The New Safe Confinement

The New Safe Confinement (NSC) at Chernobyl is a monumental engineering achievement designed to contain and isolate the radioactive remnants of the Chernobyl Nuclear Power Plant’s Reactor No. 4, the site of the infamous 1986 disaster. The NSC was constructed to address the decaying state of the original concrete sarcophagus, which had been hastily erected in the aftermath of the explosion, but was now deemed insufficient to prevent radiation from escaping.

Here’s an in-depth look at its construction and engineering principles:

Design and Construction Overview

The New Safe Confinement is a massive, arch-shaped structure that covers the original sarcophagus. Key design features include:

1. Arch Structure:

   • The NSC is primarily an arch that spans 257 meters in length, 162 meters in width, and 108 meters in height. Its design was chosen to provide maximum stability and minimize the weight on the ground.
   • The arch is supported by a robust foundation system and is designed to move on a set of rails, allowing it to be slid into place over the reactor.

2. Sealing and Radiation Protection:

   • The NSC is designed with multiple layers of shielding, including thick concrete walls and a steel frame. The combination of concrete and steel provides robust protection against radiation and contamination.
   • The structure is airtight and equipped with ventilation systems to prevent the buildup of gases inside and to manage heat.
   • Radiation shielding was a primary consideration in the design, ensuring that no radiation would escape from the reactor for at least a century.

3. Sliding Mechanism for Placement:

   • One of the most innovative aspects of the NSC is its ability to be moved into place. The entire arch was constructed in a clean zone some distance from the reactor and then slid into position over Reactor No. 4.
   • The arch was mounted on a set of rails and moved using hydraulic jacks, a process known as “strand jacking.” This allowed the structure to be placed with extreme precision over the reactor, avoiding radiation exposure to workers and minimizing risk.

4. Access and Decommissioning Systems:

   • The NSC includes systems to allow for future decommissioning work, such as robotic arms, cranes, and equipment designed for the remote handling of radioactive materials inside the reactor building.
   • These systems enable workers to safely remove debris and other hazardous materials from the reactor, without the need to directly enter the highly radioactive areas inside.

5. Structural Materials:

   • The design incorporated high-strength, corrosion-resistant materials, including steel, reinforced concrete, aluminum, and composite materials, ensuring the structure would remain intact over time and could withstand harsh conditions.
   • The steel frame was coated with special protective layers to resist radiation, and concrete was reinforced with steel rebar to provide additional strength.

Construction Process

The construction of the New Safe Confinement began in 2010 and took nearly seven years to complete, with the structure being fully operational in 2016. Below is an overview of the major phases of the construction process:

1. Pre-Construction Planning and Design:

   • Detailed planning and engineering studies were essential before construction could begin. Extensive analysis was conducted to assess the site’s geotechnical conditions, as the ground near the reactor had been affected by years of radioactive contamination.
   • Safety protocols were carefully developed, as construction had to occur in a highly radioactive environment.
   • Design teams from around the world, including engineers and architects from the European Union and other international partners, worked together to create the detailed plans for the NSC.

2. Fabrication and Construction of the Arch:

   • The construction of the NSC itself took place in a clean zone located 1,000 meters away from the reactor. This was a crucial measure to avoid radiation exposure to workers during the majority of the construction process.
   • The arch was built in a series of sections, with the steel frame being constructed first and then covered with layers of insulation, radiation shielding, and protective coatings.
   • While the arch was being built, the various decommissioning systems, including robotic arms, cranes, and other equipment, were also designed and constructed.

3. Sliding the Arch into Place:

   • Once the arch was complete, the most challenging part of the process began: sliding the massive structure into position over Reactor No. 4.
   • The arch was mounted on rails, and hydraulic jacks were used to lift and move it gradually over the reactor. The entire operation was carried out with extreme precision, as the structure needed to be placed exactly over the decaying sarcophagus.
   • The arch was moved in sections, with each phase requiring careful calibration and monitoring to ensure it would not shift or cause instability.

