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The deadline arrives: Checking in on the Reactor Pilot Program
On May 23, 2025, President Trump signed Executive Order 14301, “Reforming Nuclear Reactor Testing at the DOE,” which instructed the Department of Energy to create a Reactor Pilot Program (RPP)—a new system in which companies could pursue DOE authorization to build and test their first-of-a-kind nuclear technologies. EO 14301 set an ambitious goal for that program: three reactors achieving criticality by July 4, 2026.
Alain Hébert
Nuclear Science and Engineering | Volume 169 | Number 1 | September 2011 | Pages 81-97
Technical Note | doi.org/10.13182/NSE10-39
Articles are hosted by Taylor and Francis Online.
We are investigating a new class of linear characteristics schemes along finite-length tracks for solving the transport equation for neutral particles with scattering anisotropy. These algorithms are based on diamond differencing, as implemented with the method of discrete ordinates. The quadratic-order diamond-differencing (DD1) scheme is based on linear discontinuous coefficients that are derived through the application of approximations describing the mesh-averaged spatial flux moments in terms of spatial source moments and of the beginning- and end-of-segment flux values. This DD1 linear characteristics scheme is inherently conservative. This approach is an improvement relative to other linear characteristics schemes because no information needs to be collected on internal surfaces. Consequently, the DD1 scheme is compatible with existing tracking files for the collision-probability method. The proposed scheme is verified in one-dimensional slab geometry where it is found to be equivalent to a discrete ordinates solution and on simple two-dimensional benchmarks made of regular squares or hexagons.