The significance of air filtration systems in nuclear power plants

For the past 100 years, AAF International has been committed to providing cleaner air, developing unparalleled expertise and innovation in the field of air treatment.

Today, AAF International is a leading supplier of clean air solutions for many commercial and industrial applications but there are not many industries where clean air has a greater significance than in the nuclear sector. Air filters in Nuclear Power Plant (NPP) perform critical roles in protecting employees, the surrounding environment, and local communities. They are seen as an integral part of the safety of the overall plant.

There are two types of containment in a NPP: static or dynamic. Static containment includes the initial NPP design and relies on the structure of the plant i.e. the buildings and doors to physically contain the risk of an incident. The area must contain the pressure resulting from a potential incident without any risk of a leakage. Dynamic containment relies on air filter to ensure any potentially radioactive particles in the air are captured by a filtration system and contained in a given area of the plant. Dynamic containment is essential when an airflow is required for ventilation and relies on air cleaning systems for safety.

AAF’s nuclear grade air filtration solutions ensure a safe dynamic containment to all of the NPP systems and buildings (from the turbine hall to the reactor building). Containment is one of the most important nuclear safety functions and is directly linked to the principles of nuclear safety. It is also one of the most qualified areas of the installation, controlled by very high-quality standards and stringent requirements.

There are two main types of air filtration systems in a NPP: non-radioactive air filtration and potential radioactive air filtration systems.

Non-radioactive air filtration systems include the systems that draw in the ambient air from outside. This type of air inlet system is still performing a critical role in the overall air cleaning process, but its task is to remove contamination from the outside air, such as course dust particles. The air inlet system can also include air temperature treatment (to increase or decrease the temperature of the ambient air, depending on the outside air parameters and particularly season), inlet fans, pre-filters and HEPA filters (may be included into a dedicated casing depending on the airflow) and outlet fans. Dampers are also used to distribute the air as it is required.

Potential radioactive air filtration systems will be situated in the reactor building or containment vessel. In this area iodine is created by fission inside the fuel rods and can be present in the form of a gas or aerosol in the atmosphere. The filtration system design and set-up is similar to a non-radioactive air filtration system but with a significant addition of an iodine trap. So, the filtration stages would follow the order of prefiltration, HEPA filtration and iodine trap filtration. Iodine traps use activated carbon with a high porosity to meet adsorption needs and prevent iodine dispersion during normal operation or in the event of an incident.

The airflow is a key specification of an air filtration system to ensure the right containment is applied and to avoid any leakage from potentially contaminated air. The air filtration systems of a NPP serve to protect against radioactive particles and gases that could be generated by contaminated systems. It is therefore a crucial asset in any plant and only thoroughly tried-and-tested equipment can be considered. In order to filter radioactive gases, AAF International has developed many iodine filtration solutions (filtration cells and casings).

Innovation in the world of air filtration has played a key role in the nuclear sector. In fact it is the nuclear sector that first developed HEPA filters, created in the 1940s as part of the classified Manhattan Project, where scientists needed to develop a way of removing radioactive materials from the air. Nuclear High Efficiency Particulate Absorbent HEPA filters are now a key part of a nuclear filtration system.

Nuclear air filtration is at the core of the safety containment requirements and is essential to protect people and the environment from any potential radioactive leakage. AAF International has been heavily involved in this sector since its inception and continues to ensure high quality clean air is provided to Nuclear Power Plants around the world.