4. Finalization and Operationalization:

   • After the arch was successfully positioned, final work was done to seal it, including the installation of sealing systems, ventilation, and monitoring equipment.
   • The NSC was equipped with technology to monitor the internal environment, including radiation levels, air quality, and temperature. These systems provide real-time data to ensure that the structure continues to operate effectively for the long term.
   • Once the arch was in place, the original sarcophagus was removed, and the area beneath the NSC was sealed off, effectively containing the radioactive materials within Reactor No. 4.

5. Ongoing Monitoring and Maintenance:

   • Following the completion of construction, the NSC’s systems are regularly monitored and maintained to ensure the long-term effectiveness of the structure. These monitoring systems also help facilitate the eventual dismantling of the reactor, which is expected to take place in the coming decades.

Key Challenges Overcome

The design and construction process faced numerous challenges:

• Radioactive Environment: The high radiation levels around the reactor made it difficult for workers to be in the area for extended periods. Solutions such as remote construction and a sliding system for moving the arch helped mitigate this challenge.
• Geotechnical Issues: The ground around Reactor No. 4 had been affected by years of radiation, making it unstable. Extensive studies and careful design of the foundation system ensured that the NSC could be safely supported without causing further instability.
• Precision of the Sliding Mechanism: Moving the massive structure into place required precise engineering to ensure that the arch would land exactly over the reactor, without disturbing the unstable site.

Materials Used

The materials used in the construction of the New Safe Confinement (NSC) were carefully selected to ensure the structure’s durability, safety, and long-term effectiveness in containing radiation. Given the extreme environmental conditions at Chernobyl, including high radiation levels, severe weather, and the need for long-lasting protection, the choice of materials was paramount. Here’s a breakdown of the key materials used in the NSC’s construction:

       Steel

Role: Steel forms the core structural material of the NSC, providing strength, flexibility, and the ability to withstand both external forces (e.g., wind, seismic activity) and the weight of the structure itself.

• High-Strength Steel: Used extensively in the frame of the arch, as well as in the internal structural elements. High-strength steel is resistant to deformation, ensuring the arch maintains its integrity even under extreme conditions.
• Corrosion-Resistant Steel: Given the potential for corrosive exposure from the radioactive environment and harsh weather conditions, steel used in the NSC was specially coated to resist corrosion and degradation. This helps ensure the structure’s longevity.

      Concrete

Role: Concrete was used in both the foundation and the shielding systems of the NSC. It provides weight and stability while acting as a barrier to radiation.

• Reinforced Concrete: The base of the structure, as well as the shielding walls, is made from reinforced concrete, which includes steel rebar to enhance its strength and prevent cracking. Reinforced concrete provides structural integrity to support the arch and protects against radiation leakage.
• Radiation Shielding Concrete: The concrete used in certain parts of the NSC was specifically designed to block radiation. This concrete is denser than regular concrete, making it more effective at absorbing and blocking harmful radiation particles.

     Aluminum

Role: Aluminum was used in specific components of the NSC due to its lightweight properties and resistance to corrosion.

• Lightweight Components: Aluminum was used in the cladding and panels of the NSC, reducing the overall weight of the structure while still providing the necessary protection against radiation.
• Corrosion Resistance: Aluminum’s ability to resist corrosion makes it an ideal material for use in the outer layers of the NSC, particularly in areas exposed to harsh environmental conditions.

     Corrosion-Resistant Coatings

Role: Specialized coatings were applied to various surfaces of the NSC to protect against the harsh environment and prevent corrosion. These coatings are vital for ensuring the structure remains intact over the long term.

• Zinc Coatings: Zinc was used in some components of the steel frame to provide cathodic protection, preventing rust and corrosion by creating a protective layer that shields the steel beneath it.
• Epoxy and Polymer Coatings: These coatings were used on steel components to provide additional protection against corrosion and ensure the NSC’s longevity.

     Glass

Role: Special glass was used in certain parts of the NSC, primarily for monitoring and surveillance purposes.

