DIPARTIMENTO DI INGEGNERIA CIVILE E INDUSTRIALE
TESIDILAUREASPECIALISTICAININGEGNERIA NUCLEARE EDELLASICUREZZAINDUSTRIALE
“SIMMER Code Improvements and Applications in Safety Analysis of MYRRHA Reactor”
RELATORI IL CANDIDATO
Prof. Ing. Walter Ambrosini Simone Gianfelici
DICI
Dott. Ing. Nicola Forgione DICI
Anno Accademico 2012-2013
Abstract
As a part of collaboration between the Dipartimento di Ingegneria Civile ed Industriale (DICI) of the University of Pisa and the Institut für Kern- und Energietechnik (IKET) of the Karlsruher Institut für Technologie, a FORTRAN program, for the restarting of calculations for SIMMER III code was developed. The “SIMMER-to-SIMMER coupling program” gives great flexibility in comparison with the default RESTART capability of the code and allows modifying any option in the input file.
The first part of this thesis work describes the SIMMER-III code and the ADS reactors, in particular the MYRRHA-FASTEF reactor.
In the fourth chapter a description of the coupling program and the 2D domain adopted in the description of the MYRRHA reactor is presented. The results of a 500 s steady-state calculation are compared with those of a standard RESTART and of a restart carried out with the coupling program, both from 200 s of simulation. For both restarts, pressure and velocities are in good agreement with the steady-state analysis, while the temperatures show small differences during the two transients.
The coupling program was used to start transients of fuel release, equivalent to the mass of fuel present in a single pin, in natural and forced circulation. The results are then compared to those already obtained by DICI, started with velocity and temperature fields chosen by the user and with radius of fuel particles equal to 1 mm. Due to the different velocity and temperature fields at the beginning of the transients, a higher amount of fuel particles was calculated in proximity of the baffle in forced circulation conditions. Furthermore, for natural circulation calculations, the fuel particles released tend to concentrate more in proximity of the free level of the hot pool. According to the results of the SEARCH meetings, the radius was then set to 75 micrometers and a comparison with the previous simulation is reported. The smaller fuel particles tend to float and accumulate more, in particular in the regions where the coolant has low velocities.
Finally, to check the coherence of the geometry approximations of the 2D mesh, the results of the last analysis are compared with those of the analyses of fuel pin release performed with the 3D model of MYRRHA developed by DICI and ENEA. Differently from the 2D one, the 3D domain shows high concentration of fuel particles between the diaphragm and the vessel, and a lower amount in the pumps and the cold pool A certain amount of fuel near the baffle is anyhow predicted.
I
List of Contents
LIST OF CONTENTS ... I LIST OF FIGURES ... V LIST OF TABLES ... X NOMENCLATURE ... XI Acronyms ... XI Roman Letters ... XIV Greek letters ... XVI Subscripts ... XVI Superscripts ... XVIII 1. INTRODUCTION ... 1-1 References ... 1-5 2. SIMMER-III CODE ... 2-1 2.1 Introduction ... 2-1 2.2 Models and Methods of SIMMER-III ... 2-2 2.2.1. Code Framework and Geometry ... 2-2 2.3 Structure (fuel pin) model ... 2-6 2.4 Fluid-Dynamics Model ... 2-10 2.4.1 Fundamental Differential Equations ... 2-10 2.4.2 Overall Solution Procedure ... 2-11 2.4.3. Fluid Convection Algorithm ... 2-12 2.4.4 Flow regimes and Interfacial Area Model... 2-14 2.4.5 Momentum Exchange Functions ... 2-18 2.4.6 Heat-Transfer Coefficients ... 2-19 2.4.7 Heat and Mass Transfer Model ... 2-20 2.4.8 Inter-cell Heat Transfer ... 2-24
