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Nuclear Accident in Japan: A Summary

Nuclear Accident in Japan: A Summary. Dennis Quinn, CHP DAQ, Inc. Fukushima Nuclear Reactors. Fukushima Nuclear Reactors. Fukushima Daiichi Nuclear Reactors. Boiling Water Reactor Basic Flow. Boiling Water Reactor Design. en.wikipedia.org/wiki/ Browns_Ferry_Nuclear_Power_Plant.

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Nuclear Accident in Japan: A Summary

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  1. Nuclear Accident in Japan:A Summary Dennis Quinn, CHP DAQ, Inc.

  2. Fukushima Nuclear Reactors

  3. Fukushima Nuclear Reactors

  4. Fukushima Daiichi Nuclear Reactors

  5. Boiling Water Reactor Basic Flow

  6. Boiling Water Reactor Design en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Power_Plant

  7. Nuclear Reactor FuelDesign ~96 rods per assembly ~400-800 assemblies per Rx

  8. Key Points • The nuclear fuel contains almost all of the radioactivity (>99%). • The nuclear fuel continues to generate heat after the reactor is shut down. • 19 MW after 1 day • 12 MW after 1 week • 7 MW after 3 months • The fuel must be cooled, or there is a risk of fuel damage and release of radioactivity.

  9. Fuel Temperature (oF) Activity Available for Release (Curies) Stainless Steel Melts

  10. From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun Prior to Accident • Reactor Service Floor(Steel Construction) • Concrete Reactor Building(secondary Containment) • Reactor Core • Reactor Pressure Vessel • Containment (Dry well) • Containment (Wet Well) / Condensation Chamber Spent Fuel Pool Fresh Steam line Main Feedwater

  11. Earthquake and Loss of Electric Power • Earthquake causes loss of offsite power. • Emergency Diesel Generators supply power • Tsunami disables EDGs • Steam dumps to wet well • Water level in reactor decreases • Fuel heats up • Cladding is damaged and releases noble gases and volatile isotopes (cesium and iodine) > 99.9% of radioactivity is in the fuel From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun

  12. Accident Progression • Large volume in wet well eventually heats to boiling and no more pressure suppression • Pressure increases • Hydrogen created by high temperature reaction of cladding & steam • Operators decide to vent primary containment gas to secondary containment • Gas has fission products and hydrogen From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun

  13. Hydrogen Explosion From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun

  14. Early Releases and Dose Rates • Background is 0.005 – 0.01 mR/hr • Fukushima Daiichi Main Gate dose rates dependent on wind direction & events: • 3/14: 50 mR/hr • 3/15: 300 mR/hr due to venting from Unit 2 • 3/15: 1200 mR/hr due to explosion & fire on Unit 4 • 3/16: 850 mR/hr explosion on Unit 2 • 3/17: 1100 mR/hr – releases from Units 2 and 3 of plant • U.S. 7th Fleet ship contaminated helicopter crew. • US news crews returning after 2 wks have contaminated equipment.

  15. Emergency Planning Actions

  16. Water and Food Products • I-131, Cs-134, Cs-137 • Milk • Produce (leafy vegetables, spinach, etc.) • Drinking water (peak at 3x limit @ 30 km, now below limits). • Seawater, fish products • Initially prevented sale of food & seafood within 30 km radius • Recent identification of beef with Cesium contamination.

  17. Food and Drinking Water Japan Limits (Bq/L or Bq/kg) • *Infant water and milk limit is 100 Bq/kg • IAEA Limits based on 1 rem per year to most restrictive individual (generally infant) if consuming food for 1 year at the limit

  18. Workers Meeting for Recovery 4/1

  19. Bags of Radwaste (PPE, Plastic, etc.)

  20. Contaminated Water and Soil Control Issues Resin Spraying for Soil Control Rx 2 – Leak to the Sea

  21. Contamination Control Silt Fence

  22. Mega Float Arriving Yokohama

  23. Remote Operated Vehicle

  24. Remote Monitoring & Protection

  25. International Nuclear and Radiological Event Scale (INES) • Chernobyl • Level 7 • Fukushima Daiichi • Level 7 • TMI • Level 5

  26. Status according to World Health Org As of July 2011

  27. So How Bad Was It? • As a nuclear or industrial accident, it was major – resulted in evacuation, loss of a major electricity source, and uncertainty in the public for months. • It was not a major health catastrophe, and it is not likely that there will be significant health effects. • Why? – The emergency plan actually worked. Despite the initial confusion, people were evacuated, controls were placed on food, etc.

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