| 1. |
- Anderson, Johan, 1973, et al.
(författare)
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Derivation and quantitative analysis of the differential self-interrogation Feynman-alpha method
- 2012
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Ingår i: European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 127:2, s. 1-6
-
Tidskriftsartikel (refereegranskat)abstract
- A stochastic theory for a branching process in a neutron population with two energy levels is used to assess the applicability of the differential self-interrogation Feynman-alpha method by numerically estimated reaction intensities from Monte Carlo simulations. More specifically, the variance to mean or Feynman-alpha formula is applied to investigate the appearing exponentials using the numerically obtained reaction intensities.
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| 2. |
- Anderson, Johan, 1973, et al.
(författare)
-
Derivation and quantitative analysis of the differential self-interrogation Feynman-alpha method
- 2011
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Ingår i: Proceedings 52nd INMM Conference 17-21 July, Palm Desert, CA, USA (2011).
-
Konferensbidrag (refereegranskat)abstract
- A stochastic theory for a branching process in a neutronpopulation with two energy levels is used to assess theapplicability of the differential self-interrogation Feynman-alpha method by numerically estimated reaction intensities from Monte Carlo simulations. More specifically, the variance to mean or Feynman-alpha formula is applied to investigate the appearing exponentials using the numerically obtained reaction intensities.
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| 3. |
- Anderson, Johan, 1973, et al.
(författare)
-
Two-point theory for the differential self-interrogation Feynman-alpha method
- 2012
-
Ingår i: European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 127:8, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- A Feynman-alpha formula has been derived in a two region domain pertaining the stochastic differential self-interrogation (DDSI) method and the differential die-away method (DDAA). Monte Carlo simulations have been used to assess the applicability of the variance to mean through determination of the physical reaction intensities of the physical processes in the two domains. More specifically, the branching processes of the neutrons in the two regions are described by the Chapman-Kolmogorov equation, including all reaction intensities for the various processes, that is used to derive a variance to mean relation for the process. The applicability of the Feynman-alpha or variance to mean formulae are assessed in DDSI and DDAA of spent fuel configurations.
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| 4. |
- Batyaev, V.F., et al.
(författare)
-
Monitoring fissile and matrix materials in closed containers by means of pulsed neutron sources
- 2013
-
Ingår i: Atomic Energy. - : Springer Science and Business Media LLC. - 1573-8205 .- 1063-4258. ; 115:2, s. 116-122
-
Tidskriftsartikel (refereegranskat)abstract
- Computational and experimental studies of the possibility of determining the fissile and matrix materials by means of differential neutron attenuation are presented. The time response of 235U fission under the action of 14 MeV neutrons from an ING-07T pulsed neutron generator, fabricated by VNIIA, on a 70-liter steel container holding uranium in graphite, iron and polyethylene matrices is analyzed. It is shown that milligram quantities of 235U can be detected and the matrix type and density as well as the location of fissile material inside a container can be determined.©2013 Springer Science+Business Media New York.
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| 5. |
- Bernitt Cartemo, Petty, 1984, et al.
(författare)
-
Sensitivity of the neutronic design of an Accelerator-Driven System (ADS) to the anisotropy of yield of the neutron generator and variation of nuclear data libraries
- 2013
-
Ingår i: Proceeding of ESARDA meeting 2013.
-
Konferensbidrag (refereegranskat)abstract
- The Accelerator-Driven System concept was chosen to be a basis for the Multi-purpose Hybrid Research Reactor for High-tech Applications (MYRRHA), which can operate in both sub-critical and critical mode. Therefore, the design studies in the scope of this project were varying from accelerator and material aspects to the demonstration of transmutation possibilities of the system. However, the sensitivity of neutron characteristics of the system to the anisotropy of yield of neutron generator and variation of nuclear data libraries may appear to be an important issue.In this study the corresponding sensitivity analysis was performed in order to evaluate the sensitivity of ADS neutronic design to the variation of nuclear data libraries and influence of the anisotropy of the neutron yield of the accelerator.
