Task 1: Computational and Experimental Benchmarking for Transient Fuel Testing
T. Downar B. Martin V. SekerH. Zhou H. Smith E. MahaliScott Wilderman Ethan Pachek
University of Michigan
C. LeeArgonne National Laboratory
May 23, 2017
Task 1• Objective: A comprehensive evaluation of existing TREAT Facility neutronics data using the next generation reactor core neutronics codes. This will be performed in accordance with established guidelines per the International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhEP).
• Neutronics Codes:• Monte Carlo:
• SERPENT (UM)• MCNP (UM)• OPENMC (UM)
• Deterministic: • PARCS US NRC (UM)• PROTEUS DOE NEAMS (ANL)
• Benchmarks (UM)• Steady‐State – Two steady state condition benchmarking tests will be selected and studied.• Transient – Two transient condition benchmarking problems will be selected and studied.
Task 1.1 (Steady‐State) Schedule
Task #Task Title Sub‐Task
Owner
1. Neutronics Benchmark Task Lead – T. Downar, UM
1.1 Steady State (SS)
1.1.1 Survey candidate problems T. Downar, UM
1.1.2 Preliminary SS modeling of candidate problems T. Downar, UM
1.1.3 Down‐select to two problems for benchmark evaluation T. Downar, UM
1.1.4 SS modeling with deterministic U.S. NRC codes PARCS/AGREE T. Downar, UM
1.1.5 SS modeling with deterministic NEAMS code PROTEUS C. Lee, ANL
1.1.6 SS modeling with Monte Carlo code OPENMC K. Sun, MIT
1.1.7 Comparison of experimental data & model results T. Downar, UM
1.1.8 Benchmark level evaluation of selected problems T. Downar, UM
1.1.9 Evaluation of uncertainties in selected problems T. Downar, UM
1.1.10Preparation of IRPhEP documentation
T. Downar, UM
1.1.11Submission of SS benchmark for peer review T. Downar, UM
TREAT BENCHMARK
Benchmark completed and submitted on September 30th
Benchmark was reviewed by John Bess (INL) and Rich Lell (ANL); Recommended separating Minimum Critical and M8CAL
Benchmark was revised to accommodate their review and will be formally submitted to IRPhEP in Fall 2017
TREAT Steady State Benchmark (rev 0)Revised Benchmark includes two problems with two different cores providing complementary types of measurements:
• Minimum Critical Mass (MCM) core (temperature coefficients)
• MCM+ core (flux/reaction rates)
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Core Specifications keff
Minimum Critical
7.53ppm Boron59% Graphitization16 Zr Assembly
1.00413 ±20 pcm
MC+7.53ppm Boron
59% Graphitization1.00171 ±20 pcm
MCM
MCM+
Summary of TREAT Benchmark Analysiswith Monte Carlo (9/30/16)
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Core SERPENT(UM)
MCNP(UM)
OpenMC(MIT)
MCC 1.00413 ± 20 pcm 1.00380± 20 pcm 1.00533 ± 22 pcm
MC+ 1.00171 ± 20 pcm ‐ 1.00268 ± 24 pcm
Some Minor Modifications since 9/30/16:Minimum Critical Mass (MCM)
• The core was ~60 ih supercritical which is about 1.00160
• The control rod positioning for MCM and following experiments were different than the one in M8CAL experiments
• Some of the regular fuel elements were thermocouple fuel assemblies
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SERPENT: Revised (5/23/17) MCM Core Eigenvalue Resultskeff Δk (pcm)
Experiment 1.00160 ‐
Previous model 1.00413 253
Control rod positioningCorrection and some minor geometric corrections
1.00296 (±6 pcm) 136
Thermocouple fuel masscorrection 1.00227 (±7 pcm) 67
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• ENDF/B VII.1 Library was used for all SERPENT Calculations
• Run specs:• # of Source neutron/cycle = 200K• # of Active cycles = 1000• # of Inactive cycles = 500
MCM: Temperature Coefficient
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Hot T (K) Cold T (K) Δk/T (pcm/K)
