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The system proposed to measure the tritium to deuterium ratio on the International Thermonuclear Experimental Reactor (ITER) is a high-resolution neutron spectrometer, partly composed of a system of three Thin-foil Proton Recoil (TPR) spectrometers. This system works on the principle of converting neutrons into protons using a thin foil of polyethylene, which is then detected in silicon detectors to obtain the scattering angles and energy spectrum of the protons. The objective of this article is to show the benefit of artificial intelligence for improving a simple TPR system model written in Python to an accuracy approaching MCNP simulations, while significantly decreasing the computational cost. The first step was to model a polyethylene converter to obtain the energy-angle distribution of outgoing protons for a given incident neutron beam. When compared with MCNP, this simplified model was found to fail to account for proton energy and angular scattering. Therefore, in a second step, two neural networks were successfully trained to include these effects based on the output data of the TRIM code, assuming Gaussian distributions. The Python model was able to produce results very close (differences up to a few percent) to those obtained with MCNP by integrating these neural networks. To extend the study, the energy spectra of the protons could be obtained and subsequently used to obtain information on the ratio of deuterium and tritium in the plasma. [ABSTRACT FROM AUTHOR]

This paper is an overview of the results obtained by a collaborative team of researchers from the Institute for Nuclear Research, Russian Academy of Sciences (INR RAS), and State Scientific Center of the Russian Federation—Institute of Physics and Power Engineering (SSC RF—IPPE) using the SVZ-100 lead slowing-down neutron spectrometer. The study focuses on measuring the fission cross sections of americium isotopes 241Am, 242mAm, and 243Am when bombarded by neutrons with energies below 100 keV. The high efficiency of the SVZ-100, facilitated by its substantial working-substance mass (100 t of high-purity lead) and neutron generation through proton irradiation with a 209-MeV accelerator at the INR RAS, enables the investigation of neutron-nuclear processes in microgram samples of radioactive nuclides, which is unattainable in experiments using time-of-flight spectrometry. Unique scientific information is acquired through lead slowing-down neutron spectrometry by collaborative research efforts at the INR RAS and SSC RF—IPPE. This information partially fills gaps or complements existing but often contradictory or insufficient data from experiments conducted on both time-of-flight installations and lead slowing-down neutron spectrometers at other research centers. The results of collaboration of the INR RAS and SSC RF—IPPE are documented in international nuclear data repositories, indicating, in several instances, the need for adjustments to recommended approximating and calculated values. Information is given on some implemented and planned studies on neutron fission cross sections of americium isotopes at other centers following completion of the collaboration of the INR RAS and SSC RF—IPPE. [ABSTRACT FROM AUTHOR]

Integral experiments covering neutron leakage from geometrically simple assemblies with a 252Cf source inside are very valuable tools usable in the validation of transport cross-section data since geometric uncertainties play a much smaller role in simple geometric assemblies than in complex assemblies as for example reactor pressure vessel geometry. Since 252Cf spontaneous fission is a standard neutron source, the uncertainties connected with the source neutron spectrum can be even neglected. The paper refers to validation efforts of neutron leakage from an ~50 × 50 × 50-cm stainless steel block in the Research Center Rez. Both the neutron leakage flux at a distance of 1 m from the center of the cubical assembly using stilbene spectrometry and activation rates at different positions of the assembly were evaluated. In addition to experiments, main sources of uncertainty were identified and evaluated. The results of the stilbene measurements are consistent with the activation measurement results. [ABSTRACT FROM AUTHOR]

This contribution presents a novel single-moderator neutron spectrometer, named "TetraBall", developed at INFN and optimized for characterizing the neutron field in the CMS experimental cavern. The TetraBall condenses the functionality of several Bonner Spheres (BS) in a single moderator and it is equipped with 42 SiC radiation-hard detectors organized in a tetrahedral geometry designed to be insensitive to incident gammas and charged particles. Thanks to lead inserts, it can respond up to GeV energies. It works in single exposure mode, suitable for real-time monitoring. It is designed to be used as neutron monitor during the High-Luminosity LHC data taking. [ABSTRACT FROM AUTHOR]

The Neutron Standards Laboratory (LPN) at CIEMAT serves as the national reference for calibrating neutron measurement devices and conducts research on measuring different neutrons fields, arising the necessity of neutron spectrometry. There are different neutron fields which are attracting interest in the recent years, for example ambient neutron spectra, generated basically by cosmic rays in the atmosphere or secondary neutrons on the surroundings of accelerators, for instance in protontherapy centres. These neutrons spectra are characterized by having an important component of high energy neutrons up to hundreds MeV or even GeV. In order to do spectrometry in this kind of neutron fields, a Bonner Sphere Spectrometer extended range was designed, constructed and tested. • Response Matrix simulations for Bonner Sphere Spectrometer wit Monte Carlo code. • Digital electronics implementation to the extended Bonner Sphere Spectrometer. • Ambient neutron measurements with an extended range BSS. [ABSTRACT FROM AUTHOR]