II
2.4.9 Equations-of-State Model ... 2-25 2.5 Neutronics Model ... 2-27 References ... 2-28 3. THE ADSS SYSTEMS AND THE MYRRHA-FASTEF REACTOR ... 3-1 3.1 ADS systems ... 3-1 3.1.1 Introduction ... 3-1 3.1.2 Minor Actinides and transuranic elements as nuclear fuel ... 3-2 3.1.3 THORIUM as nuclear fuel ... 3-6 3.1.4 ADSs neutron source ... 3-8 3.1.5 Sub-critical reactor in ADS ... 3-11 3.2 The MYRRHA reactor ... 3-13 3.2.1 Introduction ... 3-13 3.2.2 Historical evolution of MYRRHA: from ADONIS to FASTEF... 3-14 3.2.3 Current MYRRHA-FASTEF design ... 3-16 3.2.4 Main components ... 3-17 References ... 3-26 4. SIMMER-TO-SIMMER COUPLING PROGRAM ... 4-1 4.1 Introduction ... 4-1 4.2 Description of the program ... 4-2 4.3 Description of the 2D mesh for the MYRRHA reactor ... 4-9 4.3.1 Vessel ... 4-10 4.3.2 Diaphragm ... 4-10 4.3.3 Core Support Structure ... 4-12 4.3.4 Pump... 4-13 4.3.5 Primary heat exchangers ... 4-13 4.3.6 Core ... 4-14 4.4 Steady-state analysis of the model ... 4-18 4.4.1 Mass flow rate ... 4-18
III
4.4.2 Temperature in the structures ... 4-19 4.4.3 Temperature in the LBE ... 4-20 4.4.4 LBE velocities ... 4-23 4.5 Default RESTART and coupling program comparison ... 4-25 4.5.1 Temperatures ... 4-25 4.5.2 Pressure ... 4-26 4.5.3 Velocities ... 4-26 4.6 Final considerations ... 4-27 References ... 4-28 5. FUEL DISPERSION ANALYSIS IN MYRRHA REACTOR ... 5-1 5.1 Generalities ... 5-1 5.2 Initial conditions and time evolution of the flow conditions ... 5-3 5.2.1 Forced circulation in the primary loop ... 5-3 5.2.2 Natural circulation in the primary loop ... 5-5 5.3 Fuel dispersion: 1 mm particle radius ... 5-8 5.3.1 Test 1 ... 5-8 5.3.2 Test 2 ... 5-14 5.3.3 Natural Circulation, comparison between 5% and 10% porosity ... 5-18 5.3.4 Test 3 ... 5-19 5.3.5 Test 4 ... 5-25 5.3.6 Forced Circulation, comparison between 5% and 10% porosity ... 5-29 5.4 Fuel dispersion: 75 µm particle radius ... 5-30 5.4.1 Test 5 and Test 6 ... 5-30 5.4.2 Test 7 ... 5-34 5.4.3 Test 8 ... 5-37 References ... 5-39 6. COMPARISON BETWEEN SIMMER-III AND SIMMER-IV RESULTS ... 6-1 6.1 Description of the 3D model ... 6-1
IV
6.2 Fuel porosity 5%, particles radius 75 µm ... 6-6 6.3 Fuel porosity 10%, particles radius 75 µm ... 6-12 References ... 6-18 7. CONCLUSIONS ... 7-1
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List of Figures
Figure 2.1: SIMMER-III Overall Code Structure ... 2-2 Figure 2.2: SIMMER-III geometry ... 2-3 Figure 2.3: Fluid-dynamics mesh cell configuration ... 2-3 Figure 2.4: Axial fuel pin representation in SIMMER-III... 2-6 Figure 2.5: Radial fuel pin representation in SIMMER-III ... 2-7 Figure 2.6: Fuel pin and can wall configuration in a mesh cell ... 2-9 Figure 2.7: Schematic Diagram of the Four-Step Method ... 2-11 Figure 2.8: Pool Flow Regime Map ... 2-15 Figure 2.9: Schematic Concept of Separating Bubbly and Dispersed Regions... 2-15 Figure 2.10: Channel Flow Regimes ... 2-16 Figure 2.11: Non-equilibrium mass transfer model in SIMMER-III ... 2-21 Figure 2.12: Basis of non-equilibrium heat-transfer limited process ... 2-22 Figure 3.1: Main trajectories of nuclear transformations in the U-Pu fuel cycle ... 3-4 Figure 3.2: Main trajectories of nuclear transformations in the Th-U fuel cycle ... 3-6 Figure 3.3: Schematics of Spallation reaction ... 3-10 Figure 3.4: Neutron emission from tungsten (W) target – estimates reported for
