RELAP5 Analyses of a Deep Burn High Temperature Reactor Core

Hongbin Zhang*, Michael Pope, Haihua ZhaoIdaho National Laboratory

*Email: Hongbin.Zhang@inl.gov2010 RELAP5 International Users SeminarSeptember 20-23, 2010, West Yellowstone, Montana

Acknowledgement: Authors are grateful for Paul Bayless’s help to set up the RELAP5 input deck.

Prismatic Deep Burn Concept

LWR used fuel

TRU kernelTRU TRISO

Compacts

Fuel ElementsDeep Burn Core

Burn-up to 750 GWD/MT is feasible

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

2D Lattice Calculations

• DRAGON – collision probability transport code developed by Institut de Génie Nucléaire, École Polytechnique de Montréal, Montréal. 172 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

Full Core Calculations

• DIF3D/REBUS

• Axial Shuffle Only

Equilibrium Cycle

• Equilibrium cycle is reached after 12 cycles

• Cycle length – 300 days

• Batch-average discharge 64% FIMA, or 600 MWD/t.

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Decay Heat Curve

Decay heat curve is from calculations by Professor Kostadin Ivanov at Penn State

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Time (Hr)

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ay h

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Fuel at 7 GWd/ton burnup

RELAP5 Model• Model started from the NGNP Point Design, INEEL/EXT-03-00870 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.

RELAP5 Nodalization

Reactor vessel, cavity and RCCS nodalization

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%

Low Pressure Conduction Cooldown Results

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High Pressure Conduction Cooldown Results

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Vessel

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.