• Radiation-Resistant Glass: Glass panels used for observation and surveillance were treated to be resistant to radiation. This allowed for safe monitoring of the reactor’s condition and the internal environment of the NSC without exposing personnel to hazardous radiation levels.

     Polyurethane Foam

Role: Polyurethane foam was used in some of the insulation layers within the NSC. It helps with thermal insulation and contributes to energy efficiency.

• Thermal Insulation: The foam helps regulate the temperature inside the NSC by reducing heat loss and providing insulation against the extremes of temperature experienced at Chernobyl. This is crucial in maintaining a stable internal environment that helps protect both the structural elements and sensitive equipment.

     Composite Materials

Role: Some composite materials were used for specific applications in the construction of the NSC, especially in areas where high strength-to-weight ratios were needed.

• Fiber-Reinforced Composites: These materials were used in some of the non-structural elements of the NSC, providing high strength while keeping the weight down. They are also resistant to radiation and extreme temperatures.

     Geotextiles

Role: Geotextile materials were used for the foundation system to ensure stability and prevent erosion around the base of the NSC.

• Soil Reinforcement: Geotextiles were incorporated into the soil beneath the NSC to provide additional reinforcement, helping to distribute the weight of the structure evenly across the unstable ground and preventing settlement.

     Rubber and Elastomers

Role: Rubber materials were used for seals and gaskets throughout the NSC.

• Sealing Systems: These rubber components are used to create airtight and waterproof seals, ensuring that the NSC remains airtight and prevents the escape of radioactive particles. The seals are also designed to be resistant to radiation degradation over time.

      High-Performance Bearings

Role: The sliding mechanism that moved the NSC into position relied on high-performance bearings to ensure smooth movement.

• Bearings for Sliding Mechanism: These bearings are made from high-durability materials designed to withstand the weight and movement of the massive structure. They needed to be strong enough to support the arch’s 36,000-ton weight and ensure precise movement into place.

Challenges and Solutions

The construction of the New Safe Confinement (NSC) at Chernobyl presented a host of unique and difficult challenges, mainly due to the highly radioactive environment surrounding Reactor No. 4 and the complex requirements for a safe and lasting solution. Here are some of the key challenges and how they were addressed during the construction process:

Radioactive Contamination

Challenge: The most immediate and significant challenge was the radioactive contamination around the reactor. With high levels of radiation still present at the site, especially near the reactor, workers could not be exposed to these dangerous conditions for prolonged periods.

Solution: The NSC was designed to be built away from the reactor in less contaminated areas. The arch itself was constructed in segments in a “clean” zone some distance from the reactor. Once the structure was completed, it was moved into position using a specially designed sliding system. This approach minimized worker exposure to radiation by allowing the majority of the construction work to be done remotely.

Complex Site Conditions

Challenge: The site around Reactor No. 4 was still unstable and presented significant risks in terms of access and safety. The original sarcophagus had already been deteriorating, and the ground was unstable in certain areas due to the weight of the structure, radiation, and the presence of radioactive debris.

Solution: To address these challenges, extensive geotechnical studies were carried out to assess the condition of the site. The NSC was designed to be both lightweight and structurally stable, ensuring that it would not add to the existing pressures on the site. The structure was built with a specialized foundation system that provided the stability needed to support its massive weight while also allowing for movement during the sliding process.

Engineering Precision for Moving the Arch

Challenge: The most ambitious engineering challenge was the need to move the massive arch into place. The NSC is a gigantic structure, weighing over 36,000 tons, and it had to be slid into place over Reactor No. 4 with extreme precision to avoid disrupting the unstable site or causing accidental radiation leaks.

Solution: The arch was constructed using a special method called “strand jacking,” which involved the use of hydraulic jacks to lift and move the structure in a controlled, incremental manner. The entire arch was mounted on a set of rails, and it was moved in small sections, ensuring that the movement was steady and precise. This complex operation required meticulous planning and coordination among a large team of engineers and technicians.

