Benchmark analysis of the High Temperature Engineering Test Reactor (HTTR) initial fully-loaded core critical.

1. Preliminary Benchmark
Evaluation of Japan’s High
Temperature Engineering
Test Reactor
John Darrell Bess
R&D Engineer – Reactor Physics
May 5, 2009

2. Objective
• The benchmark assessment of Japan’s High
Temperature Engineering Test Reactor (HTTR) is
one of the high priority activities for the Next
Generation Nuclear Plant (NGNP) Project and Very
High Temperature Reactor (VHTR) Program.
• Current efforts at the Idaho National Laboratory
(INL) involve development of reactor physics
benchmark models in conjunction with the
International Reactor Physics Experiment
Evaluation Project (IRPhEP) for use with verification
and validation (V&V) methods.
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3. IRPhEP Process
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4. IRPhEP Handbook – 2009 Edition
• 15 Contributing Countries
• Data from 36 Experimental
Series – 21 Reactor Facilities
• Data from 7 reactor types – Up
to 8 types of measurements
• Data from 33 out of the 36
series are published as
approved benchmarks
• Data from 3 out of the 36 series
are published in draft form
• http://nuclear.inl.gov/irphep/
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5. HTTR Primary Design Specifications - I
Thermal Power 30 MW
Outlet Coolant Temperature 850/950 ºC
Inlet Coolant Temperature 395 ºC
Primary Coolant Pressure 4 MPa
Core Structure Graphite
Equivalent Core Diameter 2.3 m
Effective Core Height 2.9 m Air cooler
Crane
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Average Power Density 2.5 W/cm Refueling
machine
Fuel UO2
Enrichment 3 to 10 wt. %
Spent fuel
6 wt. % (average) storage pool
Fuel Type Pin-in-Block Type
Coated Fuel Particles
Burn-Up Period (EFPD) 660 days Reactor
pressure
Fuel Block Graphite Block vessel
Coolant Material Helium Gas Intermediate
heat exchanger
Flow of Direction in Core Downward
Reflector Thickness Pressurized
water cooler
Top 1.16 m
Side 0.99 m
Bottom 1.16 m
Number of Fuel Assemblies 150 Reactor containment vessel
Number of Fuel Columns 30
Number of Pairs of Control Rods
In Core 7
In Reflector 9
Plant Lifetime 20 years
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6. HTTR Primary Design Specifications - II
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7. Fuel Specifications of the HTTR - I
Fuel Kernel Fuel Rod
Material UO2 Outer Diameter (cm) 3.4
600
Diameter (µm) Sleeve Thickness (mm) 3.75
Density (g/cm3) 10.41 Length (cm) 54.6
Number of Fuel Compacts 14
Coated Fuel Particle
Number of Rods in a Block 31 / 33
Type / Material TRISO
Graphite Sleeve
920
Diameter (µm)
Type Cylinder
Impurity (ppm) <3 (Boron Equivalent)
Material IG-110 Graphite
Fuel Compact
Impurity (ppm) <1 (Boron Equivalent)
Type Hollow Cylinder
Length (cm) 58
Material CFPs, Binder, and Graphite
Gap Width between Compact and Sleeve (mm) 0.25
Outer / Inner Diameter (m) 2.6 / 1.0
Graphite Block
Length (cm) 3.9
Type / Configuration Pin-in-Block / Hexagonal
Packing Fraction of CFPs (vol. %) 30
Material IG-110 graphite
Density of Graphite Matrix (g/cm3) 1.7
Width across Flats (cm) 36
Impurity in Graphite Matrix (ppm) <1.2 (Boron Equivalent)
Height (cm) 58
Fuel Hole Diameter (cm) 4.1
3
Density (g/cm ) 1.75
Impurity (ppm) <1 (Boron Equivalent)
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8. Fuel Specifications of the HTTR - II
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9. Fuel and Burnable Poison Loading
The top The bottom
number of number
each block represents the
represents boron content
the uranium in the burnable
enrichment. poison pellets.
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10. Fully-Loaded Core Configuration
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11. Control Rod Positions in Core
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12. Virtual Representation of Core in MCNP
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13. Uncertainty Analysis - I
• The uncertainty • All random
analysis consisted of uncertainties are
the perturbation of the treated as 25%
benchmark model systematic
parameters and a – The large number of
comparison of the components in the
computed eigenvalues reactor tend to
to determine the reduce random
effective uncertainty in uncertainties to
the model. negligible quantities
– This preserves some
of the uncertainty in
the HTTR model
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14. Uncertainty Analysis - II
• Experimental measurements • Computational analyses
– Isothermal temperature – Room return effects
– Control rod positions – Stochastic modeling of TRISO
• Geometric properties – Random number generation
– Diameter – Instrumentation bias
– Height
– Thickness
– Pitch
• Compositional variations
– Fuel enrichment
– Material density
– Impurity content
– Boron absorber content
– Isotopic abundance of boron
Ordered Lattice Uniformly-Filled
– Clad composition
– Fuel Mass Benchmark Lattice
Configuration
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15. Results
• The benchmark model eigenvalue, keff, for the fully-
loaded core critical was determined: 1.0025 ± 0.0070.
