is still low compared to the others 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: TEMP CONTOURS, CASE 2 559C Temperature in the corner still high! T max = 559C > 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: WALL TEMP CONTOURS, CASE 2 70C Circumferential temperature different in the pin corner T = 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: PRESSURE DROP, CASE bar Pressure drop between inlet (0 mm) and outlet (1200 mm) is bar LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: CASE 4 (NEW GEO & -HEATING) Wrapper-to-pin distance mm Total power released 186 kW; Lead mass flow rate is kg s -1 ; 1.26 Inlet constant velocity of 1.26 m s -1. Outlet averaged bulk temp 506 C. LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: VELOCITY CONTOURS, CASE 4 Velocity is more uniform in the XY plane due to the geometry change (increase of hydraulic 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: TEMP CONTOURS, CASE 4 536C Temperature in the corner under the limit! T max = 536C < 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: WALL TEMP CONTOURS, CASE 4 40C Circumferential temperature different in the pin corner T < 1200 mm LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: PRESSURE DROP, CASE bar Pressure drop between inlet (0 mm) and outlet (1200 mm) is bar LEADER meeting, KIT Town Office Ostendorfhaus, Nov CONCLUSIONS With the reference geometry, in the corner channel the temperatures grow above the clad temperature limit; The problem is not resolved by a gagging scheme since the problem is related to the geometry of the FA (small pin-to- wrapper distance induces a reduced hydraulic diameter); By adopting the modified geometry proposed by ENEA, the clad temperature limit is respected, even if the gamma heating is considered (total power produced in the FA); The influence of bypass on the FA temperature (in particular for corner & wall channel) is work in progress; an estimation of mass flow rate is a relevant issue. LEADER meeting, KIT Town Office Ostendorfhaus, Nov Thank you for your kind attention