Coincidence/Multiplicity Photofission Measurements (original) (raw)
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Enhanced Photofission-based, Coincidence/Multiplicity Inspection Measurements
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), 2010
An enhanced active interrogation system has been developed that integrates a transportable Idaho National Laboratory (INL) photonuclear inspection system, using a pulsed bremsstrahlung source and a reconfigurable neutron detection system, with a Los Alamos National Laboratory (LANL) list-mode data acquisition system. A series of active interrogation experiments using various nuclear materials have shown enhanced nuclear material detection and identification utilizing pulsed photofission-induced, neutron coincidence/multiplicity counting between pulses of an electron accelerator operating at energies up to 10 MeV. This paper describes the integrated inspection system and presents some key shielded and unshielded nuclear material inspection results. The enhanced inspection methodology has applicability to homeland security and possible nuclear weapon dismantlement treaties.
2000
A photonuclear interrogation method was experimentally assessed for the detection of shielded nuclear materials. Proof-of-Concept assessment was performed at the Los Alamos National Laboratory (LANL) TA-18 facility and used the INEEL VARITRON electron accelerator. Experiments were performed to assess and characterize the delayed neutron emission responses for different nuclear materials with various shield configurations using three "nominal" electron beam energies; 8-, 10-, and 11-MeV. With the exception of highly enriched uranium (HEU), the nuclear materials assessed represent material types commonly encountered in commerce. The specific nuclear materials studied include a solid 4.8-kg HEU sphere, a 5-kg multiple-object, depleted uranium (DU) [uranium with about 0.2% enrichment with U-235] target, and two 11-kg thorium disks. The shield materials selected include polyethylene, boratedpolyethylene, and lead. Experimental results, supported with numerical predictions, have shown that the photonuclear interrogation technique is quite capable of detecting shielded nuclear material via the direct measurement of the photofission-induced delayed neutron emissions. To identify or discriminate between nuclear material types (i.e., depleted uranium, HEU, and thorium), a ratio of delayed neutron counts at two different beam energies is utilized. This latter method, referred to as the dual-beam energy ratio Figure-of-Merit, allows one to differentiate among the three nuclear material types. iv v ACKNOWLEDGMENTS We wish to express our sincere thanks for the tremendous support throughout this investigation from our Los Alamos National Laboratory (LANL) colleagues: Robert (Bob) Scarlett, Charles (Chuck) Goulding, Calvin Moss, Charles Hollas and William (Bill) Myers. They made these tests possible! In addition, we want to thank Brett King of Idaho State University, for his invaluable operational support of the INEEL VARITRON electron accelerator.
2017
The purpose of this research was to use a 15 MeV (K15 model by Varian) linear electron accelerator (linac) for the photon assay of special nuclear materials (SNM). First, the properties of the photon radiation probe were determined. The stochastic radiation transport code, MCNP5, was used to develop computational models for the linac. The spectral distribution of photons as well as dose rate contour maps of the UNLV accelerator facility were computed for several linac operating configurations. These computational models were validated through comparison with experimental measurements of dose rates. The linac model was used to simulate the photon interrogation of SNM targets of various compositions and shielding materials. The spectra of neutrons produced by the irradiation of shielded SNM was characterized. The effects of shielding material and the SNM enrichment on the neutron yields following photon assay were determined. It was determined that the radiation signatures following t...
