bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiband coupling and nuclear softness in optical model calculations for even-even and odd-A actinides
Authors: Martyanov Dmitry , Soukhovitskiĩ Efrem , Capote Roberto , Quesada José M. , Chiba Satoshi
Published: September 2020

A new dispersive multiband coupled channels optical model with soft-rotator “effective” deformations is proposed to describe nucleon scattering on even-even and odd-A actinides. The impact of the introduction of axial and non-axial dynamical deformations that describe nuclear softness is discussed. Softness and multiband coupling are shown to change compound-nucleus formation cross section by up to ≈ 10% for incident neutron energies below 1 MeV.
Validating the Bohr hypothesis: Comparing fission-product yields from photon-induced fission of 240Pu and neutron-induced fission of Pu
Authors: Silano Jack , Tonchev Anton , Henderson Roger , Schunck Nicolas , Tornow Werner , Howell Calvin , Krishichayan FNU , Finch Sean
Published: September 2020

The Bohr hypothesis, one of the most fundamental assumptions in nuclear fission theory, states that the decay of a compound nucleus with a given excitation energy, spin and parity is independent of its formation. Using fission product yields (FPYs) as a sensitive probe, we have performed new high precision test of the combined effects of the entrance channel, spin and parity on the fission process. Two different reactions were used in a self-consistent manner to produce a compound 240Pu nucleus with the same excitation energy: neutron induced fission of 239Pu at En = 4.6 MeV and photon-induced fission of 240Pu at Eγ = 11.2 MeV. The FPYs from these two reactions were measured using quasimonoenergetic neutron beams from the TUNL's FN tandem Van de Graaff accelerator and quasimonenergetic photon beams from the High Intensity γ-ray Source (HlγS) facility. The first results comparing the FPYs from these two reactions will be presented. Implications for validating the Bohr hypothesis will be discussed.
The fission yield calculations with Langevin model, Hauser-Feshbach statistical decay, and beta decay
Authors: Okumura Shin , Kawano Toshihiko , Chiba Satoshi
Published: September 2020

We performed the calculations of de-excitation of the primary fission fragments by the Hauser-Feshbach statistical decay followed by the β decay of de-excited fission products. We used the primary fission fragment mass distributions YP(A), total kinetic energy TKE(A), and its width σTKE(A) as input, which were calculated with the Langevin model using macroscopic-microscopic models of the potential energy surface. The prompt neutron multiplicity v̅ and the independent fission product yield (FPY) YI(Z, A, M) and cumulative FPY YC(Z, A, M) are calculated by the Hauser-Feshbach statistical decay and β decay calculations, respectively. The calculated v̅ was overestimated approximately 17% compared to the evaluated data. The decay heats from β and γ were in accordance with the experimental results. The β delayed neutrons yieild was also overestimated.
Recent progress of a code system DEURACS toward deuteron nuclear data evaluation
Authors: Nakayama Shinsuke , Iwamoto Osamu , Watanabe Yukinobu
Published: September 2020

Toward deuteron nuclear data evaluation, we have been developing a code system dedicated for deuteron-induced reactions, called DEURACS. In this paper, we review the recent progress in the development of DEURACS. To meet increasing and diversifying demands for deuteron nuclear data, DEURACS has been developed aiming at accurate and comprehensive prediction of deuteron-induced reactions. We present the results of some comparisons between the DEURACS calculations and experimental data for a variety of deuteron-induced reactions at incident energies up to 200 MeV. Double-differential cross sections for emission of neutrons or light ions up to A = 4 and cross sections for production of residual nuclei are analyzed. Neutron yields from deuteron bombardment on thick targets are also analyzed by the Monte Carlo transport simulation based on the deuteron nuclear data provided with DEURACS. Through comparison with experimental and other calculated data, validation of the present modeling in DEURACS is discussed.
Coupled-channel analysis of deuteron scattering on 56Fe
Authors: Liu Yujie , Ye Tao , Sun Weili , Guo Hairui
Published: September 2020

