SEAL stands for Secluded Energy Access to Low-power and it represents an ideal solution to the need for accessing DC power in the event of a Station Blackout (SBO) scenario similar to the one presented at the Fukushima-Daichi plant.

This system features high power density batteries (nearly 3 times power density as current Lead-type batteries) to be placed inside a container underwater and anchored to the sea floor. These units are kept charged and under emergency situations they are called upon to provide the basic functionalities to keep the plant in a safe operating state. The string of batteries feed electricity to the charger which converts the DC power into AC power and feeds to the control panels in the reactor. These batteries are charged from the AC power of the generator (480 Volts AC). Under normal operations these batteries are responsible for providing power for the time between loss of AC power and the time diesel generators kick into full power. Under accident scenarios (Station Blackout) these batteries are intended to provide power between 4-8 hours to perform basic safety related operations. The backup DC battery system can enable an extended loss of all AC coping time of 72 hours for core and spent fuel pool cooling as well as control room integrity as needed.

The SEAL container is equipped with battery panels (shown in grey), power inverters, chargers and monitoring equipment. The most paramount characteristic of the SEAL system, is its location within the power plant space.  By designing the SEAL container to be installed under the sea level and securing it to the sea floor the potential for second modes of failure caused by the natural disaster, gets slightly reduced. The SEAL system takes advantage of the misfortunate characteristic of certain power plants to be located within close proximity to a large body of water (ocean, river, lake).