mc21 / ctf and vera multiphysics solutions to vera core physics ... · casl vera core physics...
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The Naval Nuclear Laboratory is operated for the U.S. Department of Energy by Bechtel Marine Propulsion Corporation,
a wholly owned subsidiary of Bechtel National, Inc.
MC21 / CTF and VERA Multiphysics Solutions to
VERA Core Physics Benchmark Progression Problems 6 and 7
Daniel J. Kelly, Ann E. Kelly, Brian N. Aviles
Naval Nuclear Laboratory – Knolls Atomic Power Laboratory
Andrew T. Godfrey, Robert K. Salko, Benjamin S. Collins
Oak Ridge National Laboratory
Background
• Monte Carlo reactor physics plus subchannel thermal hydraulics codes becoming more common in large scale multiphysics analysis
• Complements coupled deterministic transport reactor physics / subchannel T-H codes
• Previous large-scale MC21 analyses
• BEAVRS Benchmark
• HZP: Kelly et al., M&C 2013
• Cycle 1 depletion with MC21 internal T-H feedback: Kelly et al., PHYSOR 2014
• HB Robinson isothermal depletion: Griesheimer, et al., Annals of Nuclear Energy, 2015
• Assembly Benchmarks: MC21 / COBRA-IE
• HFP Calvert Cliffs Assembly: Gill et al., PHYSOR 2014
• HFP VERA Assembly (Problem 6): Aviles et al., PHYSOR 2016
• Current work discuss explicit MC21 coupling with CTF
• Combination of VERA and in-house tools
• Evaluate complexity of integrating in-house solver with VERA
• Validate in-house tools against VERA tools
CASL VERA Core Physics Benchmark Problems
• Based on actual fuel and core geometry from
Watts Bar Nuclear 1 initial core
• Problems demonstrate increasing capabilities
for reactor physics methods and software
• Specification: Godfrey, “VERA Core Physics
Benchmark Progression Problem Specifications”,
Revision 4, CASL-U-2012-0131-004, August 29, 2014.
• Problem 6: HFP BOC Assembly
• MC21 / CTF complements previous MC21 /
COBRA-IE solution
• Problem 7: HFP ¼-Core w/ Xenon and Critical
Boron Search
• MC21 / CTF is first Monte Carlo / subchannel
T-H solution
Existing Processes
Thermal Hydraulics (VERA/CTF) Physics (MC21)
→ Reuse Features to Couple T/H (CTF) and Physics (MC21)
react2xml.pl p7.inp
p7.xml
xml2ctf –xmlfile=p7.xml
CTF
CTF Input Files
pdeck.56.x.inp,
pmaster.inp
multistate_cobra pdeck
pdeck.h5
(pin_powers)
p7.xml
VERA Input
p7.inp
CTF Results
pdeck.ctf.h5
MC21
PUMA
MC21 Input
Files
Import File
(Temp/Density)
PUMA Model
MC21.java
Job Summary file
jobSummary.h5Fission tally file
tally.h5
multistate_cobra pdeck
MC21
MC21 Input
Files
mc21_to_ctf.py
ctf_to_mc21.py
CTF Input Files
pdeck.56.x.inp,
pmaster.inp
VERA/CTF
Initialization
MC21
Initialization
pdeck.h5
(pin_powers)
VERA Input
XML (p7.xml)
CTF Results
pdeck.ctf.h5
Fission tally file
Tally.h5
Job Summary file
jobSummary.h5
Fission tally file
Tally.h5
Job Summary file
jobSummary.h5
Temp (solid, fluids), Densities (fluid)
initTempDens.h5
CTF Results
pdeck.ctf.h5
MC21
InitializationCoupled Process
PUMA Modeling - 1
Figure[] fig26 = {
g4,
f1, f1,
f1, f1, f1,
g4, f1, f1, g4,
f1, f1, f1, f1, f1,
f1, f1, f1, f1, f1, g4,
g4, f1, f1, g4, f1, f1, f1,
f1, f1, f1, f1, f1, f1, f1, f1,
f1, f1, f1, f1, f1, f1, f1, f1, f1};
Overlay lat26= VERAUtil.makeLattice("LAT26", fig26)
• MC21 model generated using the PUMA model builder
• General purpose model builder for MC21
• PUMA input based on a Java input deck
• New VERAUtil package developed
• Facilitate MC21 model building based on VERA common input format
• Enhance model QA by enabling comparison to VERA input
• VERAUtil input cards supported
• Cell, lattice, axial, assm_map
PUMA Modeling - 2
• Standard MC21 models only
