News & Views

Japanese Nuclear Facts Sheet

By Nate Ames on Wednesday, March 16th, 2011

Due to the popularity of this fact sheet, we hosted a live conference call and webcast on Tuesday March 22nd that enabled anyone interested in hearing the information from the industry experts to listen in and ask questions.  For more information go to

I have assembled a fact sheet based on industry wide conference calls that I have participated in between Friday (March 11, 2011) and now (this is updated as needed). The most important thing that I can suggest to everyone is don’t trust anything that you find on the internet unless it is backed up by someone from the nuclear industry. The American Nuclear Society, the Nuclear Energy Institute, Nuclear Infrastructure Council, and the International Atomic Energy Agency are working diligently to distribute facts to organizations like the NFC and EWI. However, it is still extremely difficult to discern facts from hypotheses because few experts can provide firsthand accounts of the situation.

Below is a lot of information, but it should provide you with an adequate understanding of the situation in Japan at Fukushima Daiichi (at least as it is understood by me at this time). I’ve split this into two sections, Nuclear 101 and Fukushima Facts.

Nuclear 101

  • Nuclear power plants are net positive power producers, meaning that they produce more power than they consume, but they do consume electricity in order to create electricity
    • A large portion of the consumption is used to run the reactor coolant pumps
  • When a nuclear reactor undergoes an emergency shutdown, it is called “scramming the reactor”
    • When a reactor is scrammed, the control rods are lowered into place stopping the reaction from going critical
    • An operating nuclear reactor is by design “critical”, meaning the reaction is self sustaining. “Going critical” is not a bad word in the nuclear industry. It is how they are designed to operate.
  • After a reactor is scrammed, it takes approximately 3 to 4 weeks to remove all the decay heat from the system
    • The reactor coolant pumps must continue pumping or the reactor will overheat, creating over pressurization and steam in the reactor pressure vessel (RPV)
  • Nuclear power plants have multiple redundant safety features to help ensure coolant flow in an emergency
    • First are multiple redundant diesel generators to provide power for the coolant pumps and control room
    • Second (in a boiling water reactor) are steam powered pumps called reactor core isolation cooling (RCIC) pumps which use steam to power pumps to cool the reactor
    • Third is plant specific. In the case of Fukushima, this is seawater injection where seawater and boron are pumped into the reactor to cool the system
      • In the case of seawater injection, seawater is continually pumped into the reactor and subsequently boiled off. The steam is collected, the radioactive materials are removed, and the clean steam is vented out of the top of the reactor
  • The fuel rods in a nuclear reactor are made of zirconium tubes filled with enriched fuel pellets
    • When in the core, the fuel gives off heat – even when the reactor is not in operation
    • During a nuclear reaction, several radioactive fissile gases are produced, but are contained in the fuel rods and RPV
    • Zirconium undergoes a rapid oxidation reaction in the presence of high temperature steam and gives off hydrogen
      • In an emergency, the plants are designed to pipe hydrogen out of the RPV through a radioactive gas separator, then burn off the hydrogen at an external flare. This is similar to what you see being flared at an oil refinery
  • The GE Mark 1 and 2 nuclear power plant designs use a two stage containment system
    • Primary containment building (what we are used to seeing in the US – a big concrete domed structure)
    • Secondary containment, which is a steel superstructure. The superstructure is light weight and was designed to blow away, in this case explode, without imparting damaging loads on the primary containment
  • Spent or used fuel is stored onsite in two locations
    • The newest used fuel sits in a storage pool to cool down for 5 to 20 years (plant and situation dependent)
      • As long as the pools have water in them, there is little appreciable risk from used fuel
    • The older used fuel is stored in dry storage casks

Fukushima Daiichi Facts & Timeline

Friday March 11, 2011 (date in Japan)

  • The Fukushima Daiichi Nuclear Power Plant has six nuclear reactors onsite, all of which are boiling water reactors (BWRs)
    • Unit #1,  1971, 460MW, GE design
    • Unit #2,  1974, 784MW, GE design
    • Unit #3,  1976, 784MW, Toshiba
    • Unit #4,  1978, 784MW, Hitachi
    • Unit #5,  1978, 784MW, Toshiba
    • Unit #6,  1979, 1100MW, GE design
  • All six plants were designed to handle the perceived worst case scenario earthquake and resulting tsunami
    • The earthquake design basis was estimated to be a worst case earthquake of 8.0 on the Richter Scale
      • The earthquake that hit on Friday at 2:46pm (Japan time) registered 8.9 and was later upgraded to a 9.0
      • For reference the Northridge Earthquake in California (1994) was a 6.7
    • Japan and its 55 reactors have experienced seven aftershocks so far that were approaching the estimated design basis for the plant
  • The tsunami design basis is estimated to assume a worst case maximum wave height of ~19 feet
    • The actual tsunami that hit the Fukushima plant was upwards of 45 feet high
  • Approximately 80 seconds before the earthquake shook Japan, their early warning systems worked and warnings were sounded
  • Unit 1, 2, and 3 were successfully scrammed
  • Unit 4, 5, and 6 were already off line as part of a TEPCO planned outage
  • When the tsunami hit land, the Japanese electric grid began failing
  • The Fukushima plant switched over to diesel generators
  • As the tsunami washed through the plant, it damaged the diesel storage tanks for units 1, 2, and 3, thus shutting down the diesel backup
  • When the diesel generators stopped, unit #1 experienced a small loss of coolant on the core, creating hydrogen which was vented to the flue system
  • The RCIC pumps kicked in and continued to cool the reactors
  • Evacuation ordered for residents within 2 miles of Fukushima Daiichi