Neutron spectrum unfolding is a crucial process in radiation protection and dosimetry. Unfolding codes using iterative algorithms require a criterion to stop the iterations. One approach often relies on the Root Mean Square Error (RMSE) criterion to assess the convergence of iterative algorithms. The aim of this work is to present a new criteria: Average Ratio Scaled (AVGS) and Relative Change in AVGS (dAVGS) to address specific challenges associated with RMSE. Extensive validation tests were conducted, covering a range of scenarios with results showing high level of agreement between the unfolded spectra and the reference. • Novel stopping criteria, average ratio scaled (AVGS) and relative change in AVGS (dAVGS), for the SpecUnPy unfolding code. • Three unfolding algorithms from the SpecUnPy package can use the novel stopping criteria: SPUNIT, MLEM, and GRAVEL. • Validation cases have been chosen to validate the new SpecUnPy code version for conventional neutronic facilities (workplaces and calibration rooms). • SpecUnPy package comparison with the REBUNKI and UMG-MAXED codes; validation by comparison. [ABSTRACT FROM AUTHOR]

The aim of this work is to present a reproducible methodology for the evaluation of total equivalent doses in organs during proton therapy facilities. The methodology is based on measuring the dose equivalent in representative locations inside an anthropomorphic phantom where photon and neutron dosimeters were inserted. The Monte Carlo simulation was needed for obtaining neutron energy distribution inside the phantom. The methodology was implemented for a head irradiation case in the passive proton beam of iThemba Labs (South Africa). Thermoluminescent dosimeter (TLD)-600 and TLD-700 pairs were used as dosimeters inside the phantom and GEANT code for simulations. In addition, Bonner sphere spectrometry was performed inside the treatment room to obtain the neutron spectra, some relevant neutron dosimetric quantities per treatment Gy, and a percentual distribution of neutron fluence and ambient dose equivalent in four energy groups, at two locations. The neutron spectrum at one of those locations was also simulated so that a reasonable agreement between simulation and measurement allowed a validation of the simulation. Results showed that the total out-of-field dose equivalent inside the phantom ranged from 1.4 to 0.28 mSv/Gy, mainly due to the neutron contribution and with a small contribution from photons, 10% on average. The order of magnitude of the equivalent dose in organs was similar, displaying a slow reduction in values as the organ is farther from the target volume. These values were in agreement with those found by other authors in other passive beam facilities under similar irradiation and measurement conditions. [ABSTRACT FROM AUTHOR]

The aim of this work is to present a reproducible methodology for the evaluation of total equivalent doses in organs during proton therapy facilities. The methodology is based on measuring the dose equivalent in representative locations inside an anthropomorphic phantom where photon and neutron dosimeters were inserted. The Monte Carlo simulation was needed for obtaining neutron energy distribution inside the phantom. The methodology was implemented for a head irradiation case in the passive proton beam of iThemba Labs (South Africa). Thermoluminescent dosimeter (TLD)-600 and TLD-700 pairs were used as dosimeters inside the phantom and GEANT code for simulations. In addition, Bonner sphere spectrometry was performed inside the treatment room to obtain the neutron spectra, some relevant neutron dosimetric quantities per treatment Gy, and a percentual distribution of neutron fluence and ambient dose equivalent in four energy groups, at two locations. The neutron spectrum at one of those locations was also simulated so that a reasonable agreement between simulation and measurement allowed a validation of the simulation. Results showed that the total out-of-field dose equivalent inside the phantom ranged from 1.4 to 0.28 mSv/Gy, mainly due to the neutron contribution and with a small contribution from photons, 10% on average. The order of magnitude of the equivalent dose in organs was similar, displaying a slow reduction in values as the organ is farther from the target volume. These values were in agreement with those found by other authors in other passive beam facilities under similar irradiation and measurement conditions.

We conducted a real-time soft-error rate characterization of CMOS bulk 65-nm static random access memories (SRAMs) subjected to fusion neutrons during deuterium–deuterium (D-D) plasma operation at W–tungsten–Environment in Steady-state Tokamak (WEST). The test equipment, installed in the experimental hall at several locations of the tokamak, was irradiated during machine shots by a flux of particles dominated by primary 2.45-MeV neutrons. Real-time neutron metrology, neutron spectrometry, complementary characterization with monoenergetic neutrons, and Monte Carlo numerical simulations at both material and circuit levels have also been performed to analyze the experimental data. Our results suggest that higher energy neutrons, simultaneously produced by deuterium–tritium (D-T) reactions due to triton burn-up in the D-D plasma, play a significant role in the radiation response of SRAMs for which multiple cell upsets are detected and cannot be attributed to D-D neutrons. [ABSTRACT FROM AUTHOR]

