ITOKI CORPORATION (Head office: Chuo-ku, Tokyo; President: Koji Minato) has developed a special door called "BOUNCEBACK" for underground civil defense shelters and installed it in the model room of the NPO Japan Nuclear Shelter Association (Tsukuba City, Ibaraki Prefecture)*1.

Switzerland, a leading country in underground shelter construction, has a high penetration rate of underground shelters in Northern Europe, with over 100% in Switzerland and over 80% in Finland, while the current penetration rate in Japan is almost zero. On the other hand, the importance of underground shelters is high in Japan, a country prone to disasters, and the "Parliamentary League for Promoting Shelters (Strong Evacuation Facilities) and Underground Use" was launched in December 2022 to secure evacuation shelters in emergencies, and discussions on their spread are becoming more active.

Over the past half century, we have delivered approximately 3,000 special doors to advanced medical and research facilities in Japan, and have responded to a wide variety of requests and conditions with reliable quality backed by our technology. The special doors for the underground civil defense shelters we installed this time have disaster prevention and defense functions, such as shock resistance, airtightness, watertightness, and radiation shielding, and protect and block human lives and data equipment, which are the foundation of social life, from various threats such as natural disasters and terrorism. We also took operability and safety into consideration, and you can try opening and closing the doors in the model room.

In parallel with this development, we were the only special door manufacturer to be selected as a corporate committee member of the Working Group for Considering the Performance and Specifications Required for Underground Shelters in Preparedness for Emergencies in Japan, a Disaster-Prone Nation, which was launched by the Council for Resilience Japan, a general incorporated association, and is comprised of members from industry, academia, government, and the private sector.*2 We participated in formulating the original plan for the performance and specifications of shelters in Japan, and have obtained the Resilience Certification*3, which is the only certification body held by the Council for Resilience Japan, a general incorporated association.

Based on the technology and quality it has cultivated through its track record of deliveries to advanced medical and research facilities in Japan, Nippon Steel will continue to develop special doors for underground shelters and contribute to the realization of safer, more secure and more fulfilling lives for people through its active participation in the working group.

- Made in Japan, with world-leading shock resistance, airtightness, watertightness and radiation shielding performance
BOUNCEBACK is a completely Japanese product, with everything from planning and design to parts procurement and assembly completed in Japan. Its explosion-proof structure based on simulation and FEM analysis has achieved impact resistance of 400kN/m2, and the use of a 2-way hinge provides airtightness of 2m3/m2 h (at a pressure difference of 10kPa) and watertightness of 0.03m3/m2 h (at a water head of 10M). The maze-shaped handle shaft eliminates shielding defects and provides radiation shielding equivalent to 200mm of ordinary concrete.

・Despite its weight of approximately 1,400 kg, the opening, closing and tightening system can be easily operated even by women and children
The door weighs approximately 1,400 kg and is equipped with high-performance hinges and has been installed with high precision, allowing even women and children to open and close it smoothly without feeling its weight.

・Six safety measures to ensure peace of mind even in emergencies
Features include an integrated door opening/closing bar to prevent grabs at the edge, a safety cover at the base that prevents hands and fingers from getting caught, floor clearance that prevents shoes from getting caught, a 2-way hinge that opens to the frame when the handle is operated, a round, flat handle (spokeless handle) with no gaps or protrusions that will not catch hands or debris, and a handle lock mechanism that cannot be operated when the door is open. It can be operated safely even in the confusion of an emergency, preventing secondary accidents such as injuries.

The product name "BOUNCEBACK" expresses the hope that the product will bounce back from blasts, heat rays, floods, radiation, flying debris, biological/chemical agents, and EMP, and that the product will recover and bounce back from difficult situations after a disaster. The sky blue letters represent "hope and liberation," and the silver background represents "advanced thinking and the future."

The message printed on the back of the door, "Let's all work together to overcome these difficulties," is a quote from ITOKI's corporate philosophy and is written in 22 languages. It encourages cooperation and consideration among residents, while also showing consideration for foreigners in Japan and awareness of overseas expansion.

The symbol mark on the handle, which shows a circle of children surrounded by a circle of adults, teaches the importance and dignity of protecting the weak, while the five colors represent the survival environments of water, sand, earth, wood, and fire, and also suggest the five continents as borderless entities.

*1: Japan Nuclear Shelter Association (press release)
To the members and secretariat of the Working Group on Performance and Specifications Required for Underground Shelters in Preparedness for Emergencies in Japan, a Disaster-Prone Nation (dated February 9, 2024)
https://www.j-shelter.com/shelter_wg/
*2: Resilience Japan Promotion Council (press release)
Establishment of the "Working Group to Examine the Performance and Specifications Required for Underground Shelters in Preparedness for Emergencies in Japan, a Disaster-Prone Nation" (February 9, 2024)
https://www.resilience-jp.biz/wp-content/uploads/2021/09/d555496228c08e5fcc8e81a915055887.pdf
*3: Resilience Japan Promotion Council (website)
"Resilience Certification" Top Page
https://www.resilience-jp.biz/certification/