Questionnaire for the Exercise 2

Questionnaire for the OECD PBMR-400 Coupled Code Benchmark

I. Thermal Hydraulic Model (Exercises I-2, I-3, II-1, II-2, II-3, II-4, II-5, II-6) a) Core thermal-hydraulic (T-H) model and nodalization (1-D, 2-D, 3-D, and number of channels or cells with schematic if possible) – How are channels/T-H cells chosen? Answer:

b) How is the heat deposition modeled – all local in porous medium?, or deposited only in the fuel containing (5 cm diameter) region of the fuel sphere heterogeneous model?, or in the UO2 kernels? Answer:

c) How the heat transfer in the pebble-bed is modeled – using homogenized porous media or heterogeneous pebble model? Were correlations used? Answer:

d) How the change of pressure is taken into account in the T-H model? Is radial / azimuthal coolant flow possible or is flow channels isolated from each other? Answer:

e) What is the utilized pebble nodalization for Doppler feedback temperature calculation? Is the UO2 kernels modeled? or any correlation used? Answer:

f) How the heat transfer between pebble bed and side reflector is modeled? Answer:

g) How the radiation heat transfer across voided areas is modeled (effective surfaces)? (Between side reflector and barrel, barrel and RPV, RPV and RCCS) Answer:

h) Which core thermal-hydraulic initial and transient boundary conditions are used and how? Answer:

i) Used correlations for material properties vs. temperature? Answer:

j) Was the overall heat balance conserved? (fission heat compared to heat removed by the coolant and losses from the system) Answer:

Questionnaire for the OECD PBMR-400 Coupled Code Benchmark Page 1 of 4 II. Core Neutronics Model (Exercises I-1, I-3, II-1, II-2, II-3, II-4, II-5, II- 6)

a) Solution method used? (Finite-difference, nodal, diffusion / transport) Answer:

b) Radial nodalization? Answer:

c) Axial nodalization? Answer:

d) How the void areas are treated? Answer:

e) Cross-section interpolation procedure used? Answer:

f) Were the leakage / buckling dependency of the cross sections included in the model? How was the leakage / buckling calculated? Answer:

g) Were all the data (cross sections and kinetics parameters) on the library used or were any data taken from other references or data available in the code utilized? Answer:

h) Used method to get a critical reactor at the beginning of transient? Answer:

i) How Xenon effect is modeled? Answer:

j) How Decay Heat modeling is modeled? Was the decay heat spatially distributed using the calculated power distribution at initial steady state? Answer:

Questionnaire for the OECD PBMR-400 Coupled Code Benchmark Page 2 of 4 III. Coupling Schemes (Exercises I-3, II-1, II-2, II-3, II-4, II-5, II-6)

a) Hydraulics/heat structure spatial mesh overlays (mapping schemes in radial and axial plane)? Answer:

b) Heat structure/neutronics spatial mesh overlays (mapping schemes in radial and axial plane for exchange of heat sources and feedback parameters)? Answer:

c) Was the same spatial mesh overlays mapping scheme used for the fission heat and decay heat? Answer:

d) What methodology is utilized to achieve consistent mesh in heat transfer and hydraulics (gas flow) modeling? Answer:

e) Temporal coupling scheme? Answer:

f) Coupling numerics for steady state and transient– explicit, semi-implicit or implicit? Please also provide time step size, convergence criteria etc. Answer:

g) Coupling method – external or internal? Answer:

h) Coupling design – serial integration or parallel processing? Answer:

Questionnaire for the OECD PBMR-400 Coupled Code Benchmark Page 3 of 4 IV. General (All exercises)

a) User assumptions? Answer:

b) What are the code’s limitations that affect the results? Answer:

c) Specific features of the used codes? Answer:

d) Number of solutions submitted per participant? If more than one please provide comments and brief analysis on the solutions. Answer:

e) If your results are significantly different than the reference results, are there any explanations for these differences? Please explain each significant difference. Answer:

PLEASE ALSO PROVIDE YOUR CODE DESCRIPTIONS

Questionnaire for the OECD PBMR-400 Coupled Code Benchmark Page 4 of 4