Activity

Safety

Nuclear facilities approach their design and operation so as to prevent the occurrence of abnormalities and their expansion, and mitigate the development into an accident. JNFL facilities have adopted the following measures based on this "Defense in depth" philosophy:

1. To prevent occurrence abnormalities

  • Safety designs to prevent criticality, fire, explosion, and leaking.
  • Perform to a safety-side through fail-safe systems.

2. To prevent expansion abnormalities

  • Monitoring systems to detect abnormalities.
  • Automatic stop systems, so called interlock systems, to control abnormalities.

3. To mitigate consequence of accidents

  • Physical barriers with thick concrete cell to contain radioactive material and the air pressure control to prevent leaking radioactive materials out.
  • Internal air is released after filtering radioactive materials out as much as possible.

Example of safety measures based on the defense in depth philosophy at the Rokkasho Reprocessing Plant

Various initiatives were taken for the improvement of safety through the design and construction of our facilities.

The main safety measures at the Rokkasho Reprocessing Plant

Based on the lessons learned from the accident at the Fukushima Daiichi Nuclear Power Station, JNFL is coming to promote initiatives to go back to the fundamental perspective and improve safety.

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  • 1.Hydrogen explosion countermeasures
  • 2.Measures against leakage of chemicals
  • 3.Internal flooding measures
  • 4.New emergency responce facility
  • 5.Securing access routes
  • 6.Geological survey (on the ground)
  • 7.Geological survey (at sea)
  • 8.Controlling the diffusion of radioactive substances
  • 9.Securing power supply
  • 10.Evaluation of the impact of Tsunami
  • 11.Training assuming various circumstances
  • 12.Fire prevention and protection
  • 13.Securing cooling function
  • 14.Tornado measures

Hydrogen explosion countermeasures

Even if by chance all the air compressors shut down, air will continue to be sent and hydrogen will be scavenged.

Hydrogen explosion countermeasures

Air compressor with engine

Measures against leakage of chemicals

Fabricated chemical resistant sheet is wrapped around equipment that needs to be protected from chemicals, thereby preventing corrosion of the structural members

Measures against leakage of chemicals

Provision of the necessary equipment and materials
Anticipating harm (adhesion to the skin, entering the eyes etc.) caused by radioactive substances, decontamination tools, cleansing devices and shower etc. are provided.

Decontamination tools set

Decontamination tools set

Emergency shower

Emergency shower

Eye shower

Eye shower

Internal flooding measures

Weirs and water-tight doors are installed to protect the equipment, in case water floods inside the facility (breaking of the machinery or piping, sloshing of the spent fuel storage pool* etc.) *When liquid shakes due to external vibrations

Weir

Weir (Image)

Water-tight door

Water-tight door (Image)

Securing access routes

Vehicles for removing debris have been provided so that work can be accomplished quickly even in the time of a disaster.

水素爆発対策

Bulldozer

Wheel loader

Controlling the diffusion of radioactive substances

Even if by chance large scale damage occurs due to an earthquake etc. water is discharged from multiple directions and the diffusion of radioactive substances from the building is controlled.

Controlling the diffusion of radioactive substances

Water cannon

Water cannon

Water cannon training

Water cannon training

Geological survey (on the ground)

Boring survey, trench survey etc. are carried out in detail at the site environ and in the vicinity of the site, and evaluated, so as to ensure safety with respect to the design-basis earthquake ground motion.

Reflection seismic survey

Artificial seismic waves are generated and waves reflected from under the ground are received, with the help of which the underground structure is investigated.

Boring survey

The ground is excavated in a tubular form and the collected rock samples are analyzed to investigate the underground structure.

Trench survey

Surface of the earth is excavated and the geological situation under the ground is directly verified.


What is Design-basis Earthquake Ground Motion?
Design-basis earthquake ground motion refers to the maximum strength of tremors that are likely to occur in the vicinity of the facility. This is considered as the basis of seismic design. The design-basis earthquake ground motion is established by taking into account inland crustal earthquakes, inter-plate earthquakes, oceanic intra-plate earthquakes, or earthquakes for which the seismic source cannot be identified.

