| Insights | Nuclear Update Site

Enhanced Requirements for Venting Systems

Superseding the March 2012 post-Fukushima Order requiring reactors with Mark I and Mark II containments to install or improve their hardened venting systems, the NRC issued an enhanced Order requiring the vents to handle the pressures, temperatures, hydrogen concentrations and radiation levels from a damaged reactor. The enhancements also ensure plant personnel can operate the vents safely if the reactor core is damaged. The Order covers venting scenarios for both “wetwells,” structures meant to condense accident-generated steam and control pressure, and the larger “drywell” structures that surround the reactor. The Order requires plants with Mark I and Mark II containments to complete wetwell venting improvements starting in June 2014 (depending on a plant’s refueling schedule). The plants must also analyze their drywell venting scenarios and, if necessary, install a drywell venting option starting in June 2017.