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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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ANS joins others in seeking to discuss SNF/HLW impasse
The American Nuclear Society joined seven other organizations to send a letter to Energy Secretary Christopher Wright on July 8, asking to meet with him to discuss “the restoration of a highly functioning program to meet DOE’s legal responsibility to manage and dispose of the nation’s commercial and legacy defense spent nuclear fuel (SNF) and high-level radioactive waste (HLW).”
Taewan Noh, Warren F. Miller, Jr., Jim E. Morel
Nuclear Science and Engineering | Volume 123 | Number 1 | May 1996 | Pages 38-56
Technical Paper | doi.org/10.13182/NSE96-A24211
Articles are hosted by Taylor and Francis Online.
The finite element and lumped finite element methods for the spatial differencing of the even-parity discrete ordinates neutron transport equations (EPSN) in two-dimensional x-y geometry are applied. In addition, the simplified even-parity discrete ordinates equations (SEPSN) as an approximation to the EPSN transport equations are developed. The SEPSN equations are more efficient to solve than the EPSN equations due to a reduction in angular domain of one-half, the applicability of a simple five-point diffusion operator, and directionally uncoupled reflective boundary conditions. Furthermore, the SEPSN equations satisfy the same diffusion limits as EPSN in an optically thick regime, appear to have no ray effect, and converge faster than EPSN when using a diffusion synthetic acceleration (DSA). Also, unlike the case of EPSN, the SEPSN solutions are strictly positive, thus requiring no negative flux fixups. It is also demonstrated that SEPSN is a generalization of the simplified PN method. Most importantly, in these second-order approaches, an unconditionally effective DSA scheme can be achieved by simply integrating the differenced EPSN and SEPSN equations over the angles. It is difficult to obtain a consistent DSA scheme with the first-order SN equations. This is because a second-order DSA equation must generally be derived directly from the differenced first-order SN equations.