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Radiation mapping has attracted widespread research attention and increased public concerns on environmental monitoring. Regarding materials and their configurations, radiation detectors have been developed to identify the position and strength of the radioactive sources. However, due to the complex mechanisms of radiation-matter interaction and data limitation, high-performance and low-cost radiation mapping is still challenging. Here, we present a radiation mapping framework using Tetris-inspired detector pixels. Applying inter-pixel padding for enhancing contrast between pixels and neural networks trained with Monte Carlo (MC) simulation data, a detector with as few as four pixels can achieve high-resolution directional prediction. A moving detector with Maximum a Posteriori (MAP) further achieved radiation position localization. Field testing with a simple detector has verified the capability of the MAP method for source localization. Our framework offers an avenue for high-quality radiation mapping with simple detector configurations and is anticipated to be deployed for real-world radiation detection.

The hydromechanical stability of the fuel plates in parallel coolant channels of a Materials Testing Reactor (MTR) fuel element design is of great importance to the safety of research and test reactors. Previous analytical, experimental, and numerical efforts focused on parallel channels with the same or similar size; also, in the prior numerical simulations, the fuel plate was often assumed to be perfectly flat. This work presents the results of a fluid-structure interaction simulation performed to evaluate the flow-induced deflections of the fuel plates in the low-enriched uranium (LEU, <20 wt% 235U) fuel element design for the conversion (from highly enriched uranium) of the Massachusetts Institute of Technology Reactor (MITR-II, also referred to as MITR). Various manufacturing and assembly tolerances of the MITR LEU elements are considered in the analysis, and the effects of channel size disparity, nonideal plate shape, and flow rate uncertainty are investigated. Results show that, for all cases analyzed, the deflection occurs toward the larger channel, and the change in any channel stripe remains small (less than 0.021 mm) compared to fabrication tolerances. In addition to simulation work, a hydraulic performance test of the MITR LEU fuel element is currently planned to support conversion to the use of LEU fuel. [ABSTRACT FROM AUTHOR]

The dynamic period equation is the basis of several successful techniques for the closed-loop digital control of nuclear reactors. These include both the reactivity constraint approach and the MIT-SNL period-generated control laws. Information on that equation is documented here including the derivation of its standard formulation, its relation to the Inhour equation, and the method used to estimate precursor concentrations so that closed-loop control can be achieved in real time. The dynamic period equation is the parent relation to the inhour equation and as such can be used to explain the dependence of the instantaneous reactor period on both reactivity and its rate of change. It is argued that the dynamic period equation should be taught in its full form as part of nuclear engineering curricula.

The thermal-hydraulic analysis performed for a planned upgrade of the MIT Research Reactor from 5 to 6-7 MW using the existing heat removal equipment is reported. This upgrade is one of several options under consideration for the relicensing of the MIT Research Reactor in 1999. Included in this paper is a description of the calculations of thermal-hydraulic limits which include limiting safety system settings (LSSS) and safety limits (SL). The LSSS and SL were respectively chosen to avoid onset of nucleate boiling and flow instability during steady-state operation. These analyses were performed using the MULti-CHannel-II or MULCH-II code which was developed and benchmarked at MIT for design and safety analysis of the MIT Research Reactor.

A steady-state, two-fluid model to study a subcooled boiling channel's steady two-phase flow shows that the estimates of void fractions coincide with the data for a wide range of experiments. The impact of mass flux, heat flux and system pressure on the void fraction profile are attended by the model. A simple computer program provides improved solution, considering the experimental observations compared to the semi-empirical correlations.

Abstract Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (