Performance comparison of four compact room-temperature detectors – two cadmium zinc telluride (CZT) semiconductor detectors, a LaCl3(Ce) scintillator, and an NaI(Tl) scintillator

The performance characteristics of four compact, room-temperature detectors – two scintillators and two semiconductor detectors – have been studied. All are commercially-available detectors. The two scintillators were a Æ13mmX13mm lanthanum chloride [LaCl3(Ce)] detector and a Æ25mmX25mm sodium iodide [NaI(Tl)] detector. The two semiconductor detectors were a 10X10X3 mm3 cadmium zinc telluride (CZT) detector with a coplanar gridded anode and a 5X5X5 mm3 CZT detector with an extended cathode. The efficiency, resolution, and peak shape performance of these devices are compared in this work. Since LaCl3(Ce) is a relatively new commercial scintillator material, additional information on the performance of this detector is presented. Specifically, we discuss the impact of naturally-occurring radioactive 138La on the background spectra measured with this scintillator. Additionally, two of the three LaCl3(Ce) crystals that we obtained commercially were internally contaminated with an alpha particle-emitting radionuclide which we have identified as 227Ac+daughters. This contamination had a profound impact on the usefulness of these two detectors

A preliminary evaluation of certain NDA techniques for RH-TRU characterization

This report presents the results of modeling efforts to evaluate selected NDA assay methods for RH-TRU waste characterization. The target waste stream was Content Code 104/107 113-liter waste drums that comprise the majority of the INEL`s RH-TRU waste inventory. Two NDA techniques are treated in detail. One primary NDA technique examined is gamma-ray spectrometry to determine the drum fission and activation product content, and fuel sample inventory calculations using the ORIGEN code to predict the total drum inventory. A heavily shielded and strongly collimated HPGE spectrometer system was designed using MCNP modeling. Detection limits and expected precision of this approach were estimated by a combination of Monte Carlo modeling and synthetic gamma-ray spectrum generation. This technique may allow the radionuclide content of these wastes to be determined with relative standard deviations of 20 to 55% depending on the drum matrix and radionuclide. The INEL Passive/Active Neutron (PAN) assay system is the second primary technique considered. A shielded overpack for the 113-liter CC104/107 RH-TRU drums was designed to shield the PAN detectors from excessive gamma radiation. MCNP modeling suggests PAN detection limits of about 0.06 g {sup 235}U and 0.04 g {sup 239}Pu during active assays

Exploration of Non-Resonant Divertor Features on the Compact Toroidal Hybrid

Non-resonant divertors (NRDs) separate the confined plasma from the surrounding plasma facing components (PFCs). The resulting striking field line intersection pattern on these PFCs is insensitive to plasma equilibrium effects. However, a complex scrape-off layer (SOL), created by chaotic magnetic topology in the plasma edge, connects the core plasma to the PFCs through varying magnetic flux tubes. The Compact Toroidal Hybrid (CTH) serves as a test-bed to study this by scanning across its inductive current. Simulations observe a significant change of the chaotic edge structure and an effective distance between the confined plasma and the instrumented wall targets. The intersection pattern is observed to be a narrow helical band, which we claim is a resilient strike line pattern. However, signatures of finger-like structures, defined as heteroclinic tangles in chaotic domains, within the plasma edge connect the island chains to this resilient pattern. The dominant connection length field lines intersecting the targets are observed via heat flux modelling with EMC3-EIRENE. At low inductive current levels, the excursion of the field lines resembles a limited plasma wall scenario. At high currents, a private flux region is created in the area where the helical strike line pattern splits into two bands. These bands are divertor legs with distinct SOL parallel particle flow channels. The results demonstrate the NRD strike line pattern resiliency within CTH, but also show the underlying chaotic edge structure determining if the configuration is diverted or limited. This work supports future design efforts for a mechanical structure for the NRD.Comment: 26 pages, 16 figure

Design and testing of a unique active Compton-suppressed LaBr3(Ce) detector system for improved sensitivity assays of TRU in remote-handled TRU wastes

