SiLiF Neutron Counters to Monitor Nuclear Materials in the MICADO Project
<p>(<b>a</b>) The SiLiF detector arrangement as a double sided silicon diode sandwiched between two <sup>6</sup>LiF layers deposited on carbon fiber substrates; (<b>b</b>) a real detector assembled inside its aluminum box.</p> "> Figure 2
<p>Figure <b>2.</b> Sketch of the rotating support explicitly constructed for the evaporation of the <sup>6</sup>LiF converters in order to guarantee the uniformity of the deposition.</p> "> Figure 3
<p>Distribution of the deviation of the effective areal density with respect to the nominal value (in percent) for 28 tested samples.</p> "> Figure 4
<p>(<b>a</b>) 3D sketch of the SiLiF detector (in yellow) and its arrangement within the moderator (in grey); (<b>b</b>) a SiLiF hosted in a half moderator; (<b>c</b>) final assembling of a SiLiF.</p> "> Figure 5
<p>Simulated neutron detection efficiency in different moderator configurations (see the text for details).</p> "> Figure 6
<p>(<b>a</b>) The AmBe neutron source box with a SiLiF detector during a measurement in the front position. (<b>b</b>) The 4 × 4 array of SiLiF detectors during the measurement in the <span class="html-italic">top</span> position.</p> "> Figure 7
<p>(<b>a</b>) Drawing of the top view of the section at 30 cm height of the neutron source box; the source position is indicated by a small dark circle, the red squares indicate the <span class="html-italic">front</span> and <span class="html-italic">inside</span> positions where the measurements were done; (<b>b</b>) the corresponding neutron flux obtained by means of a simulation with the Fluka code.</p> "> Figure 8
<p>(<b>a</b>) Drawing of the 3D side view of the neutron source box, the red box indicates the <span class="html-italic">top</span> position; (<b>b</b>) the corresponding neutron flux obtained by means of a simulation with the Fluka code.</p> "> Figure 9
<p>Neutron flux simulated in the three measurement positions with Fluka, and with MCNP on the detectors in the radwaste package exercise with <sup>240</sup>Pu (see the Discussion section).</p> "> Figure 10
<p>The characteristic spectrum shape, measured for all the SiLiF detectors in the front position, is due to the superposition of the triton (2.73 MeV) and alpha (2.05 MeV) contribution smeared down by the effect of the emission from different depths/angles in the <sup>6</sup>LiF converter. The energy bin size is 47 keV.</p> "> Figure 11
<p>The background-subtracted neutron spectrum as compared to the background. Also highlighted are three different contributions to the background (see text).</p> "> Figure 12
<p>GEANT4 simulation of the SiLiF response to 10 MeV neutrons with the moderator surrounding the detector (see text).</p> "> Figure 13
<p>GEANT4 simulation of the SiLiF response to 10 MeV neutrons without the moderator surrounding the detector (see text).</p> "> Figure 14
<p>The γ/n ratio as a function of the chosen energy threshold, with respect to the <span class="html-italic">gamma1</span> and <span class="html-italic">gamma2</span> cases (see text).</p> "> Figure 15
<p>The deposited energy spectrum collected in the <span class="html-italic">inside</span> position with the reference detector. The colored area starts from the alpha endpoint, and contains 97% of the detected tritons (see text).</p> "> Figure 16
<p>The typical deposited energy spectrum collected in the <span class="html-italic">inside</span> position with the SiLiF detectors under test. The colored area represents the number of detected neutrons for the chosen 1.5 MeV energy threshold, and was normalized to the impinging flux to provide the detection efficiency for the chosen threshold.</p> "> Figure 17
<p>The intrinsic detection efficiency measured for the 32 SiLiF detectors in the <span class="html-italic">inside</span> configuration, with nominal energy thresholds of 1 and 1.5 MeV.</p> "> Figure 18