The deuteron elastic and inelastic scattering on 56Fe is calculated by using the coupled-channel method and the collective motion models. Based on the experimental angular distributions of scattering processes, an optimal set of parameters are obtained for the deuteron's coupled-channel optical model potential and 56Fe's deformation including first ten low-lying excited states. The calculation results are in good agreement with the experimental data at low incident energies (Ed < 30 MeV), except for 41+(2.085 MeV) and 23+(2.960 MeV), and the deviation is found for several states at 56 MeV. That indicates further analyses and discussions are necessary.
The dark side of alpha-particle optical potential: Emission from excited nuclei
Authors: Avrigeanu Vlad , Avrigeanu Marilena
Published: September 2020

Further analysis of α-particle emission from similar nuclei excited in neutron- as well as low-energy proton-induced reactions is involved concerning a possible difference between the optical model potentials (OMPs) which describe either alpha-particle elastic scattering and induced reactions or alpha-emission from excited compound nuclei. The key role of the pickup direct interaction is finally proved even at incident energies below ~10 MeV, as well as being eventually at the origin of the above-mentioned OMPs difference.
Synergy of Nuclear Data and Nuclear Theory Online
Authors: Denikin Andrey , Karpov Alexander , Naumenko Mikhail , Rachkov Vladimir , Samarin Viacheslav , Saiko Vycheslav
Published: September 2020

The paper describes the NRV web knowledge base on low-energy nuclear physics developed in the Joint Institute for Nuclear Research. The NRV knowledge base working through the Internet integrates a large amount of digitized experimental data on the properties of nuclei and nuclear reaction cross sections with a wide range of computational programs for modeling of nuclear properties and nuclear dynamics. Today, the NRV becomes a powerful instrument for nuclear physics research as well as for educational applications. Advantages of the functioning scheme of the knowledge base provide the synergy of coexistence of the experimental data and computational codes within one platform.
Experimental estimation of the “scission” neutron yield in the thermal neutron induced fission of 233U and 235U
Authors: Vorobyev Alexander , Shcherbakov Oleg , Gagarski Alexei , Val Gennadi’ski , Kuz Tatiana’mina
Published: September 2020

The analysis of angular and energy distributions of prompt neutrons from the thermal neutron induced fission of 233U and 235U measured recently in the WWR-M research reactor (Gatchina, Russia) have been performed. The yield of “scission” neutrons has been estimated by comparing the measured distributions with calculations within the model of emission of neutrons from completely accelerated fragments. Besides taking into account “scission” neutrons, for the best description of measured angular and energy distributions of fission neutrons, the calculation should be performed under the assumption that neutrons with a higher (7-9%) probability are emitted along the fission axis in the center-of-mass system of fission fragments.
FALSTAFF, an apparatus to study fission fragment properties First arm results
Authors: Deshayes Quentin , Berthoumieux Eric , Doré Diane , Thulliez Loic , Combet Michel , Kebbiri Mariam , Legou Philippe , Marcel Alain , Mols Jean-Philippe , Frégeau Marc-Olivier , Herlant Sébastien , Ledoux Xavier , Pancin Julien
Published: September 2020

Nuclear fission is a complex process that still need fundamental studies. New measurements, particularly of correlated observables, could allow to develop more sophisticated theoretical models to eventually have truly predictive capabilities for the physics of fission. Moreover, the next generation reactors concepts are mostly foreseen to operate in the fast-neutron energy domain, requiring new high quality nuclear data. In this context, a new experimental setup, called FALSTAFF, dedicated to the study of fission is under development. The FALSTAFF setup aims to investigate the fission of actinides in the fast-neutron energy domain (from a few hundreds of keV to a few MeV). Once completed, this two-arm spectrometer will detect both fragments in coincidence and allow to measure their time of flight (ToF) and kinetic energy. The average neutron multiplicity as a function of the fission fragment mass can then be assessed.

The first arm of the FALSTAFF spectrometer was built. It is composed of two main parts: first, two SED-MWPC (Multi-Wire Proportional Counter) detectors are used to measure the time-of-flight as well as the position of the fragments, thus reconstructing their velocity. Second, an axial ionisation chamber gives their kinetic energy and the energy loss profile. This proceeding will describe the FALSTAFF setup as well as the methods that are used to extract the required observables, leading up to the reconstruction of the neutron multiplicity to study the fission process. Then, the recent results obtained with the first arm of FALSTAFF will be presented, exhibiting kinetic energy, velocity and post-evaporation mass distributions. These observables will be displayed for 252Cf spontaneous fission and some of the improvements recently made will be discussed.
Back-n white neutron facility at CSNS and first-year nuclear data measurements
Authors: Tang Jingyu
Published: September 2020

