Modular High Temperature Pebble Bed Reactor Faculty Advisors Andrew C. Kadak

advertisement
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Modular High Temperature
Pebble Bed Reactor
Faculty Advisors
Andrew C. Kadak
Ronald G. Ballinger
Michael J. Driscoll
Sidney Yip
David Gordon Wilson
MPBR-1
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Student Researchers
• Fuel Performance
- Heather MacLean
- Jing Wang
• Thermal Hydraulics
- Chunyun Wang
- Tamara Galen
• Core Physics
- Julian Lebenhaft
• Safety
- Tieliang Zhai
MPBR-2
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Project Objective
Develop a sufficient technical and economic
basis for this type of reactor plant to determine
whether it can compete with natural gas and still
meet safety, proliferation resistance and waste
disposal concerns.
MPBR-3
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Generation IV Reactor
•
•
•
•
Competitive with Natural Gas
Demonstrated Safety
Improved Proliferation Resistance
Readily Disposable Waste Form
MPBR-4
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Modular High Temperature
Pebble Bed Reactor
•
•
•
•
•
•
•
110 MWe
Helium Cooled
“Indirect” Cycle
8 % Enriched Fuel
Built in 2 Years
Factory Built
Site Assembled
MPBR-5
• On-line Refueling
• Modules added to
meet demand.
• No Reprocessing
• High Burnup
>90,000 Mwd/MT
• Direct Disposal of
HLW
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
What is a Pebble Bed Reactor ?
•
•
•
•
•
•
MPBR-6
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 Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR Specifications
Thermal Power
Core Height
Core Diameter
Pressure Vessel Height
Pressure Vessel Radius
Number of Fuel Pebbles
Microspheres/Fuel Pebble
Fuel
Fuel Pebble Diameter
Fuel Pebble enrichment
Uranium Mass/Fuel Pebble
Coolant
Helium mass flow rate
Helium entry/exit temperatures
Helium pressure
Mean Power Density
Number of Control Rods
Number of Absorber Ball Systems
MPBR-7
250 MW
10.0 m
3.0 m
16 m
5.6 m
360,000
11,000
UO2
60 mm
8%
7g
Helium
120 kg/s (100% power)
450oC/850oC
80 bar
3.54 MW/m3
6
18
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Conceptual Design Layout
Turbomachinery
Module
Reactor
Module
MPBR-8
IHX Module
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Competitive With Gas ?
•
•
•
•
Natural Gas
AP 600
ALWR
MPBR
3.4 Cents/kwhr
3.62 Cents/kwhr
3.8 Cents/kwhr
3.3 Cents/kwhr
Levelized Costs (1992 $ Based on NEI Study)
MPBR-9
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-10
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Improved Fuel Particle
Performance Modeling:
Chemical Modeling
Student: Heather MacLean
Advisor: R. Ballinger
MPBR-11
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-12
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-13
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Coated Particle Fuel System
Individual Microsphere
Fuel Kernel
Buffer
IPyC
SiC
OPyC
780 µm nominal diameter
Fuel Pebble
~11,000 microspheres per fuel pebble
~350,000 pebbles per core
MPBR-14
60 mm
diameter
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Thermal Model
Calculate 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
MPBR-15
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fuel Particle Thermal Model
Calculate 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
MPBR-16
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Bounding Thermal Examples
THe(inlet) = 450 °C
Low Temperature Case
core inlet
power: average
peak T: 513 °C
∆T:
16 °C
High Temperature Case
core outlet
power: average 2x average
peak T: 968 °C 1074 °C
∆T:
17 °C
19 °C
THe(outlet) = 850 °C
MPBR-17
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Typical Particle Temperatures
Pebble Power
Axial Location
Loc. In Pebble
Average
Core Inlet
Outer Edge
Average
Core Outlet
Center
723
1123
1123
Kernel Center
786
1241
1347
Kernel Outer Edge
Buffer Outer Edge
IPyC Outer Edge
SiC Outer Edge
OPyC Outer Edge
779
771
770
770
770
1234
1225
1224
1224
1224
1340
1329
1329
1329
1328
Particle ∆T
16
17
19
Bulk He Temp.(°K)
2x Average
Core Outlet
Center
Temperatures
MPBR-18
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-19
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Chemical Interactions
• Palladium
– very destructive, local
attack
– can open a pathway
for fission product
release
– limited data
MPBR-20
• Silver
– diffuses through
intact SiC
– activity / maintenance
concern
– limited data in MPBR
proposed
temperature range
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
SiC Diffusion Experiments
• Limited data for specific
fission products and
temperatures of interest
• Develop experimental
foundation for future
study of advanced
fission product barrier
3/4 inch OD
materials
MPBR-21
30 mil thick wall
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Experimental Procedure
1. Sputter Coating
Ag or Pd
target
2. SiC Overcoating
3. Heat Treatment
4. Characterization