Measurement 310.65 295.15 1.8±0.2 10‐4
Serpent 310.65 295.15 1.7 10‐4
Cold Measurements: PR was 4 degrees warmerHot Measurements: PR was 8 degrees colder
MCM+ Flux Measurements
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Uncertainty analysis of significant factors (2016)Parameter(s) perturbed Sample size Average keff Relative uncertainty
All parameters listed in Table 1 600 1.0068±4.6835E − 4 1139.5 ± 32.9pcm
Boron content 300 1.0044±6.3435E − 4 1093.9 ± 44.7pcmFlat to flat distance of fuel block 300 1.0064±1.2939E − 4 222.7 ± 9.1pcm
Standard fuel assembly outer radius 300 1.0041±1.7732E − 5 30.6 ± 1.3pcm
Al-6063 can thickness 300 1.0044±1.9463E − 4 335.6±13.7pcm
Zr-3 can thickness 300 1.0040±5.1837E − 4 894.2±36.6pcm
Table 2. TREAT minimum critical core uncertainty analysis summary
• Reference keff : 1.00413 ±0.0002.• Evaluation of the standard error of the mean/std:
, σ , σ 2 σ SE
Status / Plans for TREAT Benchmark Reports
• TREAT Steady-State Benchmark with MCM and MCM+ Revised and re-submitted to John Bess and Rich Lell
• TREAT Transient Benchmark M8CAL• Steady-state M8CAL (Draft Completed)• Transient M8CAL
• Burst Transient (#2855 or #2857)• Shape Transient (#2864 or #2874)
M8CAL Core SERPENT Model
13keff= 1.00018 ±6 pcm
M8CAL Rod Worth Calculations
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Control/Shutdown Rods
Transient Rods
M8CAL 60in Monitor Wire
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Deterministic TREAT Modeling
• PROTEUS• NEAMS Full Core Transport
• PARCS• U.S. NRC Nodal Core Simulator• 14 group Cross Sections generated by SERPENT• Core calculation with Diffusion Theory (w/ ADFs)
Task 1.1 (Steady‐State) ScheduleTask #
Task Title Sub‐Task Owner
1. Neutronics Benchmark Task Lead – T. Downar, UM
1.1 Steady State (SS)
1.1.1 Survey candidate problems T. Downar, UM
1.1.2 Preliminary SS modeling of candidate problems T. Downar, UM
1.1.3 Down‐select to two problems for benchmark evaluation T. Downar, UM
1.1.4SS modeling with deterministic U.S. NRC codes PARCS/AGREE
T. Downar, UM
1.1.5SS modeling with deterministic NEAMS code PROTEUS
C. Lee, ANL
1.1.6 SS modeling with Monte Carlo code OPENMC K. Sun, MIT
1.1.7 Comparison of experimental data & model results T. Downar, UM
1.1.8 Benchmark level evaluation of selected problems T. Downar, UM
1.1.9 Evaluation of uncertainties in selected problems T. Downar, UM
1.1.10Preparation of IRPhEP documentation
T. Downar, UM
1.1.11Submission of SS benchmark for peer review
T. Downar, UM
Task 1.1.5 Accomplishments at ANL: PROTEUS Steady‐State
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Case Serpent PROTEUS ∆k (pcm)L5T15, G11
MinCC 3D Full Core 1.00490 (±18) ‐1M8CAL 3D Full Core * 1.00497 (±18) 66
‐ Legendre‐Tchebychev L5T15 (96 directions / 4π) and transport corrected scattering were used
‐ Eigenvalue difference decreases with higher angular order but increases with higher scattering order
* Simplified model w/o experiment vehicle
PROTEUS: M8CAL w/ Air Channel to Hodoscope
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Fast Flux
Thermal Flux352,536 elements/plane, 21 planes39 cross section sets
Power Comparison between PROTEUS and Serpent• PROTEUS and Serpent solutions agreed very well
• Excluding ‐ 1 outmost FEs for MinCC‐ 3 outmost FEs for M8CAL
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MinCC M8CAL
MinCC M8CAL
Max 0.44% 1.25%
RMS 0.22% 0.50%
MinCC M8CAL
Max 0.30% 0.97%
RMS 0.14% 0.32%
Relative Power
% Difference
Performance Improvement with CMFD Acceleration
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Note: the CMFD performance was tested for the 3D M8CAL case (simplified geometry).