Bruce Power operates a first-of-its-kind isotope production system (IPS) that enables continuous production of 177Lu within Canada Deuterium Uranium (CANDU) commercial power reactors. Located on the reactivity mechanisms deck of Unit 7, just outside of reactor containment but in close proximity to the primary heat transport (PHT) pumps, this facility offers unique advantages for 177Lu production. However, employees working in this area encounter a radiation hazard which consists primarily of photoneutrons. These originate from the base of the PHT pumps and are only present when the reactor is operating. This study evaluates neutron exposure at Bruce Power's IPS by using a nested neutron spectrometer (NNS) to determine the neutron energy spectra and absolute dosimetric quantities such as the ambient dose equivalent, H*(10). The results from the NNS are then compared to surveys performed by a portable neutron rem meter (Model NP-2 by Nuclear Research Corporation), routinely used by Bruce Power staff for workplace monitoring. While the Model NP-2 generally showed consistent results across locations, a 50% dose correction factor was identified when operators were harvesting 177Lu from the IPS. This finding highlights an opportunity to reduce the neutron dose that is assigned to operators when producing 177Lu. • Bruce Power produces 177Lu in a CANDU commercial power reactor. • Workers near the 177Lu isotope production system face exposure to photoneutrons from reactor PHT pumps. • Neutron exposure was characterized using a nested neutron spectrometer (NNS) and NP-2 survey meter. • Dose correction of 50% was identified for the NP-2 survey meter during 177Lu harvesting, reducing assigned neutron dose. [ABSTRACT FROM AUTHOR]

The natLi(p,n) system is a prominent source of mono-energetic neutrons capable of delivering neutrons in a large energy band extending from the Coulomb barrier to few hundreds MeV. These mon-energetic neutrons play a pivotal role in various academic and engineering applications. Present work emphasises on the variation of the emission yields and spectral features of natLi(p,n) neutrons at two different Li-foil thicknesses (8 and 16 mg cm−2). The study indicated a proton energy dependent variation in the emission neutron yields. At higher Li target thickness with increase in the neutron yield was observed ∼10 times for 8 MeV whereas, ∼1.5 time increase was observed with 20 MeV incident protons. The spectral shape also indicated softening of neutron spectra with possible merging of high energy emission neutron peaks with lowering of the average energy for 16 mg cm−2 thick Li target. • Yields, neutron spectra from 1H bombardment on two different natLi foil thickness were compared. • Simulation studies were performed and compared with proton irradiation of natLi foil supported on a natC target. • Measured neutron yields showed reproducible results with both targets. • Higher Li target thickness showed enhanced neutron yields and lower end point energies compared to thinner target. • Spectrometric estimates and H*(10) measurements using neutron dose equivalent meter showed comparable results. [ABSTRACT FROM AUTHOR]

To simulate secondary neutron radiation fields that had been measured at different relative positions during phantom irradiation inside a scanning proton therapy gantry treatment room. Further, to identify origin, energy distribution, and angular emission of the secondary neutrons as a function of proton beam energy. The FLUKA Monte Carlo code was used to model the relevant parts of the treatment room in a scanned pencil beam proton therapy gantry including shielding walls, floor, major metallic gantry-components, patient table, and a homogeneous PMMA target. The proton beams were modeled based on experimental beam ranges in water and spot shapes in air. Neutron energy spectra were simulated at 0°, 45°, 90° and 135° relative to the beam axis at 2 m distance from isocenter for monoenergetic 11 × 11 cm2 fields from 200 MeV, 140 MeV, 75 MeV initial proton beams, as well as for 118 MeV protons with a 5 cm thick PMMA range shifter. The total neutron spectra were scored for these four positions and proton energies. FLUKA neutron spectra simulations were crosschecked with Geant4 simulations using initial proton beam properties from FLUKA-generated phase spaces. Additionally, the room-components generating secondary neutrons in the room and their contributions to the total spectrum were identified and quantified. FLUKA and Geant4 simulated neutron spectra showed good general agreement with published measurements in the whole simulated neutron energy range of 10−10 to 103 MeV. As in previous studies, high-energy (E ≥ 19.6 MeV) neutrons from the phantom are most prevalent along 0°, while thermalized (1 meV ≤ E < 0.4 eV) and fast (100 keV ≤ E < 19.4 MeV) neutrons dominate the spectra in the lateral and backscatter direction. The iron of the large bending magnet and its counterweight mounted on the gantry were identified as the most determinant sources of secondary fast-neutrons, which have been lacking in simplified room simulations. The results helped disentangle the origin of secondary neutrons and their dominant contributions and were strengthened by the fact that a cross comparison was made using two independent Monte Carlo codes. The complexity of such room model can in future be limited using the result. They may further be generalized in that they can be used for an assessment of neutron fields, possibly even at facilities where detailed neutron measurements and simulations cannot be performed. They may also help to design future proton therapy facilities and to reduce unwanted radiation doses from secondary neutrons to patients. [ABSTRACT FROM AUTHOR]

