1. 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”

2. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 2 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

3. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 3 INTRODUCTION A preliminary thermal-hydraulic analysis of one-twelfth of central Fuel Assembly (FA) has been carried out using computational fluid dynamics (CFD).

4. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 4 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);

5. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 5 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.

6. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 6 CFD MODEL: GEOMETRY&BC Symmetry B.C. Wall B.C. Corner subchannel Wall subchannel Central subchannels

7. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 7 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]279.181.442.588.550.961.202.851.710.510.270.78300 1/12 Central FA [%]93.06%0.48%0.43%2.85% 96.82% 1/12 Central FA [kW]179.040.920.835.48 186.27 C. Petrovich, G. Grasso. D07 - Definition of the ETDR core and neutronic characterization. ENEA

8. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 8 CFD MODEL: INPUT DATA OECD/NEA. Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Materials Compatibility, Thermal-hydraulics and Technologies, 2007. ParameterCorrelation (function of T[°C])Value @ 450 °CUnits Densityρ=11041-1.1944·T10504kg m -3 Thermal conductivityk=11.2+0.011·T16.15W m -1 K -1 Heat capacityC p =155.3-2.567·10 -2 ·T+8.341·10 -6 ·T 2 145.4J kg -1 K -1 Dynamic viscosityη=4.55·10 -4 ·e 1069/(T+273.15) 2·10 -3 Pa s  Outlet pressure condition at upper boundary;  Inlet constant velocity and temperature (400 °C) at lower boundary

9. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 9 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

10. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 10 RESULTS: CASE 1  Total power released 179 kW;  Lead mass flow rate is 12.19 kg s -1 ;  Inlet constant velocity of 1.31 m s -1. Outlet averaged bulk temperature 501 °C.

11. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 11 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 wrapper @ 1200 mm

12. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 12 RESULTS: TEMP CONTOURS, CASE 1 581°C Temperature in the corner very high! T max = 581°C > 550°C @ 1200 mm

13. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 13 RESULTS: WALL TEMP CONTOURS, CASE 1 80°C Circumferential temperature different in the pin corner ΔT = 80°C @ 1200 mm

14. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 14 RESULTS: PRESSURE DROP, CASE 1 0.266 bar Pressure drop between inlet (0 mm) and outlet (1200 mm) is 0.266 bar Coherent with other similar analyses [Schikorr, Magugliani, Di Piazza]

15. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 15 RESULTS: CASE 2 (GAGGING)  Total power released 179 kW; 14.22  Lead mass flow rate is 14.22 kg s -1 ; 1.52  Inlet constant velocity of 1.52 m s -1. Outlet averaged bulk temperature 486 °C.

16. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 16 RESULTS: VELOCITY CONTOURS, CASE 2 Velocity increases a little bit but is still low compared to the others channels @ 1200 mm

17. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 17 RESULTS: TEMP CONTOURS, CASE 2 559°C Temperature in the corner still high! T max = 559°C > 550°C @ 1200 mm

18. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 18 RESULTS: WALL TEMP CONTOURS, CASE 2 70°C Circumferential temperature different in the pin corner ΔT = 70°C @ 1200 mm

19. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 19 RESULTS: PRESSURE DROP, CASE 4 0.342 bar Pressure drop between inlet (0 mm) and outlet (1200 mm) is 0.342 bar

20. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 20 RESULTS: CASE 4 (NEW GEO & γ-HEATING) 2.361  Wrapper-to-pin distance 2.361 mm  Total power released 186 kW;  Lead mass flow rate is 12.19 kg s -1 ; 1.26  Inlet constant velocity of 1.26 m s -1. Outlet averaged bulk temp 506 °C.

21. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 21 RESULTS: VELOCITY CONTOURS, CASE 4 Velocity is more uniform in the XY plane due to the geometry change (increase of hydraulic diameter). @ 1200 mm

22. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 22 RESULTS: TEMP CONTOURS, CASE 4 536°C Temperature in the corner under the limit! T max = 536°C < 550°C @ 1200 mm

23. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 23 RESULTS: WALL TEMP CONTOURS, CASE 4 40°C Circumferential temperature different in the pin corner ΔT < 40°C @ 1200 mm

24. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 24 RESULTS: PRESSURE DROP, CASE 4 0.248 bar Pressure drop between inlet (0 mm) and outlet (1200 mm) is 0.248 bar

25. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 25 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.

26. LEADER meeting, KIT Town Office Ostendorfhaus, Nov 2012 26 Thank you for your kind attention