INSIDE FUKUSHIMA DAIICHI

This is a virtual tour of the decommissioning work
underway at the Fukushima Daiichi Nuclear Power Station.
※Please watch this content in full-screen mode.

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  • GGreen ZoneRegular Uniform Area
  • YYellow ZoneProtective Clothing and a Full or Half-Face Mask Area
  • RRed ZoneProtective Clothing and a Full-Face Mask Area

PICK UP

Main work items for the decommissioning underway are picked up and introduced.

1.Fuel debris removal
Fuel in the reactor pressure vessel (RPV) that solidified once again after melting and falling is referred to as, “fuel debris.”
We are conducting various investigations in preparation for the removal of this fuel debris.
This content shows fuel debris investigations that have been conducted at Units 1~3.
2.Fuel removal
Spent fuel that was used in the course of energy production is stored in the spent fuel pools in the reactor buildings.
We are therefore engaged in preparations to remove fuel from the spent fuel pools.
This content shows fuel removal from Unit 3, which began in April 2019.
3.Contaminated water countermeasures
At 1F, various contaminated water countermeasures are being implemented in order to reduce the amount of contaminated water being generated.
This content shows initiatives to “remove” contamination sources and “isolate” water from contamination sources.
4.Radioactive waste
Rubble, etc. generated during the course of decommissioning is treated as radioactive waste.
The waste is sorted by type and the dose level and stored on site at 1F.
This content shows new facilities that have been built to store and dispose of radioactive waste in even safer ways, and also the site of future construction of waste-related facilities.
5.Work environment
At 1F we’re making improvements to the labor environment to enable all workers to safely engage in decommissioning tasks with peace of mind.
This content shows the large rest house and workers going about their duties in the new administration office building.

What does “1F” refer to?

“1F” is the abbreviation for the Fukushima Daiichi Nuclear Power Station used by workers on site.

What occurred during the accident at the Fukushima Daiichi Nuclear Power Station (1F)?

The Great East Japan Earthquake, which occurred at 2:46pm on March 11, 2011, triggered an automatic scram of Units 1~3 which were in operation at the Fukushima Daiichi Nuclear Power Station (1F), and the cooling of fuel began. The cooling of fuel, for which power was needed, continued using onsite emergency power sources after external power supply was cut off by the earthquake. However, these auxiliary power sources were ultimately rendered inoperable by the tsunami that struck the site following the earthquake, thereby resulting in a loss of cooling functions.

After fuel cooling functions were lost, the temperature of the fuel rose causing a melt-down and a significant volume of hydrogen was generated due to the chemical reaction that ensued. In Units 1 and 3, hydrogen leaking from the Primary Containment Vessel accumulated in the Reactor Building and caused explosions. An explosion also occurred at Unit 4, which was undergoing periodic inspection, due to hydrogen that flowed into the building from Unit 3 through pipes.

Please click here for more details.
https://www7.tepco.co.jp/responsibility/decommissioning/accident-e.html

What changes has Unit 1 undergone since the accident?

January
2019
December
2017
December
2016
December
2015
October
2011
March
2011

What changes has Unit 2 undergone since the accident?

January
2019
December
2017
December
2015
March
2011

What changes has Unit 3 undergone since the accident?

February
2018
December
2015
March
2011

What changes has Unit 4 undergone since the accident?

January
2018
March
2011

What kind of work is being done at Unit 1?

At Unit 1, the top part of the reactor building was severely damaged during the accident by a hydrogen explosion and rubble from that time still remains at the top of the building. This rubble must be cleared away to remove fuel from the spent fuel pool, so that is the task in which we are currently engaged.
We plan to complete construction of a large cover over the entire reactor building around FY2023 and will continue to remove rubble from underneath it.

What kind of work is being done at Unit 2?

The side panels at the top of the Unit 2 reactor building were blown open during the accident. This allowed hydrogen to escape the building thereby avoiding a hydrogen explosion.
The panels are currently closed and preparations are underway to remove fuel from the spent fuel pool using a method that is even safer and further prevents the dispersion of dust.

What kind of work is being done at Unit 3?