Back-streaming neutrons through the incoming proton channel at the spallation target station of China Spallation Neutron Source (CSNS) were exploited to build a white neutron beam line (the so-called Back-n). With a proton beam of 100 kW in beam power and 1.6 GeV in kinetic energy and a thick tungsten target and modest moderation by the cooling water through the target slices, the neutron beam is very intense which is in the order of 7.0×106 n/cm2/s at 77 m from the target and has an excellent energy spectrum spanning from 0.5 eV to 200 MeV. In addition, the time resolution related to the time-of-flight measurements is very good for neutron energy determination. Altogether, it makes the CSNS Back-n one of the best white neutron sources in the world and very suitable for nuclear data measurements, especially for neutron-induced cross-section measurements. Since the completion of the Back-n beamline and four physics spectrometers in March 2018, the first batches of experiments on nuclear data measurements have been carried out, which are summarized in this article.
Measurement of displacement cross section of structural materials utilized in the proton accelerator facilities with the kinematic energy above 400 MeV
Authors: MEIGO Shin-ichiro , MATSUDA Hiroki , IWAMOTO Yosuke , YOSHIDA Makoto , HASEGAWA Shoichi , MAEKAWA Fujio , IWAMOTO Hiroki , NAKAMOTO Tatsushi , ISHIDA Taku , MAKIMURA Shunsuke
Published: September 2020

For damage estimation of structural material in the accelerator facility, displacement per atom (DPA) is widely employed as an index of the damage calculated based on the displacement cross section obtained with the calculation model. Although the DPA is employed as the standard, the experimental data of displacement cross section are scarce for a proton in the energy region above 20 MeV. Among the calculation models, the difference exists about 8 times so that experimental data of the displacement cross section is crucial to validate the model. To obtain the displacement cross section, we conducted the experiment in J-PARC. As a preliminary result, the displacement cross section of copper was successfully obtained for 3-GeV proton. The present results showed that the widely utilized the Norgertt-Robinson-Torrens (NRT) model overestimates the cross section as suggested by the previous experiment for protons with lower energy.
Calibration of CR-39 solid state track detectors with monoenergetic protons from 0.3 MeV to 2.5 MeV
Authors: He Yangfan , Xi Xiaofeng , Guo Shilun , Guo Bing , He Changye , Liu Fulong , Lan Xiaofei , Qiu Menglin , Wang Guangfu , Wu Di , Wei Jihong , Wang Luohuan , Yang Wansha , Zhang Donghai
Published: September 2020

The2H(d,p)3H reaction is one of the most crucial reactions in the Big Bang nucleosynthesis (BBN). It is of particular interest to investigate this kind of reactions in plasma environments, generated by high intensity lasers, which are similar to real astrophysical conditions. We have experimentally investigated the2H(d,p)3H reaction using laser-driven counter-streaming collisionless plasmas at the Shenguang-II laser facility. CR-39 track detectors are widely employed as the main diagnostics in such experiments and laser-driven ion acceleration. In this work, we performed calibration of CR-39 track detectors with monoenergetic protons from the tandem accelerator, and then presented their track diameters for proton energies ranging from 300 keV to 2.5 MeV and for etching times between 4 and 28 hours. In addition, we recommended the optimal etching time at the typical etching conditions, which will be very useful for the following massive data analysis from the CR-39 detectors.
Work on the neutron standards since the completion of the standards evaluation
Authors: Carlson Allan
Published: September 2020

An evaluation of the neutron standards that included the neutron cross section standards was recently completed. It is important to maintain experimental programs to increase the quality and extend the database for the neutron cross section standards in order to improve evaluations of them. In this paper work will be reported on new or continuing efforts on the cross section standards including that on the 30 keV Maxwellian averaged cross section for the 197Au(n,γ) reaction that is now a standard and is used in neutron capture cross section measurements as a standard for reactions important for astrophysics.
Relativistic effect on atomic displacement damage for two-body inducing discrete reactions
Authors: Chen Shengli , Bernard David , De Saint Jean Cyrille
Published: September 2020

