1. RELAP5 Analyses of a Deep Burn High Temperature Reactor Core
Hongbin Zhang*, Michael Pope, Haihua Zhao
Idaho National Laboratory *
2010 RELAP5 International Users Seminar
September 20-23, 2010, West Yellowstone, Montana
Acknowledgement: Authors are grateful for Paul Bayless’s help to set up the RELAP5 input deck.

2. Prismatic Deep Burn Concept
Compacts
TRU kernel
TRU TRISO
Burn-up to 750 GWD/MT is feasible
LWR used fuel
Deep Burn Core
Fuel Elements 2

3. Fuel Composition Packing fraction of TRISO particles is 18%.
Fuel kernel diameter is 200 um.
TRU fuel representative of PWR spent fuel after 5 years of cooling.
Nuclide
Fraction (wt%)
Np-237
6.8
Pu-238
2.9
Pu-239
49.5
Pu-240
23.0
Pu-241
8.8
Pu-242
4.9
Am-241
2.8
Am-242
0.02
Am-243
1.4

4. 2D Lattice Calculations
DRAGON – collision probability transport code developed by Institut de Génie Nucléaire, École Polytechnique de Montréal, Montréal energy groups for various temperature and burnups.
23 group homogenized cross sections generated for DIF3D.
Reflector: 1-D model of the core with a representative fuel region and a reflector zone.
Schematic of 1/12 fuel block model used in DRAGON

5. Full Core Calculations
DIF3D/REBUS
Axial Shuffle Only

6. Equilibrium Cycle Equilibrium cycle is reached after 12 cycles
Cycle length – 300 days
Batch-average discharge 64% FIMA, or 600 MWD/t. 6

7. Decay Heat Curve
Decay heat curve is from calculations by Professor Kostadin Ivanov at Penn State

8. RELAP5 Model
Model started from the NGNP Point Design, INEEL/EXT Rev. 1
Core, vessel, reactor cavity and RCCS considered
Core – seven parallel coolant channels
1-D radial conduction with conduction enclosure to simulate axial direction heat conduction. 8

9. RELAP5 Nodalization
Reactor vessel, cavity and RCCS nodalization 9

10. RELAP5 Steady State Results
Reactor Power: 600 MWth.
Reactor Inlet Temperature: 491°C.
Reactor Outlet Temperature: 850°C.
Core Flow Rate: 324 KG/S
Bypass Flow Fraction: 12%

11. Low Pressure Conduction Cooldown Results

12. High Pressure Conduction Cooldown Results

13. Summary
LPCC (depressurized loss of forced cooling) transients showed fuel temperatures exceed 1600oC
However, very conservative consumptions went into the RELAP5 calculations
Burnable poisons and power flattening measures were not considered
Very conservative decay heat curve was used
Ongoing promising work by other researchers to use burnable poisons and better fuel shuffling scheme to lower fuel temperature.