<p>Deposited energy spectra obtained with the detectors SiLiF03 and SiLiF03N, belonging to two different silicon batches in the <span class="html-italic">inside</span> position. The detectors were coupled with <sup>6</sup>LiF converters deposited onto carbon fiber substrates of the A and SAT types (coming from different manufacturers) which in a second run were swapped.</p> "> Figure 19
<p>The 4 × 4 arrangement and numbering of the detector positions for the test with fast neutrons.</p> "> Figure 20
<p>Behavior of the simulated average neutron detection efficiency between thermal and 2.5 MeV in the <span class="html-italic">top</span> position. The efficiency modulation due to geometrical effects is clearly visible. The error bars indicate only the statistical uncertainty.</p> "> Figure 21
<p>Comparison between a corner (det00) and a central (det05) detector simulated efficiency. The overall shapes are similar, the difference being essentially a scale factor enhancement for the central detector due to a geometrical effect of the neighboring moderators.</p> "> Figure 22
<p>The simulated detection efficiency as a function of the impinging neutron energy for the 16 detectors in the 4 × 4 array configuration in the top position.</p> "> Figure 23
<p>(<b>a</b>) Total neutron flux simulated in the <span class="html-italic">top</span> position in correspondence of the 4 × 4 SiLiF array; (<b>b</b>) The measured total neutron flux with the 4 × 4 array. (<b>c</b>) The simulated neutron counting rates. (<b>d</b>) The measured neutron counting rates.</p> "> Figure 24
<p>Sketch of the simulated radwaste package along with four SiLiF detectors around it. (<b>a</b>) Top view; (<b>b</b>) perspective view.</p> "> Figure 25
<p>The simulated spectrum of the gamma rays impinging on the four SiLiF detectors (green line) and the corresponding cumulative distribution (red dotted line).</p> ">
Abstract
:1. Introduction
2. Materials and Methods
- 6LiF is much cheaper and more easily available than 3He;
- any solid state detector can in principle be used to detect the secondary particles;
- it is operated at low voltage, typically 30–50 V as opposed to ≈1000 V of a gas detector;
- the semiconductor and the neutron converter can be replaced independently in case of damage;
2.1. The Detector
2.2. The Neutron Moderator
2.3. The Neutron Source
3. Results
3.1. Measurements in the Front Position
3.2. Gamma/Neutron Discrimination
- The first one, a decreasing exponential extrapolated in the figure up to 1 MeV, is mainly due to the abundant 2.2 MeV gamma rays produced by the neutron capture on hydrogen in the moderator box. We name it here “gamma1” contribution.
- The second one, a decreasing exponential extending up to 1.5 MeV and extrapolated in the figure up to 2 MeV, is due to the gamma rays produced by the AmBe source itself. Indeed, whenever an alpha particle from the americium reacts with the beryllium, this decays by emitting one neutron and one gamma ray, with the gamma energy between 3.4 and 4.4 MeV. We estimated that roughly the same number of such gamma rays and neutrons hit the detector in the front measurement position. Part of this contribution is also due to the elastic scattering of neutrons on silicon, with cross section of a few barn, and maximum silicon recoil kinetic energy, from 10 MeV neutrons, of about 1.33 MeV. We name it here “gamma2” contribution.
- The third one, with an almost constant linear trend toward high energy (“HE” contribution), is due to the 28Si(n,p)28Al reaction whose threshold is around 6 MeV and which has several resonances and cross section around 300 b. In this case both the proton and the recoiling 28Al deposit kinetic energy in the detector.
- The counts above 2.73 MeV, i.e., the HE contribution, have to be ascribed to neutrons, even though not interacting with the 6LiF converter, and have to be considered in the detection efficiency evaluation.
- Fitting the two decreasing exponentials of Figure 11 can provide a realistic estimate of the gamma contribution in the measured neutron counts.