Microscopy
SIMS
ESCA
XRD
1000-1600 oC
10-1000 hours
Ar gas
Graphite
Hemisphere
(hollow shell)
Metal Coating
Deposited on
Inside of Shell
Metal Inner Coating
MTS & H2
Diffusion Couple
(cross section)
5. Data Analysis
DAg(T)
DPd(T)
DMFP(T)
CAg
Graphite Shell
SiC or ZrC overcoating
r
MPBR-22
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-23
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-24
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fuel Performance Modeling
— Mechanical Analysis
Student: Jing Wang
Advisors: Prof. Ballinger & Prof. Yip
MPBR-25
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-26
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Mechanical Model
Stress Analysis
Finite Element
ABAQUS
• Anisotropy
• Asphericity
• Substructure
Analytical
Solution
‘FUEL’ code
• Isotropy
• Fast Speed
• MC Sampling
Specialized FEM
MPBR-27
Failure Model
Pure Pressure
Vessel Failure
Crack Induced
Failure
• Stress Intensity
Factor ( KI )
• Strain Energy
Release ( G )
Fracture
Strength ( σF )
Fracture
Mechanics
Failure
Criteria
Chemistry
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-28
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Closed Form Solutions
•
•
System: IPyC/SiC/OPyC
Assumptions
–
Spherical layers
–
Elastically isotropic
–
Creep and swelling
are treated for IPyC/OPyC
–
SiC is just elastic shell
–
Three layers are
tightly bonded
Layer
Outer PyC
Thickness
(µm)
43
SiC
35
Inner PyC
53
Buffer PyC
100
UCO
195
(diameter)
Total Diameter
TRISO Fuel Particle
MPBR-29
0.66 mm
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Time Evolution of Radial Stress Distribution in TRISO
Fuel Particles
60
50
40
40-50
30
30-40
20-30
20
10-20
0-10
10
-10-0
-20--10
0
-30--20
-10
Fl u
1.632
1.428
1.02
1.224
0.816
0.612
0.408
-30
0.204
325.88
0
316.71
307.54
ns)
298.37
i cro
289.2
270.86
s (m
OPyC
280.03
261.69
252.52
234.18
Ra d
iu
MPBR-30
-20
SiC
243.35
225.01
197.5
206.67
215.84
IPyC
vt)
21 n
10 ^
(
e
enc
Radial Stress (MPas)
50-60
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Time Evolution of Tangential Stress Distribution in
TRISO Fuel Particles
200
100
0
0-100
-100-0
-200--100
-300--200
-100
-400--300
-200
21
(10 ^
nce
e
u
l
F
nvt)
1.632
1.428
1.224
1.02
0.816
0.612
0.408
0.204
-400
327.19
0
315.4
303.61
s)
291.82
cro
n
280.03
(m
i
OPyC
268.24
ius
256.45
244.66
Ra
d
MPBR-31
-300
SiC
232.87
221.08
197.5
209.29
IPyC
Tangential Stress (MPas)
100-200
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-32
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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 densities
Weibull Distribution :
Fracture strength of IPyC, SiC and OPyC
Triangular Distribution : Critical stress intensity factor of SiC )
MPBR-33
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
The Sketch for FM based Failure Model
OPyC
K I ( IPyC ) = σ T πa
SiC
IPyC
σT
PO
MPBR-34
PI
K IC (SiC )
Material Property
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
• Outputs
Cases with IPyC Failure: 595
Cases with SiC Failure: 17
Failure Probability: 5.95×10-4
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
MPBR-35
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-36
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-37
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-38
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Dynamic Modeling for
MPBR
Chunyun Wang
Advisors: Prof. R. G. Ballinger
Dr. H. C. No
(Draft) Presentation for INEEL Review
MPBR-39
Aug. 01, 00
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Current Design Schematic
803 °C
7.6MPa
850°C
7.6MPa
445°C
7.7MPa
30°C
2.0MPa
401°C
2.1MPa
MPBR-40
97°C
8.0MPa
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Objective
• Develop a dynamic model as the primary
tool for
– developing the control system
– performing transient analysis
– optimizing power conversion system
MPBR-41
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-42
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Model Structure
MPBRSim
MPBRSim
Turbo-machinery
Turbo-machinery
T-H
T-H
MPBR-43
CoreModel
Model
Core
Kinetic
Kinetic
ControlModel
Model
Control
Poisoning
Poisoning
Heatexchanger
exchanger
Heat
Gas-Gas
Gas-Gas
Gas-Liquid
Gas-Liquid
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Core Thermal-Hydraulic Model
•
•
•
•
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
MPBR-44
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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)
γI
135I
Fission
λI
γX
λX
135Xe
σaφ
MPBR-45
135Cs
136Xe
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fig. 1 Numerical result versus analytical result
for one effective group kinetics equation
5
P/P0 Normalized Power
4
Analytical (0.22% Reactivity)
3
Analytical(-0.22% Reactivity)
Numerical (0.22% Reactivity)
Numerical (-0.22% Reactivity)
2
1
0
0
5
10
15
Time (sec)
MPBR-46
20
25
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fig.2 135Xe buildup following the core shutdown
