Tetris-inspired detector with neural network for radiation mapping

In recent years, radiation mapping has attracted widespread research attention and increased public concerns on environmental monitoring. In terms of both materials and their configurations, radiation detectors have been developed to locate the directions and positions of the radiation sources. In this process, algorithm is essential in converting detector signals to radiation source information. However, due to the complex mechanisms of radiation-matter interaction and the current limitation of data collection, high-performance, low-cost radiation mapping is still challenging. Here we present a computational framework using Tetris-inspired detector pixels and machine learning for radiation mapping. Using inter-pixel padding to increase the contrast between pixels and neural network to analyze the detector readings, a detector with as few as four pixels can achieve high-resolution directional mapping. By further imposing Maximum a Posteriori (MAP) with a moving detector, further radiation position localization is achieved. Non-square, Tetris-shaped detector can further improve performance beyond the conventional grid-shaped detector. Our framework offers a new avenue for high quality radiation mapping with least number of detector pixels possible, and is anticipated to be capable to deploy for real-world radiation detection with moderate validation.Comment: 29 pages, 20 figures. Ryotaro Okabe and Shangjie Xue contributed equally to this wor

Experimental Determination of Thermal Conductivity of a Lead- Bismuth, Eutectic-Filled Annulus

In order to obtain an accurate prediction of the thermal behavior of an annular fuel assembly (see MIT-NFC-PR-048 for a description of the rods), the thermal conduction of the region from the outside of the fuel capsule to the reactor coolant (within the test assembly) must be known. The effective thermal conductivity of this composite structure is dependent on the interaction of the parts via various physical phenomena, and therefore is difficult to infer accurately from the conductivity of the constituent materials. A mock-up of the annular fuel rod containment thimble was created to allow the conductivity of the annular lead bismuth eutectic-filled gap to be measured. An electric rod heater was used to provide temperatures similar to the in-core environment, and conductivity was determined based on thermocouple temperature readings at various points across the gap. A second series of experiments substituted a steel tube for the aluminum thimble, and used a bucket of stationary water as coolant. The purpose of these changes was to increase the temperature of the eutectic and achieve a larger melted fraction, while at the same time creating a large enough temperature drop across the gap to allow reliable measurements. A third series of experiments refined the setup and were able to produce more precise measurements of the thermal conductivity. The measured conductivities were between 4 and 8 W/m-K, much lower than the reported conductivity of the lead bismuth at about 10 W/m-K. The difference must be attributed to thermal resistances at the eutectic-aluminum and eutectic-steel interfaces. This, and the inherent difficulty of measuring the interface temperature due to the finite width of the thermocouples and the existence of sharp thermal gradients makes it difficult to further reduce the uncertainty in the measured conductivity

ALD process for the preparation of noble-metal-free monolithic catalysts

Bahlawane N, Kohse-Höinghaus K, Park J-S, Gordon RG. ALD process for the preparation of noble-metal-free monolithic catalysts. In: PROCEEDINGS OF EUROCVD-15. Vol 2005-09. The Electrochemical Society; 2005: 583-590

Dynamic Reconstruction

Dynamic reconstruction is a method for generating images or image sequences from data obtained using moving radiation detection systems. While coded apertures are used as examples of the underlying information collection modality, the dynamic reconstruction method itself is more widely applicable. Dynamic reconstruction provides for recovery of depth, and has sensitivity that drops off with the inverse of distance rather than the inverse square of distance. Examples of dynamic reconstructions of moving isotopic area sources are shown, as well as dynamic reconstructions of moving objects imaged using backscattered X-rays

Three Online Neutron Beam Experiments Based on the iLab Shared Architecture

Students at MIT have traditionally executed certain experiments in the containment building of the MIT nuclear reactor as part of courses in Nuclear Engineering and the third year laboratory course for Physics majors. A joint team of faculty and research staff from the MIT Nuclear Reactor Laboratory (MIT-NRL) and MITâ??s Center for Educational Computing Initiatives have implemented online versions of three classic experiments; (a) a determination of MIT reactor coolant temperature through measurement of thermal neutron velocity, (b) a demonstration of the DeBroglie relationship of the kinetic energy and momentum of thermal neutrons and study of Bragg diffraction through a single copper crystal at various orientations, and (c) a measurement of beam depletion using a variety of shielding filters. These online experiments were implemented using the LabVIEW® virtual instrumentation package and the interactive version of the iLab Shared Architecture (ISA). Initial assessment of the online experiments indicates that they achieve comparable educational outcomes to traditional versions of the labs executed in the reactor containment building

Three Online Neutron Beam Experiments Based on the iLab Shared Architecture

Students at MIT have traditionally executed certain experiments in the containment building of the MIT nuclear reactor as part of courses in Nuclear Engineering and the third year laboratory course for Physics majors. A joint team of faculty and research staff from the MIT Nuclear Reactor Laboratory (MIT-NRL) and MIT’s Center for Educational Computing Initiatives have implemented online versions of three classic experiments; (a) a determination of MIT reactor coolant temperature through measurement of thermal neutron velocity, (b) a demonstration of the DeBroglie relationship of the kinetic energy and momentum of thermal neutrons and study of Bragg diffraction through a single copper crystal at various orientations, and (c) a measurement of beam depletion using a variety of shielding filters. These online experiments were implemented using the LabVIEW® virtual instrumentation package and the interactive version of the iLab Shared Architecture (ISA). Initial assessment of the online experiments indicates that they achieve comparable educational outcomes to traditional versions of the labs executed in the reactor containment building

Design and Testing of a High Pressure Gas Target for Fast Neutron Resonance Radiography Design and Testing of a High Pressure Gas Target for Fast Neutron Resonance Radiography

Abstract-A high pressure deuterium gas target has been designed to provide high-flux fast neutrons using the D(d,n) 3 He reaction for use as a neutron source. The deuterium gas cell holds 4 atm D 2 gas at 298K and is projected to tolerate a beam current of ~50 µA of 3.0 MeV deuterons for 8 hours of continuous use. The high-pressure gas cell is designed to provide a fast neutron flux on the order of 10 5 n/cm 2 -s at one meter. Measurements of gamma ray production from deuterium impingement have shown tungsten to generate the fewest gamma rays; the primary components of the gas target have been constructed out of tungsten to decrease the number of gamma rays. To accommodate the high gas pressure, thin foil tungsten windows have been structurally reinforced with a tungsten support allowing for more than 60% beam transmission while greatly increasing the structural reliability of the thin windows. Extensive simulation and experimental testing have demonstrated the heating tolerances of the gas target thin windows and have shown that the peak temperature of the thin foils does not exceed 600 °C, while the edges of the foil do not exceed 100 °C, well within the limits of the foil windows and the gas sealing structures

Tetris-inspired detector with neural network for radiation mapping.

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

High Performance Fuel Design for Next Generation PWRs: 11th Quarterly Report

Quarterly Report for Project DE-FG03-01SF22329 April 2004 – June 2004I. Technical Narrative: The overall objective of this NERI project is to examine the potential for a high performance advanced fuel for Pressurized Water Reactors (PWRs), which would accommodate a substantial increase of core power density while simultaneously providing larger thermal margins than current PWRs. This advanced fuel will have an annular geometry that allows internal and external coolant flow and heat removal. The project is led by the Massachusetts Institute of Technology (MIT), with collaboration of four industrial partners – Gamma Engineering Corporation, Westinghouse Electric Corporation, Framatome ANP (formerly Duke Engineering & Services), and Atomic Energy of Canada Limited