gap thickness and filler helium or liquid metal fuelpe

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4 Design Parameters (BWR)

• Fuel type oxide, hydride, (silicide, nitride)
• Fuel rod geometry
• - cladding outer diameter
• - cladding thickness
• - gap thickness and filler (helium or liquid
  metal)
• - fuel-pellet diameter
• Fuel-rod pitch in FA (distance between fuel rods)
• Assembly size (9x9 is standard)
• Reference BWR/5 core
• Uranium enrichment (as 235U) may exceed the
  current limit of 5 in UO2 fuel

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Metrics for judging new fuel

• compared to UO2, does hydride fuel
• permit higher power?
• allow for higher burnup?
• improve overall safety and/or reliability?
• reduce the cost of electricity (COE)?
• Designs must satisfy
• operational constraints core pressure drop,
  vibration, critical power for DNB (PWR) or dryout
  (BWR)
• fuel-performance constraints centerline
  temperature, cladding strain, internal
  (fission-gas) pressure, cladding corrosion

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Design methodology

• Principal design element the fuel assembly (PWR)
  or bundle (BWR)
• Assembly designs must
• - fit into an existing pressure vessel
• - be compatible with existing primary circuit
• - Utilize the methodology applied to PWR core
  designs with hydride fuel in a BWR
• Use industrial-strength computer codes
• - reactor physics MCNP/MOCUP/ORIGEN
  (LANL//ORNL)
• - thermal hydraulics VIPRE (EPRI)
• - fuel performance FRAPCON (PNNL)
• Optimization first level Maximum Achievable
  Power
• second level Minimum COE

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Sample output LHR vs D and H/HM (or P/D) core
power 3800 MWth, PWR hydride fuel
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Maximum power with T-H constraints MDNBR gt
2.35 ?pcore lt 23.5 psia bulk velocity lt 8
m/s Tfuellt 700oC
Hydride fuel
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Components of thermal-hydraulic constraints