During the accident a hydrogen explosion occurred at Unit 3. Rubble generated during this explosion that was on the uppermost floor of the reactor building has already been removed, and the removal of fuel from the spent fuel pool began in April, 2019.
70 out of 566 fuel assemblies stored in the Unit 3 spent fuel pool have been removed as of February, 2020.
All fuel removal tasks are conducted by remote control. And, the removed fuel is being stored safely in the on-site common pool.

What is the barrel-shaped structure on the top of Unit 3?

This is a cover installed to remove fuel from the spent fuel pool.
Installation was completed in February 2018.
The large cover, which is 53.5m high and 56.9m long, weighs 1,250t and was designed to prevent loads from being transferred to the damaged reactor building.

What kind of work is being done at Unit 4?

During the accident, hydrogen generated at Unit 3 flowed through pipes into Unit 4 and caused a hydrogen explosion.
Since the reactor had been shut down for periodic inspection, all the reactor fuel was in the spent fuel pool.
Removal of the 1,535 fuel assemblies stored in the spent fuel pool was completed in 2014. This fuel is being stored in the common pool thereby eliminating associated risks.

A container of removed fuel being transported

What is this gray frame installed at Unit 4?

It is a cover installed to aid with the removal of fuel from Unit 4. The frame is made from strong steel beams that support the overhead crane required for removal.
Approximately 4,000t of steel beams in total was used for the structure. That’s the same amount that was used for Tokyo Tower.
This frame was designed to prevent loads from being transferred to the damaged reactor building.

Unit 4 today

Where are the removed fuel assemblies taken from Unit 4?

They are taken to the common pool, etc. located on-site and stored appropriately in water.

Spent fuel being stored in the common pool

What is Unit 5 used for now?

Unit 5 is being used to deliberate fuel debris removal methods because its Primary Containment Vessel (PCV) is similar in structure to Units 2~4.

Can all the fuel in Units 1~4 be stored in the common pool?

6,799 fuel assemblies can be stored at cool temperatures in the common pool but the common pool is not big enough to store all the fuel.
So, fuel which has dropped in temperature is transferred in dry casks to an air-cooled storage facility. Fuel is thus stored in two ways.

Why is fuel stored in the common pool considered to be safe?

Storing all the spent fuel together in the common pool reduces risk compared with keeping it in the fuel pools of each reactor.
That’s why we are gradually relocating it to the common pool.

What is the grid-like object seen in the common pool?

This is a fuel storage rack.
Fuel is stored in racks so it can be easily moved in and out, and to make it easier to keep track of quantity.

What kind of preparations are underway at Unit 1 in order to remove fuel debris?

Investigations of the Primary Containment Vessel (PCV) are being conducted in preparation for fuel debris removal.
During these investigations we have used robots to take video and measure dose levels inside the PCV and leveraged muons (subatomic particles) hurtling through space to render a cosmic ray shadow of structures inside the PCV.

PCV inside
PCV bottom
Investigative robot (PMORPH)

What kind of preparations are underway at Unit 2 in order to remove fuel debris?

In February 2018, an investigation of the inside of the Primary Containment Vessel (PCV) was conducted in preparation for fuel debris removal.
We successfully took footage from immediately below the Reactor Pressure Vessel (RPV), where it is assumed that fuel debris exists.
Some of this footage showed deposits that are assumed to be fuel debris. The investigation also showed that water is dripping from above and keeping the fuel debris at the bottom cool and stable.
The following year in February 2019, we conducted a “contact investigation” for the first time during which we touched deposits in order to examine hardness and brittleness.
We grabbed deposits that have accumulated at the bottom of the PCV to examine their shape and size, and also confirmed that the deposits can be moved.
From 2021, we will be removing samples of fuel debris from the side of the PCV in the open air, and gradually expand the scope of fuel debris removal thereafter.

Partially deformed work foothold in the PCV
Area immediately below the RPV
Part of a fuel assembly that has fallen on the PCV


Deposit contact investigation

What kind of work is being done at Unit 3 to remove fuel debris?

