Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for ...several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The action outputs (input files and efficiency calculation results, including practical recommendations for new users) are made available on a dedicated webpage.
•Examples of the use of Monte Carlo simulation using different software.•Simple cases with two types of germanium detectors and four kinds of sources.•Calculation of full-energy peak and total efficiencies for 5 energies.•Input files and efficiency calculation results available on a dedicated webpage.
The Novel Neutron Detector for Fusion (VERDI) project aims to develop a passive detector which will provide a robust approach for neutron detection in current and future fusion devices. The detector ...comprises a low activation capsule, capable to withstand the harsh fusion conditions, containing defined added metallic elements, the activation of which provides neutron fluence and energy spectrum information. In the present work, VERDI detectors were employed for the first time to determine neutron fluence and energy spectra at the Joint European Torus (JET) Long Term Irradiation Station (LTIS) during the 2019 Deuterium-Deuterium (DD) campaign. Two materials, graphite and carbon fibre reinforced silicon carbide composite, were used for the capsule fabrication containing disc-shaped activation foils (Ag, Mn, Nb, Ni, Rh, Ti, Y). Post-irradiation gamma-spectrometry measurements were performed in order to identify the product isotopes and derive the incident neutron fluence. The results were fed into the MAXED code to reconstruct the neutron spectrum. The derived spectrum was in very good agreement with the calculated one using the MCNP code. A difference of 8% was found between the derived and the experimentally determined total integrated neutron flux. This work demonstrates the feasibility of employing VERDI detectors for neutron measurements in real fusion environments.
The goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of ...germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radionuclides. The exercise input files and calculation results with practical recommendations are made available for new users on a dedicated webpage.
•This paper details the results from an initial experiment performed at the FNG with prototype detector capsules, comprising of a graphite capsule containing a selection of dosimetry foils, ...irradiated under a 14 MeV neutron field as part of the Novel Neutron Detector for Fusion project implemented under the EUROFusion Enabling Research 2017 program.•Measured activities of each capsule are compared with activities derived from simulations performed using MCNP.•The experimental results have been applied to neutron spectrum unfolding methodologies: MAXED based on the maximum entropy method, and GRAVEL an iterative non-linear least squares algorithm.•Reaction rates calculated from unfolded neutron spectra are compared with measured reaction rates.•Simulations used in this work provide an accurate calculation for the neutron field in this experiment and the unfolding algorithms do not introduce any unphysical results. Furthermore, neither the enclosure type nor material used in this work affect the neutron activation results.
In future fusion power plants, such as DEMO, the D-T neutron emission rate is predicted to exceed 1 × 1021 n s−1. Accurately monitoring neutron energies and intensities will be the primary method for estimating fusion power, and calculating key nuclear parameters, including the tritium breeding ratio and nuclear heating. The noVel nEutRon Detector for fusIon (VERDI) project, implemented under the EUROFusion Enabling Research 2017 program, aims to develop a detector capable of withstanding the harsh environment of a future fusion power plant. The VERDI detector is based on the foil activation technique, which relies on neutron spectrum unfolding methods to process the convolution of gamma-ray measurement and detector response function to infer the neutron energy spectrum. This paper details the experimental method and results collected using six prototype VERDI detectors during an initial experiment performed in July 2017 at the ENEA Frascati Neutron Generator (FNG) under D-T neutrons (14 MeV). The measured activities of product isotopes are compared with equivalent data calculated using the FISPACT-II code to provide an average C/Eact agreement of 1.05±0.13. Experimental results from the FNG have been applied to neutron spectrum unfolding techniques using established unfolding codes, MAXED and GRAVEL.
Nine neutron induced reactions on Ge isotopes (
70
Ge(n,2n)
69
Ge,
76
Ge(n,2n)
75
Ge,
73
Ge(n,p)
73
Ga,
72
Ge(n,p)
72
Ga,
73
Ge(n,d/np)
72
Ga,
74
Ge(n,d/np)
73
Ga,
74
Ge(n,α)
71m
Zn,
72
Ge(n,α)
69m
...Zn,
73
Ge(n,nα)
69m
Zn) have been measured in this work at energies 16.4-18.9 MeV. For these reactions, most of the experimental datasets in literature were obtained with a
nat
Ge target. However, the residual nucleus produced by some reaction channels can also be produced from neighboring isotopes, acting as a contamination for the measured reactions. This contribution must be subtracted, based on theoretical calculations, bearing their own uncertainties. The use of enriched targets however, does not suffer from such contaminations, leading to accurate experimental results. In this scope, five highly isotopically enriched Ge samples have been used in this work. The quasi-monoenergetic neutron beams were produced via the
3
H(d,n)
4
He reaction at the 5.5 MV Tandem Van de Graaff accelerator of N.C.S.R. ‘Demokritos’. The cross section of these nine reactions were measured using the activation method, with respect to the
27
Al(n,α)
24
Na reference reaction.