various energy of primary protons ... 3-10 Figure 3.5: Schematic ADS configuration ... 3-12 Figure 3.6: Overview of the MYRRHA-FASTEF reactor ... 3-17 Figure 3.7: General lay-out of the pump ... 3-18 Figure 3.8: FASTEF heat exchanger, ver. 1.2 ... 3-19 Figure 3.9: FASTEF heat exchanger, ver. 1.4 ... 3-19 Figure 3.10: Overall configuration of the RVACS system ... 3-21 Figure 3.11: In-vessel fuel handling machine ... 3-21 Figure 3.12: Overview of the diaphragm ... 3-22 Figure 3.13: LBE cold and hot pools divided by the diaphragm ... 3-22 Figure 3.14: MYRRHA-FASTEF core assemblies ... 3-23 Figure 4.1: First step: name of the base file and problem time ... 4-4 Figure 4.2: Variables that the code can elaborate ... 4-5 Figure 4.3: Example of a case with missing variables ... 4-5 Figure 4.4: Variables routine ... 4-5 Figure 4.5: Variables selected (read from the variables.dat file) ... 4-6
VI
Figure 4.6: Routine to skip cells ... 4-6 Figure 4.7: Concept of the square exclusion ... 4-7 Figure 4.8: Pause to edit the skipped.dat file ... 4-7 Figure 4.9: Summary of selected cells (0 = excluded, 1 = included) ... 4-8 Figure 4.10: Section of MYRRHA-FASTEF reactor ... 4-9 Figure 4.11: SIMMER-III 2D mesh for MYRRHA ... 4-10 Figure 4.12: IVFHM and baffle in 2D mesh ... 4-11 Figure 4.13: In-vessel fuel storage and pump-PHX volumes ... 4-11 Figure 4.14: Core Support Structure... 4-12 Figure 4.15: Particular of the model of the pump... 4-13 Figure 4.16: Scheme of the PHX model ... 4-14 Figure 4.17: FA design ... 4-14 Figure 4.18: Radial power profile used in SIMMER-III calculations ... 4-15 Figure 4.19: Axial power profile used in SIMMER-III calculations ... 4-16 Figure 4.20: Modeling of the core with the related rings for SIMMER-III ... 4-17 Figure 4.21: Mass Flow rate ... 4-19 Figure 4.22: Structure temperatures in the core ... 4-20 Figure 4.23: Radial profile of structures temperature in FA ... 4-21 Figure 4.24: Radial profile of LBE temperature in the core ... 4-22 Figure 4.25: Axial LBE temperature in the PHX ... 4-22 Figure 4.26: LBE velocity in the core ... 4-23 Figure 4.27: Cells with high velocity that cause convergence problem ... 4-24 Figure 4.28: Comparison between LBE temperatures in the core for the steady-state
calculation and the two restars ... 4-25 Figure 4.29: Comparison between pressures in the gas zone ... 4-26 Figure 4.30: Comparison between velocities in the core... 4-27 Figure 5.1: Densities of LBE and MOX fuel, theoretical and with 5% and 10% of
porosity ... 5-1 Figure 5.2: LBE velocity vectors from 2D steady-state calculation, with stagnation
regions indicated in red and recirculation zones in yellow... 5-4 Figure 5.3: LBE temperature profile from steady-state analysis [°K] ... 5-5 Figure 5.4: LBE mass flow rate trend in the core for natural circulation tests ... 5-6 Figure 5.5: Time evolution of LBE velocity vectors and LBE temperature profile
[°K]: natural circulation tests, pumps trip and reactor scram at 10 s ... 5-7
VII
Figure 5.6: Comparison between LBE velocity field at 10 s in the old (left) and in the new calculation (right) ... 5-8 Figure 5.7: Time evolution of fuel particles concentration in the primary loop for test
1 (first 150 s of transient)... 5-9 Figure 5.8: Time evolution of fuel particles concentration in the primary loop for test
1 (200, 250 and 300 s of transient) ... 5-10 Figure 5.9: Input Zones for BFCAL: natural circulation ... 5-11 Figure 5.10: Test 1: BFCAL results from old calculation, 5% fuel porosity, natural
circulation ... 5-12 Figure 5.11: Test 1: BFCAL results from new calculation, 5% fuel porosity, natural
circulation ... 5-12 Figure 5.12: LBE temperature in the hot pool at 300 s, old (left) and new (right)
