An Alternative SCWR Design Based on Vertical Power Channels and Hexagonal Fuel Assemblies

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An Alternative SCWR Design Based on Vertical
Power Channels and Hexagonal Fuel Assemblies

• Jacopo Buongiorno

April 29, 2003 Madison, Wisconsin
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Concept Description
Moderation is provided by the feedwater flowing
downward in the inter-assembly gap
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Concept Description (2)
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Concept Evaluation

• Advantages
• Simple mechanical design of the fuel assembly
  with no water rods. Wire wrapping can be used as
  spacer.
• The amount of vessel internals above the core is
  minimal, which should simplify refueling
  operation.
• A favorable neutron economy due to the use of
  the zirconium-based alloy for the power channels.
•  Specific Challenges
• High local peaking due to the distance of the
  inner fuel rods from the moderator in the
  inter-power-channel gap.
• The moderator temperature rises roughly 58ºC,
  therefore the RPV lower head operates at higher
  temperature than the rest of the vessel.
• A durable insulation material for the power
  channels needs to be selected/developed.

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Thermal-Hydraulics
Temperature and density distributions in the
nominal channel appear acceptable


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Neutronics (1)
The MCNP model




BOL analysis
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Neutronics (2)
Average spectrum




Thermal tail in the fuel rods
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Neutronics (3)
Doppler and coolant reactivity coefficients
similar to LWRs.




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Neutronics (5)
Local peaking
Power skewing




Axial peaking (1.4 with uniform enrichment)
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Conclusions

• A new SCWR concept with no water rods is
  introduced.
• Moderation is provided by the feedwater in the
  inter-assembly gap.
• The fuel assembly design is simple with
  hexagonal lattice and zircaloy ducting.
• The power density is much higher than for the
  water rod design.
• The estimated fuel-cycle cost is comparable with
  that of the PWR the temperature and power
  distributions seem acceptable the Doppler and
  coolant reactivity feedbacks are both negative
  and within LWR range.