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Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging.

Rose PB, Erickson AS, Mayer M, Nattress J, Jovanovic I - Sci Rep (2016)

Bottom Line: Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source.We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material's areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission.For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

View Article: PubMed Central - PubMed

Affiliation: G.W. Woodruff School of Mechanical Engineering, Nuclear and Radiological Engineering Program, Georgia Institute of Technology, Atlanta GA 30332, USA.

ABSTRACT
Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as "searching for a needle in a haystack" because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material's areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

No MeSH data available.


Related in: MedlinePlus

Response of Cherenkov detectors to various materials of the same aerial density.(a) Energy-dependent transmission measurement of several objects composed of different materials (a complete set of objects measured is provided in Supplementary Materials). The shaded regions of the spectrum are attributed to the Cherenkov detector response to 4.438 MeV and 15.1 MeV gamma rays produced in the 11B(d,n)12C reaction. (b) The two characteristic energy regions in (a) are used to reconstruct the effective atomic number of eight test objects composed of different materials. The known photon interaction cross sections for 4.438 MeV and 15.1 MeV gamma rays are used for a comparison calculation and shown as red line. The reconstruction method for the measured Cherenkov radiation spectrum and the comparison transmission calculation are described in detail in the Supplementary Materials. Error bars calculated for the measured ratios are smaller than the plot markers (circles) and are therefore not shown.
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f2: Response of Cherenkov detectors to various materials of the same aerial density.(a) Energy-dependent transmission measurement of several objects composed of different materials (a complete set of objects measured is provided in Supplementary Materials). The shaded regions of the spectrum are attributed to the Cherenkov detector response to 4.438 MeV and 15.1 MeV gamma rays produced in the 11B(d,n)12C reaction. (b) The two characteristic energy regions in (a) are used to reconstruct the effective atomic number of eight test objects composed of different materials. The known photon interaction cross sections for 4.438 MeV and 15.1 MeV gamma rays are used for a comparison calculation and shown as red line. The reconstruction method for the measured Cherenkov radiation spectrum and the comparison transmission calculation are described in detail in the Supplementary Materials. Error bars calculated for the measured ratios are smaller than the plot markers (circles) and are therefore not shown.

Mentions: We employed a LaBr scintillation detector to measure the spectrum of photons generated by the 11B(d,nγ)12C reaction (Fig. 1b) and an array of Cherenkov detectors based on quartz18 to measure the energy-dependent opacity of objects of different areal density and elemental composition. Both types of detectors exhibit spectroscopic capability, and while the Cherenkov detectors have only crude energy resolution, it is sufficient for measurements when the gamma rays have large energy separation. Figure 2a demonstrates energy-dependent transmission measurement of several objects composed of different materials with the same aerial density (see Supplementary Table 1 for the details on objects measured). Since spectral analysis with Cherenkov detectors is not a common practice due to lack of resolved peaks, custom energy calibration methods using spectral shoulders and inflection points were developed18 specifically for this type of application. In this work the faux-peaks are integrated within bounds illustrated with shaded areas in Fig. 2a and used to determine the detected number of 15.1 MeV and 4.438 MeV photons.


Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging.

Rose PB, Erickson AS, Mayer M, Nattress J, Jovanovic I - Sci Rep (2016)

Response of Cherenkov detectors to various materials of the same aerial density.(a) Energy-dependent transmission measurement of several objects composed of different materials (a complete set of objects measured is provided in Supplementary Materials). The shaded regions of the spectrum are attributed to the Cherenkov detector response to 4.438 MeV and 15.1 MeV gamma rays produced in the 11B(d,n)12C reaction. (b) The two characteristic energy regions in (a) are used to reconstruct the effective atomic number of eight test objects composed of different materials. The known photon interaction cross sections for 4.438 MeV and 15.1 MeV gamma rays are used for a comparison calculation and shown as red line. The reconstruction method for the measured Cherenkov radiation spectrum and the comparison transmission calculation are described in detail in the Supplementary Materials. Error bars calculated for the measured ratios are smaller than the plot markers (circles) and are therefore not shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834544&req=5

f2: Response of Cherenkov detectors to various materials of the same aerial density.(a) Energy-dependent transmission measurement of several objects composed of different materials (a complete set of objects measured is provided in Supplementary Materials). The shaded regions of the spectrum are attributed to the Cherenkov detector response to 4.438 MeV and 15.1 MeV gamma rays produced in the 11B(d,n)12C reaction. (b) The two characteristic energy regions in (a) are used to reconstruct the effective atomic number of eight test objects composed of different materials. The known photon interaction cross sections for 4.438 MeV and 15.1 MeV gamma rays are used for a comparison calculation and shown as red line. The reconstruction method for the measured Cherenkov radiation spectrum and the comparison transmission calculation are described in detail in the Supplementary Materials. Error bars calculated for the measured ratios are smaller than the plot markers (circles) and are therefore not shown.
Mentions: We employed a LaBr scintillation detector to measure the spectrum of photons generated by the 11B(d,nγ)12C reaction (Fig. 1b) and an array of Cherenkov detectors based on quartz18 to measure the energy-dependent opacity of objects of different areal density and elemental composition. Both types of detectors exhibit spectroscopic capability, and while the Cherenkov detectors have only crude energy resolution, it is sufficient for measurements when the gamma rays have large energy separation. Figure 2a demonstrates energy-dependent transmission measurement of several objects composed of different materials with the same aerial density (see Supplementary Table 1 for the details on objects measured). Since spectral analysis with Cherenkov detectors is not a common practice due to lack of resolved peaks, custom energy calibration methods using spectral shoulders and inflection points were developed18 specifically for this type of application. In this work the faux-peaks are integrated within bounds illustrated with shaded areas in Fig. 2a and used to determine the detected number of 15.1 MeV and 4.438 MeV photons.

Bottom Line: Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source.We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material's areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission.For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

View Article: PubMed Central - PubMed

Affiliation: G.W. Woodruff School of Mechanical Engineering, Nuclear and Radiological Engineering Program, Georgia Institute of Technology, Atlanta GA 30332, USA.

ABSTRACT
Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as "searching for a needle in a haystack" because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material's areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

No MeSH data available.


Related in: MedlinePlus