Post on 15-Nov-2021
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-1
Modular High Temperature Pebble Bed Reactor
Faculty AdvisorsAndrew C. Kadak
Ronald G. BallingerMichael J. Driscoll
Sidney YipDavid Gordon Wilson
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-2
Student Researchers
• Fuel Performance- Heather MacLean- Jing Wang
• Core Physics- Julian Lebenhaft
• Thermal Hydraulics- Chunyun Wang- Tamara Galen
• Safety- Tieliang Zhai
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-3
Project Objective
Develop a sufficient technical and economicbasis for this type of reactor plant to determinewhether it can compete with natural gas and stillmeet safety, proliferation resistance and waste disposal concerns.
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-4
Generation IV Reactor
• Competitive with Natural Gas• Demonstrated Safety• Improved Proliferation Resistance• Readily Disposable Waste Form
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-5
Modular High TemperaturePebble Bed Reactor
• 110 MWe• Helium Cooled• “Indirect” Cycle• 8 % Enriched Fuel• Built in 2 Years• Factory Built• Site Assembled
• On-line Refueling• Modules added to
meet demand.• No Reprocessing• High Burnup
>90,000 Mwd/MT• Direct Disposal of
HLW
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-6
What is a Pebble Bed Reactor ?
• 360,000 pebbles in core• about 3,000 pebbles handled by
FHS each day• about 350 discarded daily• one pebble discharged every 30
seconds• average pebble cycles through
core 15 times• Fuel handling most
maintenance-intensive part of plant
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-7
MPBR SpecificationsThermal Power 250 MWCore Height 10.0 mCore Diameter 3.0 mPressure Vessel Height 16 mPressure Vessel Radius 5.6 mNumber of Fuel Pebbles 360,000Microspheres/Fuel Pebble 11,000Fuel UO2Fuel Pebble Diameter 60 mmFuel Pebble enrichment 8% Uranium Mass/Fuel Pebble 7 gCoolant HeliumHelium mass flow rate 120 kg/s (100% power)Helium entry/exit temperatures 450oC/850oCHelium pressure 80 barMean Power Density 3.54 MW/m3
Number of Control Rods 6Number of Absorber Ball Systems 18
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-8
TurbomachineryModule
IHX ModuleReactorModule
Conceptual Design Layout
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-9
Competitive With Gas ?
• Natural Gas 3.4 Cents/kwhr• AP 600 3.62 Cents/kwhr• ALWR 3.8 Cents/kwhr• MPBR 3.3 Cents/kwhr
Levelized Costs (1992 $ Based on NEI Study)
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-10
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-11
Improved Fuel Particle Performance Modeling:
Chemical ModelingStudent: Heather MacLean
Advisor: R. Ballinger
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-12
Objective• Model fuel particle chemical environment
– particle temperature distributions– internal particle pressure
• Model chemical interactions with coatings (SiC)– migration of fission products (Ag) through coatings
(SiC)– chemical attack (Pd) of SiC
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-13
Accomplishments• Analyzed likely temperatures in fuel
particles in different core locations– ∆T across any particle < 20 °C– peak kernel temperature range: 500-1100 °C
• Diffusion experiment in progress– 2 diffusion couples heated, continuing– characterization in progress
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-14
Coated Particle Fuel SystemFuel Kernel
BufferIPyC
SiCOPyC
Individual Microsphere780 µm nominal diameter
60 mmdiameter
~11,000 microspheres per fuel pebble~350,000 pebbles per core
Fuel Pebble
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-15
Thermal ModelCalculate temperatures in a pebble:• Linear axial bulk He temperature rise (450-850 °C)• Packed-bed He heat transfer correlation
(∆T across He film surrounding a pebble)⇒ Pebble surface temperature for any core location• Homogenized (volumetric averages) pebble thermal
conduction model based on core average power• Thermal conductivity depends on temperature⇒ Temperature distribution inside a pebble⇒ Fuel particle thermal model
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-16
Fuel Particle Thermal ModelCalculate temperatures in a particle:• Particle surface temperature determined by radial
location in a pebble• Fuel kernel fission product swelling data
1% volume swelling per 10 GWd/T• Buffer densification to accommodate kernel swelling• Kernel thermal expansion -- 10-6 K-1
