Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events
The Nuclear Regulatory Commission (NRC) is proposing to amend its regulations to provide updated fracture toughness requirements for protection against pressurized thermal shock (PTS) events for pressurized water reactor (PWR) pressure vessels. The proposed rule would provide new PTS requirements based on updated analysis methods. This action is desirable because the existing requirements are based on unnecessarily conservative probabilistic fracture mechanics analyses. This action would reduce regulatory burden for licensees, specifically those licensees that expect to exceed the existing requirements before the expiration of their licenses, while maintaining adequate safety. These new requirements would be voluntarily utilized by any PWR licensee as an alternative to complying with the existing requirements.
Consideration of Aircraft Impacts for New Nuclear Power Reactor Designs
The U.S. Nuclear Regulatory Commission (NRC or the Commission) is proposing to amend its regulations to require applicants for new standard design certifications that do not reference a standard design approval; new standard design approvals; combined licenses that do not reference a standard design certification, standard design approval, or manufactured reactor; and new manufacturing licenses that do not reference a standard design certification or standard design approval to assess the effects of the impact of a large, commercial aircraft on the nuclear power plant. Based on the insights gained from this assessment, the applicant shall include in its application a description and evaluation of design features, functional capabilities, and strategies to avoid or mitigate, to the extent practicable, the effects of the aircraft impact with reduced reliance on operator actions. The impact of a large, commercial aircraft is a beyond-design- basis event, and the NRC's requirements applicable to the design, construction, testing, operation, and maintenance of design features, functional capabilities, and strategies for design basis events would not be applicable to design features, functional capabilities, or strategies selected by the applicant solely to meet the requirements of this rule. The objective of this rule is to require nuclear power plant designers to perform a rigorous assessment of design features that could provide additional inherent protection to avoid or mitigate, to the extent practicable, the effects of an aircraft impact, with reduced reliance on operator actions.