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| 6. |
- Chernikova, Dina, 1982, et al.
(författare)
-
A direct method for evaluating the concentration of boric acid in a fuel pool using scintillation detectors for joint-multiplicity measurements
- 2013
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 714, s. 90-97
-
Tidskriftsartikel (refereegranskat)abstract
- The present investigations are aimed at the development of a direct passive non-intrusive method for determining the concentration of boric acid in a spent fuel pool using scintillation detectors with the purpose of correcting joint-multiplicity measurement results. The method utilizes a modified relation between two gamma lines with energy of 480 keV and 2.23 MeV, respectively. The gamma line at 480 keV belongs to the thermal neutron capture in boron. The 2.23 MeV gamma line characterizes the capture of thermal neutrons in hydrogen. Thus, the relation between them can reveal the concentration of the boron in the fuel pool. In order to test this method, first MCNPX and MCNP-PoliMi simulations were performed. Then, based on the results of Monte Carlo simulations, the method was verified by an experimental study with a 241Am-Be source and EJ-309 scintillation detectors. The concentration of boron in water varied from 1550 ppm to 4000 ppm. The results of these tests are provided in the paper and they show that the spectral ratio between these two lines can in principle be used to determine the boron content.
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| 7. |
- Chernikova, Dina, 1982, et al.
(författare)
-
A general analytical solution for the variance-to-mean Feynman-alpha formulas for a two-group two-point, a two-group one-point and a one-group two-point cases
- 2014
-
Ingår i: European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 129:11, s. Art. no. 259-
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a full derivation of the variance-to-mean or Feynman-alpha formula in a two-energy-group and two-spatial-region treatment. The derivation is based on the Chapman-Kolmogorov equation with the inclusion of all possible neutron reactions and passage intensities between the two regions. In addition, the two-group one-region and the two-region one-group Feynman-alpha formulas, treated earlier in the literature for special cases, are extended for further types and positions of detectors. We focus on the possibility of using these theories for accelerator-driven systems and applications in the safeguards domain, such as the differential self-interrogation method and the differential die-away method. This is due to the fact that the predictions from the models which are currently used do not fully describe all the effects in the heavily reflected fast or thermal systems. Therefore, in conclusion, a comparative study of the two-group two-region, the two-group one-region, the one-group two-region and the one-group one-region Feynman-alpha models is discussed.
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| 8. |
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| 9. |
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| 10. |
- Chernikova, Dina, 1982, et al.
(författare)
-
A potential alternative/complement to the traditional thermal neutron based counting in Nuclear Safeguards and Security
- 2016
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 810, s. 164-171
-
Tidskriftsartikel (refereegranskat)abstract
- A new concept for thermal neutron based correlation and multiplicity measurements is proposed in this paper. The main idea of the concept consists of using 2.223 MeV gammas (or 1.201 MeV, DE) originating in the (1) H (n,gamma)D-2-reaction instead of using traditional thermal neutron counting. Results of investigations presented in this paper indicate that gammas from thermal neutron capture reactions preserve the information about the correlation characteristics of thermal (fast) neutrons in the same time scale. Therefore, instead of thermal neutron detectors (or as a complement) one may use traditional and inexpensive gamma detectors, such as Nal, BGO, CdZnTe or any other gamma detector. In this work we used D8 x 8 cm(2) Nal scintillator to test the concept. Thus, the new approach helps to address the problem of replacement of He-3-counters and problems related to the specific measurements of spent nuclear fuel directly in the spent fuel pool. It has a particular importance for Nuclear Safeguards and Security. Overall, this work represents the proof of concept study and reports on the experimental and numerical evidence that thermal neutron capture gammas may be used in the context of correlation and multiplicity measurements. Investigations were performed using a (252)-Cf-correlated neutron source and an Am-241-Be-random neutron source. The related idea of the Gamma Differential Die-Away approach is investigated numerically in this paper as well, and will be tested experimentally in future work.