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-17
Bounding Thermal ExamplesTHe(inlet) = 450 °C
THe(outlet) = 850 °C
Low Temperature Case
High Temperature Case
core inletpower: average peak T: 513 °C∆T: 16 °C
core outlet power: average 2x averagepeak T: 968 °C 1074 °C∆T: 17 °C 19 °C
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-18
Typical Particle TemperaturesPebble Power Average Average 2x AverageAxial Location Core Inlet Core Outlet Core OutletLoc. In Pebble Outer Edge Center Center
Bulk He Temp.(°K) 723 1123 1123
Temperatures
Kernel Center 786 1241 1347Kernel Outer Edge 779 1234 1340Buffer Outer Edge 771 1225 1329IPyC Outer Edge 770 1224 1329SiC Outer Edge 770 1224 1329OPyC Outer Edge 770 1224 1328
Particle ∆T 16 17 19
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-19
Significance of Temperatures• Small ∆T across all particles
⇒ can use average temperature in a particle for chemical analyses
• Variation in particle peak temperature⇒ chemistry phenomena (diffusion) vary
exponentially with temperature• Gradient across particle
⇒ significant impact on mechanical phenomena
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-20
Chemical Interactions• Palladium
– very destructive, local attack
– can open a pathway for fission product release
– limited data
• Silver– diffuses through
intact SiC– activity / maintenance
concern– limited data in MPBR
proposed temperature range
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-21
SiC Diffusion Experiments• Limited data for specific
fission products and temperatures of interest
• Develop experimental foundation for future study of advanced fission product barrier materials 3/4 inch OD 30 mil thick wall
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-22
Experimental Procedure
Ar gas
1. Sputter Coating
Metal Coating Deposited on
Inside of Shell
Ag or Pd target
Graphite Hemisphere
(hollow shell)
3. Heat Treatment
1000-1600 oC10-1000 hours
5. Data Analysis
DAg(T)DPd(T)DMFP(T)
r
CAg
4. Characterization
MicroscopySIMSESCAXRD
Metal Inner Coating
Diffusion Couple(cross section)
Graphite Shell
SiC or ZrC overcoating
2. SiC Overcoating
MTS & H2
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-23
Status of Experiments• Experimental procedure defined• System operational• 2 diffusion heat treatments completed
– 1500 °C, 24 hours, Ag-SiC– 1400 °C, 44 hours, Ag-SiC– other temperatures in progress
• Characterization in progress
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-24
Future Work• Continue diffusion couple heat treatments• Collect and analyze diffusion experiment
data• Update thermal and pressure models
– include UCO data– include radial and axial power peaking
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-25
Fuel Performance Modeling— Mechanical Analysis
Student: Jing WangAdvisors: Prof. Ballinger & Prof. Yip
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-26
Objective• Develop a mechanical model to predict the
mechanical behavior of TRISO fuel particles, including failure, that can be used as a tool in understanding past behavior and in developing advanced particles
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-27
Mechanical ModelStress Analysis Failure Model
Analytical Solution
Finite Element
ABAQUS ‘FUEL’ code
• Anisotropy• Asphericity• Substructure
Specialized FEM
• Isotropy• Fast Speed• MC Sampling
Crack Induced Failure
Pure Pressure Vessel Failure
Fracture Mechanics
Failure Criteria
Fracture Strength ( σF )
• Stress IntensityFactor ( )
• Strain EnergyRelease ( G )
KI
Chemistry
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-28
Conclusion• Currently with closed form solutions,
the fracture mechanics based failure model, developed as part of this task, yields a good prediction of the failure probability of TRISO fuel particles
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-29
Closed Form Solutions
• System: IPyC/SiC/OPyC• Assumptions– Spherical layers
– Elastically isotropic
– Creep and swellingare treated for IPyC/OPyC
– SiC is just elastic shell
– Three layers aretightly bonded
Layer Thickness(µm)
Outer PyC 43
SiC 35
Inner PyC 53
Buffer PyC 100
UCO 195
(diameter)
Total Diameter 0.66 mm
TRISO Fuel Particle
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-30
Time Evolution of Radial Stress Distribution in TRISO Fuel Particles
197.
