Chernobyl Belt and the CIGEO Project are two prime examples of nuclear projects where fire safety engineering models, including fire risk analysis, heat and smoke emission models, fire propagation models, structural behavior models, etc., have been applied.
Chernobyl Nuclear Power Plant
Fire safety engineering studies have been conducted to determine the fire resistance of the containment belt to be constructed for the protection of the Chernobyl Nuclear Power Plant . The project involves the construction of a steel belt that will cover Unit 4 of the Chernobyl Nuclear Power Plant . The containment belt project has been developed to create a structure that will function for over 200 years, contain radioactive particles during dismantling and removal of the facility, and protect the unit from atmospheric effects.
In 2010, a modeling study was conducted to verify the reliability of the NSC steel arch structure during a fire , simulating a real fire scenario where the bituminous coating on the roof of the existing building (Turbine Hall and Air Decontamination Facility) would burn .
For the project, a benchmark study was created between EFECTIS and IETP (Institute of Thermophysical Engineering, National Academy of Sciences of Ukraine), and the methodologies and software for calculating fire spread and thermal load were jointly analyzed. It was observed that both engineering studies yielded very similar and convergent results.
The same approach was successfully applied in collaboration with the relevant Ukrainian institute URDISC for mechanical load and structural behavior calculations. All details and results of the study were approved by the Ukrainian authorities (specifically, the State Fire Safety Department, the authorized institution) and shared with Ukrainian experts.
Chernobyl NPP Unit 4 Nuclear Safety Belt
Figure: Modeling of the fire safety behavior of the steel structure of the Chernobyl NPP Unit 4 Nuclear Safety Belt – structure height 100 m, width 200 m and length 800 m. (a) Configuration – (b) Fluid temperatures – (c) Structural displacement under fire load
CIGEO Project
ANDRA is the French Agency for Radioactive Waste Management , and one of its main tasks is the definition and implementation of the CIGEO project, a deep geological landfill project for spent radioactive fuels and high-level (HL) and medium-level long-life (IL-LL) radioactive waste. ANDRA’s work aims to ensure long-term operational safety and landfill reversibility.
In 2012, the project entered the industrial design phase. For CIGEO , fire safety, encompassing both nuclear safety in operational areas and the construction site, as well as the safety of workers and response teams, constitutes some of the key issues.
Figure: Examples of fire risk analysis and fire safety design for the CIGEO Radioactive Waste Storage Area.
During the project preparation phase in 2012, the overall architectural structure of the design, operational approaches, equipment and site management, construction timeline, and budget were determined. Regarding fire risks, architectural and electromechanical design studies identified the fundamental needs, enabling the development of methods to control fire risks and implement partitioning, heat/smoke extraction, and ventilation.
In 2014, a four-year project began to finalize and approve the design through a fire risk assessment. Following the approval process, construction will begin between 2019 and 2020, and the Cigéo Andra facility will be commissioned in 2025.
Efectis’s contribution to this project is a very detailed and comprehensive fire safety engineering application that considers and analyzes the fire behavior of tunnels, mines, and nuclear facilities; including fire risk analysis, smoke emission and ventilation during a fire, fire development modeling using CFD (computational fluid mechanics) and FEM (finite element modeling) software, structural behavior models and collapse modes of structures, and performance modeling of active fire safety systems.
In addition to modeling, full-scale fire resistance tests were developed and subsequently conducted in the laboratory to determine the effectiveness of nuclear waste concrete containment structures during a fire.
The project is ongoing, and during and after the work, design revisions are being made by updating fire risks according to real fire scenarios.
Conclusion
Fire safety engineering, particularly in high-risk and complex structures such as nuclear facilities where complying with regulatory requirements alone is insufficient, provides a performance-based approach alternative. This allows project owners, operators, designers, contractors, and material/system manufacturers to achieve safer and more manageable designs and structures thanks to today’s advanced fire safety testing methods and modeling options.
However, fire safety engineering practices also have a fundamental disadvantage: complexity and difficulty in implementation. Therefore, for a fundamental risk category such as fire, which concerns public safety and public health, calculations, modeling, analysis, testing, and verification/certification studies must be carried out by competent, qualified, and accredited third-party organizations.
Source: İlker İBİK, Aeronautical Engineer