Worker Safety

Challenge: The construction of the NSC required workers to be in close proximity to the radioactive site during certain phases, which posed significant health risks. Any exposure to radiation could result in severe health consequences.

Solution: To mitigate this risk, advanced radiation shielding and safety protocols were implemented. Most of the construction was carried out remotely, with the majority of workers not needing to enter the high-radiation zone. For those who did, strict safety measures were enforced, including limited exposure times, protective gear, and constant monitoring of radiation levels. Additionally, a system of ventilation was integrated into the NSC to ensure that any airborne radioactive particles were contained, further reducing the risk of contamination.

Design and Durability

Challenge: One of the fundamental goals for the NSC was to create a structure that could withstand the harsh environmental conditions around the reactor while providing long-term protection from radiation. The original sarcophagus, while effective in the short term, was deteriorating and could not ensure long-term containment.

Solution: The NSC was built using corrosion-resistant materials, including steel coated with advanced protective layers, to ensure the structure could endure extreme weather, seismic activity, and other potential environmental factors. The materials used were carefully selected to ensure the NSC would remain functional for at least 100 years, a significant improvement over the temporary nature of the original sarcophagus.

Structural Integrity and Seismic Resistance

Challenge: The NSC had to be able to withstand seismic activity, particularly given the unpredictable nature of the area surrounding Chernobyl. Any movement of the structure could potentially lead to cracks or leaks, which could compromise its ability to contain radiation.

Solution: Engineers incorporated seismic-resistant designs into the structure, ensuring that the arch would be able to withstand significant forces without collapsing or shifting. This included using reinforced steel and concrete, along with advanced anchoring techniques to secure the structure to the ground.

Technological Innovations for Remote Dismantling

Challenge: The long-term goal for the NSC was not just to contain the radiation but also to allow for the eventual dismantling of Reactor No. 4, which would require workers to handle highly radioactive materials from within the structure.

Solution: The NSC includes advanced decommissioning systems, such as robotic arms and remote-controlled machinery, to handle the removal of radioactive debris and materials without the need for workers to enter the reactor building. These systems ensure that any dangerous materials can be safely removed, while minimizing human exposure to radiation.

Time Constraints and Budget

Challenge: The project was a monumental and costly endeavor, and there was immense pressure to complete the structure as quickly as possible to prevent further environmental damage. Balancing the urgency with the complexity of the engineering work posed logistical and financial challenges.

Solution: Despite these constraints, the NSC was built with great care and precision. International funding and collaboration helped overcome financial obstacles, while the construction process was meticulously planned to avoid delays. The work was carried out in stages, with each phase being completed before moving on to the next, ensuring that the project remained on schedule.

Comparison to the Original Sarcophagus

The original sarcophagus, built shortly after the explosion, was intended as a temporary solution. It was constructed hastily using concrete and steel, without the advanced design considerations that went into the NSC. Over the years, the sarcophagus showed significant signs of wear and degradation, and concerns grew about its ability to contain radiation for the long term.

In comparison, the NSC is a far more sophisticated and long-lasting structure. It is designed not only to prevent radiation from escaping but also to allow for the eventual dismantling of the reactor in a safe, controlled manner. Unlike the original sarcophagus, which was built with limited technology, the NSC incorporates state-of-the-art engineering techniques and materials that guarantee its durability for at least a century.

Technological Features

• Moving the Arch: One of the most impressive engineering feats involved in the construction of the NSC was the method of moving the entire arch into place. The structure was assembled on a track system and moved into position over Reactor No. 4 using a series of jacks. The final positioning was achieved with an extraordinary level of precision to ensure it was securely over the reactor.

• Decommissioning System: The NSC is equipped with a complex decommissioning system, which will allow workers to dismantle the reactor over time without having to enter the highly radioactive zone. This system includes robotic arms and other remote technologies that can safely remove debris and handle radioactive materials.

• Temperature and Ventilation Control: The interior of the NSC is equipped with systems to control temperature and humidity levels, reducing the risk of corrosion and ensuring the stability of the reactor’s containment.