A.K. Nayak, PhD Reactor Engineering Division Bhabha Atomic Research Centre Trombay, Mumbai 400085

1. IAEA Meeting on INPRO Collaborative Project “Performance Assessment of Passive Gaseous Provisions (PGAP)”13-15 December, 2011, Vienna A.K. Nayak, PhD Reactor Engineering Division Bhabha Atomic Research Centre Trombay, Mumbai 400085

2. GFR DHR Analysis for Transient 1 • Computer code used : RELAP5/MOD3.2 • Power = 2400 MWth • No. of DHR Loops = 1 • Full reactor is simulated in the RELAP5/MOD3.2 to study the passive decay heat removal behaviour of the reactor. • Thermal inertia of all the components in the main circuit have been considered. • Heat exchange between DHR hot and cold ducts through the insulation has been considered. • Steady state calculations are continued until 500 sec.

3. Inputs for Analysis of Main Loop • Physical parameters Main CKT: Power = 0- 2400 MW increased linearly in 100 seconds Pressure = 6.98 MPa at t=0 sec Mass Flow Rate = 0 kg/s at t=0 sec Temperature = 673K at t=0 sec Main Secondary CKT: Mass flow Rate = 2685 kg/s at t = 0 to t = 500 sec Inlet Temperature = 839 K at t = 0 to t = 500 sec Inlet Pressure = 6.5 MPa at t = 0 to t = 500 sec

4. Steady State Analysis • Transient Calculations continued for 500 sec to achieve the steady state • CODE achieved Steady state after 125 sec

5. Inputs for Analysis of DHR Loop – Initial Conditions • DHR secondary mass flow rate = 0 • DHR secondary pressure = 1.0 MPa • DHR secondary Temperature = 323 K POOL INITIAL CONDITIONS: • Pool pressure= 0.1 MPa • Pool Temperature= 323 K

6. Assumptions • Local resistances in the fuel element is considered such that the pressure difference in the core part is matched with the steady state conditions given. • Since the geometry of the core is complex, the lumped model is used for the simulation of the core. • The core is divided into 7 channels (6 heat generating and one bypass). Each channel is divided into 25 volumes. • The flow area and the heat transfer area are same as in the actual reactor core. • Heat transfer coefficient in the heat structure parts viz: in the core, in main IHX, in DHR IHX and in the pool IHX, is decided by the RELAP5 inbuilt models.

7. Dimensions Considered • BLOWER Main features are: • Flow Area= 3.14m2 • Length =3.0m • Rated velocity= 470.24 rad/s • Initial blower velocity/rated velocity=1 • Rated flow =340.0m3/s • Rated head= 30000m • Rated torque= 15019N.m • Moment of inertia=0.0676 Kg/m2 • Rated density of fluid= 5.58 Kg/m3 • Pump closing takes place in 50seconds as per the velocity given.

8. Important dimensions

9. Important dimensions

10. RELAP 5 Nodalization of Main circuit of GFR

11. GFR Nodalization

12. Mass Flow rate (Various Channels)

13. Mass Flow rate (total core)

14. Pressure in the lower and upper plenum

15. Helium temperature in lower and upper plenum

16. Variation of clad surface temperature along the height

17. Fuel Centre line Temperature (Steady State)

18. Individual Channel power at Steady State

19. Total Core Power at Steady State

20. Model Qualification – summary of Steady-state results Error defined as: 20

21. Model Qualification – summary of Steady-state results

22. SBO Transient

23. DHR Analysis for SBO • After 500 sec transient calculation were continued for the DHR • Reactor Was Tripped at 500 sec • Blower Stops in 50 sec after 500 sec • valves in main loops start closing at 47 sec and gets completely closed at 49 sec after 500 sec. • DHR Circuit Was Valved In After 55 sec Seconds And Valve Fully Opened In 60 Sec after 500 sec.

24. Main vessel pressure

25. DHR secondary side pressure

26. DHR secondary side Temperature

27. DHR water side flow rate

28. Gas Temperature at Main Vessel Inlet/ Outlet

29. Channel Flow rate

30. Total core flow rate

31. Power to the various channels

32. Power to the Core

33. Power to and from DHR secondary loop

34. Sensitivity analysis – Parameters considered and their variations • Core ∆P variation ±15% • Core Power variation ±2% • Residual Power variation ±10% • Heat Transfer area variation ±25% • DHR Heat Transfer area variation ±25% • DHR inlet Loss coefficient variation ±200% • DHR outlet Loss coefficient variation ±200% • Thermal Inertia variation ±15% • Main Circuit Pressure variation ±2bar • Primary Blower Inertia ±25%

35. Failure Criteria

36. Effect of Blower Inertia ±25%

37. Effect of Blower Inertia ±25%

38. Effect of Blower Inertia ±25%

39. Effect of Core Power ±2%

40. Effect of Core Power ±2%

41. Effect of Core Power ±2%

42. Effect of Residual Power variation ±10%

43. Effect of Residual Power variation ±10%

44. Effect of Residual Power variation ±10%

45. Effect of Core ∆P variation ±15%

46. Effect of Core ∆P variation ±15%

47. Effect of Core ∆P variation ±15%

48. Effect of Heat Transfer area variation ±25%

49. Effect of Heat Transfer area variation ±25%

50. Effect of Heat Transfer area variation ±25%