ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
This division promotes the development and timely introduction of fusion energy as a sustainable energy source with favorable economic, environmental, and safety attributes. The division cooperates with other organizations on common issues of multidisciplinary fusion science and technology, conducts professional meetings, and disseminates technical information in support of these goals. Members focus on the assessment and resolution of critical developmental issues for practical fusion energy applications.
2021 ANS Winter Meeting and Technology Expo
November 30–December 3, 2021
Washington, DC|Washington Hilton
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Matthew Denman: On Probabilistic Risk Assessment
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).
Nuclear energy holds the atoms that make up our universe together. This energy is released both when larger atoms split apart, undergoing fission, and when smaller atoms combine together, known as fusion. The amount of energy released in fission is tremendous -- millions of times more than other forms of energy. Fusion releases four times as much energy as fission. Fission or fusion, all of that energy is released using reactors.
Nuclear Fission provides about 10% of the world’s electricity, powers naval vessels around the world, and has powered space missions.
The energy released by fission is a million times greater than the chemical energy released by combustion, so a small amount of nuclear fuel, usually uranium, produces an enormous amount of heat. Over four hundred nuclear power plants around the world produce 400 GW of electricity, enough for 300 million US homes.
The fission reactors at each of these nuclear power plants create steam that turns a turbine to generate electricity, just as coal and gas plants do. Find out how nuclear reactors of the present and future work.
Pressurized Water Reactors and Boiling Water Reactors
Pressurized Water Reactor
Pressurized Water Reactors (PWR) and Boiling Water Reactors (BWR) are the most common reactors in the world today. In both PWRs and BWRs, light enriched uranium fuel, arranged in the reactor's core, heats water. PWRs use high pressure to prevent water from turning to steam in the core; steam is created in a secondary loop using a steam generator.
Boiling Water Reactor
BWRs generate steam directly in the core of the reactor, eliminating the need for some equipment, but resulting in radioactive steam in the turbine.
Control rods, neutron absorbing movable rods, are used in both reactors to control the chain reaction caused by neutrons from fissioning atoms being released and creating more fissions. By absorbing neutrons, the control rods sustain the chain reaction and keep it at an efficient rate.
Small Modular Reactors (SMRs) and Microreactors
SMRs and microreactors gained significant attention in recent years. These reactors are small in terms of size and energy production, compared to large existing reactors, so they can be constructed in a factory. When more energy production is needed, more SMRs can be added.
There are a number of significant advantages to SMRs and microreactors.
SMRs and microreactors may be small, but they can utilize a wide variety of nuclear technologies and open new markets at lower cost. The first United States SMR Design Certification is expected before the end of 2020. The first non-water based microreactor License Application was submitted in March of 2020 and is expected to be approved in 2022. SMRs and microreactors are in development or operation around the world, including floating SMRs in Russia, heat generating reactors in China, and a variety of other concepts.
Non-Light Water Reactors (LWRs) and Advanced Reactors
Advanced reactors build on the lessons learned from LWRs and non-LWRs and offer the potential of more economic, safer, diverse, and efficient ways to generate clean energy for the future. Water based and non-water based advanced reactors are under development all over the world and significant progress towards widespread use is expected in this decade.
Learn more about fission
The Tokamak and its plant systems housed in their concrete home. An estimated one million parts will be assembled in the machine alone.
Nuclear fusion has the potential to provide large amounts of energy and has been the focus of billions of dollars in international scientific collaboration. Fusion research and development has yet to achieve breakeven power production (producing more power than consumed), and numerous public and private organizations are pursuing different forms of technology. Three approaches are Magnetic Confinement Fusion (MCF), where magnets compress and contain a heat fusion plasma; Intertial Confinement Fusion (ICF), where lasers strike a fuel target to create the conditions for fusion; and Magnetized Target Fusion, a combination of elements of MCF and ICF.
Learn more about fusion
Last modified June 25, 2021, 2:32pm CDT