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HKIE Professional Assessment - Nuclear Discipline study materials
HKIE Professional Assessment - Nuclear Discipline study resources

HKIE Professional Assessment - Nuclear Discipline: Nuclear Fuel Cycle and Materials

HKIE Professional Assessment - Nuclear Discipline · Work through your exam, one topic at a time.

All guide sections

Nuclear Fuel Cycle and Materials

This domain tests the front end, reactor fuel performance and the back end of the fuel cycle, including material degradation mechanisms.

Core rules

  • The front end includes mining, milling, conversion, enrichment and fuel fabrication. The back end includes interim storage, reprocessing or direct disposal, and waste management.
  • Natural uranium contains about 0.711% U-235. Light-water reactor fuel is typically enriched to 3–5% U-235. Enrichment produces enriched product and depleted tails; mass balance must account for both.
  • UO2 pellets are sealed in zirconium-alloy cladding. Cladding performance is limited by corrosion, hydriding, pellet-clad interaction, fission gas release, swelling and radiation damage.
  • Criticality safety is essential in fuel fabrication and reprocessing: geometry, mass, concentration and neutron absorbers are used as controls.
  • Reprocessing separates uranium and plutonium; direct disposal treats spent fuel as waste. Safeguards and material accountancy apply to fissile material.

Worked example

How much natural uranium feed is needed to produce 1 kg of 4.5% enriched uranium if the feed is 0.711% U-235 and the tails assay is 0.25%?

Use F = P(xp − xw)/(xf − xw). Here xp = 0.045, xw = 0.0025, xf = 0.00711. F = 1 × (0.045 − 0.0025)/(0.00711 − 0.0025) = 0.0425/0.00461 = 9.22 kg. The tails mass is 8.22 kg. The reasoning is a uranium mass balance; separative work is a separate energy-like measure and is not the same as feed mass.

Traps

Do not confuse enrichment percent with fraction: 4.5% is 0.045. Do not forget tails assay; assuming zero tails overestimates feed. Do not equate SWU with kilograms of uranium. Do not ignore cladding as a safety barrier. Do not overlook criticality controls in fuel fabrication.

Key points

  • Natural uranium is about 0.711% U-235.
  • LWR fuel is typically enriched to 3–5%.
  • Mass balance includes product, tails and feed.
  • Zirconium alloy cladding is the first fission-product barrier.
  • PCI, hydriding and fission gas release limit fuel performance.
  • Criticality safety uses geometry, mass and absorbers.