Saturday March 12, 2011

  • The RCICs use DC (battery powered) valves. After eight hours of RCIC cooling the batteries were consumed
  • Seawater injection began in unit 1
    • Once seawater is injected the reactors, they cannot be used again
  • The flue systems were damaged during either the earthquake or the aftershocks, causing hydrogen to escape to the secondary containment building
    • The hydrogen in the secondary containment building caused the explosion of unit 1’s secondary containment superstructure
  • Evacuation ordered for residents within 6 miles of Fukushima Daiichi, then extended to 12.5 miles later the same day

Sunday March 13, 2011

  • Seawater injection began in unit 3
  • The difference between units 1 and 3 is that the Japanese were cognizant that #3 might blow its superstructure when the hydrogen levels reached a critical point
  • Portable diesel generators were installed onsite and some power was restored
  • Several of the buildings around the onsite storage pools were destroyed by the tsunami and subsequent events

Monday March 14, 2011

  • Unit #3 exhibited a pressure increase and a subsequent loss of coolant on the core, creating hydrogen which was vented to the flue system
    • Similar to unit 1, its secondary containment then exploded
    • 7 workers were injured during the explosion, all were conscious and were taken to a hospital for treatment
  • The Japanese worked to locate additional heat exchangers so they can stop venting steam and more rapidly remove decay heat
  • The USS Ronald Reagan measured radiation (mostly in form of Cesium) 60 miles off the coast of Japan
    • The levels measured were not sufficient to cause a health concern
  • Unit #2 had a loss of coolant, TEPCO measured 80-cm of exposed fuel
  • Seawater unjection began in unit 2
  • The Japanese immediately announced that secondary containment on reactor 2 was likely to follow suit with 1 and 3
  • A release valve stuck on unit 2 caused a pressure fluctuation in the RPV
    • This lead to 2.7-m of the fuel (1/2 the fuel) being uncovered and exposed to steam
  • At this point, no radiation levels had been released that would cause a health risk
    • Most of the release appears to be coming from unit 3

Tuesday March 15, 2011

  • 800 workers remained onsite, 750 of which are dedicated to cooling units 1, 2, and 3
  • Unit 2 had an explosion or blast, but it was not the secondary containment
    • The blast originated near the primary containment, but what was damaged was unknown
    • The blast corresponded with a release of higher radiation, exceeding levels that could cause health concerns for humans
    • Radiation level retuned to safe levels quickly following the blast
  • A fire began at unit 4
    • The fire was an oil fire caused by a leak in water recirculation system
      • The fire is releasing radioactive substances into the air, but they were not at unsafe levels
    • The fire was extinguished at unit 4
  • An explosion at unit 4 damaged part of the superstructure roofing
    • There was no reported damage to the primary containment
  • A second fire at unit 4 was reported, but later determined by the fire department to be a false alarm
  • Units 1, 3, 4, 5, and 6 were deemed stable and cooling was being maintained
    • Units 1 and 3 RPV cooling was maintained via seawater injection
  • Radiation levels in the control rooms of reactors 1, 2, and 3 exceeded safe limits
  • All but 50 plant personnel were evacuated from the site
  • Residents between 12.5 and 18.5 miles of Fukushima Daiichi asked to stay in doors

Wednesday March 16, 2011

  • Work was focused on unit 2, attempting to bring it to a more stable position
  • Seawater injection was able to increase the water level of unit 2 and keep the fuel covered
  • Radiation release continued to rise to unsafe levels and then subsequently fall back to safe levels at various locations around the plant and reactors throughout the day
    • The remaining 50 workers initiated a temporarily evacuation due to radiation risk, but  returned and work to stabilize the facility
    • An additional 50 to 100 workers re-entered the plant to help with the effort
  • Units 1, 3, 4, 5, and 6 were reported to have properly functioning primary containment
  • Unit 2 was struggling to maintain adequate water levels in the core
    • There is now enough data to support the theory that the explosion in unit 2 (March 15) may have compromised the primary containment
  • There appears to be damage to the lining of the fuel storage pools for units 3 and 4
    • The storage pools have water in them, but levels are becoming dangerously low
  • Water levels are dropping in fuel storage pools 2 and 5, due to normal evaporation
  • The grid is beginning to stabilize in the area around Fukushima, so workers began making temporary connections to reestablish external power to the plant
  • The US Embassy in Japan issued a recommendation that all US citizens evacuate a 50 mile radius of the Fukushima Daiichi

