French nuclear conglomerate AREVA presented this slide deck during an invitation-only meeting at Stanford University on 21 March 2011. The Fukushima Daiichi Incident outlines the probable course of events, from the earthquake to the meltdowns. Most of this information hasn’t received widespread media coverage, but Arnie Gunderson and the folks at Fairewinds have liberated it for us.    Diagram of Fukushima Daiichi reactor, showing meltdown, depressurization of containment, and release of radioactive materials. Dr. Matthias Braun / AREVA / Fairewinds.com

By Dr. Matthias Braun, AREVA
7 April 2011

2. Accident Progression At ~1800°C [expected Unit 1,2,3]

  • Melting of the cladding
  • Melting of the steel structures

At ~2500°C [expected Unit 1,2]

  • Breaking of the fuel rods
  • Debris bed inside the core

At ~2700°C [maybe Unit 1]

  • Significant melting of uranium-
    zirconium-oxides

Release of fission products during meltdown

  • Xenon, cesium, iodine, …
  • Uranium/plutonium remain in core
  • Fission products condense to airborne aerosols

Containment

  • Last barrier between fission products and environment
  • Wall thickness ~3cm
  • Design Pressure 4-5bar

Actual pressure up to 8 bars

  • Normal inert gas filling (nitrogen)
  • Hydrogen from core oxidation
  • Boiling condensation chamber (like a pressure cooker)

First depressurization of containment

  • Unit 1: 12 March 2011, 04:00
  • Unit 2: 13 March 2011, 00:00
  • Unit 3: 13 March 2011, 08:41

Spent fuel stored in pool on reactor service floor

  • Due to maintenance in Unit 4 entire core stored in spent fuel pool
  • Dry-out of the pools
    · Unit 4: in 10 days
    · Unit 1-3, 5, 6 in few weeks
  • Leakage of the pools due to earthquake?

Consequences

  • Core melt in fresh air
  • Nearly no retention of fission products
  • Large release

Areva Fukushima Report