calculations ... 5-13 Figure 5.13: Test 2: BFCAL results from old calculation, 10% fuel porosity, natural
circulation ... 5-14 Figure 5.14: Test 2: BFCAL results from new calculation, 10% fuel porosity, natural
circulation ... 5-15 Figure 5.15: Time evolution of fuel particle concentration in the primary loop for test
2 (first 150 s of transient) ... 5-16 Figure 5.16: Time evolution of fuel particle concentration in the primary loop for test
2 (200, 250 and 300 s of transient) ... 5-17 Figure 5.17: Comparison between fuel particles volume fractions of test 1 (5% fuel
porosity, left) and test 2 (10% fuel porosity, right) at the end of transient . 5-18 Figure 5.18: Time evolution of fuel particle concentration in the primary loop for test
3 (first 150 s of transient) ... 5-20 Figure 5.19: Time evolution of fuel particle concentration in the primary loop for test
3 (200, 250 and 300 s of transient) ... 5-21 Figure 5.20: Input Zones for BFCAL for the tests in forced circulation ... 5-22 Figure 5.21: Test 3: BFCAL results from old calculation, 5% fuel porosity, forced
circulation ... 5-24 Figure 5.22: Test 3: BFCAL results from new calculation, 5% fuel porosity, forced
circulation ... 5-24 Figure 5.23: Time evolution of fuel particle concentration in the primary loop for test
4 (first 150 s of transient) ... 5-26
VIII
Figure 5.24: Time evolution of fuel particle concentration in the primary loop for test 4 (200, 250 and 300 s of transient) ... 5-27 Figure 5.25: Test 4: BFCAL results from old calculation, 10% fuel porosity, forced
circulation ... 5-28 Figure 5.26: Test 4: BFCAL results from new calculation, 10% fuel porosity, forced
circulation ... 5-28 Figure 5.27: Comparison between fuel particles volume fractions of test 3 (5% fuel
porosity, left) and test 4 (10% fuel porosity, right) at the end of transient . 5-29 Figure 5.28: Time evolution of fuel particles concentration in the primary loop for
test 5 ... 5-31 Figure 5.29: Time evolution of fuel particles concentration in the primary loop for
test 6 ... 5-32 Figure 5.30: Test 5: BFCAL results, 5% fuel porosity, particles radius 75 µm, natural
circulation ... 5-33 Figure 5.31: Test 6: BFCAL results, 10% fuel porosity, particles radius 75 µm,
natural circulation ... 5-34 Figure 5.32: Time evolution of fuel particles concentration in the primary loop for
test 7 ... 5-35 Figure 5.33: Test 7: BFCAL results, 5% fuel porosity, particles radius 75 µm, forced
circulation ... 5-36 Figure 5.34: Test 8: BFCAL results, 10% fuel porosity, particles radius 75 µm,
forced circulation ... 5-37 Figure 5.35: Time evolution of fuel particles concentration in the primary loop for
test 8 ... 5-38 Figure 6.1: Horizontal section of the 3D mesh for SIMMER-IV ... 6-2 Figure 6.2: Overall view of 3D mesh for SIMMER-IV ... 6-2 Figure 6.3: View of velocities in proximity of the baffle ... 6-3 Figure 6.4: Comparison between 2D and 3D meshes ... 6-4 Figure 6.5: Position of the release in the core ... 6-5 Figure 6.6: View of the PHX-pump volume ... 6-5 Figure 6.7: Comparison between time evolutions of fuel dispersion in 2D and 3D
domains, fuel porosity 5% and particles radius 75 µm (first 150 s of calculation) ... 6-7
IX
Figure 6.8: Comparison between time evolutions of fuel dispersion in 2D and 3D domains, fuel porosity 5% and particles radius 75 µm (200, 250 and 300 s of calculation)... 6-8 Figure 6.9: Stagnation regions (in yellow) in 3D calculation, vertical section. LBE
coolant velocity vectors in black. ... 6-9 Figure 6.10: Horizontal view of the fuel particles volume fraction ... 6-10 Figure 6.11: Stagnation regions (in yellow) in 3D calculation, horizontal section.