Liquid organic scintillators are important devices for measurements of neutron radiation. Currently, large-scale liquid organic scintillators have capabilities of detecting neutrons, but the determination of the neutron energy spectra is a challenge. This work aims to measure the responses of two liquid two-component scintillators to mono-energetic neutron radiation and to determine their light output function, which is necessary for proper neutron energy spectra determination. Both scintillators are composed of the solvent di-iso-propyl-naphthalene (DIPN) mixed isomers. The first scintillator, labeled PYR5/DIPN, contains the luminophore 1-phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline with a concentration of 5 g/L. The second scintillator labeled THIO5/DIPN contains the luminophore 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene also with a concentration of 5 g/L. The responses to neutron energies of 1.5 MeV, 2.5 MeV, and 19 MeV are measured at PTB in Braunschweig. The responses to neutron energies of 2.45 MeV and 14 MeV were measured at CTU in Prague using DD and DT reactions. The responses to a silicon filtered beam were measured at Research Centre Řež. The measurements were processed using a two-parameter spectrometric system NGA-01 to discriminate neutrons from gamma rays. The obtained responses are dominated by recoil protons from elastic collisions of neutrons with hydrogen atoms. The edge of the response of recoil protons gives information about the light output of neutrons, compared to gamma rays for the same radiation energy. The light output function for protons in the PYR5/DIPN scintillator is L(Ep)=0.6294Ep−1.00(1−exp(−0.4933Ep0.95)). The light output function for protons in the THIO5/DIPN scintillator is L(Ep)=0.6323Ep−1.00(1−exp(−0.4986Ep0.9883)). The light output functions well resemble the standard shape, and they are quite similar to each other. That suggests a weak influence of the luminophore on the light output function. The light output functions are ready to be incorporated to the response matrix for the neutron energy spectra determination.

We present the measured spectra of γ and neutron radiation generated in the 9Be(3He,pγ)11B and 9Be(3He,nγ)11C nuclear reactions at an energy of 2.57 MeV of 3He ions using a BC-501A organic detector and an HPGe semiconductor spectrometer. Line shapes of 6.9-MeV γ-transitions from the 9Be(3He,nγ)11C reaction and 8.92-MeV transitions from the 9Be(3He,pγ)11B reaction, measured at angles of 0°, 30°, 60°, 90°, and 120° have been determined. The angular distribution of protons emitted when populating the 8.92-MeV level of the 11B nucleus in 9Be(3He,pγ)11B reaction, as well as the energy distribution of neutrons in 9Be(3He,nγ)11C reaction, have been reconstructed. [ABSTRACT FROM AUTHOR]

A test setup for measuring the neutron electric charge using spin interferometry and the effect of the double-crystal focusing of neutrons upon Laue diffraction is described. It is shown that a considerable increase in the distance between the crystals (up to 1 m) is needed to improve the accuracy of neutron-charge measurements. This is a difficult task because the setup becomes sensitive to slight external influences (temperature, vibration, etc.). To determine the degree of these influences, temperature tests with combined (active and passive) thermal protection were carried out. It is shown that under conditions of the reactor hall with temperature fluctuations of several degrees, the experimental setup provides a temperature stability of the crystals no worse than 0.01 K and stability of the temperature differences for the crystals and between them at a level of ~0.005 K. Measurements of the vibration level in the area of the PF1b cold neutron beam at the ILL reactor (Grenoble, France) allow estimation of the rate of displacement of crystals relative to each other at a level of ~10–3 cm/s. As follows from the data obtained, the angular resolution of the setup, without taking into account the influence of the imperfection of real crystals, can be at the level of 10–3 of the Bragg-reflection width, which is ~0.001 arc-second. [ABSTRACT FROM AUTHOR]

Measurement of the energy spectrum of secondary neutrons were carried out at the OncoRay Proton Therapy facility in Dresden, following an approach originating in neutron metrology which is well suited for both the characterization of secondary neutron fields at proton therapy facilities and the validation of Monte Carlo simulations. For the experiment, a brass target was placed in the proton beam and Bonner spheres measurements were made at a distance of 2 m from the target and at different angles, 15° to 120°, with respect to the incoming proton beam. The measured spectra were compared to Monte Carlo simulations.

