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.
Explore membership for yourself or for your organization.
Conference Spotlight
2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
Standards Program
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!
Latest Magazine Issues
Sep 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
September 2025
Nuclear Technology
Fusion Science and Technology
October 2025
Latest News
A wave of new U.S.-U.K. deals ahead of Trump’s state visit
President Trump will arrive in the United Kingdom this week for a state visit that promises to include the usual pomp and ceremony alongside the signing of a landmark new agreement on U.S.-U.K. nuclear collaboration.
Valerio Mascolino, Alireza Haghighat
Nuclear Science and Engineering | Volume 198 | Number 3 | March 2024 | Pages 592-627
Research Article | doi.org/10.1080/00295639.2023.2197844
Articles are hosted by Taylor and Francis Online.
The available three-dimensional (3-D), time-dependent neutron transport algorithms and codes (deterministic or Monte Carlo) are very computationally intensive and are impractical for the simulation of real-world reactors. Henceforth, commonly approximate forms of the transport equation (e.g., diffusion or SPn) are used with expected loss of accuracy. We have developed a hybrid deterministic and Monte Carlo algorithm that not only preserve a Monte Carlo–level accuracy but can achieve a solution in seconds or minutes. This algorithm has been incorporated into the RAPID code system and tested for a number of benchmark problems. This novel time-dependent algorithm, referred to as tRAPID, utilizes a transient fission matrix methodology and allows for fast and accurate simulation of 3-D time-dependent neutron transport problems. The tRAPID algorithm is used to calculate neutron kinetics parameters (such as and Rossi-) and 3-D time-dependent prompt and delayed fission source distributions for two reference models: the Flattop-Pu critical assembly and the Jožef Stefan Institute TRIGA Mark-II benchmark core. Results are compared to experiments reported in the International Criticality Safety Benchmark Evaluation Project Handbook as well as to a reference Serpent Monte Carlo calculation. The tRAPID results are in excellent agreement with both the experimental data and Serpent predictions, while requiring minimal computing resources.