What is the primary purpose of containment venting in a severe accident scenario?

The primary purpose of containment venting in a severe accident scenario is to protect the containment building from over-pressurization, which could lead to a breach and a large, uncontrolled release of radioactive materials to the environment. In a severe accident involving core damage, large amounts of steam, hydrogen, and other gases can be generated inside the containment. If these gases are not managed, the pressure within the containment can increase to levels that exceed its design limits. Containment venting is a controlled release of these gases to the atmosphere, typically through filtered pathways, to reduce the pressure inside the containment and prevent it from failing. The venting process usually involves passing the gases through filters designed to remove radioactive particles, such as iodine and cesium, to minimize the amount of radioactive material released. Containment venting is considered a last-resort measure when other accident management strategies, such as containment spray systems, have failed to adequately control the pressure. While venting does release some radioactive materials, it is considered preferable to an uncontrolled breach of the containment, which would likely result in a much larger release. The decision to vent the containment is a complex one, involving careful consideration of the potential benefits of preventing containment failure versus the potential risks of releasing radioactive materials. Procedures for containment venting are carefully developed and implemented to ensure that the release is conducted in a controlled manner and that the impact on the public is minimized.