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| 11. |
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| 12. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Analysis of 235U, 239Pu and 241Pu content in a spent fuel assembly using Lead Slowing Down Spectrometer and time intervals matrix
- 2012
-
Ingår i: JNMM, Journal of the Institute of Nuclear Materials Management. - 0893-6188. ; 40:2, s. 9-18
-
Tidskriftsartikel (refereegranskat)abstract
- Nowadays knowledge of the physical parameters of irradiated nuclear fuel is going to be a key issue for the continued and future use of nuclear energy. One of the major characteristics of spent fuel which plays an important role in international nuclear materials Safeguards is the quantity of plutonium (Pu) in wastes. It can be obtained through using of various techniques, one of which is the non-destructive assay (NDA) method of slowing-down time spectrometry in lead where the energy spectrum of neutrons can be represented as being monoenergetic with minor deviation from the peak value in each time moment after a fast neutron pulse. This fact was successfully used in developing several methods of Pu mass determination and confirmed the potential of the Lead Slowing Down Spectrometer (LSDS) to get detailed information about spent fuel [1-2]. A method, which we presented earlier [3], was based on a matrix of time intervals where large differences in the number of fissions of 235U and 239Pu are observed. This technique allows increasing precision in the Pu evaluation by decreasing the self-shielding effect significantly. As opposed to homogeneous-volume approximations used in our previous research, we describe the detailed Monte Carlo models of real fuel assemblies, as well as the effects of the influence of the scintillation detector to the system in question. Although the proposed method for characterization of spent fuel assemblies has only been studied using Monte Carlo simulations, it was possible to demonstrate the determination of 239Pu using a DT pulsed neutron source, a Lead Slowing Down Spectrometer, and fast timing scintillator that is sensitive to both photons and neutrons. Additional information about the system can be obtained from n-γ pulse shape discrimination.
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| 13. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Application of the two-group - one-region and two-region - one-group Feynman-alpha formulas in safeguards and accelerator-driven system (ADS)
- 2013
-
Ingår i: Proceeding of ESARDA meeting 2013.
-
Konferensbidrag (refereegranskat)abstract
- The applicability of the two-group (one-region) and two-region (one-group) Feynman-alpha (variance to mean) formulas was assessed with regards to applications in safeguards and accelerator-driven system (ADS) considered as an option for transmutation of nuclear wastes. Since two-group calculations with the master equation technique when both thermal and fast fissions are included, have not been performed earlier, investigation of this problem has a methodological value of its own. The potential applications of the two-group - one-region and two-region - one-group Feynman-alpha approaches in nuclear safeguards were evaluated and compared to the results of Monte-Carlo simulations.
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| 14. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Derivation of two-group two-region Feynman-alpha formulas and their application to Safeguards and accelerator-driven system (ADS)
- 2013
-
Ingår i: Proceeding of INMM 54th Annual Meeting.
-
Konferensbidrag (refereegranskat)abstract
- The theory of the Feynman-alpha method was extended to two-energy groups and two-regions by the use of the Chapman - Kolmogorov equation with complete description of various processes including all reaction intensities for neutrons. This paper presents a full derivation of the variance to mean formula with the forward approach, as well as quantitative evaluation of the formula with regards to applications in safeguards and accelerator-driven system. The quantitative assessment was made through MCNPX and MCNP-PoliMi simulations. The motivation for this work is related to the fact that the traditional one-group (and one-region) variance to mean formula was elaborated and used for thermal systems in which the thermal flux and the lifetime of thermal neutrons dominates. However, this approach does not fully describe the fast neutron systems, as well as heavily reflected thermal systems, since the effects of the reflector play a significant role in the latter. Thus, a two-group two-point master equation approach might lend the possibility of treating a fast multiplying material surrounded with a reflector in a more accurate way, by treating the counts separately in the fast and the thermal groups (or in the fissile and reflector regions). Investigation of this problem has a methodological value of its own since, for example, two-group calculations with the master equationtechnique when both thermal and fast fissions are included, have not been performed earlier.
