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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