In order to remove fuel debris, in July 2017, the inside of the Primary Containment Vessel (PCV), which contained 6.4m of stagnant water, was investigated and an underwater robot was used to take footage on the inside.
The footage from directly below the RPV, where fuel debris probably exists, revealed structures and deposits that are assumed to have melted and fallen.

PCV bottom
Immediately below the RPV (1)
Immediately below the RPV (2)

What is the freezer room for?

The freezer room is a facility for lowering the temperature for coolant used to create an ice wall (land-side impermeable wall) to -30°C.The coolant passes through pipes that enclose Units 1~4.
This underground ice wall, which is 1,500m long in total and extends 30m below the surface, was created to block the flow of groundwater.

Land-side impermeable wallCross-section of ground

To what temperature is the ground frozen with the coolant?

About -10°C.

Ground surface

Doesn’t the land-side impermeable wall melt in summer?

No, it doesn’t, because the ice wall is underground, which is less affected by the external air.
And, coolant temperature is maintained 24/7.

How is the coolant channeled from the freezer room to the area surrounding Units 1~4?

Pipes that encompass Units 1~4 under the ground are used to circulate coolant.

Pipes connecting the freezer room with the area surrounding Units 1~4

What other countermeasures are being implemented to prevent the generation of contaminated water?

For example, groundwater flowing down from the mountains is pumped up using wells that comprise a groundwater bypass and discharged outside the port.
Groundwater flowing near the buildings is pumped up and discharged into the port using sub-drain wells.
And, ground surfaces are being paved or faced to prevent rainwater falling on-site from seeping into the ground and becoming groundwater.

What is the high performance multi-nuclide removal equipment for?

This is a facility that houses purification equipment to remove the radioactive materials contained in contaminated water.
By passing contaminated water through special filters, this equipment can remove most of the radionuclides present in contaminated water with the exception of tritium.
Click here for more information on the “treated water*” resulting from the purification of contaminated water.

Note on “Water treated with multi-nuclide removal equipment etc.” is notated.
Treated water for which the sum of concentration ratios required by law, with the exception of tritium, is less than 1 is notated as either, “water treated with multi-nuclide removal equipment etc.” or “treated water,” and treated water that has not been completely treated is notated as, “water treated with multi-nuclide removal equipment etc. (for which the sum of concentration ratios required by law equals or exceeds 1)”. When referring to both of the aforementioned types of treated water collectively, the notation, “treated water*” is used.

What is tritium?

Tritium is a naturally occurring radioactive material that is present in seawater and water vapor in the atmosphere. It emits very little radioactive energy compared to other radioactive materials.
Tritium has the same characteristics as hydrogen and is present in the water stored in tanks. Since it is almost undifferentiable from hydrogen it is very difficult to remove only tritium.

What protective equipment do workers wear at the high performance multi-nuclide removal equipment that treats contaminated water?

This is an area for treating contaminated water so workers wear protective clothing and full-face masks.

How much contaminated water can the high performance multi-nuclide removal equipment treat per day?

The entire multi-nuclide removal system can treat a maximum of approximately 2,000 tons of contaminated water per day.

Is the water treated with equipment other than the multi-nuclide removal equipment?

First, cesium and strontium, which account for most of the radioactive materials in contaminated water, are removed using a cesium adsorption apparatus before the contaminated water is treated with the multi-nuclide removal equipment.
After cesium and strontium are removed, the water is run through a desalination system to remove salt.
Then, some water is reused as cooling water to cool fuel debris without being treated with multi-nuclide removal equipment.

What is stored in the tanks?

Water that has been treated with multi-nuclide removal equipment etc. (treated water*) is stored in these tanks.
The concentrations of most radioactive materials in this water have been reduced, with the exception of tritium.

Note on “Water treated with multi-nuclide removal equipment etc.” is notated.
Treated water for which the sum of concentration ratios required by law, with the exception of tritium, is less than 1 is notated as either, “water treated with multi-nuclide removal equipment etc.” or “treated water,” and treated water that has not been completely treated is notated as, “water treated with multi-nuclide removal equipment etc. (for which the sum of concentration ratios required by law equals or exceeds 1)”. When referring to both of the aforementioned types of treated water collectively, the notation, “treated water*” is used.