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| 15. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Development of the Neutron-Gamma-Neutron (NGN) approach for the fresh and spent fuel assay
- 2012
-
Ingår i: Proceedings of The 53nd Annual Meeting of the Institute of Nuclear Materials Management.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In connection with current safety and complexity limitations for installations which usekeV neutrons for irradiation in the fresh and spent fuel assay, in medicine, geophysicaland detection fields, there is a long felt need of effective, light, inexpensive systems withlonger lifetimes and the possibility to ”switch off” the source during transportation andwork break. The present paper discusses an opportunity of creating a novel technique basedon using a pulsed neutron generator, hydrogen moderator and beryllium, which will enablecreation of a compact and inexpensive facility capable to satisfy all requirements. The mainidea of the proposed method consists in using photonuclear reaction in beryllium due togamma irradiation originating from (n,gamma) reaction in a hydrogen containing moderator.After the neutron pulse of a modern compact DD neutron generator in hydrogen-containingmoderator, high-energy neutrons (approximately 2.5 MeV) get slowed down mainly by elasticscattering to near thermal energies. At thermal energies, the neutrons diffuse through thematerial until they undergo thermal capture (capture is dominated by hydrogen neutronabsorbers). When a hydrogen atom captures a thermal neutron, it turns into deuteriumwith the release of a large component of 2.23 MeV gamma-rays. Beryllium is one of thefew elements in nature that undergoes a photonuclear reaction with this gamma energyrange (e.g. deuterium has a low energy 2.225 MeV photonuclear threshold). Thus, as theberyllium has lower neutron-binding energy, 1.667 MeV (photonuclear reaction threshold),a photonuclear reaction will take place with emission of neutrons with energy defined by thekinematic equation. Thus, this method allows to obtain a high quality epithermal neutronbeam without using a complex system with particle accelerator or radioisotope sources withlimited decay time. The proposed method has been studied using Monte Carlo simulations,which made it possible to define the theoretical limits of the use of the NGN approach inindustrial applications. The paper will presents the results of these investigations.
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| 16. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Experimental and numerical investigations of radiation characteristics of Russian portable/compact pulsed neutron generators: ING-031 ING-07, ING-06 and ING-10-20-120
- 2014
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 746, s. 74-86
-
Tidskriftsartikel (refereegranskat)abstract
- The present paper discusses results of full-scale experimental and numerical investigations of influence of construction materials of portable pulsed neutron generators ING-031, ING-07, ING-06 and ING-10-20-120 (VNIIA, Russia) to their radiation characteristics formed during and after an operation (shutdown period). In particular, it is shown that an original monoenergetic isotropic angular distribution of neutrons emitted by TiT target changes into the significantly anisotropic angular distribution with a broad energy spectrum stretching to the thermal region. Along with the low energetic neutron part, a significant amount of photons appears during the operation of generators. In the pulse mode of operation of neutron generator, a presence of the construction materials leads to the "tailing" of the original neutron pulse and the appearance of an accompanying photon pulse at similar to 3 ns after the instant neutron pulse. In addition to that, reactions of neutron capture and inelastic scattering lead to the creation of radioactive nuclides, such as Co-58, Cu-62, Cu-64 and F-18, which form the so-called activation radiation. Thus, the selection of a portable neutron generator for a particular type of application has to be clone considering radiation characteristics of the generator itself. This paper will be of interest to users of neutron generators, providing them with valuable information about limitations of a specific generator and with recommendations for improving the design and performance of the generator as a whole. (c) 2014 Elsevier B.V. All rights reserved.