3.3. Intrinsic Detection Efficiency Measurement
3.4. Test with Fast Neutrons
4. Discussion
Fissioning Species | 240Pu |
---|---|
T1/2 [y] | 6561 |
T1/2 [s] | 2.07 × 1011 |
decay constant τ [y] | 9466 |
decay constant τ [s] | 2.99 × 1011 |
decay rate [1/s] | 3.35 × 10−12 |
fission Branching Ratio | 5.70 × 10−8 |
fission rate [1/s] | 1.91 × 10−19 |
atomic mass [amu] | 240.05 |
N atoms/gram | 2.51 × 1021 |
sample mass [g] | 100 |
N atoms in sample | 2.51 × 1023 |
fission rate in sample [1/s] | 4.79 × 104 |
<prompt neutrons>/fission | 2.16 |
neutron rate from sample [1/s] | 1.03 × 105 |
Radwaste Package Matrix | Inox/CH2 67/33% |
---|---|
RWP radius [cm] | 28.5 |
RWP extended radius [cm] | 38.5 |
RWP height [cm] | 86 |
RWP extended side area [cm2] | 20,804 |
RWP top + bottom area [cm2] | 9313 |
RWP total exit area | 30,117 |
SiLiF active area [cm2] | 9 |
number of SiLiF units | 4 |
rough geometrical efficiency | 1.20 × 10−3 |
thermal neutron detection efficiency | 4% |
total neutron counting efficiency | 4.8 × 10−5 |
n absorption factor (guess) | 0.1 |
counts/s in 4 SiLiF from sample | 4.5 |
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
- MICADO Project. Available online: https://www.micado-project.eu/ (accessed on 16 March 2021).
- Italy in MICADO WP7. Available online: https://www.micado-project.eu/news/particles-of-italian-innovation-project/ (accessed on 30 March 2021). (and video at minute 1:10).
- Finocchiaro, P. DMNR: A new concept for real-time online monitoring of short and medium term radioactive waste. In Radioactive Waste: Sources, Types and Management; Nova Science Publishers: New York, NY, USA, 2011; pp. 1–40. [Google Scholar]
- Finocchiaro, P. Radioactive Waste: A System for Online Monitoring and Data Availability. Nucl. Phys. News 2014, 24, 34. [Google Scholar] [CrossRef]
- Cosentino, L.; Calì, C.; De Luca, G.; Guardo, G.; Litrico, P.; Pappalardo, A.; Piscopo, M.; Scirè, C.; Scirè, S.; Vecchio, G.; et al. Real-Time Online Monitoring of Radwaste Storage: A Proof-of-Principle Test Prototype. IEEE Trans. Nucl. Sci. 2012, 59, 1426–1431. [Google Scholar] [CrossRef]
- Finocchiaro, P.; Ripani, M. Radioactive Waste Monitoring: Opportunities from New Technologies. In Proceedings of the IAEA International Conference on Physical Protection of Nuclear Material and Nuclear Facilities, IAEA-CN-254/117. Vienna, Austria, 13–17 November 2017. [Google Scholar]
- Henzlova, D.; Kouzes, R.; McElroy, R.; Peerani, P.; Aspinall, M.; Baird, K.; Bakel, A.; Borella, M.; Bourne, M.; Bourva, L.; et al. Current Status of 3He Alternative Technologies for Nuclear Safeguards; NNSA USDOE EURATOM, LA-UR-15-21201; Los Alamos National Laboratory: Los Alamos, NM, USA, 2015. [Google Scholar] [CrossRef]
- Barbagallo, M.; Cosentino, L.; Forcina, V.; Marchetta, C.; Pappalardo, A.; Peerani, P.; Scire, C.; Scire, S.; Schillaci, M.; Vaccaro, S.; et al. Thermal neutron detection using a silicon pad detector and 6LiF removable converters. Rev. Sci. Instrum. 2013, 84, 033503. [Google Scholar] [CrossRef] [PubMed]