520
6.67
215.
8422
5.01
234.
18
243.
35
252.
52
261.
69
270.
86
280.
03
289.
2
298.
37
307.
54
316.
71
325.
88 0
0.20
4
0.40
8
0.61
2
0.81
6
1.02
1.22
4
1.42
8
1.63
2
-30
-20
-10
0
10
20
30
40
50
60
Rad
ial S
tres
s (M
Pas)
Radius (microns)
Fluence (10^21nvt)
50-6040-5030-4020-3010-200-10-10-0-20--10-30--20
IPyCSiC
OPyC
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-31
Time Evolution of Tangential Stress Distribution in TRISO Fuel Particles
197.
520
9.29
221.
08
232.
87
244.
66
256.
45
268.
24
280.
03
291.
82
303.
61
315.
4
327.
19 0
0.20
4
0.40
8
0.61
2
0.81
6
1.02
1.22
4
1.42
8
1.63
2
-400
-300
-200
-100
0
100
200
Tang
entia
l Stre
ss (M
Pas)
Radius (microns)
Fluence (10^21nvt)
100-2000-100-100-0-200--100-300--200-400--300
IPyCSiC
OPyC
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-32
Finite Element Method• Check with analytical solutions and other calculations• Study the non-ideal particles
– anisotropy of material– anisotropy of geometry
• Evaluate the effects of crack and debonding• Combine with analytical solutions to predict failure
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-33
Fracture Mechanics based Failure Model
• Consider the impact of the cracking of IPyC to SiC• Stress distributions come from closed form solutions• Currently use stress intensity factor to evaluate local
stresses
• Predict failure probability with MC sampling process(Gaussian Distribution : Layer thickness, kernel & buffer densitiesWeibull Distribution : Fracture strength of IPyC, SiC and OPyCTriangular Distribution : Critical stress intensity factor of SiC )
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-34
IPyCSiC
OPyC
PIPO
)(SiCKIC
aIPyCK TI πσ=)(
Material PropertyσT
The Sketch for FM based Failure Model
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-35
Prediction by FM based Failure Model• Inputs
SiC layer –– (Sampled with triangular distribution)KIC(SiC) (mean) = 3300MPa·µm1/2 [1] Standard Deviation = 530MPa·µm1/2
IPyC layer –– (Sampled with Weibull distribution)σF(IPyC) (mean) = 384MPa [2] Weibull modulus = 8.6 [2]
End-of-life Burnup –– 75% FIMA
Particles Sampled –– N=1,000,000
• OutputsCases with IPyC Failure: 595 Failure Probability: 5.95×10-4
Cases with SiC Failure: 17 Failure Probability: 1.70×10-5
[1] Material Specification No. SC-001, Morton Advanced Materials, 185 New Boston Street, Woburn, MA 01801[2] J. L. Kaae, et al., Nucl. Tech., 35, 1977, p368
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-36
Conclusions• The previous mechanical model, based on a pressure
vessel failure by overpressure, from INEEL predicts zero fuel failure
• New fracture mechanics based failure model gives reasonable prediction of the failure probability of TRISO fuel particles
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-37
Future Work• Use finite element method (ABAQUS) to incorporate
non-ideal particles• Improve the fracture mechanics based failure model• Build a more realistic pyrocarbon model• Use specialized finite element method
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-38
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-39
Chunyun Wang Advisors: Prof. R. G. Ballinger
Dr. H. C. No
(Draft) Presentation for INEEL Review Aug. 01, 00
Dynamic Modeling for MPBR
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-40
Current Design Schematic
97°C 8.0MPa
30°C 2.0MPa
803 °C 7.6MPa
401°C 2.1MPa
445°C 7.7MPa
850°C 7.6MPa
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-41
Objective
• Develop a dynamic model as the primary tool for– developing the control system– performing transient analysis– optimizing power conversion system
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-42
Summary• Have developed dynamic models for core ,
heat exchanger. A simple steady state turbo-machinery model is used.