The US Department of Energy’s transuranic (TRU) waste inventory includes about 4,500 m3 of remote-handled TRU (RH-TRU) wastes composed of a variety of containerized waste forms having a contact surface dose rate that exceeds 2 mSv/hr (200 mrem/hr) containing waste materials with a total TRU concentration greater than 3700 Bq/g (100 nCi/g). As part of a research project to investigate the use of active Compton-suppressed room-temperature gamma-ray detectors for direct non-destructive quantification of the TRU content of these RH-TRU wastes, we have designed and purchased a unique detector system using a LaBr3(Ce) primary detector and a NaI(Tl) suppression mantle. The LaBr3(Ce) primary detector is a cylindrical unit ~25 mm in diameter by 76 mm long viewed by a 38 mm diameter photomultiplier. The NaI(Tl) suppression mantle (secondary detector) is 175 mm by 175 mm with a center well that accommodates the primary detector. An important feature of this arrangement is the lack of any “can” between the primary and secondary detectors. These primary and secondary detectors are optically isolated by a thin layer (.003") of aluminized kapton, but the hermetic seal and thus the aluminum can surrounds the outer boundary of the detector system envelope. The hermetic seal at the primary detector PMT is at the PMT wall. This arrangement virtually eliminates the “dead” material between the primary and secondary detectors, a feature that preliminary modeling indicated would substantially improve the Compton suppression capability of this device. This paper presents both the expected performance of this unit determined from modeling with MCNPX, and the performance measured in our laboratory with radioactive sources

Development of an IEC neutron source for NDE

This paper concerns the development of a neutron so based on the inertial electrostatic confinement (IEC) of a low density fusion plasma in a gridded, spherically-focusing device. With the motivation of using such sources for nondestructive evaluation (NDE) applications, the focus of the development is on : Small size devices, sealed operation with D{sub 2} or D{sub 2}/T{sub 2} mixtures, Power-utilization and neutron-output optimization, and integration into an assay system. In this paper, we describe an experimental system that has been established for the development and testing of IEC neutron sources, and we present preliminary results of tests conducted for 25-cm and 15-cm diameter IEC devices

DESIGN OF AN ON-LINE, MULTI-SPECTROMETER FISSION PRODUCT MONITORING SYSTEM (FPMS) TO SUPPORT ADVANCED GAS REACTOR (AGR) FUEL TESTING AND QUALIFICATION IN THE ADVANCED TEST REACTOR

The US Department of Energy (DOE) is embarking on a series of tests of coated-particle reactor fuel for the Advanced Gas Reactor (AGR). As one part of this fuel development program a series of eight (8) fuel irradiation tests are planned for the Idaho National Laboratory’s (INL’s) Advanced Test Reactor (ATR). The first test in this series (AGR-1) will incorporate six separate “capsules” irradiated simultaneously, each containing about 51,000 TRISO-coated fuel particles supported in a graphite matrix and continuously swept with inert gas during irradiation. The effluent gas from each of the six capsules must be independently monitored in near real time and the activity of various fission gas nuclides determined and reported. A set of seven heavily-shielded high-purity germanium (HPGe) gamma-ray spectrometers and sodium iodide [NaI(Tl)] scintillation detector-based total radiation detectors have been designed, and are being configured and tested for use during the AGR-1 experiment. The AGR-1 test specification requires that the AGR-1 fission product measurement system (FPMS) have sufficient sensitivity to detect the failure of a single coated fuel particle and sufficient range to allow it to “count” multiple (up to 250) successive particle failures. This paper describes the design and expected performance of the AGR-1 FPMS

Identifying dynamical modules from genetic regulatory systems: applications to the segment polarity network

BACKGROUND It is widely accepted that genetic regulatory systems are 'modular', in that the whole system is made up of smaller 'subsystems' corresponding to specific biological functions. Most attempts to identify modules in genetic regulatory systems have relied on the topology of the underlying network. However, it is the temporal activity (dynamics) of genes and proteins that corresponds to biological functions, and hence it is dynamics that we focus on here for identifying subsystems. RESULTS Using Boolean network models as an exemplar, we present a new technique to identify subsystems, based on their dynamical properties. The main part of the method depends only on the stable dynamics (attractors) of the system, thus requiring no prior knowledge of the underlying network. However, knowledge of the logical relationships between the network components can be used to describe how each subsystem is regulated. To demonstrate its applicability to genetic regulatory systems, we apply the method to a model of the Drosophila segment polarity network, providing a detailed breakdown of the system. CONCLUSION We have designed a technique for decomposing any set of discrete-state, discrete-time attractors into subsystems. Having a suitable mathematical model also allows us to describe how each subsystem is regulated and how robust each subsystem is against perturbations. However, since the subsystems are found directly from the attractors, a mathematical model or underlying network topology is not necessarily required to identify them, potentially allowing the method to be applied directly to experimental expression data

