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In this article, a new method to quantify the activity of spatially distributed gamma-emitting isotopes (hotspots) in homogenous content waste drums without the use of a collimator is presented. The method utilizes a spatial digital filter derived using maximum likelihood (ML) to determine multiple sources’ positions and then calculate their activities. To solve the multidimensional maximization problem, we use an alternating projection (AP) technique, which transforms the problem into a considerably simpler 1-D maximization problem. A dynamic grid search was developed to further decrease the computational load. The mathematical simulations demonstrate the improved accuracy when compared to that of industrial segmented gamma scanning (SGS) systems and the same accuracy as that of newer methods. Furthermore, the new method offers the benefit of replacing the heavy mechanical collimator with a “virtual collimator” formed by digital filters and an advanced algorithm to create a “digital virtual scan” of drum volume to locate hotspots.

A method to improve radioactive waste drum activity estimation in Segmented Gamma Scanning (SGS) systems was developed for homogenous content. We describe a method to quantify the activity of spatially distributed gamma-emitting isotopes (‘hot spots’) in homogenous content waste drums without the use of a collimator. Instead of averaging all the detector's readings we treat it as many different spatial samples as if we have multiple detectors surrounding the waste drum ("virtual detectors"). From these readings, we form a general linear model. Next, we derive the Maximum Likelihood Estimator (MLE) for the multiple sources position and activity. We solve this hyper-dimensional search problem using an Alternating Projections (AP) technique which transforms the problem into a simpler one-dimensional maximization problem. We tested this method using a mathematical simulation with a various number of sources, at random activities and positions for several energy bands. The preliminary results are consistent and show large improvement of the accuracy with comparison to industrial SGS systems and the same accuracy as new methods which exploits the spatial samples. Furthermore, since this method eliminates the need for heavy led collimator, none of the sources is blocked for the whole measurement period, which provides increased count rates and decreases the total measurement time.

Metals undergo a combination of rapid loading and rapid heating during normal and high speed machining processes. Constitutive models for these materials, however, generally lack any information regarding kinetics of thermally-induced transformations, such as austenite formation in carbon steels, that can have profound effects on their mechanical viscoplastic behavior. The NIST electrically-pulse-heated Kolsky bar was developed specifically to probe material response under conditions approaching those present during machining operations. We have achieved heating rates in excess of 1,000 °C/s combined with strain rates above 1,000 s−1 with this system. This paper presents recent experimental results for AISI 1045 and AISI 1075 steel using the pulse-heated Kolsky bar, and examines some aspects of the uncertainty of the method.

Radiation Portal Monitors (RPMs) are radiation detection devices which provide passive, non-intrusive means for fast screening of transportation of vehicles, baggage and passengers for the presence of nuclear and radiological materials.

This work presents specially designed radiation monitoring system for baggage screening at airports and border crossing points for the presence of radioactive and Special Nuclear Materials (SNM). Border monitoring equipment plays a key role in combating illicit trafficking. The conveyor monitor is designed to meet the detection level determined by the standard for Radiation Portal Monitors (RPM). The obtained sensitivity results of the system and an analytical analysis of the implemented algorithms contributing to the detection performances are presented. The system consists of highly sensitive gamma and neutron detectors, electronic data-processing unit, computer interface and unique algorithms. The system's electronic unit interfaces with the conveyor control system using two signals, an input signal for the conveyor operation status and an output signal for stopping the conveyor in case of alarm. This interface and the implemented algorithm reduce the number of false alarms and improve the detection level by considering the background variation. Further significant improvement in the detection level is achieved by implementing an advanced algorithm based on the detector reading profile versus time. The online computer software provides the user with friendly interface for retrieving the archived data and analyzing the history of alarms.

Fast deployment, real time Environmental Radiation Monitoring System (ERMS), developed to meet pre and post radiological event necessities. The full system enables online environmental and radiation data transfer to multiple clients from a variety of sensor's types, e.g. radiation gamma field, wind direction and speed, assembled on a fast deployment monitoring station. The complete system enables temporal and spatial analysis for radiation safety and post event risk analysis.