Computed Eigenvalues for the HTTR Benchmark.
Neutron Library Ordered Uniform Difference (C-E)/E
ENDF/B-V.2 1.0233 1.0231 0.02% 2.1%
ENDF/B-VI.8 1.0253 1.0237 0.16% 2.3%
ENDF/B-VII.0 1.0260 1.0242 0.18% 2.3%
JEFF-3.1 1.0271 1.0252 0.18% 2.5%
JENDL-3.3 1.0216 1.0200 0.16% 1.9%
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16. Systematic vs. Random Uncertainty
0.014
Random Systematic Total
0.012
Maximum Total Uncertainty
0.010
0.008
0.006
0.004
0.002
0.000
0.00 0.25 0.50 0.75 1.00
Fraction of Random Uncertainty Treated as Systematic
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17. Points of Interest - I
• The most significant contributions to the overall uncertainty
include the impurities in the IG-110 graphite blocks and PGX
graphite reflector blocks.
– -0.0131 ± 0.0003 ∆keff/ppm – IG-110 graphite.
– -0.0019 ± 0.0003 ∆keff/ppm – PGX graphite.
– Other ICSBEP/IRPhEP benchmarks demonstrate similar
sensitivities to graphite impurities.
• The influence of random uncertainty is negligible: <0.0005 ∆keff
– Dominant uncertainties are systematic in nature.
– Better characterization of these parameters will reduce the
overall uncertainty.
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18. Points of Interest - II
• Calculated eigenvalues are 2 to 3% greater than
expected benchmark experiment values.
– Other ICSBEP/IRPhEP benchmarks have 1 to 2%
biases.
– Previous Japanese HTTR benchmarking efforts
also demonstrated 1 to 3% biases.
– This model is based on available public HTTR
data; much of the HTTR data is proprietary and
unpublished because the reactor is currently in
operation.
– The inclusion of more detailed HTTR data should
reduce the computational bias in the benchmark.
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19. Current Efforts – Annular Core Criticals
• Current benchmark efforts include the analysis of the initial
core critical geometries generated during the initial fuel
loading of the HTTR.
– These core configurations involved the replacement of
dummy fuel graphite blocks with fueled assemblies.
– Configurations include the initial critical with 19 fuel
columns, a thin annular core with 21 fuel columns, two
cores with 24 fuel columns (one controlled with the central
control rods and the other with the reflector control rods),
and a thick annular core with 27 fuel columns.
– The fully-loaded configuration contains 30 fuel columns.
• The most significant contributions to the overall uncertainty
include the impurities in the IG-110 graphite blocks, PGX
graphite reflector blocks, and IG-11 graphite dummy blocks.
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20. 19- and 21- Fuel-Column Cores
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21. 24- and 27- Fuel-Column Cores
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22. Annular Core Benchmarking Effort
Comparison of keff for HTTR Start-Up Cores
(MCNP5 with ENDF/B-VII.0)
1.035
Case 2
Case 4
Case 1
1.030
Case 3
1.025 Full Core
Case 5
1.020
1.015
keff ± 1σ
1.010
1.005
1.000
0.995
Uniformly-Filled Lattice Ordered Lattice Benchmark
0.990
18 20 22 24 26 28 30 32
Number of Filled Fuel Zones
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23. Future Benchmark Analyses
• Reactivity measurements from the initial start-up core physics
tests
– Isothermal temperature coefficient
– Axial reaction rate distribution
– Kinetics measurements
– Shutdown margin
– Control rod worth
– Excess reactivity
• Hot zero-power critical
• Rise-to-power tests
• Irradiation tests
• Radiation shielding
• Safety demonstration tests
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24. Acknowledgments
• Funding for the HTTR benchmark was provided by
the INL VHTR Program.
• The author would like to acknowledge the time and
expertise provided by N. Fujimoto from the Japan
Atomic Energy Agency; Luka Snoj from the Jožef
Stefan Institute; Atsushi Zukeran, acting as Senior
Reactor Physics Consultant; and Blair Briggs,
Barbara Dolphin, Dave Nigg, and Chris White from
the INL, for review, preparation, and presentation of
the HTTR benchmark.
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25. Questions?
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