LBE Coolant velocity vectors in black. ... 6-11 Figure 6.12: Comparison between time evolutions of fuel dispersion in 2D and 3D
domains, fuel porosity 10% and particles radius 75 µm (first 150 s of calculation) ... 6-13 Figure 6.13: Comparison between time evolutions of fuel dispersion in 2D and 3D
domains, fuel porosity 10% and particles radius 75 µm (200, 250 and 300 s of calculation) ... 6-14 Figure 6.14: LBE temperature distribution in 3D simulation [°K] ... 6-15 Figure 6.15: Fuel particles dispersion at the free level for 3D domain with 10% fuel
porosity ... 6-16
X
List of Tables
Table 2.1: SIMMER-III Fluid Dynamics Structure Field Components ... 2-4 Table 2.2: SIMMER-III Fluid Dynamics Liquid Field Components ... 2-5 Table 2.3: SIMMER-III Fluid Dynamics Vapor Field Components ... 2-5 Table 2.4: SIMMER-III Fuel-Pin Components ... 2-5 Table 3.1: Values of the fission parameters of selected actinides ... 3-4 Table 3.2: Average composition of spent nuclear fuel (main radionuclides/1GWe*year .. 3-5 Table 3.3: Actinides content in PWR fuel [g/t] (BU 30 GWd/t) ... 3-7 Table 3.4: Energy cost of neutrons from various accelerator-based sources ... 3-9 Table 3.5: MYRRHA pump updated parameters ... 3-18 Table 4.1: Input and Output variables in SIMMER-III; correlation between region-
wise input options XRGN, cell-wise input options XCWD and output variables in SIMBF ... 4-3 Table 4.2: Main characteristics of the MYRRHA reactor ... 4-18 Table 5.1: Simulation matrix ... 5-2
XI
Nomenclature Acronyms
ADS Accelerator Driven System
AFDM Advanced Fluid-Dynamics Model
BoC Beginning of Cycle
BoL Beginning of Life
CAD Computer-Aided Design
CDA Core Disruptive Accident
CDT Central Design Team
CEA Commissariat A L'energie Atomique
CFD Computational Fluid-Dynamic
CP Continuous Phase
CPU Central Processor Unit
CR Control Rod
CRGT Control Rod Guide Tube
CSS Core Support Structure
DA Dummy Assembly
DBC Design Basis Condition
DHR Decay Heat Removal
DICI Dipartimento di Ingegneria Civile ed Industriale of University of Pisa
DPIN Detailed Fuel-Pin Model
EFIT European Facility for Industrial Transmutation
ENEA Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile
XII
EoC End of Cycle
EoL End of Life
EOS Equation Of State
ETD European Transmutation Demonstration
FA Fuel Assembly
FASTEF Fast Spectrum Transmutation Experimental Facility
FC Forced Circulation
FZK Forschungszentrum Karlsruhe
GFR Gas Fast Reactor
GIF Generation IV International Forum
HLM High Liquid Metal
HMT Heat and Mass Transfer model
HTC Heat Transfer Coefficient
IAEA International Atomic Energy Agency
IFA InterFacial Area model
IKET Institut für Kern- und Energietechnik
IPS In-Pile Section
IVFHM In-Vessel Fuel Handling Machine
IVFS In-Vessel Fuel Storage
JNC Japan Nuclear Cycle Development Institute KIT Karlsruhe Institute of Technology
LANL Los Alamos National Laboratory
LBE Lead-Bismuth Eutectic
LFR Lead Fast Reactor
XIII
LMFR Liquid Metal Fast Reactor
LWR Light Water Reactor
M/F Melting/Freezing
MA Minor Actinide
MFBT Minimum Film Boiling Temperature
MFC Multi-Functional Channel
MOX Mixed OXide fuel
MRK Modified Redlich-Kwong
MSR Molten Salt Reactor
MWC Melt Water Contact
MYRRHA Multi-purpose hYbrid Research Reactor for High-tech Applications
NC Natural Circulation
P&T Partitioning & Transmutation
PBA Protected Blockage Accident