What is Design-basis Earthquake Ground Motion?

Geological survey (at sea)

Marine sonic prospecting or seabed boring survey are conducted and the safety of the facility is verified.

Marine sonic prospecting
Sound waves are generated in sea water by means of a sonic wave generator and the sound waves reflected by the seabed or the sub-bottom geological strata are received with the help of a streamer cable, and these are used to investigate the sub-bottom structure.

Marine sonic prospecting

Seabed Boring Survey

(Rise drilling vessel "Chikyu")

Seabed boring survey off Shimokita off the Pacific Coast
(Rise drilling vessel "Chikyu")

Boring core

ボーリングコア

The underground structure is investigated by observing and analyzing the cylindrical rock samples that are collected.

New emergency responce facility

An emergency response facility with a seismic isolated structure has been established as a base for emergency response. (Commencement of operation in December 2011)
The facility is fully equipped with 1 week's worth of food, fuel and equipment, and is provided with communication equipment etc. in case there is public and internal telecommunications infrastructure failure.
Further, a new emergency response facility, which will be about twice the size of the existing emergency response facility (for approx. 200 persons), will be established in order to enhance the workability of the response personnel and to increase the equipment and materials, in case a severe accident occurs simultaneously.

Emergency response facility
Emergency response facility

Securing power supply

In order to maintain safety at the facility, electricity needs to be supplied at all times.
Power source is multiplexed so as to ensure that electricity does not get interrupted due to natural disasters etc.


Framework for securing power supply

External power supply lines (2 lines)

External power supply lines (2 lines)

Even if
power
transmission
stops
Emergency Diesel Generator

Emergency Diesel Generator

Even if
this
malfunctions
Power supply vehicle

Power supply vehicle

Evaluation of the impact of Tsunami

The reprocessing plant is located at an elevation of approx. 55m at a distance of approx. 5km from the coast. It is assessed that the reprocessing plant will not have any direct impact even if the highest class tsunami were to occur. Further, a study has been conducted assuming the highest class of tsunami in Aomori Prefecture and the results indicate that "there will be absolutely no impact on the nuclear fuel cycle facility etc.".

Evaluation of the impact of Tsunami

Tornado measures

A steel protective net for protecting the outdoor cooling tower has been installed, in case there is a high class tornado.

Cooling tower (before construction)

Cooling tower (before construction)

Installation of protective net (image after construction)

Installation of protective net (image after construction)


Measures to prevent vehicles from being blown away
Sturdy car ports or sufficiently strong lashing devices are installed so as to prevent the vehicles from being blown away in the event of a tornado.

Sturdy car ports or sufficiently strong lashing devices are installed so as to prevent the vehicles from being blown away in the event of a tornado.

Image of measures to prevent being blown away

Training assuming various circumstances

Training is conducted even under conditions that make it difficult to work, such as in the night or during the winter season, so that disaster response activities can be smoothly carried out even in the event of a large-scale disaster.
In the future as well, by implementing various trainings, efforts will be made to acquire and enhance knowledge and techniques.

Countermeasures office

Countermeasures office

Cable connection training at night

Cable connection training at night

Training on drawing water from the pond during winter

Training on drawing water from the pond during winter

Training on operating the robot for disaster recovery work

Training on operating the robot for disaster recovery work

Critical convergence training

Critical convergence training

Securing cooling function

Arrangements have been made for various equipment including portable pumps, so that high level radioactive liquid waste etc. can be cooled even if the existing cooling function is lost. Also, water required for cooling can be acquired from a diversity of sources, such as river, pond etc. in addition to the water storage tank within the site environ.

Large transfer pump vehicle

Large transfer pump vehicle

Medium sized transfer pump vehicle

Medium sized transfer pump vehicle

Portable pump

Portable pump

Fire prevention and protection

Measures have been taken to ensure that fire fighting activities can be carried out within the building even in the event of an earthquake.
Fire engines that can carry out fire fighting activities such as moving around and discharging water even if debris is scattered have been provided.

Large chemical fire engine

Large chemical fire engine

Fire engine that can move around on uneven ground

Fire engine that can move around on uneven ground