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. [ABSTRACT FROM AUTHOR]

Abstract 241Americium–beryllium neutron sources are used in a variety of applications, spanning from the civil engineering to the oil industry, and to the radiation dosimetry. The ISO 8529-1 Standard reports a reference distribution for the energy of the emitted neutrons, which extends from 0.1 to 11 MeV. Nevertheless every source exhibits a slightly different spectrum, depending on the material and dimension of the capsule, and on the amount of active material. This source-to-source variability is expected to mainly affect the energy region below 0.1 MeV. As these differences can be important in the fields of neutron dosimetry and metrology, some relevant source formats have been investigated with spectrometric methods. The neutron calibration laboratory of the Politecnico di Milano recently acquired a CZ/1003/S — 96 type 241 Am–Be source (nominal emission rate 2.2E+6 s−1). As this type of source is in use in a number of European laboratories, its spectrum was determined through a neutron spectrometry experiment, involving two Bonner sphere spectrometers with well-known responses. The experimental spectrum is compared to that published for a similar source and to the ISO-recommended one. [ABSTRACT FROM AUTHOR]

Abstract CYSP-BEAM is a directional neutron spectrometer formed by a thick polyethylene cylindrical collimator followed by a sensitive capsule that contains several active thermal neutron detectors located at different depths along the cylindrical axis. Due to a thick lateral shield made of polyethylene and borated rubber, only neutrons from the direction identified by the collimating aperture can reach the internal detectors. As the response function of the internal detectors tend to peak at increasing energies as the detector depth increases, the device has spectrometric properties. This type of moderated spectrometer, whose prototype was the CYSP (CYlindrical SPectrometer), is capable to combine the functionalities of Bonner Spheres in a single device, thus requiring only one exposure to measure all the energy components of the incident beam, from thermal up to GeV neutrons. The neutron spectrum is obtained via few-channel unfolding methods. With respect to the original CYSP, the new CYSP-BEAM device is optimized to operate in the direct intense beam of neutron producing installations, such as large scale neutron science facilities. Compared with CYSP, CYSP-BEAM has narrower collimating aperture and the internal detectors have sensibility a factor 100 lower. Its response matrix was simulated using MCNPX. This paper describes the new device focusing on the internal detectors, the response matrix and the test measurement performed using the 14 MeV beam produced at the ENEA Frascati Neutron Generator (FNG). [ABSTRACT FROM AUTHOR]

Abstract The 9Be(d,n)10B reaction was proposed in the past as a neutron source for Accelerator-Based Boron Neutron Capture Therapy. Based on numerical models and scarce experimental information about the neutron spectra, it was proven that low energy deuterons on a thin target may provide neutron beams of therapeutic quality. In particular, an 8–9 μm target bombarded by 1.45 MeV deuterons presents itself as a convenient option. The aim of this work is to provide experimental validation to these numerical models. For this purpose, neutron spectra at 0°, 35°, 60°, 90° and 123° from a (9 ± 1) μm 9Be target were measured at the CN accelerator of the Laboratori Nazionali di Legnaro. A micro-time projection chamber (μ-TPC) was used as a neutron spectrometer. [ABSTRACT FROM AUTHOR]

Abstract Time-of-flight measurements were performed to determine the 4He pressurized fast neutron scintillation detectors response function and the ability of the detectors to be applied as a spectrometer. An experimentally validated neutron energy response function was used in conjunction with an iterative least squares unfolding technique to unfold a 252Cf spontaneous fission spectrum, a PuBe (α , n) spectrum, and a deuterium–deuterium (D–D) fusion reaction spectrum. The ability of the detectors to retain incident neutron energies makes them suitable for applications such as nuclear non-proliferation and spent nuclear fuel monitoring. [ABSTRACT FROM AUTHOR]

Abstract The cyclotron-based fast neutron sources of the white- and quasi-monoenergetic spectra are operated at the NPI Rez Fast Neutron Facility utilizing the variable proton (up to 36 MeV) and deuteron (up to 20 MeV) beams delivered by the U-120M isochronous cyclotron and target stations with the Be(thick), D 2 O(thick), and Li(C) neutron production targets. The upgraded beryllium target station provides the high intensity neutron field of broad spectra up to 33 MeV with mean energy of 14 MeV. The energy range corresponds to the main energy part of IFMIF (International Fusion Material Irradiation Facility) neutron spectrum. This IFMIF-like source is appropriate for the radiation hardness tests of materials and electronics, validation of activation cross-section data within the fusion relevant research programs, and fast neutron activation analysis experiments. At the NPI CAS, the neutron field of p + Be source reaction was studied for proton beam energy of 35 MeV using the multi-foil activation technique. The modified version of SAND-II deconvolution tool was used for neutron spectrum reconstruction up to 33 MeV (i.e. energy region with a lack of experimental neutron spectral data). Highlights • Development of Accelerator-driven neutron sources and neutron fields. • Fast neutron spectrometry by multi-foil activation technique. • Nuclear data measurement and validation in the energy range of the IFMIF. [ABSTRACT FROM AUTHOR]