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| 17. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Novel passive and active tungsten-based identifiers for maintaining the continuity of knowledge of spent nuclear fuel copper canisters
- 2015
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 75, s. 219-227
-
Tidskriftsartikel (refereegranskat)abstract
- A new approach to provide a long-term safeguards identification of spent nuclear fuel containers, in particular copper canisters, is presented in this paper. The approach proposes the use of a tungsten insert marked with a binary code and placed inside the container. The insert is read with a combination of two independent techniques, radiation and ultrasonic measurements, in order to get a unique identification of the cask. Passive and active versions of the tag are considered. The passive version makes use of the radiation coming from the spent nuclear fuel itself. The active version of the tag is based on the use of an artificially introduced mixture of α-emitting isotopes, such as 241Am with materials, 11B and 23Na, which easily undergo α-induced reactions with emission of specific γ-lines, 2313 keV and 1809 keV, respectively. The paper discusses results of the radiation and ultrasonic measurements and Monte-Carlo evaluations as the first proof of the concept. The results of the investigations show the strong potential for this concept to maintain the continuity of knowledge of spent nuclear fuel copper canisters for a time scale up to a few thousands years without compromising the environmental safety of the casks.
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| 18. |
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| 19. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Testing a direct method for evaluating the concentration of boron in a fuel pool using scintillation detectors, and a 252Cf and an 241Am-Be source
- 2013
-
Ingår i: Proceeding of ESARDA meeting 2013.
-
Konferensbidrag (refereegranskat)abstract
- The present investigations are aimed at the development and testing of a direct non-destructive method for evaluating the concentration of boron in a fuel pool using scintillation detectors. The method uses a modified ratio between two gamma lines with energy of 480 keV and 2.23 MeV. These lines belong to the capture of a thermal neutron in boron and hydrogen, respectively. The relation between them can reveal the concentration of boron in the fuel pond.The method proposed was tested in a laboratory experiment with a 252Cf and an 241Am-Be source. EJ-309 liquid scintillation detectors were used for measurements of gamma spectra. The concentration of boron in water varied from 1550 ppm to 4200 ppm. The optimization and test studies were performed via MCNPX simulations.The results of these tests are provided in the present paper and they show that the boron content in water can be determined through using the characteristics of gamma lines with energy of 480 keV and 2.23 MeV.
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| 20. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Testing of small detectors with glass rod light guides for multiplicity measurement purposes
- 2012
-
Ingår i: Proceedings of The 53nd Annual Meeting of the Institute of Nuclear Materials Management.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we investigate the applicability of small scintillators with glass rod lightguides to measure both neutrons and gamma rays from the sample. Experimental test ofthese detectors and their suitability for the task can be performed at Lund University usingnatural uranium rods, therefore the MCNPX simulation set-up corresponds to the Lund con-figuration. The long-term goal of this research is to develop a method of joint-multiplicitycounting for fuel evaluation into a technology capable of quantifying plutonium in the fuelpool, where a lot of factors, such as presence of neutron absorbers (boron acid), can affect al-most all parameters, such as multiplication etc. Therefore, part of the present investigationswas devoted to the development of a direct method for determination of the concentrationof boron acid in the fuel pool using scintillation detectors with further correction of mea-surement results. For this purpose we suggest a method which utilizes a relation betweengamma lines with energy of 480 keV and 2.23 MeV for the direct evaluation of concentrationof boron acid in water. Test results of the new method, and an answer to questions regardingthe ability to measure both neutron and gamma rays using small scintillation detectors withglass rod light guides are provided in this paper.
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| 21. |
- Chernikova, Dina, 1982, et al.
