On the possibility of using 235U(n,f) resonance reactions for localized pulsed neutrons beams monitoring in the epithermal energy region at the ISIS spallation source

AbstractThe pure alpha emitter 148Gd may have a significant radiological impact in terms of internal dose to exposed humans in case of accidental releases from a spallation source using a tungsten target, such as the one to be used in the European Spallation Source (ESS). In this work we aim to present an approach to indirectly estimate the whole-body burden of 148Gd and the associated committed effective dose in exposed humans, by means of high-resolution gamma spectrometry of the gamma-emitting radiogadolinium isotopes 146Gd and 153Gd that are accompanied by 148Gd generated from the operation of the tungsten target. Theoretical minimum detectable whole-body activity (MDA) and associated internal doses from 148Gd are calculated using a combination of existing biokinetic models and recent computer simulation studies on the generated isotope ratios of 146Gd/148Gd and 153Gd/148Gd in the ESS target. Of the two gamma-emitting gadolinium isotopes, 146Gd is initially the most sensitive indicator of the presence of 148Gd if whole-body counting is performed within a month after the release, using the twin photo peaks of 146Gd centered at 115.4 keV (MDA < 1 Bq for ingested 148Gd, and < 25 Bq for inhaled 148Gd). The corresponding minimum detectable committed effective doses will be less than 1 µSv for ingested 148Gd, but substantially higher for inhaled 148Gd (up to 0.3 mSv), depending on operation time of the target prior to the release. However, a few months after an atmospheric release, 153Gd becomes a much more sensitive indicator of body burdens of 148Gd, with a minimum detectable committed effective doses ranging from 18 to 77 µSv for chronic ingestion and between 0.65 to 2.7 mSv for acute inhalation in connection to the release. The main issue with this indirect method for 148Gd internal dose estimation, is whether the primary photon peaks from 146 and 153Gd can be detected undisturbed. Preliminary simulations show that nuclides such as 182Ta may potentially create perturbations that could impair this evaluation method, and which impact needs to be further studied in future safety assessments of accidental target releases.

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Analysis of Shielding Performance of Radiation-Shielding Materials According to Particle Size and Clustering Effects

Applied Sciences ◽

10.3390/app11094010 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4010

Author(s):

Seon-Chil Kim

Keyword(s):

Particle Size ◽

Polymer Material ◽

Energy Region ◽

High Energy ◽

Radiation Shielding ◽

High Energy Region ◽

Particle Structure ◽

Effect Of Particle Size ◽

Extensive Body ◽

Shielding Material

In the field of medical radiation shielding, there is an extensive body of research on process technologies for ecofriendly shielding materials that could replace lead. In particular, the particle size and arrangement of the shielding material when blended with a polymer material affect shielding performance. In this study, we observed how the particle size of the shielding material affects shielding performance. Performance and particle structure were observed for every shielding sheet, which were fabricated by mixing microparticles and nanoparticles with a polymer material using the same process. We observed that the smaller the particle size was, the higher both the clustering and shielding effects in the high-energy region. Thus, shielding performance can be improved. In the low-dose region, the effect of particle size on shielding performance was insignificant. Moreover, the shielding sheet in which nanoparticles and microsized particles were mixed showed similar performance to that of the shielding sheet containing only microsized particles. Findings indicate that, when fabricating a shielding sheet using a polymer material, the smaller the particles in the high-energy region are, the better the shielding performance is. However, in the low-energy region, the effect of the particles is insignificant.

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Adjustment of Terahertz Properties Assigned to the First Lowest Transition of (D+, X) Excitonic Complex in a Single Spherical Quantum Dot Using Temperature and Pressure

Applied Sciences ◽

10.3390/app11135969 ◽

2021 ◽

Vol 11 (13) ◽

pp. 5969

Author(s):

Noreddine Aghoutane ◽

Laura M. Pérez ◽

Anton Tiutiunnyk ◽

David Laroze ◽

Sotirios Baskoutas ◽

...

Keyword(s):

Refractive Index ◽

Quantum Dot ◽

Energy Region ◽

Practical Importance ◽

High Energy ◽

Spherical Quantum Dot ◽

Terahertz Region ◽

Mass Approximation ◽

Optical Responses ◽

Temperature And Pressure

This theoretical study is devoted to the effects of pressure and temperature on the optoelectronic properties assigned to the first lowest transition of the (D+,X) excitonic complex (exciton-ionized donor) inside a single AlAs/GaAs/AlAs spherical quantum dot. Calculations are performed within the effective mass approximation theory using the variational method. Optical absorption and refractive index as function of the degree of confinement, pressure, and temperature are investigated. Numerical calculation shows that the pressure favors the electron-hole and electron-ionized donor attractions which leads to an enhancement of the binding energy, while an increasing of the temperature tends to reduce it. Our investigations show also that the resonant peaks of the absorption coefficient and the refractive index are located in the terahertz region and they undergo a shift to higher (lower) therahertz frequencies when the pressure (temperature) increases. The opposite effects caused by temperature and pressure have great practical importance because they offer an alternative approach for the adjustment and the control of the optical frequencies resulting from the transition between the fundamental and the first excited state of exciton bound to an ionized dopant. The comparison of the optical properties of exciton, impurity and (D+,X) facilitates the experimental identification of these transitions which are often close. Our investigation shows that the optical responses of (D+,X) are located between the exciton (high energy region) and donor impurity (low energy region) peaks. The whole of these conclusions may lead to the novel light detector or source of terahertz range.

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Dosimetry of Thermal Neutron Beamlines at a Pulsed Spallation Source for Application to the Irradiation of Microelectronics

IEEE Transactions on Nuclear Science ◽

10.1109/tns.2021.3064681 ◽

2021 ◽

pp. 1-1

Author(s):

Carlo Cazzaniga ◽

Davide Raspino ◽

G. Jeff Sykora ◽

Christopher D. Frost

Keyword(s):

Thermal Neutron ◽

Spallation Source

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DK I = 0, $$ D\overline{K} $$ I = 0, 1 scattering and the $$ {D}_{s0}^{\ast } $$(2317) from lattice QCD

Journal of High Energy Physics ◽

10.1007/jhep02(2021)100 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

Gavin K. C. Cheung ◽

◽

Christopher E. Thomas ◽

David J. Wilson ◽

Graham Moir ◽

...

Keyword(s):

Elastic Scattering ◽

Scattering Amplitudes ◽

Lattice Qcd ◽

Finite Volume ◽

Energy Region ◽

Light Quark ◽

Bound State ◽

Vector Resonance ◽

Quark Masses ◽

Partial Waves

Abstract Elastic scattering amplitudes for I = 0 DK and I = 0, 1 $$ D\overline{K} $$ D K ¯ are computed in S, P and D partial waves using lattice QCD with light-quark masses corresponding to mπ = 239 MeV and mπ = 391 MeV. The S-waves contain interesting features including a near-threshold JP = 0+ bound state in I = 0 DK, corresponding to the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ (2317), with an effect that is clearly visible above threshold, and suggestions of a 0+ virtual bound state in I = 0 $$ D\overline{K} $$ D K ¯ . The S-wave I = 1 $$ D\overline{K} $$ D K ¯ amplitude is found to be weakly repulsive. The computed finite-volume spectra also contain a deeply-bound D* vector resonance, but negligibly small P -wave DK interactions are observed in the energy region considered; the P and D-wave $$ D\overline{K} $$ D K ¯ amplitudes are also small. There is some evidence of 1+ and 2+ resonances in I = 0 DK at higher energies.

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