Design and Preliminary Monte Carlo Calculations of an Active Compton Suppressed LaBr3(Ce) Detector System for TRU Assay in Remote-Handled Wastes

Recent studies indicate LaBr3(Ce) scintillation detectors have desirable attributes, such as room temperature operability, which may make them viable alternatives as primary detectors (PD) in a Compton suppression spectrometer (CSS) used for remote-handled transuranic (RH-TRU) waste assay. A CSS with a LaBr3(Ce) PD has been designed and its expected performance evaluated using Monte Carlo analysis. The unique design of this unit minimizes the amount of "dead" material between the PD and the secondary guard detector. The analysis results indicate that this detector will have a relatively high Compton-suppression capability, with greater suppression ability for large angle-scattered photons in the PD. J. K. Hartwell1, M. E. McIlwain1, R. P. Gardner2, J. Kulisek3 1) Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415-2114 USA 2) North Carolina State University, Dept of Nuclear Eng., PO Box 7909, Raleigh, NC 27695 USA 3) Ohio State University, Columbus, Ohio 43210 The US Department of Energy’s transuranic (TRU) waste inventory includes about 4,500 m3 of remote-handled TRU (RH-TRU) wastes. The RH-TRU waste stream is composed of a variety of containerized waste forms having a contact surface dose rate that exceeds 2 mSv/hr (200 mrem/hr) containing waste materials with a total TRU concentration greater than 3700 Bq/g (100 nCi/g). As part of a research project to investigate the use of active Compton-suppressed room-temperature gamma-ray detectors for direct non-destructive quantification of the TRU content of these RH-TRU wastes, we have designed and purchased a unique detector system using a LaBr3(Ce) primary detector and a NaI(Tl) suppression mantle. The expected detector performance has been modeled using MCNP-X [1] and CEARCPG [2], and incorporates certain design features modeled as important to active Compton suppression systems in previously-published work [3]. The unique detector system is sketched in Fig. 1. The ~25 mm diameter by 75 mm long LaBr3(Ce) primary detector is inserted in the 25.4 mm diameter well of a 175 mm by 175 mm NaI(Tl) secondary (suppression) detector and is viewed by a 38 mm diameter PMT. An important feature of this arrangement is the lack of any "can" between the primary and secondary detectors. These primary and secondary detectors are optically isolated by a thin layer of aluminized Mylar, but the hermetic seal and thus the aluminum can surrounds the outer bound of the detector system envelope. The hermetic seal at the primary detector PMT is at the PMT wall. This arrangement virtually eliminates the "dead" material between the primary and secondary detectors, a feature that modeling indicates will substantially improve the Compton suppression capability of this device. This detector arrangement has been carefully modeled using the MCNP-X and the CEARCPG Monte Carlo codes. The results of these design calculations are compared with each other and with preliminary laboratory measurements performed on a detector system procured to these specifications. References [1]John S. Hendricks, MCNPX version 2.5c, Report LA_UR_03-2202, 2003. [2]Xiogang Han, Robin P. Gardner, and W. A. Metwally, CEARCPG: A Monte Carlo Simulation Code for Normal and Coincidence Prompt Gamma-ray Neutron Activation Analysis (PGNAA), in press Nuclear Science and Engineering, American Nuclear Society. [3]Wade Scates, John K. Hartwell, Rahmat Aryaeinejad, and Michael E. McIlwain, Optimization studie

DETERMINATION OF THE QUANTITY OF I-135 RELEASED FROM THE AGR-1 TEST FUELS AT THE END OF ATR OPERATING CYCLE 138B

The AGR-1 experiment is a multiple fueled-capsule irradiation experiment being conducted in the Advanced Test Reactor (ATR) in support of the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program. The experiment began irradiation in the ATR with a cycle that reached full power on December 26, 2006 and ended with shutdown of the reactor for a brief outage on February 10, 2007 at 0900. The AGR-1 experiment will continue cyclical irradiation for about 2.5 years. In order to allow estimation of the amount of radioiodine released during the first cycle, purge gas flow to all capsules continued for about 4 days after reactor shutdown. The FPMS data acquired during part of that shutdown flow period has been analyzed to elucidate the level of 135I released during the operating cycle