(författare)
-
The effect of capture gammas, photofission and photonuclear neutrons to the neutron-gamma Feynman variance-to-mean ratios (neutron, gamma and total)
- 2015
-
Ingår i: Mathematics and Computations, Supercomputing in Nuclear Applications and Monte Carlo International Conference, M and C+SNA+MC 2015, Nashville, United States, 19-23 April 2015. - 9781510808041 ; 2, s. 1040-1051
-
Konferensbidrag (refereegranskat)abstract
- Two versions of the neutron-gamma variance-to-mean (Feynman-alpha) formula for separate gamma detection and total neutron-gamma detection were recently derived and evaluated by Chernikova, et. al. [1]. However, the neutrons and gammas emitted in a photofission reaction or the release of gammas in certain thermal neutron capture reactions were not included in the theoretical models of Chernikova, et. al. [1]. In this paper, in order to evaluate the influence of these type of reactions to the values the neutron-gamma Feynman variance-to-mean ratios (neutron, gamma and total), we derive the enhanced Feynman-alpha formulae for separate neutron, gamma detection and total neutron-gamma detections. The theoretical derivation is based on the Chapman-Kolmogorov equation with inclusion of general reactions, photofission and capture gammas. The quantitative evaluation of the effect of capture gammas and photonuclear neutrons to the neutron-gamma Feynman variance-to-mean ratios (neutron, gamma and total) is done by using reaction intensities obtained from MCNPX simulations. The new enhanced formulas and their impact to the final values of different variance-to-mean ratios are the main subject of the discussion in the present paper.
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| 22. |
- Chernikova, Dina, 1982, et al.
(författare)
-
The Inclusion of Photofission, Photonuclear, (n, xn), (n, n ' x gamma), and (n, x gamma) Reactions in the Neutron-Gamma Feynman-Alpha Variance-to-Mean Formalism
- 2017
-
Ingår i: Nuclear Science and Engineering. - 0029-5639 .- 1943-748X. ; 185:1, s. 206-216
-
Tidskriftsartikel (refereegranskat)abstract
- This paper sets up a formalism that is sufficiently general to describe the effects of photofission, photonuclear, (n, xn), (n, n?x?), and (n, x?) reactions on the neutron-gamma Feynman-alpha variance-to-mean ratios. Such a formalism is obtained using the Chapman-Kolmogorov (master) forward equation for the above-mentioned set of nuclear reactions. Thereafter, the issue of estimating reaction intensities for gammas in the master equation is highlighted by the paper. As an example, a quantitative evaluation of reaction intensities is given for a case when (n, ?), photonuclear, and (n, 2n) reactions are relevant for the system. However, an evaluation of the influence of these types of reactions to the values of the Feynman variance-to-mean ratios is not within the scope of this paper. Overall, the results obtained in this paper are intended to give an extended systematic framework for the study of the neutron- and gamma-based nondestructive assay problems in nuclear reactor applications and materials control.
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| 23. |
- Chernikova, Dina, 1982, et al.
(författare)
-
The neutron-gamma Feynman variance to mean approach: Gamma detection and total neutron-gamma detection (theory and practice)
- 2015
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 782, s. 47-55
-
Tidskriftsartikel (refereegranskat)abstract
- Two versions of the neutron gamma variance to mean (Feynman-alpha method or Feynman-Y function) formula for either gamma detection only or total neutron gamma detection, respectively, are derived and compared in this paper. The new formulas have particular importance for detectors of either gamma photons or deleclors sensitive to both neutron and gamma radialion. If applied to a plastic or liquid deleclor, he total neutron-gamma detection Feynman-Y expression corresponds Lo a situation where no discrimination is made between neutrons and gamma parlicles. The gamma variance Lo mean formulas are useful when a detector of only gamma radialion is used or when working with a combined neutron-gamma deleclor at high count rates. The theoretical derivation is based on the Chapman-Kolmogorov equation with the inclusion of general reactions and corresponding intensities for neutrons and gammas, but with the inclusion of prompt reactions only. A one energy group approximation is considered. The comparison of the two different theories is made by using reaction intensities obtained in MCNPX simulations with a simplified geometry for two scintillation detectors and a Cf-252-source. In addition, the variance to mean ratios, neutron, gamma and total neutron-gamma are evaluated experimentally for a weak Cf-252 neutron-gamma source, a Cs-137 random gamma source and a Na-22 correlated gamma source. Due to the focus being on the possibility of using neutron-gamma variance to mean theories for both reactor and safeguards applications, we limited the present study to the general analytical expressions for Feynman-alpha formulas.
