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Defense in Depth

The concept of “defense in depth” refers to the layers of defense that the OPEN100 plant relies on to protect the local environment from any unregulated release of radioactivity. Unlike current PWR plants, OPEN100 focuses on a fail safe design in which more emphasis is placed on the result of an upset condition rather than the extravagant systems needed to guarantee the avoidance of an upset condition. This results in a more straightforward, easy-to-understand design that reduces plant cost and complexity.

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Defense in Depth
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Beyond the Design Basis Response

The beyond design basis response is the design facet of a plant to respond to any unexpected event and maintain a safe mode where no release of radioactive material can be expected. Events such as floods, fires, lightning strikes, hurricanes and explosions, while not normal, are nonetheless considered and evaluated as part of the plant licensing review. In every occasion, the OPEN100 team will be able to show that the events do not result in a condition that threatens the local communities.

Beyond Design
Probabilistic Risk

Probabilistic Risk Analysis

The 3 "levels" of a Probabilistic Risk Assessment (PRA) are: Level 1 estimates the likelihood that a reactor core could be damaged, Level 2 assumes core damage and estimates how much radioactive material reaches the environment, and how quickly the material could be released, and Level 3 estimates the health effects and economic losses that might result if radioactive material reaches the environment. While current PWRs safety defenses focus on a Level 1 PRA, which requires extensive modeling of all reactor protective and accident mitigations systems, OPEN100 designs are based on a Level 2 analysis and is therefore focused on public safety rather than equipment reliability. This approach allows an assumption of the worst case scenario and still demonstrates a negligible risk to the public, resulting in a simplified and higher guarantee analysis.

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