• Verification of core kinetic model• Verification heat exchanger model• Provide control methods and use PID
controller to implement them
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-43
Model StructureMPBRSimMPBRSim
Core ModelCore Model
T-HT-H KineticKinetic PoisoningPoisoning
Turbo-machineryTurbo-machinery Heat exchangerHeat exchangerControl ModelControl Model
Gas-GasGas-Gas Gas-LiquidGas-Liquid
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-44
• Nodalization• Assumptions
– Fuel region is treated as a homogeneous region
– Helium heat conduction is negligible – The heat loss from the reactor vessel
is negligible• Pebble bed effective thermal
conductivity (GE correlation, taking into account both conduction and radiation).
• Helium convection:KFA correlation
Core Thermal-Hydraulic Model
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-45
Core neutronics, product poisoning and verification
• One effective group point kinetics equation (Fig. 1)
• Fission product poisoning (Fig.2)• Temperature coefficient of reactivity(Doppler effect)
σaφ
FissionγXγI
135I 135Xe
136Xe
λXλI 135Cs
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-46
Fig. 1 Numerical result versus analytical result for one effective group kinetics equation
0
1
2
3
4
5
0 5 10 15 20 25Time (sec)
P/P0
Nor
mal
ized
Pow
er
Analytical (0.22% Reactivity)
Analytical(-0.22% Reactivity)
Numerical (0.22% Reactivity)
Numerical (-0.22% Reactivity)
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-47
Fig.2 135Xe buildup following the core shutdown
0
1
2
3
4
5
6
0 20 40 60 80 100
Time (Hour)
Nor
mal
ized
Con
cent
ratio
n
Xe-135 Concentration(Normalized)
I-135 Concentration(Normalized)
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-48
Heat Exchanger Model
• Heat exchanger model– For counter flow heat exchanger– Divide it into many equally length sections– In each section, for gas side, ignore the gas mass,
therefore ignore the gas stored energy
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-49
Fig. 3 Recuperator steady state temperature distribution
Recuperator steady-state temperature distribution
50
100
150
200
250
300
350
400
0 2 4 6 8 10 12 14 16 18
Axial Positions (m)
Tem
pera
ture
(C)
Hot SideSteel WallCold Side
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-50
Fig. 4 Recuperator transient response to a step temperature increase of 200 C at hot helium inlet side
0
100
200
300
400
500
600
700
0 500 1000 1500 2000 2500
Tiem (sec)
Tem
pera
ture
(C)
Hot helium inletHot helium outletCold helium inletCold helium out
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-51
Fig. 5 Helium energy storage’s effect on the recuperator performance
23
23.2
23.4
23.6
23.8
24
24.2
24.4
24.6
24.8
25
0 2 4 6 8 10 12 14 16
Hehlium Pressure (MPa)
Tim
e Co
nsta
nt (
sec)
Model including heliumenergy storageModel excluding heliumenergy storage
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-52
Control Model
• Control methods– Control rod motion– Primary circulator speed– Bypass control in the power conversion system– Inventory control in the power conversion
system• Controller: PID
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-53
Summary• Have developed dynamic models for core ,
heat exchanger. A simple steady state turbo-machinery model is used
• Verification of core kinetic model• Verification of heat exchanger model• Provide control methods and use PID
controller to implement them
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-54
Future Work• Use programmed turbo-machinery
characteristic maps (Cooperate with NREC) in the model
• Develop valve model• Simulate electric load ramp
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-55
Comparison Between Air and Helium for Use as Working Fluids in the Energy-
Conversion Cycle of the MPBR
Student: Tammy GalenFaculty: D. G. Wilson
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-56
Objective:
Comparisons:•Cycle efficiency•Component design
•Size•Efficiency•Possible development work required
To assess the relative advantages of using air and helium for the working fluid in the MPBR energy-conversion cycle.
