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55th annual Nuclear News Buyers Guide now available
For American Nuclear Society members and Nuclear News subscribers, the 2024 Buyers Guide is now available in the ANS Digital Nuclear Library. The print version will be mailed along with the May “Capacity Factors/Nuclear Security” issue of Nuclear News magazine.
The corresponding ANS online Buyers Guide database is available year-round to all readers—updated with the latest products, services, and suppliers contact information for more than 600 nuclear-related companies.
Tengfei Zhang, Yongping Wang, E. E. Lewis, M. A. Smith, W. S. Yang, Hongchun Wu
Nuclear Science and Engineering | Volume 188 | Number 2 | November 2017 | Pages 160-174
Technical Paper | doi.org/10.1080/00295639.2017.1350002
Articles are hosted by Taylor and Francis Online.
A three-dimensional variational nodal method (VNM) is presented for pressurized water reactor core calculations without fuel-moderator homogenization. The nodal functional is presented and discretized to obtain response matrix equations. Within the nodes, finite elements in the x-y plane and orthogonal polynomials in z are used to approximate the spatial flux distribution. On the lateral interfaces, orthogonal polynomials are employed. On the axial interfaces, the finite elements facilitate a spatially accurate current representation that has proven to be a challenge for the method of characteristics–based two-dimensional/one-dimensional approximations which typically rely on spatial homogenization. The angular discretization utilizes an even-parity integral method within the nodes, with the integrals evaluated using high-order Chebyshev-Legendre cubature. On the lateral and axial interfaces, low-order spherical harmonics (Pn) are augmented by high-order Pn expansions to which quasi-reflected conditions are applied. With quasi-reflected conditions, the solution converges to the high-order Pn solution for an infinite lattice of identical cells with no gradient, while the low-order Pn expansions handle global gradients in both the radial and axial directions. The method is implemented in the PANX code and applied first to a number of model problems to study convergence of the space-angle approximations and then to the C5G7 benchmark problems. Multigroup Monte Carlo solutions provide reference values for eigenvalues and pin-power distributions.