Seven Layers of Defense
NuScale’s design incorporates seven layers of defense to prevent the release of contamination into the environment, including: 1) oxide fuel pellet and cladding; 2) reactor vessel; 3) containment vessel; 4) reactor pool; 5) underground stainless steel lined concrete pool walls and floor; 6) biological shield; and 7) a Seismic Category 1 building with HVAC filtration. The reactor building and reactor pool are described below.
The reactor building houses the systems and components required for plant operation and shutdown. The reactor building is a Seismic Category 1 reinforced concrete structure designed to withstand the effects of aircraft impact, environmental conditions, natural phenomena, postulated design basis accidents, and design basis threats. The reactor building also provides radiation protection for plant operation and maintenance personnel.
The NuScale Power ModulesTM reactor pool and the spent fuel pool are located at or below nominal plant grade level, while the hoisting and handling equipment is located above grade.
To the maximum extent practical, equipment rooms or vaults within the reactor building are partitioned to provide separation between primary and supporting systems for each NuScale Power Module.
The reactor pool consists of a large, below-grade concrete pool with a stainless steel liner that provides stable cooling for the NuScale Power Modules for an unlimited period of time following any actuation of the Emergency Core Cooling System (ECCS).
Water inventory in the reactor pool is large enough to remove core decay heat from all the NuScale Power Modules for an unlimited period of time without adding water.