The linear hydrodynamic stability of proto–neutron stars (PNSs) is considered taking into account dissipative processes such as neutrino transport and viscosity. We obtain the general instability criteria which differ essentially from the well-known Ledoux criterion used in previous studies. We apply the criteria to evolutive models of PNSs that, in general, can be subject to the various known ...

The DIII-D tokamak is equipped with neutral beam sources that inject in four different directions; in addition, the plasma can be moved up or down to compare off-axis with on-axis injection. Fast-ion data for eight different conditions have been obtained: co/counter, near-tangential/near-perpendicular and on-axis/off-axis. Neutron measurements during short beam pulses assess prompt and delayed ...

The shift towards multi-core architectures has ushered in a new era of shared memory parallelism for scientific applications. This transition has introduced challenges for the nuclear engineering community as it seeks to design high-fidelity full-core reactor physics simulation tools. This paper describes the parallel transport sweep algorithm in the OpenMOC method of characteristics (MOC) neut...

We address the homogenization of an eigenvalue problem for the neutron transport equation in a periodic heterogeneous domain, modeling the criticality study of nuclear reactor cores. We prove that the neutron flux, corresponding to the first and unique positive eigenvector, can be factorized in the product of two terms, up to a remainder which goes strongly to zero with the period. One term is ...

Neutron radiography (NR) can investigate the diffusion mechanisms of moisture transport within the silica gel material. Dynamic neutron radiography (DNR) possesses the possibility to investigate the moisture profile inside the silica gel filter. The technique explained the relationship between moisture movement and time. This study investigated the diffusion mechanisms (absorption and infiltrat...

Neutron howitzers are routinely used in universities to activate samples for instructional laboratory experiments on radioactivity. They are also a convenient source of neutrons and gammas for research purposes, but they must be used with caution. This paper describes the modeling, design, construction, and testing of a portable, economical shield for a 1.0 Curie neutron howitzer. The Monte Car...

The neutron yield per proton from thick targets of lead and lithium irradiated with 100 MeV protons has been measured and calculated. The water bath method was used to measure the neutron production, and a Faraday cup for the the beam current determination. Measured yields are 0.343 + 0.021 for lead and 0.123 2 0.007 for lithium. Corresponding yields calculated with the nucleon-meson transport ...

Experimental measurements of elastic neutron scattering from U resonances were used to benchmark neutron scattering models in Monte Carlo transport codes. It was found that the implementation of the free gas model to determine the scattered neutron energy and angle in popular Monte Carlo codes is inaccurate. Differences up to a factor of two in the energy dependent angular distribution were obs...

The development of a stochastic cellular automata model for low-density highly concentrated neutron sources is presented. The model was implemented for purely reflecting and absorbing media with no fission source. Results of numerical experiments for one benchmark case with the new model is compared to a traditional neutron diffusion calculation. Similarities and differences of the model with M...

By means of two-dimensional (2D) simulations we study hydrodynamic instabilities during the first seconds of neutrino-driven supernova explosions. We use a PPM hydrodynamics code, supplemented with an approximative, gray, nonequilibrium treatment of radial neutrino transport, based on an analytic integration of the neutrino number and energy equations. Tests show that this treatment reproduces ...