Abstract The presented paper summarizes the methodology of fast neutron leakage fluxes measurement using a stilbene scintillation detector on spherical benchmark assemblies. The experiments are realized in a spherically simple geometry, which does not need validation of the neutron transport model. Hence, this type of experiment is suitable for validation of the nuclear cross sections of various isotopes. The 252Cf neutron source is always placed in the center of a sphere of different pure materials. The selection is focused on structural materials used in the nuclear industry. In the presented set, the materials include light water, heavy water and nickel. For example, the light and heavy water spheres can be used to eliminate the effect of hydrogen and estimate the effect of oxygen. The neutron spectra in the region of 1–10 MeV are measured in a room where the background could substantially influence the final result. For this reason, the estimation of the scattered neutrons is crucial for the correct evaluation of the experiment. The comparison of the calculated and measured neutron fluxes and background signal share are presented. Calculations were performed using the MCNP6 program with the ENDF/B-VII.1 nuclear data library. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the impact of various factors on neutron spectrum unfolding, including track parameters (major axis, minor axis and depth), polyethylene (PE) thickness, and etching time. The Monte Carlo code Geant4 and proton track parameter calculation program TRACK_P were applied to simulate the response matrix and track parameters spectrum. Four test spectra—252Cf spectrum, Gaussian broadened deuterium–deuterium fusion neutron spectrum, 241Am–Be spectrum, and Gaussian broadened deuterium–tritium fusion neutron spectrum—were studied using the maximum-likelihood expectation maximization algorithm for neutron spectrum unfolding. The unfolded spectra were in good agreement with the reference spectra. Results showed that the major and minor axes were more suitable than the track depth for neutron spectrum unfolding. For high-energy neutrons, a thick PE layer is required. Moreover, etching time does not significantly affect the unfolded spectra. This study explores the factors influencing the unfolding of fast neutron spectrum based on simulation calculations and preliminary experiments that can be useful for applying CR-39 to neutron spectrum measurements. • The response matrices of track parameters are calculated using Monte Carlo simulation and the TRACK_P program. • The track parameter spectrum and maximum likelihood expectation maximization are used for neutron spectrum unfolding. • The impact factors of track parameters, polyethylene thickness and etching time on neutron spectrum unfolding are discussed. [ABSTRACT FROM AUTHOR]

The response functions (RFs) of a Bonner Sphere Spectrometer (BSS) with a 6LiI thermal neutron detector were calculated using the Monte Carlo codes PHITS (version 3.26) and MCNPX (version 2.7.0), with their own default nuclear data libraries, and physics models. RFs were compared with other published data, obtained for the same spectrometer using the MCNP6.1 code with its own physics models. A discussion on the influence of using different nuclear data libraries and physics models using these codes/versions is analyzed. • Response functions (RFs) of a BSS with a 6LiI thermal neutron detector were calculated with the codes PHITS and MCNPX. • Use of the default nuclear data libraries, and physics models of the codes. • RFs were compared with other published data. • RFs obtained can be used for neutron spectrometry in workplaces. [ABSTRACT FROM AUTHOR]

Bonner Sphere Spectrometers (BSS) are widely used for neutron spectrometry. Spectra are obtained by unfolding detector readings. In this work, a Python Graphical User Interface Application (GUI/App) for spectrum unfolding is presented; SpecUnPy. In this App, the user can choose three unfolding algorithms: SPUNIT/MLEM/GRAVEL. There is no limit for energy bins or detectors and after unfolding, a ".xlsx" file and a graphical comparison can be downloaded. This paper presents SpecunPy and some tests performed to validate it. • A Python Graphical User Interface Application (GUI/App) for neutron spectrum unfolding is presented. • SpecUnPy App uses three unfolding algorithms: SPUNIT, MLEM, and GRAVEL. • The GUI/App was tested using data from IAEA compendium and EURADOS exercise. • SpecUnPy App is easy, friendly, intuitive, and reliably solves the neutron spectrum unfolding problem. [ABSTRACT FROM AUTHOR]

Boron neutron capture therapy (BNCT) is a promising cancer treatment that uses energetic ions released from 10B(n, α) 7 Li reactions. Accurate assessment of neutron energy spectra is important for simulation-based evaluation of neutron doses during BNCT. In this study, a proof-of-concept study was conducted for a neutron spectrometry technique that involves the use of a water phantom, which is commonly used for quality assurance in BNCT, as a moderator. The technique involves applying unfolding to the count rate distribution of the thermal neutron counter measured within the phantom to derive the energy spectrum. We performed experiments using a spherical 3 He proportional counter in neutron fields generated by 252Cf and 241Am-Be sources. The results demonstrated that the spectrometer reasonably reproduced neutron spectra and showed the potential of using a water phantom as a moderator for such a technique. • A neutron spectrometer using a water phantom for BNCT was proposed. • Spectrometer consists of a thermal neutron detector and a cubic water phantom. • A proof-of-concept was demonstrated with Cf and Am-Be sources. • The spectra were reproduced with an acceptable accuracy by unfolding. [ABSTRACT FROM AUTHOR]

