Fukushima daichi disaster
-
Upload
giannis-bitharas -
Category
Documents
-
view
548 -
download
0
Transcript of Fukushima daichi disaster
Failure and Accident Analysis
Ioannis Bitharas
Fukushima Nuclear Disaster
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 bar
Pictures source:
GE Hitachi Nuclear Energy
BWR Mk.I Layout Operating
conditions
600K 70 bar
Pictures source:
GE Hitachi Nuclear Energy
BWR Mk.I Layout Operating
conditions
600K 70 bar
Pictures 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
gradual core meltdown Unit 1 Units 2-3
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 severe
accidents were installed, concern would spread in host communities that
the 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 promotes
the use of atomic power, hampered a quick response to the disaster at
Tokyo 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?