Maintaining RIPB in commercial LWRs

September 1, 2022, 12:08PMNuclear NewsKent B. Welter

The new standard ANSI/ANS-30.3-2022, Light Water Reactor Risk-Informed, Performance-Based Design, has just been issued by the American Nuclear Society. Approved by the American National Standards Institute (ANSI) on July 21, 2022, the standard provides requirements for the incorporation of risk-informed, performance-based (RIPB) principles and methods into the nuclear safety design of commercial light water reactors. The process described in this standard establishes a minimum set of process requirements the designer must follow in order to meet the intent of this standard and appropriately combine deterministic, probabilistic, and performance-based methods during design development.

The Level 1 probabilistic risk assessment standard for nuclear power plant applications

August 29, 2022, 9:30AMNuclear NewsPatricia Schroeder

The American Society of Mechanical Engineers/American Nuclear Society Joint Committee on Nuclear Risk Management (JCNRM) has issued a new edition of its flagship standard, ANSI/ASME/ANS RA-­S-­1.1-­2022, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications. This standard was approved by the JCNRM, the ANS Standards Board, and the ASME Board on Nuclear Codes and Standards before being approved on May 11 by the American National Standards Institute (ANSI), earning the title of an American National Standard. With most of the text stable for the past year, the production process was started early, allowing the 400-­page standard to be published on May 31, 2022.

Matthew Denman: On Probabilistic Risk Assessment

September 24, 2021, 3:32PMNuclear News

Matthew Denman

Probabilistic risk assessment is a systematic methodology for evaluating risks associated with a complex engineered technology such as nuclear energy. PRA risk is defined in terms of possible detrimental outcomes of an activity or action, and as such, risk is characterized by three quantities: what can go wrong, the likelihood of the problem, and the resulting consequences of the problem.

Matthew Denman is principal engineer for reliability engineering at Kairos Power and the chair of the American Nuclear Society and American Society of Mechanical Engineers Joint Committee on Nuclear Risk Management’s Subcommittee of Standards Development. As a college student at the University of Florida, Denman took a course on PRA but didn’t enjoy it, because he did not see its connection to the nuclear power industry. Later, during his Ph.D. study at the Massachusetts Institute of Technology, his advisor was Neil Todreas, a well-known thermal hydraulics expert. Todreas was working on a project with George Apostolakis, who would leave MIT to become a commissioner of the Nuclear Regulatory Commission. The project, “Risk Informing the Design of the Sodium-Cooled Fast Reactor,” was a multi-university effort funded through a Department of Energy Nuclear Energy Research Initiative (NERI) grant. Todreas and Apostolakis were joined in this project by a who’s who of nuclear academia, including Andy Kadak (MIT, ANS past president [1999–2000]), Mike Driscoll (MIT), Mike Golay (MIT), Mike Lineberry (Idaho State University, former ANS treasurer), Rich Denning (Ohio State University), and Tunc Aldemir (Ohio State University).

Post-Fukushima safety enhancements

April 2, 2021, 2:47PMNuclear NewsLeah Parks, Carl Mazzola, Jim Xu, and Brent Gutierrez
A map of Japan highlighting the Fukushima prefecture.

March 11 will mark the 10-­year anniversary of the Fukushima Daiichi event, when a 45-­foot tsunami, caused by the 9.0-­magnitude Great Tohoku Earthquake, significantly damaged the reactors at Japan’s Fukushima Daiichi nuclear power plant. In response to this event, the U.S. Nuclear Regulatory Commission took actions to evaluate and mitigate beyond-­design-­basis events, including a new requirement for the staging of so-­called Flex equipment, as well as changes to containment venting and improvements to emergency preparedness. The U.S. Department of Energy also addressed beyond-­design-­basis events in its documented safety analyses.