PDS-XADS Preliminary Design Studies of an eXperimental Accelerator Driven System
PHX Primary Heat eXchanger
PNC Power Reactor and Nuclear Fuel Development Corp
PTOP Protected Transient OverPower
RVACS Reactor Vault Air Cooling System R&D Research & Development
RIA Reactivity Induced Accident
RV Reactor Vessel
SA Sub-Assembly
SAEOS Simplified Analytic EOS
XIV
SCARA Selective Compliant Assembly (Articulated) Robot Arm
SCRAM Safety Control Rod Axe Man
SCWR Super Critical Water Reactor
SEARCH Safe ExploitAtion Related CHemistry for HLM reactors
SFR Sodium Fast Reactor
SG Steam Generator
S-S Steady-State
SR Safety Rod
SS Stainless Steel
SPIN Simplified Fuel-Pin Model
TRU TRansUranium element
V/C Vaporization/Condensation
VHTR Very High Temperature Reactor
VF Volume Fraction
WP WorkPackage
XS eXtenSion (SIMMER)
XT-ADS eXperimental Transmuter and irradiation facility based on ADS concept
Roman Letters
A interfacial area (m-1)
a binary-contact area per unit volume (m-1) ALPGK volume fraction of gas
ALPLK4 volume fraction of fuel particles ALPLK5 volume fraction of clad particles
XV CORF orifice coefficient
c heat capacity (J/kg/K)
Dh hydraulic diameter (m)
E entrainment
e specific internal energy (J/kg)
f volume fraction
g gravity (m/s2)
Gr Grashof number
H heaviside unit function
h heat transfer coefficient (W/m2/K)
i specific enthalpy (J/kg)
K inter-field momentum exchange function (kg/m3/s)
L characteristic length (m)
Nu Nusselt number
p pressure (Pa)
Pr Prandtl number
Q heat transfer rate (W/m3) q heat transfer rate (W/m3)
R gas constant (J/kg/K)
r radius (m)
Ra Rayleigh number
Re Reynolds number
S interfacial area source term (1/m/s)
T temperature (K)
XVI
TLK3 LBE temperature (°C)
TIPINK center pin temperature (°C) TSK1 surface pin temperature (°C) TSK4 clad temperature (°C) TSK8 can wall temperature (°C
v specific volume of the structure V
ur velocity (m/s)
v
r velocity (m/s)
VM
uuur virtual mass (kg/m2/s2)
We Weber number
Greek letters
α volume fraction or void fraction
δ thermal penetration length (m)
Γ mass-transfer rate per unit volume (kg/s/m3)
κ thermal conductivity (W/m/K)
µ dynamic viscosity (Pa·s)
ρ density (kg/m3)
ρ macroscopic density (kg/m3)
σ surface tension (N/m)
τ time constant (s)
Subscripts
a fuel pin interior node
B bubbly flow regime
XVII
b fuel pin surface node
c cladding or continuous phase
CP continuous phase
Crt critical (temperature)
D dispersed flow regime
d dispersed phase
f fuel
film film region
FS liquid film
G vapour mixture
GL Terms existing at interface between vapour and liquid velocity
Gm energy component m in a vapour field
hb fluid and fuel pellet surface (rate of energy interchange between) hc fluid and cladding (rate of energy interchange between)
HT heat transfer
int fuel pin interior node
L liquid component
LCW left can wall
Lm energy component m in a liquid field
M material number or energy component
m density component
MF melting/freezing (rate of energy interchange due to)
N nuclear (heating rate)
nf non-flow volume
XVIII
P particle component
PIN fuel pin
pool pool flow regime q, 'q velocity fields
qq ' terms existing at interface between two velocity fields
RCW right can wall
S Structure component
slug slug flow regime
Sm energy component m in a structure
str structure
VC vaporization/condensation (rate of energy interchange due to)
VS vapour structure
Superscripts
I interface quantity