For future fusion plants, there is a great need for detectors capable to accurately monitor neutrons under the harsh fusion environment. In particular, detectors required in Test Blanket Modules must ...be capable to accurately measure neutron fluence under high and variable neutron fluxes, high gamma background, high temperature, high and variable magnetic fields. The noVEl neutRon Detector for fusIon (VERDI) project aims to develop a detector which will provide a robust approach for neutron detection in fusion plants. The detector comprises a low activation capsule containing a defined concentration of added metallic elements. The neutron fluence and energy spectrum will be derived by the analysis of the multiple gamma lines produced by the metallic elements activation. In this work, the candidate metallic elements for the VERDI detector are defined. A benchmark experiment with a number of prototype detectors was performed at the ENEA Frascati Neutron Generator under DT operation to demonstrate the feasibility of VERDI detectors to measure neutron fluence under a reference fusion relevant field. The results of product isotopes measurements are compared to respective calculated data using the FISPACT-II code and very good agreement is observed. Preliminary unfolding of the neutron spectrum was also performed.
Several cross-section measurements of neutron-induced reactions on Ge found in literature, are performed utilizing natGe targets. The production of the same residual nucleus as the measured one might ...occur as a result of the unavoidable presence of neighboring isotopes in the same target, acting as a contamination. Corrections must be made based on theoretical calculations and models in order to resolve this problem. The accuracy and limits of a methodology for these "theoretical corrections" are investigated in this work using isotopically enriched targets, which can produce very accurate results without the need for such corrections. Experimental cross-section measurements have been made for the 76Ge(n,2n)75Ge, 72Ge(n,α)69mZn and 72Ge(n,p)72Ga reactions, via the activation technique, with the 27Al(n,α)24Na reaction used as reference, employing both a natGe and isotopically enriched Ge targets. The 3H(d,n)4He (D-T) reaction was used for producing the quasi-monoenergetic neutron beam in the 5.5 MV Tandem Accelerator Laboratory of the National Centre for Scientific Research "Demokritos" in Athens, Greece, at an incident deuteron beam energy of 2.9 MeV. Using HPGe detectors, γ-ray spectroscopy was applied to determine the induced γ-ray activity of the residual nuclei.
An internal consistency test of the calculation of coincidence-summing correction factors FC for volume sources is presented. The test is based on exact equations relating the values of FC calculated ...for three ideal measurement configurations. The test is applied to a number of 33 sets of FC values sent by 21 teams. Most sets passed the test, but not the results obtained using the quasi-point source approximation; in the latter case the test qualitatively indicated the magnitude of the bias of FC.
•A self-consistency test of coincidence summing calculations is presented.•It is based on equations relating FC values for 3 ideal volume geometries.•Can be easily applied in any laboratory for checking the quality of FC software.•33 sets of FC values (various computations) for 60Co, 133Ba, 134Cs, 152Eu evaluated.•Inconsistency and bias of FC based on quasi-point source approximation revealed.
This paper presents the Compton Suppression System, recently installed at the Nuclear Engineering Department of NTUA. The system consists of an XtRa Ge detector coupled with a NaI(Tl) guard detector. ...The electronic set-up allows for the simultaneous collection of both the suppressed and the unsuppressed spectra. System performance is investigated using certified point and volume sources. Parameters such as Peak Suppression Factors, peak-to-Compton ratios and minimum detectable activity for specific radionuclides are determined.
•The installation of the new Compton Suppression System at NED-NTUA is presented.•Simultaneous collection of both suppressed and unsuppressed spectrum.•Peak-to-Compton improvement by a factor of ~5.•Peak Suppression Factors range from 1 to 0.066, depending on energy and isotope.•MDA reduction by 13–50%.
The purpose of this work was to investigate the effect of particle size on radionuclides in soil, particularly in relation to depth. A set of soil samples at the 0–10cm and 10–20cm depth layers were ...collected, separated into size fractions using a sieving machine and analyzed by gamma spectrometry to determine 238U, 226Ra, 210Pb, and 137Cs. Significant variations between different size fractions and depth layers were observed. A 0–20cm depth profile was also investigated.
•Analysis of 2cm resolution depth profile in size fractions.• 210Pb increased in 0–10cm, finer size fractions.•Variation among size fractions.•Analysis of 137Cs, 238U, 210Pb and 226Ra by gamma spectrometry.•Soil sampled at 0–10cm and 10–20cm depth layer and sieved.
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