- McGregor, D.S.; Hammig, M.D.; Yang, Y.H.; Gersch, H.K.; Klann, R.T. Design consideration for thin film coated semiconductor thermal neutron detectors –I: Basics regarding alpha particle emitting neutron reactive films. Nucl. Instrum. Methods Phys. Res. Sect. A 2003, 500, 272. [Google Scholar] [CrossRef]
- Baker, C.A.; Green, K.; Van der Grinten, M.G.D.; Iaydjiev, P.S.; Ivanov, S.N.; Al-Ayoubi, S.; Harris, P.G.; Pendlebury, J.M.; Shiers, D.B.; Geltenbort, P. Development of solid-state silicon devices as ultra cold neutron detectors. Nucl. Instrum. Methods Phys. Res. Sect. A 2002, 487, 511. [Google Scholar] [CrossRef]
- Phlips, B.F.; Kub, F.J.; Novikova, E.I.; Wulf, E.A.; Fitzgerald, C. Neutron detection using large area silicon detectors. Nucl. Instrum. Methods Phys. Res. Sect. A 2007, 579, 173. [Google Scholar] [CrossRef]
- Uher, J.; Fröjdh, C.; Jakůbek, J.; Kenney, C.; Kohout, Z.; Linhart, V.; Parker, S.; Petersson, S.; Pospíšil, S.; Thungström, G. Characterization of 3D thermal neutron semiconductor detectors. Nucl. Instrum. Methods Phys. Res. Sect. A 2007, 576, 32. [Google Scholar] [CrossRef]
- Voytchev, M.; Iñiguez, M.P.; Méndez, R.; Mañanes, A.; Rodríguez, L.R.; Barquero, R. Neutron detection with a silicon PIN photodiode and 6LiF converter. Nucl. Instrum. Methods Phys. Res. Sect. A 2003, 512, 546. [Google Scholar] [CrossRef]
- Pappalardo, A.; Barbagallo, M.; Cosentino, L.; Marchetta, C.; Musumarra, A.; Scirè, C.; Scirè, S.; Vecchio, G.; Finocchiaro, P. Characterization of the silicon+6LiF thermal neutron detection technique. Nucl. Instrum. Methods Phys. Res. Sect. A 2016, 810, 6. [Google Scholar] [CrossRef] [Green Version]
- Lo Meo, S.; Cosentino, L.; Mazzone, A.; Bartolomei, P.; Finocchiaro, P. Study of silicon+6LiF thermal neutron detectors: GEANT4 simulations versus real data. Nucl. Instrum. Methods Phys. Res. Sect. A 2017, 866, 48. [Google Scholar] [CrossRef] [Green Version]
- Finocchiaro, P.; Cosentino, L.; Lo Meo, S.; Nolte, R.; Radeck, D. Absolute efficiency calibration of 6LiF-based solid state thermal neutron detectors. Nucl. Instrum. Methods Phys. Res. Sect. A 2018, 885, 86. [Google Scholar] [CrossRef] [Green Version]
- Cosentino, L.; Musumarra, A.; Barbagallo, M.; Colonna, N.; Damone, L.; Pappalardo, A.; Piscopo, M.; Finocchiaro, P. Silicon detectors for monitoring neutron beams in n-TOF beamlines. Rev. Sci. Instrum. 2015, 86, 073509. [Google Scholar] [CrossRef] [PubMed]
- Pappalardo, A.; Vasi, C.; Finocchiaro, P. Direct comparison between solid state Silicon+6LiF and 3He gas tube neutron detectors. Results Phys. 2016, 6, 12. [Google Scholar] [CrossRef] [Green Version]
- Agostinelli, S.; Allison, J.; Amako, K.; Apostolakis, J.; Araujo, H.; Arce, P.; Asai, M.; Axen, D.; Banerjee, S.; Barrand, G.; et al. Geant4—A simulation toolkit. Nucl. Instrum. Methods Phys. Res. Sect. A 2003, 506, 250. [Google Scholar] [CrossRef] [Green Version]