requires a pin cell definition to
represent grid spacers
• For MC21 / CTF coupling require
each pin cell to be subdivided
into quadrants
• PUMA attributes are used assign
“tags” to designate specific MC21
source and sink numbering
• Numbering based on VERA / CTF
VERA Problem 6 Results
• Single PWR fuel assembly (Westinghouse
17x17-type fuel assembly)
• Conditions
• Beginning of Life (BOL)
• Hot Full Power (HFP)
• First successful demonstration of coupled
MC21 / CTF
• 2 Models (Physics, T-H) – same configuration
• Used available input/output capabilities to
couple and iterate, modifying solver
parameters as required
VERA Problem 6 Results
• Comparison to MC21 / COBRA-IE and VERA (MPACT / CTF)
• 9 coupled iterations (neutronics and T-H converged after data exchange 5)
Code SystemEigenvalue
(95% CI)
Difference
(pcm)
MC21 / COBRA-IE 1.16424 (2.6E-05) Reference
MC21 / CTF 1.16424 (2.6E-05) 0
MPACT / CTF 1.16361 -63
MC21 Eigenvalue and Number of Active Neutron
Histories during MC21 / CTF Data Exchanges
Calculated Eigenvalues for
Problem 6, ¼-Assembly0.0
0.5
1.0
1.5
2.0
1.16380
1.16385
1.16390
1.16395
1.16400
1.16405
1.16410
1.16415
1.16420
1.16425
1.16430
1.16435
1.16440
0 2 4 6 8 10
Ac
tive
His
tori
es
(B
illi
on
Neu
tro
ns)
MC
21
Eig
en
va
lue
MC21/CTF Data Exchange Index
MC21 Eigenvalue
Active Neutron Histories
VERA Problem 6 T-H Convergence Metrics
CTF Convergence Metrics for Subchannel Coolant
Temp during MC21 / CTF Data ExchangesCTF Convergence Metrics for Fuel Temp during
MC21 / CTF Data Exchanges
Neutronics and T-H Converged After Data Exchange 5
VERA Problem 6 Comparison
Axially Integrated ¼ Assembly Normalized
Pin Fission Rate Comparison,
Agree to (-0.19%, +0.17%)
RMS Difference = 0.09%
Subchannel Exit Coolant Temperature
Comparison,
Agree to ±0.1 C
RMS Difference = 0.02 C
VERA Problem 7
• Full Core (Westinghouse 17x17-type fuel assemblies in Watts Bar
Unit 1 initial cycle)
• Conditions
• Beginning of Cycle (BOC)
• Hot Full Power (HFP) with equilibrium xenon
• Nominal Power and Flow
• CASL benchmark specification: calculate critical boron concentration
• Used capabilities developed with Problem 6 for coupling of MC21
and CTF for Problem 7
• 2 Models (Physics, T-H) – same configuration
• Instrument Tubes replaced by Guide Tubes for ¼-core symmetry
VERA Problem 7 Models
H G F E D C B A
8 2.1 2.6 2.1 2.6 2.1 2.6 2.1 3.1
9 2.6 2.1 2.6 2.1 2.6 2.1 3.1 3.1
10 2.1 2.6 2.1 2.6 2.1 2.6 2.1 3.1
11 2.6 2.1 2.6 2.1 2.6 2.1 3.1 3.1
12 2.1 2.6 2.1 2.6 2.6 2.6 3.1 0
13 2.6 2.1 2.6 2.1 2.6 3.1 3.1 0
14 2.1 3.1 2.1 3.1 3.1 3.1 0 0
15 3.1 3.1 3.1 3.1 0 0 0 0
¼-Core Symmetric Model
VERA / CTF Assembly & Enrichment Layout PUMA / MC21 Model Layout
MC21 / CTF Problem 7 Results
Picard
Iter.Actions
Boron
(ppm)
Active
Histories(generation
size)
kcalc
(95% CI)
1Fixed Boron,
Isothermal,
eqXe900.0
50 million
(500,000)
1.01133
(1.8E-4)
2
Boron
Search, T/H
Feedback,
eqXe
859.7100 million
(1 million)
0.99989
(1.2E-4)
3
Boron
Search, T/H
Feedback,
eqXe
852.3100 million
(1 million)
1.00003
(1.0E-4)
4
Fixed Boron,
T/H
Feedback,
eqXe
852.3500 million
(1 million)
1.00031
(4.8E-5)
5
Fixed Boron,
T/H
Feedback,
eqXe
854.530 billion
(4 million)
0.99994
(6.8E-6)
MC21 / CTF Running Strategy
Distribution of MC21 Relative Uncertainty in
Relative Power Distribution, 30 Billion NeutronsVERA Predicted Critical Boron = 853.7 ppm
Distribution of MC21 Relative Power Uncertainties
Uncertainty >1%, 30 Billion Neutrons Uncertainty >2%, 30 Billion Neutrons
Max = 3.59%
MC21 Pin Power Distributions
MC21 Axially-Integrated Relative Pin Power Distribution.
