The U.S. Nuclear Regulatory Commission (NRC) is releasing Revision 4 to their Regulatory Guide 1.136, titled “Design Limits, Loading Combinations, Materials, Construction, and Testing of Concrete Containments.” This guide updates the standards and guidance for materials and procedures used in building concrete containment structures in nuclear power plants. It endorses, with specific exceptions, the 2019 version of codes set by the American Society of Mechanical Engineers (ASME) related to such constructions. The document also clarifies that the new guide isn't mandatory for license holders, meaning they aren't required to follow it, though it provides useful methodologies to meet existing regulatory requirements.
Simple Explanation
The U.S. group that checks on nuclear plants wants to use new, better rules for building safe concrete walls around reactors. They say these rules aren't required, but they help make sure everything is built well.