Abstract The neutron flux distribution behind a reactor pressure vessel (RPV) is an important parameter that is monitored to determine neutron fluence in the RPV. Together with mechanical testing of surveillance specimens, these are the most important parts of in-service inspection programs that are essential for a realistic and reliable assessment of the RPV residual lifetime. The fast neutron fluence values are determined by a calculation. These calculation results are accompanied by measurements of induced activities of the activation foils placed in the capsules behind the RPV at selected locations, namely in azimuthal profile. In case of discrepancies between the measured and calculated activities of the activation foils placed behind the pressure vessel, it is difficult to determine the source of the deviation. During such analysis, there arises a question on the influence of power peaking near core boundary on neutron profile behind the RPV. This paper compares the calculated and measured increase of the neutron flux density distribution behind the reactor pressure vessel in the azimuthal profile that has arisen from the replacement of 164 fuel pins located close to reactor internals by pins with the higher enrichment. This work can be understood as the first step in the characterization of the effect of incorrectly calculated pin power or burn-up in the fuel assembly at the core boundary relative to the neutron flux distribution behind reactor pressure vessel. Based on a good agreement between the calculated and experimental values, it can be concluded that the mathematical model used to evaluate the power increase is correct. Highlights • Measurement of neutron flux density profile behind RPV in azimuthal profile. • Comparison of calculated and measured neutron flux density profile behind RPV. • Measurement of local power increase on neutron flux density behind RPV simulator. • Measurement and calculation of neutron spectra behind RPV simulator of VVER-1000 reactor. [ABSTRACT FROM AUTHOR]

Abstract CSYP (CYlindrical SPectrometer) is a directional neutron spectrometer based on a single moderator embedding multiple thermal neutron detectors. Similarly to Bonner Spheres, CYSP responds from thermal up to GeV neutrons and the spectrum is obtained via few-channel unfolding methods. CYSP has the shape of a polyethylene cylinder with diameter 50 cm and height 65 cm. Owing on a thick collimator and on a specifically designed shielding structure, the internal detectors only respond to neutrons coming from a known direction. Internal thermal neutron detectors are one-cm2 6LiF-covered silicon diodes. Un upgraded version of CYPS was developed to work in low intensity applications, such as cosmic field measurements. It is called CYSP-HS (High-Sensitivity) and is equipped with large area 6LiF-covered silicon diodes (LATND, Large Area Thermal Neutron Detectors). Compared with the former CYSP, the sensitivity increased approximately by an order of magnitude. This paper presents CYSP-HS focusing on the new internal detectors, the response matrix and its verification in a reference field of Am-Be available at the Politecnico di Milano. Highlights • A high-sensitivity, single-modetator, directional neutron spectrometer, CYSP-HS, was developed. • CYSP-HS is an upgrade of the neutron spectrometer CYSP. • Large Area semiconductor-based thermal neutron detectors were used. • CYSP-HS and CYSP response matrices were compared. • CYSP-HS response matrix was verified in a reference Am-Be field. [ABSTRACT FROM AUTHOR]

Abstract The correct description of neutron transport in lead is an essential task for correct description of tritium production in the DEMO (DEMOnstration Power Station) breeding blanket because some concepts deal with lead as a major component: namely the WCLL (water cooled lithium lead blanket), HCLL (helium cooled lithium lead blanket), and DCLL (dual cooled lithium lead blanket). Concerning the improvement of the knowledge about the transport of fast neutrons in lead, a set of experiments and calculations was carried out to study this problem with a well-defined neutron beam. The neutron flux behind various lead arrangements positioned along the beam axis was measured using a stilbene scintillation crystal (10 mm × 10 mm) with neutron and gamma pulse shape discrimination. The measurement was performed along the beam axis and in the case of the thick target also above the axis, to estimate the neutron angular scatter in lead. The calculations were realized using MCNP6 with various nuclear data libraries. Discrepancies in the angular distribution description in the energy region of about 1 MeV were discovered by these experiments. Highlights • Neutron spectra behind various Pb targets. • Comparison of the experimental data with calculation. • Study of angular distribution of neutron scatter in Pb. • Discrepancies between calculational and experimental neutron spectra. [ABSTRACT FROM AUTHOR]