Minimum = 0.1684, Maximum = 1.3658
MC21 Pin Power vs. VERA
• Maximum Relative Pin Power
• MC21: 1.3658 in pin (4,5) in D-12
• VERA: 1.3670 in the same pin
• Minimum Relative Pin Power
• MC21: 0.1684 in pin (17,17) in C-14
• VERA: 0.1673 in the same pin
H G F E D C B A
8
9
10
11
12
13
14
15
MC21 / CTF Local Results
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 50 100 150 200 250 300 350 400
Rela
tiv
e P
in L
inear
Heat
Rate
Axial Height (cm)
MC21/CTF: Assembly D-12, pin (5,4)
VERA: Assembly D-12, pin (5,4)
3D Octant View of CTF Subchannel
Temperature Distribution for MC21 / CTF,
RMS Difference vs. VERA = 0.08 C
Axial Relative Linear Heat Rate for Pin (5,4)
in Assembly D-12, MC21 / CTF vs. VERA
• MC21 / CTF: 1.9198 ± 0.34%
• VERA: 1.9214 (agrees w/in MC21
uncertainty)
Axial Power Results
Axially-Integrated Assembly Relative Power
MC21/CTF and VERA
RMS Difference = 0.22%
Core Relative Axial Power and Axial Offset
MC21/CTF and VERA
RMS Difference = 0.25%
-3%
-2%
-1%
0%
1%
2%
3%
0.0
0.3
0.5
0.8
1.0
1.3
1.5
0 50 100 150 200 250 300 350 400
% D
iffe
rence
: V
ER
A v
s.
MC
21
/CT
F
Re
lative
Po
we
r (-
)
Axial Height (cm)
MC21/CTF
VERA
% Difference: VERA vs. MC21/CTF
Axial Offset:
MC21/CTF = -11.06%
VERA = -11.03%
Exit Coolant Temperature Comparisons
Assembly-Averaged Exit Coolant Temperature (C)
MC21/CTF and VERA
RMS Difference = 0.13 C
Difference in Subchannel Exit Coolant
Temperature (C), VERA – (MC21/CTF),
RMS Difference = 0.13 C
Fuel Pin Temperature
Difference in Volume-Averaged Fuel Pin Temp (C) at
Axial Plane 19, VERA – (MC21/CTF)
RMS Difference = 2.1 C
• RMS difference between VERA and
MC21/CTF for all fuel pin volume-
average temperature regions in the
3D ¼-core model is 1.8 C
• Observable octant tilt resulting from
the non-symmetric MC21 solution
• Final solution based on 30B
histories (~0.5% error at this
plane)
• Previous iterations have larger
uncertainty causing stochastic
noise
Conclusions
• Successfully coupled Monte Carlo neutron transport code MC21 with
subchannel T-H code CTF
• Combination of CASL tools and in-house Python code
• Simulated VERA Benchmark Problems 6 and 7
• First published results for coupled Monte Carlo neutronics & subchannel T-H
solution for Watts Bar Unit 1 at HFP, BOC, w/ xenon and critical boron
search (Problem 7)
• Results in excellent agreement with VERA