Status of the prototype Pulsed Photonuclear Assessment (PPA) inspection system
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
The Idaho National Laboratory, in collaboration with Idaho State University's Idaho Accelerator Center and the Los Alamos National Laboratory, continues to develop the Pulsed Photonuclear Assessment (PPA) technique for shielded nuclear material detection in large volume configurations, such as cargo containers. In recent years, the Department of Homeland Security has supported the development of a prototype PPA cargo inspection system. This PPA system integrates novel neutron and gamma-ray detectors for nuclear material detection along with a complementary and unique gray-scale, density mapping component for significant shield material detection. This paper will present the developmental status of the prototype system, its detection performance using several INL Calibration Pallets, and planned enhancements to further increase its nuclear material detection capability.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018
Augmenting or interchanging current international safeguards shift register−based data acquisition systems with list mode data acquisition systems gives nondestructive assay (NDA) systems greater versatility. Neutron list mode data analysis offers comparable analytical results to the more widely used shift register analysis in nuclear material quantification applications and offers several diagnostic tools that are specifically beneficial to in-laboratory characterization and calibration measurements. These benefits include identification of non-ideal behavior, optimization of operational parameters from a single measurement, and an improved understanding of the physics-based behavior of NDA systems for a more precise system representation and more confident assay results. In this work the advantages of using list mode data acquisition for detector characterization are demonstrated experimentally. Two commercial-off-the-shelf International Atomic Energy Agency-supported technologies are used for a typical detector characterization procedure and their performance is compared. Specifically, a 3 He-based Canberra Industries JCC-71 Neutron Coincidence Collar is characterized using the Hungarian Institute of Isotopes' Pulse Train Recorder-32 (PTR-32) list mode data acquisition system, and the results are compared to those obtained using the standard Canberra Industries JSR-15 model shift register. The quantitative results from the two systems are in agreement, which demonstrates that the PTR-32 is a technically viable alternative to conventional shift register electronics for this task. A suitable procedure for full instrument characterization is described, and the added benefits of list mode for characterization and data collection are discussed. This is an important step toward establishing a procedure for the routine use of list mode data acquisition and analysis for neutron NDA system characterization in safeguards field applications.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2012
A variety of neutron interrogation techniques exists for the identification and characterization of fissile materials. Typically the sample is irradiated continuously or in pulses, and the neutron or gamma response is used for the characterization of the sample. Active neutron coincidence counting is one of these techniques, based on the detection of correlated prompt neutrons from induced fission in 235 U, in order to quantify uranium. Typically AmLi neutron sources are used for the interrogation so far. In this study we used for the first time a guided cold neutron beam for interrogation, which is a far more intense source of uncorrelated neutrons. A pilot neutron coincidence setup was installed at a neutron beam of the Budapest Neutron Centre, and samples of small volumes and various uranium contents were measured. It was proven that the detection of fission events (Doubles) is feasible even for micrograms of 235 U and the detector response is proportional to the fissile content of the sample.
Pulsed Photonuclear Assessment (PPA) Technique: CY-05 Project Summary Report
2005
is developing an electron accelerator-based, photonuclear inspection technology, called the Pulsed Photonuclear Assessment (PPA) system, for the detection of nuclear material concealed within air-, rail-, and, primarily, maritime-cargo transportation containers. This report summarizes the advances and progress of the system's development in 2005. The contents of this report include an overview of the prototype inspection system, selected Receiver-Operator-Characteristic curves for system detection performance characterization, a description of the approach used to integrate the three major detection components of the PPA inspection system, highlights of the gray-scale density mapping technique being used for significant shield material detection, and higher electron beam energy detection results to support an evaluation for an optimal interrogating beam energy.
Photonuclear-based Detection of Nuclear Smuggling in Cargo Containers
AIP Conference Proceedings, 2003
The Idaho National Engineering and Environmental Laboratory (INEEL) and the Los Alamos National Laboratory (LANL) have performed experiments in La Honda, California and at the Idaho Accelerator Center in Pocatello, Idaho to assess and develop a photonuclear-based detection system for shielded nuclear materials in cargo containers. The detection system, measuring photonuclear-related neutron emissions, is planned for integration with the ARACOR Eagle Cargo Container Inspection System (Sunnyvale, CA). The Eagle Inspection system uses a nominal 6-MeV electron accelerator and operates with safe radiation exposure limits to both container stowaways and to its operators. The INEEL has fabricated custom-built, helium-3-based, neutron detectors for this inspection application and is performing an experimental application assessment. Because the Eagle Inspection system could not be moved to LANL where special nuclear material was available, the response of the Eagle had to be determined indirectly so as to support the development and testing of the detection system. Experiments in California have successfully matched the delayed neutron emission performance of the ARACOR Eagle with that of the transportable INEEL electron accelerator (i.e., the Varitron) and are reported here. A demonstration test is planned at LANL using the Varitron and shielded special nuclear materials within a cargo container. Detector results are providing very useful information regarding the challenges of delayed neutron counting near the photofission threshold energy of 5.5-6.0 MeV, are identifying the possible utilization of prompt neutron emissions to allow enhanced signal-to-noise measurements, and are showing the overall benefits of using higher electron beam energies. FIGURE 1. The INEEL Varitron system.