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| 24. |
- Chernikova, Dina, 1982, et al.
(författare)
-
Time intervals matrix analysis of 235U and 239Pu content in a spent fuel assembly using Lead Slowing down Spectrometer
- 2011
-
Ingår i: Proceedings: Special Session on Determination of Pu Mass in Spent Fuel with NDA of the 52nd Annual Meeting of the Institute of Nuclear Materials Management.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A key motivation for developing the technology capable of quantifying plutonium (Pu) in spent fuel assemblies with nondestructive assay (NDA) techniques is knowledge of the physical parameters of irradiated nuclear fuel which is important both for nuclear safeguards and nuclear fuel management. One of the most attractive NDA approaches applied for the determination of the total amount of plutonium using a pulsed neutron source is the method of slowing-down time spectrometry in lead where the energy spectrum of neutrons can be represented as being monoenergetic with minor deviation from the peak value in each time moment after a fast neutron pulse. This fact was successfully used in developing several methods of Pu mass determination and confirmed the potential of the Lead Slowing Down Spectrometer (LSDS) to get detailed information about spent fuel [1-2].A method which we presented earlier is based on a matrix of time intervals where large differences in the number of fissions of 235U and 239Pu are observed [3]. This technique allows increasing precision in the Pu evaluation by decreasing the self-shielding effect significantly. As opposed to homogeneous-volume approximations used in our previous research in this work we describe the detailed Monte Carlo models of real fuel assemblies, as well as the effects of the influence of the scintillation detector to the system in question. Although the proposed method for spent fuel assemblies characterization has only been studied using Monte Carlo simulations, it was possible to demonstrate the 239Pu determination using a DT pulsed neutron source, Lead Slowing Down Spectrometer and fast timing scintillatior which is sensitive to both photons and neutrons, and n-γ pulse shape discrimination allows to get additional information about the system.
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| 25. |
- Romodanov, V. L., et al.
(författare)
-
A method for nondestructive assay of nuclear materials in facilities with a pulse neutron generator and a digital technology for discrimination between neutrons and photons
- 2013
-
Ingår i: Instruments and Experimental Techniques. - 1608-3180 .- 0020-4412. ; 56:6, s. 620-627
-
Tidskriftsartikel (refereegranskat)abstract
- A method for determining the U-235 concentration in fuel assemblies of a high-power channel-type PBMK reactor is described. The measure of U-235 content of an analyzed sample is the number of neutrons from thermal-neutron fission of U-235, normalized to the number of gamma quanta produced in thermal neutron capture by hydrogen nuclei in the scintillator or by B-10 in the glass of a photomultiplier tube. A pulse neutron generator based on DT reaction is the neutron source, and an organic scintillator with the pulse shape discrimination between neutrons and gamma rays with the aid of the digital technology is a detector. The scintillator is also used as a neutron moderator. Simulation of the method shows that the U-235 content of the analyzed sample can be determined for 1 min with an accuracy of 1% or better. The efficiency of the method has been confirmed by experimental investigations on a model of the setup.
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| 26. |
- Romodanov, V. L., et al.
(författare)
-
Sensitivity of nonstationary neutron spectra in lead to nuclear data variations
- 2012
-
Ingår i: Atomic Energy. - : Springer Science and Business Media LLC. - 1573-8205 .- 1063-4258. ; 112:4, s. 281-287
-
Tidskriftsartikel (refereegranskat)abstract
- The computed variations of the parameters of nonstationary neutron spectra in lead moderator due to the use of different libraries of the constants characterizing the sensitivity of these parameters to nuclear data variations are presented. The testing of the nuclear constants is based on the varying neutron spectra formed in a lead sphere at different times after a neutron pulse from a source. The computational studies showed considerable sensitivity of the differential and integral time characteristics of the neutron field in lead to the nuclear data library and showed that the constant component of the computational error in the neutron spectra in lead moderator must be taken into account.