6
Xe-135 Concentration
(Normalized)
Normalized Concentration
5
I-135 Concentration
(Normalized)
4
3
2
1
0
0
20
40
60
Time (Hour)
MPBR-47
80
100
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-48
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fig. 3 Recuperator steady state temperature distribution
Recuperator steady-state temperature distribution
400
350
Temperature (C)
300
250
Hot Side
Steel Wall
Cold Side
200
150
100
50
0
2
4
6
8
10
Axial Positions (m)
MPBR-49
12
14
16
18
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fig. 4 Recuperator transient response to a step
temperature increase of 200 C at hot helium inlet side
700
Temperature (C)
600
500
Hot helium inlet
Hot helium outlet
Cold helium inlet
Cold helium out
400
300
200
100
0
0
500
1000
1500
Tiem (sec)
MPBR-50
2000
2500
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fig. 5 Helium energy storage’s effect on the recuperator
performance
25
Model including helium
energy storage
Time Constant (sec)
24.8
24.6
Model excluding helium
energy storage
24.4
24.2
24
23.8
23.6
23.4
23.2
23
0
2
4
6
8
10
Hehlium Pressure (MPa)
MPBR-51
12
14
16
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-52
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-53
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Future Work
• Use programmed turbo-machinery
characteristic maps (Cooperate with NREC) in
the model
• Develop valve model
• Simulate electric load ramp
MPBR-54
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Comparison Between Air and Helium for
Use as Working Fluids in the EnergyConversion Cycle of the MPBR
Student: Tammy Galen
Faculty: D. G. Wilson
MPBR-55
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Objective:
To assess the relative advantages of using
air and helium for the working fluid in
the MPBR energy-conversion cycle.
Comparisons:
•Cycle efficiency
•Component design
•Size
•Efficiency
•Possible development work required
MPBR-56
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Conclusion
Use 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.
MPBR-57
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Three cycles investigated
•Air open cycle
•Air closed cycle
•Helium closed cycle
Closed Cycle
Open Cycle
HX
Tb
C
HX
MPBR-58
HX
C
Tb
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Influence of choice of working fluid
Working
Fluid
Component
Efficiency
Development
Work
MPBR-59
Component
Design
Cycle
Efficiency
Component
Size
Component
Cost
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Thermophysical Properties of Helium and Air at 700K and 2MPa
Turbines and Compressors
↑ Specific heat
↑ Number of stages
Air
Helium
↓ Viscosity, ↑Re #
↑ Efficiency
Molecular weight
28.97 4.003
Specific heat (J/kgK)
1074 5193
↑ Sonic velocity,
↑ Compressor blade speed
↓ Mean diameter
Sonic velocity (m/s)
590
1500
Thermal conductivity .056
(W/mK)
Viscosity (10-5)
3.33
.273
3.56
Density (kg/m3)
1.42
↑ Density
↓ Mean diameter
Heat Exchangers
↑ Thermal conductivity
↓ Size
MPBR-60
9.96
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-61
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Industrial experience conclusions
•Open-cycle air plant
•Least amount of development work required for MPBR
deployment
•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 helium
turbomachinery testing in Germany, 1995
MPBR-62
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Busbar Efficiency
• Deducts
– Primary circulator work, 7.7 MW
– 3.5 MW station load
– 98% electric generator efficiency
MPBR-63
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Baseline Thermodynamic Comparison
Helium
Air closed
Air open
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
Pressure ratio
Reactor inlet temperature constrained to 718K*
Helium
Pressure ratio
3.7
Busbar efficiency 44.8%
Turbine Tin (K)
1101
Air closed
7.4
46.0%
1101
Air open
7.3
46.8%
1101
*Permissible using 9Cr-1-Mo-V as the vessel material according to
ASME Class 2 &3 pressure-vessel in Codes Case N-47
MPBR-64
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Turbine Design Choices
MPBR-65
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 Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Component volumes (m3)
IHX
HP turbine
LP turbine
LP compressor
Recuperator
Precooler
Intercooler 1
Intercooler 2
Sum
MPBR-66
Helium
17
0.27
0.58
0.35
13
50
41
41
Air-closed
86
0.06
0.22
0.13
61
97
80
80
Air-open
260
2.2
13
2.7
180
--180
180
160
400
820
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Final Cycle Conclusions
Pressure ratio
Busbar efficiency
Turbine Tin (K)
3
Component volume (m )
Number of flatbed trucks*
Helium
3.7
45.3%
1101
160
1
Air-closed
7.1
47.1%
1101
400
2
Air-open
7.1
47.3%
1101
820
N/A
*Based on volume analysis, carries all components
except IHX and ducting
MPBR-67
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Conclusion
Use 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.