The relativistic effect on two-body discrete reaction inducing atomic recoil energy and the sequent damage energy is studied for 6Li, 56Fe, 184W, and 238U. The relativistic correction is within 1% if incident neutron energy is below 20 MeV. For incident neutron energy up to 200 MeV or even 800 MeV, the relativistic effect should be taken into account for treating two-body kinematics. The relativistic correction is about 0.05Ein/MeV% for neutron elastic scattering for nuclei from 56Fe to 238U and smaller for (n,α) and (n,t) reactions. Analyses on damage energy show that the relativistic corrections are generally within 2% for incident neutron below 200 MeV for nuclei lighter than 56Fe because of the “saturation” of damage energy. However, the current damage theory cannot be applied for Primary Knock-on Atom (PKA) energy higher than 24.9ARZR4/3 keV, which is 10 times lower than the maximum PKA energy for D+T fusion neutron elastic scattering of 6Li.
Calculation of electron scattering cross-section using different theoretical methods
Authors: Li Xiazhi , Zhu Jinhui , Zuo Yinghong , Li Ya
Published: September 2020

Aiming at the simulation of the fine process of the electron transportation in gamma detectors, we calculate electron differential scattering cross-section (DCS) of several typical materials including Fe, ethylene and polyethylene. Based on two different calculation methods, which are partial wave methods based on Dirac equation and R-matrix theory, we find differences of the cross section at low energy region. The result indicates that both partial wave method and R-matrix theory associated with independent atom method (IAM) are not suitable for low energy electron impacting on strong coupled molecule, for example, electron-ethylene. For high energy electron interacting with atom and molecule, the result shows no critical difference because the kinetic energy of the incident electron is severely higher than the electron bound energy in molecule or the excitation energy of a certain atom.
CENDL-3.2: The new version of Chinese general purpose evaluated nuclear data library
Authors: Ge Zhigang , Xu Ruirui , Wu Haicheng , Zhang Yue , Chen Guochang , Jin Yongli , Shu Nengchuan , Chen Yongjing , Tao Xi , Tian Yuan , Liu Ping , Qian Jing , Wang Jimin , Zhang Huanyu , Liu Lile , Huang Xiaolong
Published: September 2020

A new version of Chinese Evaluated Nuclear Data Library, namely CENDL-3.2, has been completed under the joint efforts of CENDL working group. This library is constructed with the general purpose to provide high-quality nuclear data for the modern nuclear science and engineering. 272 nuclides from light to heavy are covered in CENDL-3.2 in total and the data for 134 nuclides are new or updated evaluations in energy region of 10-5 eV-20 MeV. The data of most of the key nuclides in nuclear application like U, Pu, Th, Fe et al. have been revised and improved, and various evaluation techniques have been developed to produce the nuclear data with good quality. Moreover, model dependent covariances data for main reaction cross sections are added for 70 fission product nuclides. To assess the accuracy of CENDL-3.2 in application, the data have been tested with the criticality and shielding benchmarks collected in ENDITS-1.0.
New evaluation of general purpose neutron data for stable W-isotopes up to 200 MeV
Authors: Konobeyev A.Yu. , Fischer U. , Pereslavtsev P.E. , Simakov S.P.
Published: September 2020

In the frame of the Power Plant Physics and Technology of EUROfusion, new evaluations of general purpose neutron cross-section data were performed for the 180,182,183,184,186W isotopes covering the neutron energy up to 200 MeV. A special version of the TALYS nuclear model code implementing the geometry dependent hybrid model supplied with models for the non-equilibrium cluster emission was applied for calculations of the nuclide production and the energy distribution of the emitted particles. The parameters of the GDH model were properly estimated using measured data for individual tungsten isotopes. The neutron cross-sections were evaluated making use of available experimental data, systematics including estimated A-dependence of components of gas production cross-sections, and covariance information produced as part of the evaluation process. The BEKED code package, developed at KIT, was applied for calculations of co-variances using a dedicated Monte Carlo method. The evaluated data were processed into standard ENDF data format using the TEFAL code and the FOX module of the BEKED system. The evaluated data files were checked for errors and inconsistencies, processed with the NJOY code into ACE data format, and benchmarked against available integral experiments with MCNP neutron transport calculations.
Evaluation of neutron induced reactions on 56Fe with CONRAD
Authors: Diakaki M. , Chen S. , Noguere G. , Bernard D. , Tamagno P. , Archier P.
Published: September 2020

