The Mitigation of Beyond-Design-Basis-Events Rule will require US commercial reactors to maintain resources and procedures to cool a reactor’s core and used fuel pool, as well as preserving containment, after an event that disables all of a site’s normal and emergency electrical power sources, as well as the site’s ability to safely transfer heat to the environment. Reactors must also maintain equipment that can reliably measure water levels in used pools following a severe event, and “preserve the resources” needed to protect the core, containment and used fuel pool from external hazards.
Most US nuclear power plants must comply with the rule’s requirements within two years and 30 days of its publication in the Federal Register, which the NRC said will happen in the spring of 2019. Some plants – those which are subject to the NRC’s Containment Venting Order of March 2013 – have an additional year to comply with the requirements.
The NRC in March 2012 made orders for immediate post-Fukushima safety enhancements across the US commercial reactor fleet. The regulator on 24 January said the final rule applies more broadly than the 2013 venting order, the Mitigation Strategies Order of 2012, or conditions included in new reactor licences issued since then. It therefore includes language that ends the previous orders and licence conditions once the final rule’s requirements are in place. It also lays out the process for ending the requirements for a plant that has permanently shut down. The rule additionally resolves five petitions for rulemaking submitted in July 2011, and partially resolves a sixth petition submitted in May 2011.
“The NRC and its nuclear power plant licensees will continue post-Fukushima efforts outside of the rulemaking context, including analyses of whether additional safety improvements are necessary in response to updated site-specific seismic and flooding risk assessments,” the regulator said.
NRC said its staff had responded to public comments on the draft rule – which was completed in 2016 – by “removing, reorganising, clarifying and enhancing” several sections.