Thursday March 17, 2011

  • Helicopters began air dropping water on the storage pools to reestablish their water levels
    • The storage pools are located several stories up, so access to them from the ground is limited due to radiation risks
  • Radiation release from the plant continues to increase, having momentary instances of unsafe levels.
    • Readings taken at the boundary of the Japanese evacuation zone (12 miles from plant) were ~33 mrems per hour
      • 33 mrems is not a health concern, the average American receives 620 mrems per year just as part of life on planet earth.
      • ANS has a radiation dose chart that will calculate your specific dose based on the activities that you do for work and play
  • Fuel storage pools are showing an increased temperature
    • No temperature reading from unit 4 have been available since 7:00pm March 13th
    • Units 5 & 6 are up to ~65 C, they are normally kept between 25 and 30 C
  • Operations focused on filling the unit 3 spent fuel storage pool by spraying water from the ground

Friday March 18, 2011

  • Power cables are laid to connect the electric grid to unit 1 & 2
  • Water temperature in spent fuel pools for units 5 & 6 increased
    • The temperature increase is due to lack of water circulation because electricity has not yet been restored
  • Vent holes cut in secondary containment buildings for units 5 & 6 as a preventative measure to avoid hydrogen build up

Saturday March 19, 2011

  • Emergency diesel generators are re-connected to units 5 & 6
  • Residual heat removal (RHR) pumps restarted in unit 5
  • Fuel storage pool cooling restarted for units 5 & 6
  • The pressure in unit 3 RPV was increasing
    • If the pressure continued to increase, the reactor would have to be vented to reduce the risk of over pressurization

Sunday March 20, 2011

  • Emphasis placed on filling the fuel storage pool for unit 4 by spraying water from the ground
  • The pressure in unit 3 RPV was reported as stable and no longer increasing
  • Seawater injection into unit 2 storage pool took place
  • Units 5 & 6 are in cold shutdown and stable

Monday March 21, 2011

  • There was grey smoke reported coming out of unit 3, this led to a temporary evacuation of the area, the smoke subsided and there were no indications of increased radiation, so work resumed shortly thereafter
  • White smoke or steam was reported coming out of unit 2

Tuesday March 22, 2011

  • AC power has reached all units (1 – 6)
    • System integrity checks are underway and must be completed before energizing the systems
      • This is to ensure that systems shorted out and/or water logged by the tsunami are not energized
    • Lighting and ventilation fans were restored in the unit 3 control room

Wednesday March 23, 2011

  • AC power has replaced emergency diesel generators in units 5 & 6
  • Black smoke emerged from unit 3
    • The smoke was reported as not a major issue because the reactor and the fuel storage pools are adequately filled with water
  • The RHR system on unit 5 stopped working when TEPCO connect the AC power. 
    • They connected a back up pump until AC power could be stabilized
  • The RPV temperature in Unit 1 has continued to drop indicating the facility is further stabilizing.

Thursday March 24, 2011

  • White steam visibly emerged from unit 1
    • This is not a surprise because they have been venting the reactor as the pressure increases from seawater injection
  • Feed water was injection into unit 3 spent fuel storage pool began using the reactor water clean up system
  • AC power was turned on for the lighting system of the unit 1 control room
  • Unit 5’s RHR system restarted and the system progressed to standard shut down cooling mode.
    • Indicating that unit 5 is functioning as designed
  • Units 1, 2, 3, and 4 RPVs and fuel storage pools have continued to cool
    • Units 5 and 6 have been at safe levels for the last few days

Friday March 25, 2011

  • Seawater injection was replaced with fresh water injection in both units 1 and 3
  • TEPCO reported that contaminated reactor water from unit 2 had leaked into general/storm water drainage systems
  • High radiation levels in containment buildings is impeding restart of reactor coolant pumps
  • Spent fuel storage pools in Units 3 & 4 are still reported as having low water levels
  • Ocean water samples off the coast of the plant show trace levels of iodine, cesium, ruthenium and tellurium
  • Water injection to units 2 & 4 spent fuel pools transitioned to plant water clean up pumping systems
  • Japanese government extended voluntary evacuation zone to 30 km (19 miles)

Saturday March 26, 2011

  • Seawater injection was replaced with fresh water injection in unit 2
  • AC power reconnected to unit 2 control room-lights and exhaust fans were turned on