- Fasso, A.; Ferrari, A.; Ranft, J.; Sala, P.R. FLUKA: A Multi-Particle Transport Code; CERN Technical Report No. INFN/TC_05/11; CERN-2005-10; Stanford University: Stanford, CA, USA, 2005. [Google Scholar]
- Werner, C.J.; Bull, J.S.; Solomon, C.J.; Brown, F.B.; Mckinney, G.W.; Rising, M.E.; Dixon, D.A.; Martz, R.L.; Hughes, H.G.; Cox, L.J.; et al. MCNP6.2 Release Notes; Report LA-UR-18-20808; Los Alamos National Laboratory: Los Alamos, NM, USA, 2018. [Google Scholar]
- American National Standard Performance Criteria for Mobile and Transportable Radiation Monitors Used for Homeland Security. In ANSI N42.43-2016 (Revision of ANSI N42.43-2006); IEEE: New York, NY, USA, 2016; pp. 1–54. [CrossRef]
- American National Standard for Evaluation and Performance of Radiation Detection Portal Monitors for Use in Homeland Security. In ANSI N42.35-2016 (Revision of ANSI N42.35-2006; IEEE: New York, NY, USA, 2016; pp. 1–70. [CrossRef]
- The Portable Neutron Spectrometer. Available online: https://www.admnucleartechnologies.com.au/425069461 (accessed on 16 March 2021).
- Nordlund, K.; Zinkle, S.J.; Sand, A.E.; Granberg, F.; Averback, R.S.; Stoller, R.E.; Suzudo, T.; Malerba, L.; Banhart, F.; Weber, W.J.; et al. Primary radiation damage: A review of current understanding and models. J. Nucl. Mater. 2018, 512, 450. [Google Scholar] [CrossRef]
- Amaducci, S.; Cosentino, L.; Barbagallo, M.; Colonna, N.; Mengoni, A.; Massimi, C.; Meo, S.L.; Finocchiaro, P.; Aberle, O.; Andrzejewski, J.; et al. Measurement of the 235U(n,f) cross section relative to the 6Li(n,t) and 10B(n,α) standards from thermal to 170 keV neutron energy range at n TOF. Eur. Phys. J. A 2019, 55, 120. [Google Scholar] [CrossRef] [Green Version]
- The US National Nuclear Data Center. Available online: https://www.nndc.bnl.gov/ (accessed on 16 March 2021).
Measured Counts/s | Simulated Counts/s | |
---|---|---|
front | 31.32 ± 0.16 | ≈32 |
inside | 39.78 ± 0.18 | ≈54 |
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |
© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Share and Cite
Cosentino, L.; Ducasse, Q.; Giuffrida, M.; Lo Meo, S.; Longhitano, F.; Marchetta, C.; Massara, A.; Pappalardo, A.; Passaro, G.; Russo, S.; et al. SiLiF Neutron Counters to Monitor Nuclear Materials in the MICADO Project. Sensors 2021, 21, 2630. https://doi.org/10.3390/s21082630
Cosentino L, Ducasse Q, Giuffrida M, Lo Meo S, Longhitano F, Marchetta C, Massara A, Pappalardo A, Passaro G, Russo S, et al. SiLiF Neutron Counters to Monitor Nuclear Materials in the MICADO Project. Sensors. 2021; 21(8):2630. https://doi.org/10.3390/s21082630
Chicago/Turabian StyleCosentino, Luigi, Quentin Ducasse, Martina Giuffrida, Sergio Lo Meo, Fabio Longhitano, Carmelo Marchetta, Antonio Massara, Alfio Pappalardo, Giuseppe Passaro, Salvatore Russo, and et al. 2021. "SiLiF Neutron Counters to Monitor Nuclear Materials in the MICADO Project" Sensors 21, no. 8: 2630. https://doi.org/10.3390/s21082630