MPBR-68
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-69
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Pebble-Bed Reactor Physics
Research at MIT
Julian Lebenhaft
Professor Michael Driscoll
MPBR-70
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Overview
ƒ Statement of progress
ƒ Program goals
ƒ Neutronic design methodology
• MCNP/VSOP model of PBMR
• Preliminary results
ƒ Proliferation resistance of PBMR
ƒ Path forward
MPBR-71
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Progress
ƒ MCNP4B benchmark of HTR-10 completed
ƒ VSOP94 fuel management code implemented
ƒ Procedure established for linking MCNP and
VSOP for core neutronic calculations
ƒ MCNP/VSOP model of PBMR developed and
preliminary analysis performed
ƒ Proliferation resistance of PBMR investigated
MPBR-72
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Program Goals
• Establish a Monte-Carlo based methodology for
modeling neutron and photon transport in PBRs
• Ability to model cores with fuel burnup
• Integrated computer-aided design tools
• Perform preliminary design calculations
• Investigate fuel cycles and assess their proliferation
resistance
• Validation of codes and methods
MPBR-73
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Neutronic Design Methodology
• Monte Carlo method for
accurate analysis of:
–
–
–
–
–
control rod worth
void effects
geometry changes
shielding
heat deposition
diffusion code
composition
of
fuel
• Diffusion-theory code
for burnup calculation
A versatile
design tool!
MPBR-74
Monte Carlo
code
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-75
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
VSOP
Very Superior Old Programs
Widely used for PBRs
Diffusion theory
Comprehensive code suite:
- Neutronics
- Thermal hydraulics
- Fuel cycles
- Economics
• Installed at MIT
• Verification in progress
ƒ
•
•
•
MPBR-76
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MCNP/VSOP Model of PBMR
Detailed MCNP4B model of ESKOM
Pebble Bed Modular Reactor:
•
•
•
•
reflector and pressure vessel
18 control rods
(HTR-10)
17 shutdown sites (KLAK)
36 helium coolant channels
Core idealization based on VSOP
model for equilibrium fuel cycle:
• 57 fuel burnup zones
• homogenized compositions
MPBR-77
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MCNP4B Model of Core
reflector
coolant
control
reflector
fuel
shutdown
pressure
vessel
MPBR-78
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MCNP4B Model of Control Rod
B4C
vertical view
s/s
helium
graphite
horizontal view
MPBR-79
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MCNP4B Model of Shutdown Site
1
3
1) empty channel
2) channel filled with
absorber balls
3) 0.25 in. absorber ball
with graphite coating
2
MPBR-80
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MCNP4B/VSOP Model Output
Power Density in PBMR Equilibrium Core
Control Rods 1/4 Inserted (z = 201.25 cm)
8
Power density
in annular
core regions
7
MW/m 3
6
5
4
3
7.00E+00-8.00E+00
2
6.00E+00-7.00E+00
5.00E+00-6.00E+00
1
4.00E+00-5.00E+00
top0
MPBR-81
175
134
108
0
725
ion
(cm
)
644
2.00E+00-3.00E+00
483
Pos
it
402
Ax ia
l
242
Top of
core
161
0
3.00E+00-4.00E+00
Radial
Position
(cm)
1.00E+00-2.00E+00
0.00E+00-1.00E+00
Massachusetts Institute of Technology
Department of Nuclear Engineering
Bottom
of core
Advanced Reactor Technology Pebble Bed Project
MCNP4B/VSOP Model Output .. 2
Thermal Neutron Flux in PBMR Equilibrium Core
Control Rods 1/4 Inserted (z = 201.25 cm)
4.E+14
Average flux
in annular
Average
flux
core regions
in annular
core regions
3.E+14
2.E+14
3E+14-3.5E+14
2.5E+14-3E+14
2.E+14
2E+14-2.5E+14
MPBR-82
73
108
0
top
134
0
156
(c m
)
161
os
itio
n
0.E+00
242
Ax
ial
P
402
0-5E+13
483
5E+13-1E+14
5.E+13
644
1E+14-1.5E+14
1.E+14
bottom
725
1.5E+14-2E+14
Radial
Position
(cm )
Neutrons.cm -2.s -1
3.E+14
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MCNP4B/VSOP Model Output .. 3
Fast Neutron Flux in PBMR Equilibrium Core