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-57
ConclusionUse of helium in a closed-cycle configuration is best suited to the modularity requirement of the MPBR. It results in the smallest sized components, high efficiency, and implements well established turbomachinery technology.
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-58
Three cycles investigated
Closed Cycle
HX
HX
TbC
Open Cycle
Tb
HX
C
•Air open cycle•Air closed cycle•Helium closed cycle
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-59
Influence of choice of working fluid
Component Design
Development Work
Cycle Efficiency
Component Cost
Component Size
Component Efficiency
Working Fluid
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-60
Thermophysical Properties of Helium and Air at 700K and 2MPa
Air Helium
Molecular weight 28.97 4.003
Specific heat (J/kgK) 1074 5193
Sonic velocity (m/s) 590 1500
Thermal conductivity(W/mK)
.056 .273
Viscosity (10-5) 3.33 3.56
Density (kg/m3) 9.96 1.42
Turbines and Compressors↑ Specific heat↑ Number of stages
↓ Viscosity, ↑Re #↑ Efficiency
↑ Sonic velocity, ↑ Compressor blade speed ↓ Mean diameter
↑ Density↓ Mean diameter
Heat Exchangers↑ Thermal conductivity↓ Size
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-61
Turbomachinery industrial experience• Air open-cycle experience
– Majority of gas-turbomachinery experience– Combustion-gas turbines: power and aircraft industries
• Air closed-cycle experience– Less popular demand and less industrial experience to date– First built in 1939 by Escher Wyss in Switzerland– 20 plants built in Europe following WW2
ranging in power under 20MWe • Helium experience:
– 2 facilities part of HHT international high temperature gas reactor project• Oberhausen II (50MWe, 2MPa), HHV(90MWe, 5MPa)
– Circulators from previous gas reactors
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-62
Industrial experience conclusions•Open-cycle air plant
•Least amount of development work required for MPBRdeployment
•Closed-cycle helium and closed-cycle air plants•Comparable amount of development work required•Technology has been tested and judged successful*•Open-cycle turbomachinery design methodology and operating experience is directly applicable
*IAEA Summary report on technical experiences from high-temperature heliumturbomachinery testing in Germany, 1995
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-63
Busbar Efficiency
• Deducts–Primary circulator work, 7.7 MW–3.5 MW station load–98% electric generator efficiency
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-64
Baseline Thermodynamic ComparisonHelium Air closed Air open
Pressure ratio 3.0 4.7 4.6
Busbar efficiency 45.2% 46.9% 47.7%
Reactor Tin (K) 767 792 797
Turbine Tin (K) 1101 1101 1101
Reactor inlet temperature constrained to 718K*Helium Air closed Air open
Pressure ratio 3.7 7.4 7.3Busbar efficiency 44.8% 46.0% 46.8%Turbine Tin (K) 1101 1101 1101
*Permissible using 9Cr-1-Mo-V as the vessel material according to ASME Class 2 &3 pressure-vessel in Codes Case N-47
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-65
Turbine Design Choices
Maximum blade speed at tip (m/s) 550
Work Coefficient (Ψ) 1 and 2
Flow coefficient (φ) 0.5
Reaction (%) 50
Hub shroud ratio at turbine outlet 0.6
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-66
Component volumes (m3)Helium Air-closed Air-open
IHX 17 86 260HP turbine 0.27 0.06 2.2LP turbine 0.58 0.22 13LP compressor 0.35 0.13 2.7Recuperator 13 61 180Precooler 50 97 ---Intercooler 1 41 80 180Intercooler 2 41 80 180Sum 160 400 820
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-67
Final Cycle ConclusionsHelium Air-closed Air-open
Pressure ratio 3.7 7.1 7.1Busbar efficiency 45.3% 47.1% 47.3%Turbine Tin (K) 1101 1101 1101Component volume (m3) 160 400 820Number of flatbed trucks* 1 2 N/A
*Based on volume analysis, carries all components except IHX and ducting
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-68
ConclusionUse of helium in a closed-cycle configuration is best suited to the modularity requirement of the MPBR. It results in the smallest sized components, high efficiency, and implements well established turbomachinery technology.