What is the capacity of each tank?

There are many types of tanks. A standard tank can hold approximately 1,000m3of water.

How many tanks are there on-site?

As of January 2020, there are approximately 1,000 tanks on site in which approximately 1.18 million tons of treated water* is stored.
We plan to build more tanks by the end of December 2020 to increase total capacity to approximately 1.37 million m3, but it is expected that these will become full around the summer of 2022.
See the Treated Water Portal Site for more details.

Note on “Water treated with multi-nuclide removal equipment etc.” is notated.
Treated water for which the sum of concentration ratios required by law, with the exception of tritium, is less than 1 is notated as either, “water treated with multi-nuclide removal equipment etc.” or “treated water,” and treated water that has not been completely treated is notated as, “water treated with multi-nuclide removal equipment etc. (for which the sum of concentration ratios required by law equals or exceeds 1)”. When referring to both of the aforementioned types of treated water collectively, the notation, “treated water*” is used.

What are the tents around the bottoms of the tanks?

These tents have been set up to prevent rainwater from entering leak prevention dikes.
In the slight chance that a tank did leak, this would enable us to accurately measure and analyze the amount of water that leaked.

What is the difference between white, gray and blue colored tanks?

The various tank manufacturers use different colors.
There is no difference in performance.

Will treated water be stored in tanks forever?

A basic plan on how to handle the water treated with multi-nuclide removal equipment, etc. (treated water*) in the future that is currently being stored in tanks will be put forth by the government based on the discussions by the government subcommittee on the handling of treated water, and upon obtaining the understanding of stakeholders, such as the local community.
TEPCO will listen to the opinions of stakeholders and carefully make decisions to take an appropriate course of action based on the policy put forth by the government.
Until this time, we will continue to keep the treated water* safely stored in tanks.
See the Treated Water Portal Site for information on the future handling of treated water*.

Note on “Water treated with multi-nuclide removal equipment etc.” is notated.
Treated water for which the sum of concentration ratios required by law, with the exception of tritium, is less than 1 is notated as either, “water treated with multi-nuclide removal equipment etc.” or “treated water,” and treated water that has not been completely treated is notated as, “water treated with multi-nuclide removal equipment etc. (for which the sum of concentration ratios required by law equals or exceeds 1)”. When referring to both of the aforementioned types of treated water collectively, the notation, “treated water*” is used.

What do the G, Y and R zones refer to?

Site areas are color-coded based on the level of contamination. The three zone colors are the same as a traffic light: G (for Green), Y (for Yellow) and R (for Red)

G zone
Workers may wear simple dust masks and regular uniforms
Y zone
Workers must wear protective clothing and a full or half-face mask
R zone
Workers must wear protective clothing and a full-face mask
G zone equipment
Y zone / R zone equipment

From here into the PCV is a Y zone because the reactor was in operation prior to the accident and dust containing radioactive materials that still remain in the PCV may cling to clothing.

What percentage of the entire site is designated as a G zone where regular work uniforms can be worn?

96% of the entire site. The map has been color-coded to show zone demarcations in accordance with radioactive substance contamination conditions.

How is the radiation exposure dose of workers at 1F managed?

By law, workers must be registered as radiation workers before working on site.
Each of these workers wears a dosimeter to strictly manage daily radiation exposure doses.
Total exposure dose must be less than 50 mSv during a single year, and less than 100 mSv over five years.
Currently, work plans are created to reduce exposure doses, and the average exposure dose of workers is sufficiently lower than legal limits. The health of personnel engaged in radiation work is also managed through periodic checkups.

Where is the removed rubble taken from reactor buildings?

After being sorted by type and dose level, rubble and other waste is stored in waste storage buildings and other facilities located on-site.

What happens to the work uniforms used for work and tours?

Used equipment is stored appropriately as waste. In order to reduce volume it will be incinerated step-by-step, and ashes generated will be stored.

What will be built at the site preparation related to waste treatment?