Control Rods 1/4 Inserted (z = 201.25 cm)
2.E+14
2.E+14
1.E+14
Average flux
in annular
core regions
1.E+14
1.E+14
8.E+13
6.E+13
1.8E+14-2E+14
4.E+13
1.6E+14-1.8E+14
2.E+13
1.4E+14-1.6E+14
0.E+00
MPBR-83
0
73
108
134
156
0
81
161
242
al P
osit
i on
(cm
)
322
403
8E+13-1E+14
483
A xi
1E+14-1.2E+14
564
644
805
bottom
Bottom
ofofcore
core
1.2E+14-1.4E+14
bottom
725
Neutrons.cm-2.s-1
2.E+14
Radial
Position
(cm)
6E+13-8E+13
4E+13-6E+13
2E+13-4E+13
0-2E+13
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Nonproliferation
Pebble-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
MPBR-84
Spent Fuel
Pu238
Pu239
Pu240
Pu241
Pu242
5.5%
24.1
25.8
12.6
32.0
First Pass
Pu238
Pu239
Pu240
Pu241
Pu242
~0 %
64.3
29.3
5.6
0.8
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MCNP4B Analysis of Heavy Balls
Supercell Model
1 Ball with depleted U
2 Surrounded by BCC
lattice of driver balls
3 Spherical driver core
with fuel composition
from VSOP model
• Critical core (keff = 1)
• 238U(n,γ)239U
MPBR-85
1
UO2
2
R = 2.1 cm
3
driver
fuel
R = 1.75 m
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Path Forward
• Complete implementation of MCNP/VSOP link
• Improve model of PBMR ⇒ ESKOM input
• Validate MCNP4B using PROTEUS criticals &
VSOP predictions of PBMR startup core
• Investigate proliferation resistance of PBR fuel
cycles using VSOP (Th/LEU, OTTO-PAP2)
• Assess applicability of Monteburns to modeling
burnup in PBRs using MCNP4B and ORIGEN2
MPBR-86
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-87
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
The Safety Analysis of PBMR
Student: Tieliang Zhai
Advisors: Prof. A. Kadak
Dr. W.Y. Kato
MPBR-88
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-89
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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 Performance
B. Completely Passive System for Ultimate Heat Sink
C. Air Ingress
D. Lack of Containment
E. Calculation of Source Term
MPBR-90
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Air Ingress Accident
• Important parameters governing these reactions:
Gas flow rates
Temperature
Pressure
• 3 steps
• Mainly Depends on Possibility of Enough and
continuous air supply
MPBR-91
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-92
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Specific areas for additional research:
•
Chimney effect
•
Airflow rate
•
The extent that a below-grade confinement building
could limit the supply of air
MPBR-93
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-94
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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
MPBR-95
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
MPBR-96
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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.
MPBR-97
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
The Temperature Curve of the Hot-Points
1600
the HotPoint of
the Core
1400
Te m pe ra ture (C )
1200
The HotPoint of
the
Vessel
1000
The HotPoint of
the
Concrete
Wall
800
600
400
200
0
0
50
100
150
200
250
Time (hr)
MPBR-98
300
350
400
450
500
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Fig-3: Temperature Distribution on the 8th Day
1600
1400
1200
1400-1600
1000-1200
800-1000
600-800
400-600
200-400
0-200
Temperature (C)
1200-1400
1000
800
600
400
MPBR-99
-8.1
-7.7
-7.3
-4.5
-2.5
-0.5
1.5
3.5
5.5
7.1
7.5
7.9
6.4
8.3
4.4
3.2
2.8
2.4
Distance to the Central
Line of the Core r (m)
2
1.6
1.2
0.8
0.4
0
0
-6.5
200
The Depth Z (m)
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
Temperatures with Convection
1400
Temperature (K)
1200
1000
800
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)
600
400
200
0
50
100
150
200
Time(Hrs)
MPBR-100
250
300
350
Massachusetts Institute of Technology
Department of Nuclear Engineering
Advanced Reactor Technology Pebble Bed Project
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.
MPBR-101
Download