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We describe the Neutron Imaging Camera (NIC) being developed for the detection of special nuclear materials by NASA/GSFC and NSWC/Carderock. The NIC is a self-contained, robust, omni-directional and 3He-independent neutron detector based on the Three-Dimensional Track Imager (3-DTI) technology developed at GSFC for gamma-ray astrophysics applications. The 3-DTI is a large volume time-projection chamber...
US efforts to equip key points of entry with large area neutron detectors to intercept Special Nuclear Materials (SNM) have been undermined by a critical shortage of 3He gas. Yearly demand for 3He in US security applications alone is roughly 22,000 liters, exceeding current world supply. Neutron science, safeguards, defense, and other applications that depend on 3He detectors have been severely limited...
Lithium glass scintillator made from 6Li-enriched substrate is a well known for its neutron detection capability. In spite of neutron interaction, cross section of 6Li happens to be lower than that of 3He. However, the neutron detection efficiency could be higher due to higher volume content of 6Li nuclear in the solid scintillator vs. gas filled proportional counter. At the same time, as lithium...
Radiation detector systems for homeland security applications have been usually equipped with 3He tubes to detect the distinguished neutron signature of Special Nuclear Materials (SNMs). The serious shortage of 3He gas, however, recently initiated substantial efforts to develop alternative neutron detectors, particularly for large-area Radiation Portal Monitors (RPMs). Most activities are currently...
We developed a new thermal neutron calibration method to be able to experimentally determine an energy response function of a neutron detector using a pulse parallel beam and the time-of-flight (TOF) technique. The calibration method was experimentally demonstrated for a 3He proportional counter and an electric personal dosimeter using a pulsed thermal neutron beam from the research reactor, JRR-3M...
Silicon diodes with large aspect ratio perforated microstructures backfilled with 6LiF show a dramatic increase in neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology using detector stacking methods to increase thermal neutron detection efficiency. The highest efficiency devices thus far have delivered...
In intense, pulsed active detection, a single, intense pulse of radiation is used to induce photofission in fissionable material, increasing its detectability. The Mercury pulsed-power generator was converted to positive polarity (+3.7 MV, 325 kA, 50-ns FWHM) to drive an intense, pulsed radiation source based on the FIGARO active detection concept. The probing radiation source consisted of an ion-beam...
As a candidate for the alternatives to 3He neutron detector, 2 inch size LiF-based eutectic composites were fabricated by Bridgman technique. The eutectic composites showed a good transparency and well ordered lamellar structure. Neutron response of the several eutectic composites were evaluated and LiF/SrF2:Ce performed the better alpha/gamma ratio and high light yield. The preliminary test of neutron...
Long counters are widely used as neutron fluence monitors by utilizing their flat-response feature. A bulky neutron moderator is required however to achieve the flat-response feature, which can be a disadvantage from the viewpoint of portability as well as an undesirable source of scattered neutrons. Just downsizing the moderator deteriorates the flat response especially for high-energy neutrons....
Active well coincidence counters (AWCCs) are widely used for nondestructive assay and nuclear-safeguards applications, mainly for special nuclear material. The measurement method is based on the detection of time-correlated neutrons from fission by 3He tubes embedded in a polyethylene moderator. The purported advantage of this method over traditional gamma-ray spectral analysis is the greater penetrability...
Countries around the world are deploying radiation detection instrumentation to interdict the illegal shipment of radioactive material crossing international borders. These efforts include deployments in the U.S. and in a number of other countries by governments and international organizations. Most deployed radiation portal monitor systems are based on plastic scintillator for gamma-ray detection...
Performance of a He-3 counter and a B-10 loaded liquid scintillator EJ309B5 has been studied in terms of neutron detection efficiency. The measurements were carried out in a mixed field of neutron and gamma radiation from an intense ( ~ 106 neutrons/s/4π)252Cf source. The response of both detectors to background and high intensity gamma radiation ( ~ 100 μSv/h at a detector) from a 60Co source has...
The detection of illicit nuclear sources and SNM requires a ubiquitous network of sensors. While 3He proportional counters are excellent neutron detectors, there is an insufficient global supply of 3He to create the required number of detectors. Alternatives to 3He must be efficient, insensitive to gamma radiation, easily manufactured, rugged, and inexpensive to enable the procurement of a large numbers...
Performance of a He-3 counter and a B-10 loaded liquid scintillator EJ309B5 has been studied in terms of neutron detection efficiency. The measurements were carried out in a mixed field of neutron and gamma radiation from an intense (~106 neutrons/s/4??) 252Cf source. The response of both detectors to background and high intensity gamma radiation (~100 ??Sv/h at a detector) from a 60Co source has...
He proportional counters have long been used as neutron detectors for both passive and active detection of Special Nuclear Material (SNM). The optimal configuration of these detectors as far as gas pressure, amount of moderating material, and size are concerned is highly dependent on what neutron signatures are being used to detect and identify SNM. We present here a parametric study of the neutron...
The Rotating Modulation Collimator has been modified to image thermal neutron sources. The components of the RMC imaging system were modified to suit thermal neutrons. The experiment compared two detectors (He3 and BF3) and two mask materials (cadmium and borated epoxy) for a 77mCi PuBe source. Preliminary results indicate that both He3 and BF3 detectors may be used with the RMC. Further efforts will...
Complex measurement system for full-scale VVER models (mock-ups), created in the research reactor LR-0, is discussed. Fast neutron (energy from 0.5 to 10 MeV) and gamma spectra are measured in several representative points of mock-ups by two-parameter spectrometer with cylindrical stilbene scintillation detectors. Measurements in the thermal and epithermal neutron region are carried out with activation...
To answer safety authority requirements and to optimise the management of radioactive waste produced in retrieval and decommissioning activities, which contains a large variety of matrix materials, the accuracy of neutron measurement techniques has to be continuously improved. Active neutron measurements such as the Differential Die-Away (DDA) technique involving pulsed neutron generator as the neutron...
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