Facilities to incinerate, compact and store waste. Approximately 770,000m3 of waste is estimated to be generated over the next decade.
The volume will be reduced to approximately 260,000m3 by incineration and crushing after which the waste will be appropriately stored and managed.

When will the construction of these facilities planned at the site preparation be completed?

The Miscellaneous Solid Waste Incineration Facility has already been put into use.
The other facilities will be put into use one-by-one as preparations are completed.

How large is the site preparation related to waste treatment?

The facilities will be built in an area approximately 14ha in size.

What is the difference between radiation, radioactivity and radioactive materials?

Radiation is like a strong ray of light.
If we use a flashlight as an analogy, radioactive material is the flashlight and the radiation is the light emitted by the flashlight.
“Radioactivity” refers to the ability of a substance to emit radiation, which is analogous to the ability of a flashlight to emit light.

How is the radiation exposure dose of tour participants managed?

During a tour each visitor is provided with a dosimeter to attach to their clothing.
The tour route has been set to limit the maximum total radiation exposure dose to 0.1mSv or less, which is lower than the exposure dose received during a roundtrip flight from Tokyo and New York.

How are the radiation levels shown at the bottom of the screen measured?

Dose level monitors (dosimeters) at 90 locations on site measure air dose rates in real time.
The dose levels shown at the bottom of the screen indicate the levels measured by these monitors or measurements taken with portable dosimeters depending on the location.
※Displayed data was taken between January, 2018 and February, 2020.

Dosimeter

How high were radiation levels in the main control room at the time of the accident?

Six workers were confirmed to have been exposed to more than 250mSv, which is the dose limit for workers responding to an emergency.
All of these workers were either operators monitoring instruments or electricians/instrument system engineers in the main control room.
The average annual dose at the Fukushima Daiichi NPS before the accident was 1.4mSv/yr (FY2009).

What is this steel tower near Unit 1?

It is an exhaust stack which was used before the accident as part of the reactor building’s air-conditioning system to vent air outside.
The exhaust stack is no longer in use.
The seismic resistance of this exhaust stack exceeds requirements, but to eliminate the risk of it falling over the top 60m of the stack is being dismantled in cooperation with a local contractor.

What is the gray box attached to the front of the Unit 2 reactor building?

This is called an anticum and was constructed to investigate the roof of the reactor building.
The anticum prevents dust, etc. that contains radioactive materials from being dispersed into the environment when boring holes in the wall of the reactor building.
The anticum is 30m high, 38m long and 16m wide.

Can workers enter the uppermost floor of Unit 3?

They can enter the uppermost floor area for short times.
In this area, where radiation levels remain high, remote-controlled cranes were used for decontamination and the installation of radiation shielding.
These preparations enabled workers to enter the top floor.

Are units 5 and 6 currently generating power?

No. The decision has already been made to decommission Units 5 and 6.

What is the layout of the reactor buildings?

This is a simplified diagram of the Unit 1~5 reactor buildings.
Fuel rods are put inside the pressure vessel, and the heat generated by them is used to produce electricity.
The spent fuel pools are used to store unused fuel and also to cool spent fuel that continues to generate heat.

What is the condition like in Reactor Pressure Vessel when electricity is generated?

In nuclear power generation, water in the reactor is boiled using the thermal energy generated from the nuclear fission of Uranium.
The high temperature and highly pressurized steam that is produced turns a turbine that generates electricity.
In Unit 5, steam pressure was approximately 7Mpa and steam temperature was approximately 286 degrees Celsius in the Reactor Pressure Vessel (RPV) when generating electricity.

What was the main control room originally used for?

This facility was originally used to monitor and operate the reactors and turbines, and also control radiation.
It is currently not in use.

ABOUT

The Fukushima Daiichi Nuclear Power Station is steadily being decommissioned with the cooperation of a great many people. An important part of the decommissioning process is conveying what conditions in the field are like to as many people as possible in an easy-to-understand manner. That is why we created INSIDE FUKUSHIMA DAIICHI. This virtual tour allows anyone, anywhere to experience what it’s like to be on the front lines of decommissioning. February, 2020

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