2. Outline
• Introduction
— The LIFE Project
— Design Constraints
• Methods
— MCNP Model
— Modeling Techniques
• Results
— Validation
— Effects of a shutter
— Radiation heating
— Material irradiation damage
• Conclusion
3. Introduction: The LIFE Project
• Laser Inertial Fusion Energy (LIFE) [1]
• A fusion power plant designed to be a safe, economically viable
solution to the world’s growing energy needs.
• Based on the physics established by the National Ignition Facility
(NIF)
• Utilizing available technologies and materials
Conceptual View of a LIFE Engine [1]
[1] life.llnl.gov
4. Introduction: Design Constraints
• In order to meet baseload electricity demands,
LIFE must meet certain requirements.
— Ignite fusion targets many times per
second
– Pilot plant: 8 shots per second
– Commercial plant: 15+ shots per
second
— Maintain high plant availability
– Lifetime components
– Online Maintenance
• Frequent fusion events impose a high
radiation environment unto LIFE Plant critical
components
— First Wall
— Final Optics
— Fuel Injection Systems
• Proper shielding is needed in order to enable
components to perform for their expected
lifetimes.
LIFE Injection Chamber
5. Methods: MCNP Model
• Monte Carlo N-Particle (MCNP) is an export controlled, general purpose code
created at Los Alamos National Laboratory
— Used to statistically model neutron, photon, electron, or coupled radiation
transport.
• MCNP Version 5 was used to create a simplified model of the injection systems.
• The model contains the injector chamber, its contents, and a radiation source at
the fusion chamber center (11.5 meters below injector chamber)
• Preliminary design helped establish the groundwork for variance reduction and
initial results
Preliminary Design Increased Fidelity Design Cross-section View at Carousel
7. Methods: Modeling Techniques
• Getting results in a radiation shielding problem is arduous
— Goal is to eliminate as many particles as possible from
reaching your target of interest
— Getting convergent results requires as many particles as
possible to reach your target…
— Catch-22
• An analog problem would take far too long to achieve results
• Variance reduction is necessary
— Cell Importances
— Source Biasing
• Design Variables considered for this project
— Shutter Material
— Shutter Geometry
— Concrete Thickness
8. Results: Validation
• Need to ensure that results produced are trustworthy and
match what would be expected in real life
• Simplistic method used was a check on energy
conservation
— 17.5 MeV produced in a DT Fusion event
– 14.1 MeV neutron and 3.4 MeV alpha
— MCNP5 only modeled a neutron source,
ignoring any contributions made by alpha
particles
– Only 80% of energy is accounted for
— Using a reflecting boundary condition (to eliminate leakage),
the amount of energy deposited into the entire geometry measured by
MCNP5 matched that of the expected value
• Without a reflecting boundary, total energy deposited decreased by 25% due
to neutron leakage
— The missing energy would mainly be deposited in concrete walls, leaving
the inside mostly unaffected whether there was a reflector or not
• The following results have been have validated within 2% of expected energy
conservation values.
No Reflector
Reflector
10. Results: Radiation Heating
Energy Flux (W/cm2)
5.9e-3
2.2e-6
8.5e-10
3.1e-13
1.1e-16
15.6
8.5e-4
4.2e-8
2.2e-12
1.1e-16
85% of total energy goes into
concrete floor (~25 MW)
With Floor
Floor Not Shown
NOTE: Image based on results that did
not have a reflecting boundary condition
11. Results: Radiation Heating
• Results Based on an 1104 MWf plant, operating at 8 shots per second,
using a Boron Carbide Shutter
Heating (Watts)
Injector # Barrel Interior Barrel Wall Steel Casing Support Systems
1† *9.74E-06 ± 1.4% *1.43E-01 ± 1.3% 5.76E+00 ± 0.82% 5.59E+02 ± 0.22%
2 *8.94E-06 ± 7.0% 1.29E-01± 1.1% *5.25E+00 ± 0.86% 4.76E+02 ± 0.24%
3 *7.58E-06 ± 1.6% *1.18E-01 ± 1.2% 4.81E+00 ± 0.94% 3.95E+02 ± 0.26%
4 *8.60E-06 ± 1.5% 1.30E-01 ± 1.1% 5.27E+00 ± 0.87% 4.76E+02 ± 0.24%
Support Structures Top Bottom
Carousel 4.60E+02 ± 0.25% 3.63E+03 ± 0.09%
X-axis supports 2.48E+02 ± 0.35% 1.10E+03 ± 0.16%
Y-axis supports 1.77E+02 ± 0.42% 9.35E+02 ± 0.17%
Target Loader 2.36E+02 ± 0.61%
Shutter 1.72E+03 ± 0.22%
† Injector in Active Carousel Position
*Either Photon or Neutron Tally Missed one or more
statistical check
X-axis supports
Y-axis supports
Carousel
1†
2
3
4
12. Results: Material Irradiation Damage
Material Damage (dpa/year) Expected Life (years)
Injector # Steel Casing Support Systems Steel Casing Support Systems
1† 2.73E-05 ± 0.40% 3.33E-05 ± 0.16% 3.66E+05 3.00E+05
2 2.43E-05 ± 0.46% 2.89E-05 ± 0.17% 4.11E+05 3.46E+05
3 2.15E-05 ± 0.46% 2.46E-05 ± 0.18% 4.66E+05 4.07E+05
4 2.44E-05 ± 0.43% 2.89E-05 ± 0.17% 4.10E+05 3.46E+05
Support Structures Top Bottom Top Bottom
Carousel 8.55E-06 ± 0.20% *7.97E-05 ± 0.07% 1.17E+06 1.25E+05
X-axis supports 1.36E-05 ± 0.29% *6.57E-05 ± 0.12% 7.35E+05 1.52E+05
Y-axis supports 1.08E-05 ± 0.34% *6.06E-05 ± 0.13% 9.30E+05 1.65E+05
Target Loader *6.34E-06 ± 0.51% 1.58E+06
X-axis supports
Y-axis supports
Carousel
1†
2
3
4
† Injector in Active Carousel Position
*Missed one statistical check (slope was < 3)
• Expected Life is based on a 10 dpa limit for FMS materials
13. Conclusion
• A shutter mechanism is paramount in shielding critical components
and should be optimized to be as “long” as possible, thereby
putting as much material between the injector components and the
radiation source.
— Steel performed the same as Boron Carbide
— Boron Carbide is both lighter and a ceramic, making it a better
choice for a shutter in a high heat environment
• Current data suggests that all critical components will perform for
their expected lifetime.
• Some form of cooling may be necessary in order to manage
radiation heating.
— Concrete/Shutter
— Steel Components
• Ongoing research is showing that the addition of another meter of
concrete to the floor will greatly reduce all radiation effects by
potentially 3 orders of magnitude.
14. Conclusion: Future Work
• Integrate the higher fidelity injection systems model into the large
scale LIFE model
— Determine incoming radiation flux from all sides; not just from
target implosions
• Look into an optimal concrete floor thickness
— Potentially between 1 and 2 meters
• Increase detail of model as design evolves
— Shutter (Mechanisms, supports, etc.)
— Target Loader
— Maintenance Components
• Look into designs that reduce photon heating from radiation
— High Z liner inside room
• Decrease run time for model
