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
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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
Aug 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
September 2025
Nuclear Technology
Fusion Science and Technology
August 2025
Latest News
Startup looks to commercialize inertial fusion energy
Another startup hoping to capitalize on progress the Department of Energy’s Lawrence Livermore National Laboratory has made in realizing inertial fusion energy has been launched. On August 27, San Francisco–based Inertia Enterprises, a private fusion power start-up, announced the formation of the company with the goal of commercializing fusion energy.
Maria Pusa
Nuclear Science and Engineering | Volume 182 | Number 3 | March 2016 | Pages 297-318
Technical Paper | doi.org/10.13182/NSE15-26
Articles are hosted by Taylor and Francis Online.
The burnup equations can, in principle, be solved by computing the exponential of the burnup matrix. However, the problem is extremely stiff, and the matrix exponential solution was long considered infeasible for entire burnup systems containing short-lived nuclides. After discovering that the eigenvalues of burnup matrices are confined to the vicinity of the negative real axis, the Chebyshev rational approximation method (CRAM) was introduced for solving the burnup equations and it was shown to be capable of providing accurate and efficient solutions without the need to exclude the short-lived nuclides. The main difficulty in using CRAM is determining the coefficients of the rational approximant for a given approximation order, with the previously published coefficients enabling only approximations up to order 16 for computing the matrix exponential. In this paper, a Remez-type method is presented for the computation of higher-order CRAM approximations. The optimal form of CRAM for the solution of burnup equations is discussed, and the method of incomplete partial fractions is proposed for this purpose. The CRAM coefficients based on this factorization are provided for approximation orders 4, 8, 12, . . ., 48. The accuracy of the method is demonstrated by applying it to large burnup and decay systems. It is shown that higher-order CRAM can be used to solve the burnup equations accurately for time steps of the order of 1 million years.