Deterministic TREAT Modeling
• PROTEUS• NEAMS Full Core Transport
• PARCS• U.S. NRC Nodal Core Simulator• 7‐14 group Cross Sections generated by SERPENT• Core calculation with Diffusion Theory (w/ ADFs)
Deterministic: PARCS RESULTS Core SERPENT
PARCS
MCM 1.00413 ± 20 pcm 1.00177
MCM+ 1.00171± 20 pcm 0.99769
M8CAL 1.00394 ± 20 pcm 1.02120
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• Cross section generation• Serpent 2.26• 7‐14G • Fuel cross section
• 2‐D Fuel Assembly unit cell
• Control rod color set
Quasi‐Diffusion Equations
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1 , ,· J , , Σ , , , , , ,
• Scalar Flux Equation
Eddington factors
1 , ,· , , , , Σ , , , , , ,
• Current Equation (integrate transport equation over 4π with weight Ω)
• If ignore the off‐diagonal elements, quasi‐diffusion is reduced to
, E, t 3
Transient Test Problem: PARCS Results
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• Rod bank #1 is ejected and inserted back to create a transient.
Task 1.2 (Transient) Schedule
1.2 Transient (TR)
1.2.1 Survey available TREAT TR data for benchmark problem T. Downar, UM
1.2.2 Preliminary TR modeling of candidate problems T. Downar, UM
1.2.3Down‐select to two problems for benchmark evaluation
T. Downar, UM
1.2.4 Perform TR modeling with deterministic U.S. NRC codes PARCS/AGREE T. Downar, UM
1.2.5Perform S.S./TR modeling with deterministic NEAMS code PROTEUS
C. Lee, ANL
1.2.6 Perform TR modeling with Monte Carlocode OPENMC W. Martin, UM
1.2.7 Benchmark level evaluation of selected problems T. Downar, UM
1.2.7 Evaluation of uncertainties in selected problems T. Downar, UM
1.2.8 Preparation of IRPhE Documentation T. Downar, UM
1.2.9 Submission of TR benchmark for peer review T. Downar, UM
Task 1.2.3 Downselect to two Transients for Benchmark
• BURST / Temperature Limited Transients– Three temperature-limited transients (nos. 2855, 2856 and 2857) were
experimentally performed in the half-slotted HEU core (loading no. 6541) in 1992.
– The largest and smallest reactivity insertions #2855 and #2857 were selected for analysis
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TransientNumber
InsertedReactivity
Peak FuelTemperature (C)
PeakPower (MW)
CoreEnergy (MJ)
2855 1.81% 236 1281 7922857 3.87% 488 12493 2265
• Shape Transients– Transients #2874 and #2864 were identified as a prime candidate because
these transients were among with the highest total core energy performed in the M8CAL experiment series.