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-69
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-70
Pebble-Bed Reactor PhysicsResearch at MIT
Julian Lebenhaft Professor Michael Driscoll
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-71
OverviewStatement of progressProgram goalsNeutronic design methodology• MCNP/VSOP model of PBMR• Preliminary results
Proliferation resistance of PBMRPath forward
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-72
ProgressMCNP4B benchmark of HTR-10 completedVSOP94 fuel management code implementedProcedure established for linking MCNP and VSOP for core neutronic calculationsMCNP/VSOP model of PBMR developed and preliminary analysis performedProliferation resistance of PBMR investigated
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-73
Program Goals•• Establish a MonteEstablish a Monte--Carlo based methodology for Carlo based methodology for
modeling neutron and photon transport in PBRsmodeling neutron and photon transport in PBRs
•• Ability to model cores with fuel burnupAbility to model cores with fuel burnup
•• Integrated computerIntegrated computer--aided design toolsaided design tools
•• Perform preliminary design calculationsPerform preliminary design calculations
•• Investigate fuel cycles and assess their proliferation Investigate fuel cycles and assess their proliferation resistanceresistance
•• Validation of codes and methodsValidation of codes and methods
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-74
Neutronic Design Methodology
• Monte Carlo method for accurate analysis of:– control rod worth– void effects– geometry changes– shielding– heat deposition
• Diffusion-theory code for burnup calculation
diffusion code
Monte Carlocode
compositionof
fuel
A versatile design tool!
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-75
Why MCNP?
• Solves the Boltzmann equation by the Monte-Carlo method
• Exact representation of neutron and photon transport
• Continuous-energy cross sections• Detailed geometry specification• Millions of n-histories used
to generate ensemble averages
accurate calculations
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-76
VSOPVery Superior Old Programs
• Widely used for PBRs• Diffusion theory• Comprehensive code suite:
- Neutronics- Thermal hydraulics- Fuel cycles- Economics
• Installed at MIT• Verification in progress
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-77
MCNP/VSOP Model of PBMR
Detailed MCNP4B model of ESKOMPebble Bed Modular Reactor:• reflector and pressure vessel• 18 control rods (HTR-10) • 17 shutdown sites (KLAK) • 36 helium coolant channels
Core idealization based on VSOPmodel for equilibrium fuel cycle:• 57 fuel burnup zones• homogenized compositions
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-78
MCNP4B Model of Core
reflectorcoolantcontrolreflectorfuel
shutdownpressurevessel
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-79
MCNP4B Model of Control Rod
graphite
s/s
B4C
helium
horizontal view
verti
cal v
iew
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-80
MCNP4B Model of Shutdown Site
1
2
3
1) empty channel2) channel filled with
absorber balls3) 0.25 in. absorber ball
with graphite coating
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-81
MCNP4B/VSOP Model Output
Top ofcore
top
0
161
242
402
483
644
725
0 108 13
4 175
0
1
2
3
4
5
6
7
8
MW
/m3
Axial Position (cm)
Radial Position
(cm)
Power Density in PBMR Equilibrium CoreControl Rods 1/4 Inserted (z = 201.25 cm)
7.00E+00-8.00E+006.00E+00-7.00E+005.00E+00-6.00E+004.00E+00-5.00E+003.00E+00-4.00E+002.00E+00-3.00E+001.00E+00-2.00E+000.00E+00-1.00E+00
Power density in annular core regions