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| 27. |
- Tampouratzi, Tatiani, 1965, et al.
(författare)
-
A Comparison of Artificial Neural Network Performance: the Case of Neutron/Gamma Pulse Shape Discrimination
- 2013
-
Ingår i: IEEE Symposium on Computational Intelligence for Security and Defense Applications (CISDA). - 9781467359115 ; , s. 88-95
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Konferensbidrag (refereegranskat)abstract
- Pulse shape discrimination is investigated using artificial neural networks, namely linear vector quantization and self organizing maps which are employed for classifying neutron and gamma rays at a variety of energies and for different relative sizes of the training and test sets. While classification performance confirms that both approaches are capable of excellent discrimination, some differences between the approaches are observed: linear vector quantization is particularly accurate in classifying the training set; the self organizing map, on the other hand, demonstrates higher prediction accuracy, with its clustering capabilities rendering it less sensitive to classification errors. Comparisons with existing analytical as well as artificial neural network approaches are made.
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| 28. |
- Tampouratzi, Tatiani, 1965, et al.
(författare)
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Pulse shape discrimination of neutrons and gamma rays using Kohonen artificial neural networks
- 2013
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Ingår i: Journal of Artificial Intelligence and Soft Computing Research. - : Walter de Gruyter GmbH. - 2449-6499 .- 2083-2567. ; 3:2, s. 77-88
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Tidskriftsartikel (refereegranskat)abstract
- The potential of two Kohonen artificial neural networks (ANNs) - linear vector quantisa- tion(LVQ)andtheselforganisingmap(SOM)-isexploredforpulseshapediscrimination (PSD), i.e. for distinguishing between neutrons (n’s) and gamma rays (γ’s). The effect that (a) the energy level, and (b) the relative size of the training and test sets, have on iden- tification accuracy is also evaluated on the given PSD dataset. The two Kohonen ANNs demonstrate complementary discrimination ability on the training and test sets: while the LVQ is consistently more accurate on classifying the training set, the SOM exhibits higher n/γ identification rates when classifying new patterns regardless of the proportion of training and test set patterns at the different energy levels; the average time for decision making equals ˜100 µs in the case of the LVQ and ˜450 µs in the case of the SOM.
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| 29. |
- Vesterlund, Anna, 1980, et al.
(författare)
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Characterization of strong 241Am sources
- 2015
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 99, s. 162-167
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Tidskriftsartikel (refereegranskat)abstract
- Gamma ray spectra of strong 241Am sources may reveal information about the source composition as there may be other radioactive nuclides such as progeny and radioactive impurities present. In this work the possibility to use gamma spectrometry to identify inherent signatures in 241Am sources in order to differentiate sources from each other, is investigated. The studied signatures are age, i.e. time passed since last chemical separation, and presence of impurities. The spectra of some sources show a number of Doppler broadened peaks in the spectrum which indicate the presence of nuclear reactions on light elements within the sources. The results show that the investigated sources can be differentiated between by age and/or presence of impurities. These spectral features would be useful information in a national nuclear forensics library (NNFL) in cases when the visual information on the source, e.g. the source number, is unavailable.
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| 30. |
- Vesterlund, Anna, 1980, et al.
(författare)
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Characterization of strong 241Am sources
- 2014
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Ingår i: International Conference on Advances in Nuclear Forensics: Countering the Evolving Threat of Nuclear and Other Radioactive Material out of Regulatory Control, Vienna, IAEA; 07/2014.
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Konferensbidrag (refereegranskat)
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