Sunday March 27, 2011

  • TEPCO begun pumping contaminated water in the turbine basements of units 1, 2, & 3 into the condenser facilities
  • Work continues to re-establish reactor coolant pumps in units 1, 2 and 3.
  • Steam-like substance is coming off units 1, 2, 3, and 4. 
    • The amount of rubble makes it difficult to determine where the “steam” is coming from and thus difficult to confirm if its steam or smoke
    • This can be seen via the Japanese Defense Ministry video available at

Monday March 28, 2011

  • Most of the radioactive materials in the ocean appear to be iodine-131.  They are reported to be 1150 times above normal. 
    • This is less severe than it may seem because (luckily) iodine-131 is an isotope with a half life of about 8 days.
  • Radioactive substances (iodine-131, cesium-134 and cesium-137) have been monitored 330 miles east of Fukushima
    • Levels have been dropping over the last few days

Tuesday March 29, 2011

  • Plutonium-238 and plutonium-239/240 reading are equivalent to the normal readings in Japan
    • Japan’s soil has a measurable, yet safe, level of these isotopes as a result of Japanese nuclear weapons testing
    • The ratio of 238 to 239/240 indicates that it is possible some plutonium was released from the Fukushima plant, but numbers are so small that it can not yet be proven or disproven
  • AC power and lights were restored to the Unit 4 control room

Wednesday March 30, 2011

  • Units 1, 2 & 3 appear to be leaking radioactive water from the containment building. 
  • Freshwater injection via water cannon continues in units 1,2 & 3 storage pools
  • Fish were analyzed off the coast of Fukushima
    • 80% were found to have no detectable concentrations of radioactive isotopes or radioactivity
    • 20% were found to have detectable concentrations of Cesium-137.  Detection was at the detectable limit and well below that which would cause concern for fish or human consumption
  • TEPCO announced that they will decommission units 1-4.  Stating that damage from the tsunami left them with little choice.

Thursday March 31, 2011

  • Workers began transferring highly contaminated water from condenser storage facilities to surge tanks in unit 1
  • Water injection into the spent fuel pools continues at each unit.  Injection/spraying is done intermittently as needed by the pools

Sunday April 3, 2011

  • TEPCO working to determine where the radioactive water leakage is originating.  Early hypotheses are that there is a leak in the concrete under unit 2, the water is seeping out through the spaces around electrical and water conduits, or it is escaping though the water intake piping.
    • Attempts to pour a dye into the reactor to trace the origin were unsuccessful
    • Polymer sealants were poured into conduit to slow leakage (unsuccessful)
    • Concrete was poured into the pit under unit 2 with no success at slowing leakage
    • The net-net is that they are not sure where the leakage is coming from, and as such are using whatever means possible to attack the highest possible leak paths.  Rubble and high levels of radiation prevent workers from getting close enough adequately troubleshoot the problem.

Monday April 4, 2011

  • TEPCO announced that they will be releasing 11,500 tons of water contaminated with radioactive iodine-131 into the ocean.  This is necessary to make room for the highly contaminated water inside the facility.  TEPCO needs to move the highly contaminated water into the condenser facility so that worker exposure can be reduced.
    • There are no long term health effects anticipated from this release–even if the local people eat the fish from the contaminated water.

Tuesday April 5, 2011

  • The leak in the concrete pit under unit 2 has been stopped using a “water glass” a sodium silicate compound that was injected into the leakage point.  This leak is the underlying reason for the water accumulation in the tunnels and basement under unit 2.

Thursday April 7, 2011

  • Another earthquake hit at Japan.  It was rated a magnitude of 7.1, downgraded from its initial rating of a 7.4.  The epicenter was 12 miles from the Onagawa Nuclear Power Plant.  No series damage occurred, but 2 of the 3 power lines connecting Onagawa to Fukushima Daiichi were damaged causing a short disruption in power resulting in a lapse in cooling supply to one of the spent fuel pools.
  • TEPCO began injecting nitrogen gas into the Unit 1 containment vessel.  This was started to leverage the high stability of nitrogen and counteract the volatile gases present inside the reactor that resulted from the fuel rods being partially exposed.
  • Approximately 1.5M gallons of low-level radioactive waste water were released into the ocean, TEPCO believes they will only need to release another 375,000 gallons in order to have enough room for all the high level radioactive waste water. 

I can’t reiterate enough that facts are few and far between. I am not a nuclear engineer nor do I claim to be a nuclear expert, but the lack data, without all the media sensationalism, was discerning. I hope you find value in this, I will do my best to keep it up to date.

Thank you/Nate Ames
NFC | Director
Mail: 1250 Arthur E. Adams Dr., Columbus OH 43221
Phone: 614.688.5000
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