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-82
MCNP4B/VSOP Model Output .. 2
bottom
top
Average fluxin annularcore regions
Bottomof core
016124
240248
364472
5
0
73
108
134
156
0.E+00
5.E+13
1.E+14
2.E+14
2.E+14
3.E+14
3.E+14
4.E+14
Neu
tron
s.cm
-2. s
-1
Axial Position (cm)Radial
Position (cm)
Thermal Neutron Flux in PBMR Equilibrium CoreControl Rods 1/4 Inserted (z = 201.25 cm)
3E+14-3.5E+142.5E+14-3E+142E+14-2.5E+141.5E+14-2E+141E+14-1.5E+145E+13-1E+140-5E+13
Average fluxin annularcore regions
bottom
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-83
MCNP4B/VSOP Model Output .. 3
bottom
Bottomof core
08116124
232240
348356
464472
5805
073
108
134
156
0.E+00
2.E+13
4.E+13
6.E+13
8.E+13
1.E+14
1.E+14
1.E+14
2.E+14
2.E+14
2.E+14
Neu
tron
s.cm
-2.s
-1
Axial Position (cm)
RadialPosition
(cm)
Fast Neutron Flux in PBMR Equilibrium CoreControl Rods 1/4 Inserted (z = 201.25 cm)
1.8E+14-2E+14
1.6E+14-1.8E+14
1.4E+14-1.6E+14
1.2E+14-1.4E+14
1E+14-1.2E+14
8E+13-1E+14
6E+13-8E+13
4E+13-6E+13
2E+13-4E+13
0-2E+13
Average fluxin annularcore regions
bottomof core
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-84
NonproliferationPebble-bed reactors are highly proliferation resistant:• small amount of uranium (9 g/ball)• high discharge burnup (100 MWd/kg)• TRISO fuel is difficult to reprocess• small amount of excess reactivity limits
number of special production balls
Diversion of 8 kg Pu requires:
• 260,000 spent fuel balls – 2.6 yrs• 790,000 first-pass fuel balls – 7.5• ~50,000 ‘special’ balls – 3
Spent Fuel
Pu238 5.5%Pu239 24.1Pu240 25.8Pu241 12.6Pu242 32.0
First Pass
Pu238 ~0 %Pu239 64.3Pu240 29.3Pu241 5.6Pu242 0.8
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-85
MCNP4B Analysis of Heavy Balls
1 Ball with depleted U2 Surrounded by BCC
lattice of driver balls3 Spherical driver core
with fuel compositionfrom VSOP model
• Critical core (keff = 1)• 238U(n,γ)239U
2
R = 1.75 m
UO2
driverfuel
R = 2.1 cm
1
3
Supercell Model
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-86
Path ForwardPath Forward•• Complete implementation of MCNP/VSOP linkComplete implementation of MCNP/VSOP link•• Improve model of PBMR Improve model of PBMR ⇒⇒ ESKOM inputESKOM input•• Validate MCNP4B using PROTEUS criticals &Validate MCNP4B using PROTEUS criticals &
VSOP predictions of PBMR startup coreVSOP predictions of PBMR startup core
•• Investigate proliferation resistance of PBR fuelInvestigate proliferation resistance of PBR fuelcycles using VSOP (Th/LEU, OTTOcycles using VSOP (Th/LEU, OTTO--PAP2)PAP2)
•• Assess applicability of Monteburns to modelingAssess applicability of Monteburns to modelingburnup in PBRs using MCNP4B and ORIGEN2burnup in PBRs using MCNP4B and ORIGEN2
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-87
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-88
The Safety Analysis of PBMR
Student: Tieliang ZhaiAdvisors: Prof. A. Kadak
Dr. W.Y. Kato
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-89
Objectives• Identification of the Safety Issues for MHTGR
• Analysis of a Major Accident
• The Temperature Distribution Calculation After the Depressurization With the Failure of RCCS
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-90
The Identification of the Safety Issues
• Review of Safety Literature on HTGR• Based on a Specific Design Concept, Identified the
Critical Safety Issues:A. Fuel PerformanceB. Completely Passive System for Ultimate Heat SinkC. Air IngressD. Lack of ContainmentE. Calculation of Source Term
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-91
Air Ingress Accident• Important parameters governing these reactions:
Gas flow ratesTemperaturePressure