The evaluation of the 56Fe neutron induced reactions is currently ongoing at the CEA-Cadarache using the code CONRAD, with the goal to cover the whole energy range from the Resolved Resonance Region to the continuum and estimate the corresponding uncertainties and covariance matrices. Some first results and issues occurred from this work are presented and discussed here, more specifically on the analysed transmission and capture data in the Resolved Resonance Region, as well as the optical and statistical model calculations in the fast neutron energy range.
New perspectives in neutron reaction cross-section evaluation using consistent multichannel modeling methodology: Application to 17O*
Authors: Nizigama Aloys , Bouland Olivier , Tamagno Pierre
Published: September 2020

The traditional methodology of nuclear data evaluation is showing its limitations in reducing significantly the uncertainties in neutron cross sections below their current level. This suggests that a new approach should be considered. This work aims at establishing that a major qualitative improvement is possible by changing the reference framework historically used for evaluating nuclear model data. The central idea is to move from the restrictive framework of the incident neutron and target nucleus to the more general framework of the excited compound-system. Such a change, which implies the simultaneous modeling of all the reactions leading to the same compound-system, opens up the possibility of direct comparisons between nuclear model parameters, whether those are derived for reactor physics applications, astrophysics or basic nuclear spectroscopy studies. This would have the double advantage of bringing together evaluation activities performed separately, and of pooling experimental databases and basic theoretical nuclear parameter files. A consistent multichannel modeling methodology using the TORA module of the CONRAD code is demonstrated across the evaluation of differential and angle-integrated neutron cross sections of 16O by fitting simultaneously incident-neutron direct kinematic reactions and incident-alpha inverse kinematic reactions without converting alpha data into the neutron laboratory system. The modeling is fulfilled within the Reich-Moore formalism and an unique set of fitted resonance parameters related to the 17O* compound-system.
Depletion uncertainty analysis to the MYRRHA fuel assembly model
Authors: Hernandez Solis Augusto , Stankovskiy Alexey , Fiorito Luca , Van den Eynde Gert
Published: September 2020

In this work, the objective is to perform an uncertainty analysis on a MYRRHA -Rev.1.6 irradiation cycle study, being applied to a depletion scenario of a single fresh fuel assembly while assuming reflective boundary conditions. Such analysis is statistically based on the application of Wilk’s method of building tolerance limits after 100 depletion calculations were performed with the SERPENT2 code. Due to the computational burden of such type of simulations, this propagation of nuclear data covariances study (allowed by the fast computational performance of SERPENT2) was done at constant power, constant flux and, in a final exercise, at constant power with the addition of fission yield uncertainties (all of these cases employed ENDF/B-VII.1 data). It was observed that while depleting at constant power, the statistical variation of key fission products such as148Nd is almost not present because of the normalization factor applied to the flux. In contrast, the irradiation at constant flux reveals dependence on burnup. Finally, the added fission yield uncertainties make clear the fact that they directly impact the degree of final uncertainty computed for fission products exemplified by148Nd and135Xe important for burnup estimation and reactor operation, respectively.
Method and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files: Major findings of the NEA WPEC Subgroup 39
Authors: Salvatores Massimo , Palmiotti Giuseppe
Published: September 2020

Nuclear data adjustments using integral experiments play since several decades a crucial role in providing reactor designers and fuel cycle analysts with nuclear data with reduced and validated uncertainties in order to allow design optimization while meeting safety and economics requirements. Adjustment methods, choice of integral experiments and covariance data assessment should be carefully defined in order to produce credible and physically acceptable adjustments, applicable to a wide range of systems. The OECD-NEA has established a series of Expert Groups since 2005 to investigate the key scientific issues and to provide recommendations for applications. The present paper discusses the major results of the most recent of these Expert Groups together with an indication of the path forward .
Nuclear data adjustment using Bayesian inference, diagnostics for model fit and influence of model parameters
Authors: Kumar D. , Alam S. B. , Sjöstrand H. , Palau J.M. , De Saint Jean C.
Published: September 2020