The neutron flux distribution in the internal parts of a reactor is an important parameter which affects the absorbed dose, temperature, and gas production in the materials. Therefore, the knowledge of neutron flux distribution, for example in the baffle, is important for estimation of the radiation-induced swelling and activation of this internal component. The power distribution in the periphery fuel assemblies, mostly the lateral 2–3 pin rows, has considerable influence on neutron and gamma flux in the internal reactor elements. The power distribution in the core is mostly calculated by the reactor operator using diffusion codes. These data are used as an input for transport calculations, e.g., with Monte Carlo for the fluences, displacements per atoms, gamma heating and other important values for radiation damage estimation. This paper aims to compare the experimental and calculated reaction rate distribution in a mock-up of VVER-1000 (VVER-1000 Mock-Up) internals placed in the LR- 0 reactor and compares these quantities in case of a partial change of enrichment in one fuel assembly adjacent to the baffle simulator. [ABSTRACT FROM AUTHOR]

In boron neutron capture therapy, it is important to evaluate the dose administered to a patient's body outside the tumour area. The exposure dose is evaluated by calculation; however, the calculated value must be validated using a measured value. The dose evaluations based on the measured neutron spectrum are investigated. Multi-foil activation, combined with a LiCaAlF 6 scintillation detector and an imaging plate, is proposed as a measurement method. The proposed method can measure the neutron spectrum at various points quickly. [ABSTRACT FROM AUTHOR]

Neutron field measurements around individual DPT type spent fuel transport and storage casks were performed at the storage installation of Trillo Nuclear Power Plant. Neutron spectra were determined at five different positions using a Bonner sphere system. These measurements were used to validate the dosimetry measurements of two neutron monitors. Axial and angular measurements were used to determine the ambient dose equivalent. The results are consistent with the cask design and no field correction is needed when using these monitors. [ABSTRACT FROM AUTHOR]

An intense neutron beam produced via 7 Li(p, n) 7 Be reaction on a newly developed high-power liquid Lithium target (LiLiT) is available at SARAF (Soreq Applied Research Accelerator Facility) facility, Israel. Its spectrum was determined using the CYSP (CYlindrical SPectrometer), a new directional neutron spectrometer which incorporates the functionality of the Bonner spheres in a single cylindrical moderator. The advantages of this spectrometer are that the neutron spectrum is derived in only one exposure, and that its directional response is not affected by room- and air-scattered neutrons. The data from the CYSP spectrometer were analysed using the FRUIT unfolding code. [ABSTRACT FROM AUTHOR]

Validation of neutronic parameters for lead-cooled systems, by integral and local experiments, became of primary interest with advances in ALFRED lead cooled reactor demonstrator design. Notably, aiming at advancing the core design from the conceptual to the basic stage, the assessment of uncertainties coming from numerical simulation, with respect to real experiments, was of paramount importance to support the claims of outstanding safety demonstration meant for ALFRED. Among the required evidences, the assessment of the spatial distribution of the neutron flux and power in fuel pins required conceiving ad-hoc experiments, and disposing of state-of-the-art post-irradiation examination capabilities. For all these reasons, these experiments were one of the main focuses of the collaboration between the Research Centre Rez and ENEA. This paper presents the conception phase of the test and discusses some of the main results of the first phase of the experimental campaign, dealing with neutrons propagation, collected during its execution at the LR-0 research reactor (hence before the post-irradiation examination of the experimental pins placed in the lead test rig). The experimental work involved at first neutron spectrum measurements in the energy range from 0.1 to 10 MeV. Additionally, measurement of basic neutronic parameters of lead were performed, such as its reactivity worth, its effect on the neutron spectrum and its slowing-down properties. The comparison of calculations and experimental results shows good agreement. In case of calculation in benchmark model with different nuclear data libraries, the criticality is systematically over-predicted by approximately 150 pcm, which is, however, in the 1σ of the uncertainty interval. Neutron spectrum measurement shows only slight variations being around 10% most of the time. [ABSTRACT FROM AUTHOR]

A Bonner Sphere spectrometer employing a large, 11 mm diameter × 3 mm thickness, 6 LiI(Eu) scintillator (LL-BSS), was assembled. The purpose was to produce a BSS similar in sensitivity to those based on 3 He sensors, but using alternative sensors. With respect to the traditional BSS based on the 4 mm (diameter) × 4 mm (height) 6 LiI(Eu), this new BSS is a factor of 3 more sensitive. LL-BSS response matrix, determined with MCNPX, was experimentally evaluated with monoenergetic reference neutron fields of 144 keV, 565 keV and 1.2 MeV available at NPL (Teddington, UK). The results of the experiment confirmed the correctness of the response matrix within an overall uncertainty lower than ±2%. [ABSTRACT FROM AUTHOR]

Neutron fields inside and outside the independent spent fuel storage installation of Trillo Nuclear Power Plant are characterized exhaustively in terms of neutron spectra and ambient dose equivalent, measured by Bonner sphere system and LB6411 monitor. Measurements are consistent with storage casks and building shield characteristics, and also with casks distribution inside the building. Outer values at least five times lower than dose limit for free access area are found. Measurements with LB6411 and spectrometer are consistent with each other. [ABSTRACT FROM AUTHOR]