• 3 steps• Mainly Depends on Possibility of Enough and
continuous air supply
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-92
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-93
Specific areas for additional research:
• Chimney effect• Airflow rate• The extent that a below-grade confinement building
could limit the supply of air
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-94
The Temperature Distribution Calculation After the Depressurization With the Failure of RCCS
• The Code “Heating-7”Heating-7 is a general-purpose 3-D
conduction heat transfer program written in Fortran 77. It can solve steady-state and/or transient heat conduction problems
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-95
The Model Established• 20-Region 3-Dimensional model. The core void is filled with
stagnant helium at atm.• The air in the confinement is steady and heat transfer only through
conductivity and radiation.• The outer radius of this model is 28.4m, i.e. all the heat transfer
happen only in this huge volume.• The Materials and their thermal properties (Conductivity, Density
and Specific Heat): In the case that the thermal properties could not been fully determined, the conservative values would be selected
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-96
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-97
The Conclusion• The core peak temperature is 15570C. This is below the 1600 C SiC fuel
temperature target and No Core Melt is predicted assuming only conduction.
• 192 hours (8 days) later, the peak temperatures of the pressure vessel and the Concrete Wall will be 1348 °C and 1322°C , respectively. The temperatures of the vessel and the concrete wall are out of the design capability range
.• The sensitivity analyses of the initial temperature of the core, the conductivity
of the air, the initial temperature of the air gap, the conductivity of the concrete wall and the soil indicate that: The key factors that determine the temperatures of the pressure vessel and concrete wall are the conductivity and heat capacity of the concrete and soil.
• Some convection cooling will be required to keep the temperature of the vessel and concrete within acceptable ranges - conduction alone is not sufficient.
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-98
The Temperature Curve of the Hot-Points
0
200
400
600
800
1000
1200
1400
1600
0 50 100 150 200 250 300 350 400 450 500
Time (hr)
Tem
pera
ture
(C)
the Hot-Point ofthe Core
The Hot-Point oftheVessel
The Hot-Point oftheConcreteWall
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-99
0
0.4
0.8
1.2
1.6
2
2.4
2.8
3.2
4.4
6.4
8.3 7.
9 7.5 7.
1 5.5 3.
5 1.5 -0.5 -2
.5 -4.5 -6
.5 -7.3 -7
.7 -8.1
0
200
400
600
800
1000
1200
1400
1600
Tem
pera
ture
(C)
Distance to the Central Line of the Core r (m)
The Depth Z (m)
Fig-3: Temperature Distribution on the 8th Day
1400-16001200-14001000-1200800-1000600-800400-600200-4000-200
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-100
200
400
600
800
1000
1200
1400
0 50 100 150 200 250 300 350
Vessel Temperature (v=0.0)Vessel Temperature (v=0.5)Vessel Temperature (v=1.0)Vessel Temperature (v=2.0)Concrete Temperature (v=0.0)Concrete Temperature (v=0.5)Concrete Temperature (v=1.0)Concrete Temperature (v=2.0)
Tem
pera
ture
(K)
Time(Hrs)
Temperatures with Convection
Massachusetts Institute of TechnologyDepartment of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-101
Future Work
• The perfection of the model, especially how to
model the core of the reactor and the heat transfer
through convection and how to obtain the accurate
initial condition of the accident.
• Air ingress accident simulation.