The mathematical models used for nuclear data evaluations contain a large number of theoretical parameters that are usually uncertain. These parameters can be calibrated (or improved) by the information collected from integral/differential experiments. The Bayesian inference technique is used to utilize measurements for data assimilation. The Bayesian approximation is based on the least-square or Monte-Carlo approaches. In this process, the model parameters are optimized. In the adjustment process, it is essential to include the analysis related to the influence of model parameters on the adjusted data. In this work, some statistical indicators such as the concept of Cook’s distance; Akaike, Bayesian and deviance information criteria; effective degrees of freedom are developed within the CONRAD platform. Further, these indicators are applied to a test case of 155Gd to evaluate and compare the influence of resonance parameters.
Using covariance weighted euclidean distance to assess the dissimilarity between integral experiments
Authors: Kai Fan , Fu Li , Jiangmeng Wang , Yanpeng Yin , Linli Song , Sanbing Wang
Published: September 2020

Integral experiments especially criticality experiments help a lot in designing either new nuclear reactor or criticality assembly. The calculation uncertainty of the integral parameter which is introduced in by the nuclear data uncertainty is larger than the experimental uncertainty for most high-enriched uranium metal experiments, therefore the integral experiment is still very useful. There are lots of integral experiments have been done and documented. It should be considered carefully that which integral experiments should be used in applications. For instance, if the aim of the application is to validate the criticality design of a new reactor, integral experiments which are similar to the new reactor should be used. There are several similarity measures which have been used to assess the similarity between integral experiments, such as E similarity measure, G similarity measure and C similarity measure. But, there is no standard rule to choose which similarity measure should be used to assess the similarity between integral experiments in specific application. Another shortage of these similarity measures is that the thresholds of these similarity measures which should be set to judge whether the integral experiments are similar to each other or not have no clear physical meaning. In this paper, we will analyze the existing similarity measures which have been used to assess the similarity between integral experiments, and test some other similarity or dissimilarity measures which have been used in other research fields. After testing the Tanimato similarity measure and Euclidean distance, we find that the covariance weighted Euclidean distance is well suit to assess the dissimilarity between integral experiments, and the physical meaning of its threshold is clear. We recommend using covariance weighted Euclidean distance to assess the dissimilarity between integral experiments.
Comprehensive stochastic sensitivities to resonance parameters
Authors: TAMAGNO Pierre , VANDERMEERSCH Elias
Published: September 2020

Integral experiments in reactors or critical configurations claim to have very small experimental and technological uncertainties. Therefore these latter can be considered valuable experimental information in nuclear data evaluation. Because in the evaluation process the information is carried by model parameters, to perform a rigorous feedback on a nuclear model parameters p - for instance using a measured reactivity ρ-sensitivities S =∂ρ/ρ⁄∂p/p are needed. In usual integral feedbacks, sensitivity to multi-group cross sections are first obtained with deterministic code using perturbation theory. Then these multi-group cross section sensitivities are “convoluted” with parameter sensitivities in order to provide the sensitivity on nuclear model parameter. Recently stochastic approaches have been elaborated in order to obtain continuous cross-section sensitivities thus avoiding the multi-group discretization. In the present work we used the recent Iterated Fission Probability method of the TRIPOLI4 code [1] in order to obtain directly the sensitivity to nuclear physics parameters. We focus here on the sensitivity on resonance parameters and exemplified the method on the computation of sensitivities for 239Pu and 16O resonance parameters one the ICSBEP benchmark PST001. The underlying nuclear model describing resonant cross sections are based in the R-matrix formalism [2] that provides not only the interaction cross sections but also the angular distribution of the scattered neutrons i.e. differential cross sections. The method has thus been updated in order to compute parameter sensitives that include both contributions: cross section and angular distributions. This extension of the method was tested with exact perturbation of angular distribution and fission spectrum.
Experimental validation of the temperature behavior of the ENDF/B-VIII.0 thermal scattering kernel for light water
Authors: Marquez Damian Jose Ignacio , Dawidowski Javier , Granada Rolando Jose , Cantargi Florencia , Romanelli Giovanni , Helman Christian , Krzystyniak Matthew , Skoro Goran , Roubtsov Danila
Published: September 2020

