arXiv subjects

Christian Reiter

Publications and source records attributed to Christian Reiter.

4 recordsLinked to original sources

arXiv2025

MULE -- A Co-Generation Fission Power Plant Concept to Support Lunar In-Situ Resource Utilisation

For a sustained human presence on the Moon, robust in-situ resource utilisation supply chains to provide consumables and propellant are necessary. A promising process is molten salt electrolysis, which typically requires temperatures in excess of 900{\deg}C. Fission reactors do not depend on solar irradiance and are thus well suited for power generation on the Moon, especially during the 14-day lunar night. As of now, fission reactors have only been considered for electric power generation, but the reactor coolant could also be used directly to heat those processes to their required temperatures. In this work, a concept for a co-generation fission power plant on the Moon that can directly heat a MSE plant to the required temperatures and provide a surplus of electrical energy for the lunar base is presented. The neutron transport code Serpent 2 is used to model a ceramic core, gas-cooled very-high-temperature microreactor design and estimate its lifetime with a burnup simulation in hot conditions with an integrated step-wise criticality search. Calculations show a neutronically feasible operation time of at least 10 years at 100kW thermal power. The obtained power distributions lay a basis for further thermal-hydraulic studies on the technical feasibility of the reactor design and the power plant.

physics.comp-ph↗

arXiv2025

On Energy-Dependent Neutron Diffusion

While the energy-dependent neutron diffusion equation is widely employed in nuclear engineering, its status as an approximation to the transport equation is not yet completely understood, and several different approximations are in use to determine the diffusion coefficients. Past work on the theory underlying the diffusion approximation has often made use of asymptotic arguments; in the energy-dependent case, however, papers have appeared that differ substantially in their findings. Here we present a formal asymptotic derivation of the multigroup diffusion equation which addresses these differences, along with the varying and sometimes physically stringent assumptions employed in these works. Further, we show a way to exactly invert the relationship between flux and current in the P1 approximation, giving a matricial expression for the multigroup diffusion coefficient which is formally exact, has clear physical meaning, and which can be easily computed to arbitrary precision on the basis of cross-section data already produced by lattice calculations. The resulting 2-group diffusion coefficient for an infinite medium of hydrogen is calculated with Monte Carlo, and compared to the those deriving from the Cumulative Migration Method and from the out-scatter approximation.

physics.comp-ph↗

arXiv2025

VNS Tokamak OpenMC-Serpent Validation for Medical Isotope Studies

The Volumetric Neutron Source (VNS) tokamak is a proposed fusion reactor for testing and qualification of reactor components for future use in a fusion power facility, and has potential use for radioisotope production. The VNS geometry is modeled in the Serpent and OpenMC neutronics codes. Analog neutron-photon coupled simulations are carried out to compare the model's vacuum vessel and blanket components across codes. In the vacuum vessel, neutron and photon flux maps are calculated, while in the blanket region, neutron and photon spectra, (n,T), and (n,2n) reaction rates are calculated and compared between models. The detector response comparisons found the following: neutron flux and (n,T) reactions achieved excellent agreement, the (n,2n) detector response had good agreement, and photon flux had regional discrepancies depending on Serpent tracking used. Hybrid tracking lead to a relative difference of about 20% in the outboard side blanket, where as employment of delta tracking resulted in less than 1% relative difference. On an HPC cluster, Serpent was found to have shorter computation time than OpenMC in neutron photon coupled simulations using both hybrid tracking and delta tracking, but longer in neutron only simulations. An exemplary radioisotope production case is presented for the demonstration of additional VNS capabilities.

physics.comp-ph↗

arXiv2025

A novel approach to process TRISO nuclear fuel using plasma-aided chemistry

This paper provides a unique and to the best of our knowledge first-of-a-kind attempt to develop chemical processes that may contribute to the volume reduction of SMR TRISO-based fuels and aims at the eventual ability to reprocess the spent fuel. To this end, the etching behavior of two materials, silicon carbide, SiC and pyrolytic carbon, PyC, that are generally used for the different barrier layers of a TRISO particle has been investigated. Either F/NFx or O radicals were used as etching agents and were obtained from NF3 and molecular O2, respectively, using a microwave plasma generated in a remote plasma source RPS. Laser heating of the sample materials of up to 1200 {\deg}C allowed for determination of etching rates. The results of these experiments show that chemical processing of TRISO particles via plasma-assisted etching is possible and complete removal of the encapsulation and TRISO layers can be achieved. Additional research on the waste streams and off-gases, in particular the possibility of introducing intermediate steps to reduce the CO2 formed in the chemical reactions is needed.

physics.chem-ph↗