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Fukushima daichi disaster

Fukushima daichi disaster






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    Fukushima daichi disaster Fukushima daichi disaster Presentation Transcript

    • Fukushima Nuclear Disaster Failure and Accident Analysis Ioannis Bitharas
    • 2011 Tōhoku Earthquake 9 on Richter scale, with duration 140- 160s Fukushima is 178 km from the earthquake’s epicentre Power plants sustain minor damage and go into shutdown (scram) Power lines are destroyed by the earthquake
    • Anti-Seismic design Design basis was for 7.9 Richters Historically, earthquakes greater than the design values had been recorded in the area Damage from earthquake cannot be estimated due to ensuing events
    • Fukushima Daiichi Overview
    • Earthquake’s Aftermath Workers evacuate plants after nationwide alert Skeleton crew of 50 is left on Daiichi site to manage crisis Devastating tsunami follow 7 waves of ~70mph Peak wave height ~14m Wave barriers (10m high) could not completely stop waves Emergency backup power is lost due to flooding
    • Tsunami vs Wall
    • Tsunami vs Car
    • Affected Power Plants
    • BWR Mk.I Layout Operating conditions 600K 70 barPictures source:GE Hitachi Nuclear Energy
    • BWR Mk.I Layout Operating conditions 600K 70 barPictures source:GE Hitachi Nuclear Energy
    • BWR Mk.I Layout Operating conditions 600K 70 barPictures source:GE Hitachi Nuclear Energy
    • Reactor loss of cooling Radioactive rods inside reactor heat up The low-pressure core spray, residual heat removal, low-pressure coolant injection system main pumps and the automatic depressurization systems all require AC power Reactor cannot contain pressure/temperature and leaks in several points Release valves were assumed to be working Primary containment failure and Unit 1 Units 2-3 gradual core meltdown
    • The Fukushima 50
    • The Fukushima 50
    • Spent fuel assemblies• 1000-1500 tonnes of water required to fill each pool• The heat from each pool evaporates 70 tons per day• Cladding triggers hydrogen explosions after 500oC
    • Hydrogen-Air explosions
    • Hydrogen-Air explosions
    • Radioactive elements release Iodine-131 Caesium-137 2012 Estimation: 9x1017 Bq 84,000 evacuated on 20km radius
    • Affected Power Plants
    • Lack of H&S from operator Lack of seismic and tsunami protection in Design Basis Probabilistic Safety Analyses (PSA) underestimated dangers Reactor upgrades were recommended by regulatory authorities, including the Japanese government Numerous studies found Fukushima prefecture power plants inadequately protected The company’s own engineers, nuclear safety experts and even court orders were ignored, claiming all hazard reports were unrealistic
    • Cause: deliberate oversight TEPCO claimed that they had been afraid to consider the risk of such a large tsunami, fearing admissions of risk could result in public pressure to shut plants down“There were concerns that if new countermeasures against severeaccidents were installed, concern would spread in host communities thatthe current plants had safety problems,” the report said.
    • Nuclear & Industrial Safety Agency NISA had deemed the plant operations as safe Part of the ministry of trade, economy and industry Ministry also responsible for promoting Nuclear Energy Conflict of interests"NISA’s lack of independence from the trade ministry, which promotesthe use of atomic power, hampered a quick response to the disaster atTokyo Electric Power Co.’s Fukushima Dai-Ichi plant this year“ Key people fired and NISA was disbanded on 2012 Nuclear Regulation Authority formed September 2012
    • References Fukushima Nuclear Accident Interim Report, TEPCO, November 2011 Fukushima Dai-ichi NPP Accident, International Atomic Energy Agency, June 2011 Lessons Learned and Recommendations from the Fukushima Dai‐ichi Nuclear Accident, National Nuclear Security Administration, May 2012 Japanese earthquake and tsunami: Implications for the UK nuclear industry Final Report, HSE, September 2011 Executive Summary of the Interim Report, Investigation Committee on the Accidents at Fukushima Nuclear Power Stations of TEPCO, December 2011 Reuters, NY Times Allthingsnuclear.org, Wikipedia
    • Thanks for watching Questions?