– One important difference in the transients was the type of monitor wires used in the experiments
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TransientNumber
Description WireNumber
PeakPower (MW)
CoreEnergy (MJ)
Axial PeakAbsolute f/g
of wire(x10E13)
2874Half-slotted
8-sPeriod
H91-8-2 262 1807.13.685
+/- 0.028
2864Half-slotted
8-sPeriod
L91-8-4 1864.43.583
+/- 0.023
Task 1.2 (Transient) Schedule1.2 Transient (TR)
1.2.1 Survey available TREAT TR data for benchmark problem T. Downar, UM
1.2.2 Preliminary TR modeling of candidate problems T. Downar, UM
1.2.3 Down-select to two problems for benchmark evaluation T. Downar, UM
1.2.4 Perform TR modeling with deterministic U.S. NRC codes PARCS/AGREE T. Downar, UM
1.2.5Perform S.S./TR modeling with deterministic NEAMS code PROTEUS
C. Lee, ANL
1.2.6 Perform TR modeling with Monte Carlo code OPENMC W. Martin, UM
1.2.7 Benchmark level evaluation of selected problems T. Downar, UM
1.2.7 Evaluation of uncertainties in selected problems T. Downar, UM
1.2.8 Preparation of IRPhE Documentation T. Downar, UM
1.2.9 Submission of TR benchmark for peer review T. Downar, UM
Participants on Task 1.2.6
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Bill Martin (lead) Dr. Scott Wilderman (Research staff) Ethan Pacheck (PhD student at UM)
Assistance from Dr. Volkan Seker (UM) Assistance from Dr. Ben Betzler (ORNL)
Background for Task 1.2.6
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TRMM Uses the forward/adjoint eigenfunctions and corresponding eigenvalues that
correspond to a core configuration in a specified state (SS or perturbed) to model the time-dependent evolution of the neutron angular flux and precursor concentrations
These are the eigenfunctions and eigenvalues of a transition rate matrix (TRM) whose elements are estimated by a continuous energy Monte Carlo code (OpenMC)
OpenMC Estimates the TRM elements for an initial critical state as well as a perturbed
state. The expansion then models the time-dependent evolution of the system
Progress on Task 1.2 – TRMM simulation
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Initial modeling of 200x200x200 cm homogeneous water/fuel mixture for validation with Betzler’s original work
Extended to supercritical case Have investigated: 5x5x5, 15x15x1, 3x3x3, and 1x1x1 geometries Steady state, supercritical, prompt supercritical,
subcritical Local reactivity insertions (positive, negative) Full-core reactivity changes
Recently used to analyze TREAT-equivalent fuel lattice with B10-equivalent temperature feedback that was studied by DeHart et al using Mammoth.
Progress on Task 1.2.6 – COMSOL/Matlab Coupling
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COMSOL has been able to successfully model the exact temperature fluctuations of the TREAT reactor during reactivity insertions
COMSOL has been coupled to a PK solver in MATLAB to allow temperature feedback via PK equations. This shows feasibility of using COMSOL as a TH solver for the PK equations.
Possible next step: couple OpenMC and COMSOL directly, perhaps with a Python script. Alternatively, it may be possible to couple OpenMC and COMSOL via Matlab.
Questions?
Minimum Critical Core (MCM)
• 133 Standard Fuel Elements• 8 Control Rod Fuel Elements• 16 Zr‐Cladded Dummy Fuel Element
• Control rods are above the upper reflector (completely out of the core)
• Specs from INL/EXT‐15‐35372‐BATMAN report
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Temperature Δk (inhr)
Temperature CoefficientHot (°C) Cold (°C) (inhr/°C) (Δk/°C)
Short Rods 35.0 15.5 131 6.74 1.8 ± 0.2 x 10‐4
Long Rods 37.5 22.0 104.5 6.76 1.8 ± 0.2 x 10‐4
MCM+ Core Measurements
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1
Control Rod Positioning
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MCM
MCM Core Loading
• The exact location of thermocouple assemblies are unknown.
• Due to the drilled holes for the thermocouple installation, the fuel mass of thermocouple assemblies are less than standard assemblies.
• This reduction is applied homogeneously.
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SERPENT Model for MCM
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Axial Radial
MCM+ Core Flux Measurements
• Measurements were done with fission counters and foils of U235, Pu239,Pu‐Al, Gold.
• Only U235 foil measurements were simulated with SERPENT.
• The foils were 1cm square and 1 mil thickness.
• The U235 foils were places in the coolant channel on the upper left corner (K‐10) of the central fuel element.
• SERPENT Run Specs: 200K n/cycle, 5000 active – 500 inactive cycles
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