The Neutron Physics Department at Centro Atómico Bariloche developed new models for the interaction of thermal neutrons with water which have been validated against experimental data, including new thermal scattering experiments, and were adopted for the release of ENDF/B-VIII.0. Although the older models are, in general, good for most applications, some discrepancies had appeared in the case of heavy water, and this motivated new measurements that validated the new model. In the case of light water, the new model predicts a reduction of the total cross section around 0.025 eV when the temperature is increased from room temperature. This reduction, that is not predicted by the existing models, and potentially affects the calculation of temperature reactivity coefficients in nuclear reactors, has been traced to a shift in the vibrational frequency spectrum of liquid water. The only experimental data previously available is from an experiment performed at the Demokritos reactor in the ’60s at 293 K and 473 K, which validates the new model when the cross section ratios are computed. In order to verify this effect at a lower temperature range, a transmission experiment was carried out at the VESUVIO spectrometer in the ISIS facility in the UK in June 2018, measuring the total neutron cross section in the range from 283 K to 353 K. Here, we present this new experimental data and its comparison with the models.
Thermal neutron scattering data for liquid molten salt LiF-BeF2
Authors: Wang Jia , Song Hongzhou , Bai Yun , Sun Weili
Published: September 2020

Ab initio molecular dynamics (AIMD) methods were used to calculate the density of states (DOS) for liquid molten salt Li2BeF4 (LiF-BeF2) in different temperatures. The Egelstaff and Schofield effective width model was used to obtain the diffusion-type spectrum of the DOS and the corresponding partial s (α, β). Finally, the thermal neutron scattering data for liquid molten salt LiF-BeF2 were given.
High-resolution neutron time-of-flight measurements for light water at the Spallation Neutron Source (SNS), Oak Ridge National Laboratory
Authors: Leal Luiz , Jaiswal Vaibhav , Kolesnikov Alexander I.
Published: September 2020

Series of light water inelastic neutron scattering experiments have been made at the Oak Ridge National Laboratory (ORNL), Spallation Neutron Source (SNS) covering temperatures ranging from 295 K to 600 K and pressures of 1 bar and 150 bar. The temperatures and pressures ranges correspond to that of pressurized light water reactors. The inelastic scattering measurements will help the development of light water thermal scattering kernels, also known asS(α,β) thermal scattering law (TSL), in a consistent fashion given the amount and the quality of the measured data. Light water thermal scattering evaluations available in existing nuclear data libraries have certain limitations and pitfalls. This paper introduces the state of the art of the light water thermal scattering cross-section data not only for room temperature but as well as for reactor operating temperatures, i.e. 550 - 600 K. During the past few years there has been a renewed interest in re-investigating the existing TSL models and utilize the recent experimental data or perform molecular dynamics simulations. It should be pointed out that no single TSL evaluation is based entirely on experimental data and one has to rely on TSL models or a combination of both. New TOF measurement of light water at the SNS, with a detailed description of the experimental setup, measurement conditions, and the associated foreseen results is presented in this paper. The analysis of the experimental data would help in validating the existing approach based on old experimental data or based on molecular dynamic simulations using classical water models, knowledge of which is very important to generate TSL libraries at reactor operating conditions.
Utilizing nuclear data in delayed gamma-ray spectroscopy inverse Monte Carlo analysis
Authors: Rodriguez Douglas Chase , Abbas Kamel , Crochemore Jean-Michel , Koizumi Mitsuo , Nonneman Stefan , Pedersen Bent , Rossi Fabiana , Seya Michio , Takahashi Tohn
Published: September 2020

Safeguards verification of uranium and plutonium in high-radioactivity nuclear material is currently performed using destructive analysis techniques. However, the preparation method is a burden on both the safeguards inspectors and facility operators. While nondestructive assay (NDA) techniques would improve the efficiency and time, there are no passive NDA techniques available to directly verify the U and Pu content. As an alternative, the JAEA and JRC are collaboratively developing the Delayed Gamma-ray Spectroscopy (DGS) active-interrogation NDA technique to evaluate the fissile composition from the unique fission product yield distributions. To analyze the data we are developing an Inverse Monte Carlo (IMC) method that simulates the interrogation and evaluates the individual contributions from the mixed nuclear material to the composite spectrum. While the current nuclear data affects the ability to evaluate the composition, the IMC analysis method can be used to determine the systematic uncertainty contributions and has the potential to improve the nuclear data. We will present the current status of the DGS collaborative work as it relates to the development of the DGS IMC analysis.
Charged particle activation facility in NPI CAS and in future GANIL/SPIRAL2-NFS
Authors: Mrazek Jaromir , Simeckova Eva , Behal Radomir , Glagolev Vadim , Vesely František , Stefanik Milan , Majerle Mitja , Novak Jan , Ansorge Martin , Sivacek Ivan , Vrzalova Jitka , Ledoux Xavier , de Oliveira Santos Francois , Fischer Ulrich , Klix Axel , Avrigeanu Marilena , Avrigeanu Vlad
Published: September 2020

