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-ω model;  4.8·10 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 Densityρ= ·T10504kg m -3 Thermal conductivityk= ·T16.15W m -1 K -1 Heat capacityC p = ·10 -2 ·T+8.341·10 -6 ·T J kg -1 K -1 Dynamic viscosityη=4.55·10 -4 ·e 1069/(T ) 2·10 -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 1 581°C Temperature in the corner very high! T max = 581°C > 1200 mm

LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: WALL TEMP CONTOURS, CASE 1 80°C Circumferential temperature different in the pin corner ΔT = 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 2 559°C Temperature in the corner still high! T max = 559°C > 1200 mm

LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: WALL TEMP CONTOURS, CASE 2 70°C Circumferential temperature different in the pin corner ΔT = 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 & γ-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 4 536°C Temperature in the corner under the limit! T max = 536°C < 1200 mm

LEADER meeting, KIT Town Office Ostendorfhaus, Nov RESULTS: WALL TEMP CONTOURS, CASE 4 40°C Circumferential temperature different in the pin corner ΔT < 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