The proton, deuteron and alpha induced reactions are of a great interest for the assessment of induced radioactivity of accelerator components, targets and beam stoppers as well as isotope production for medicine and also to nuclear astrophysics. We present a new irradiation chamber for activation measurements, that forms a prolongation of long-term experimental activities using stacked-foil activation technique in NPI CAS, Řež. The chamber is based on an airlock system and is coupled to a pneumatic transfer system delivered by KIT Karlsruhe. This system is installed in GANIL/SPIRAL2-NFS and will be used for proton, deuteron and alpha particle activation measurements with long- and short-lived isotopes.
Neutron spectrum determination of p+Be reaction for 30 MeV protons using the multi-foil activation technique
Authors: Stefanik Milan , Simeckova Eva , Bem Pavel , Majerle Mitja , Novak Jan , Ansorge Martin , Mrazek Jaromir , Stursa Jan
Published: September 2020

At the NPI in Rez, the p + Be source reaction was investigated for 30 MeV proton beam and thick beryllium target. For neutron field determination of the p(30)+Be source reaction in close source-to-sample distance, the multi-foil activation technique with a set of 10 activation materials (Au, Co, Lu, Ti, In, Al, Y, Fe, Ni, Nb) was utilized. From resulting reaction rates, the neutron spectrum was reconstructed using the SAND-II unfolding code. New neutron field of white spectrum up to 28 MeV has an intensity of 8.6 × 1010 cm−2s−1 close to target. The obtained neutron field extends the utilization of cyclotron-based fast neutron sources at the NPI and provides new experimental opportunities for future irradiation experiments such as fast neutron activation analysis, nuclear data validation, and radiation damage study of electronics and materials for nuclear energetics.
New detection systems at U-120M cyclotron
Authors: Novák Jan , Ansorge Martin , Bém Pavel , Majerle Mitja , Mrázek Jaromír , Šimečková Eva , Štefánik Milan
Published: September 2020

Intensive neutron beams with energies up to 33 MeV are produced using cyclotron driven broad-spectrum and quasi-monoenergetic neutron generators at the NPI CAS. The neutron beams are well characterized with the TOF and PRT measurements. The segmented Fe-CH2 collimator is used to collimate the neutron beam and two detection systems are being developed for the studies of the reactions with neutrons. The first one is the detection system of the charged particles at different angles from the (neutron, charged particle) reactions in a vacuum chamber, the second is an array of four HPGe detectors for the detection of direct and delayed gamma photons produced in reactions of the studied material with neutrons. The advanced bunching system is also being developed at the U120M cyclotron. It will allow to direct a short (few ns long) pulse of accelerated particles to the neutron converter with the 1 µs delay between bunches. Together with 7 m long flight path this extension will open new possibilities in the cross section measurements.
Current overview of ICSBEP and IRPhEP benchmark evaluation practices
Authors: Bess John Darrell , Ivanova Tatiana
Published: September 2020

Two projects sanctioned by the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) have over two decades of experience developing established and comprehensive data sets in handbooks supporting criticality safety and reactor physics. The International Criticality Safety Benchmark Evaluation Project (ICSBEP) and the International Reactor Physics Experiment Evaluation Project (IRPhEP) serve as examples of quality and excellence in preserving our experimental data heritage and establishing integral benchmark standards upon which current and future modeling, validation, and safety efforts can be supported. Evaluation practices have evolved with each year of these projects to include additional benchmark experiment data, establish more comprehensive techniques for evaluation of uncertainties and biases, and encourage established high-quality peer-review efforts. This paper will summarize the current format of the handbooks, best-practices for a comprehensive benchmark evaluation, recent activities and protocol within these projects, and a look into future identified needs and activities.
Measurement of the delayed-neutron multiplicity and time constants in the thermal neutron induced fission of 235U at ILL
Authors: Foligno Daniela , Leconte Pierre , Serot Olivier , Geslot Benoit , De Izarra Grégoire , Chebboubi Abdelhazize , Sardet Alix , Diakaki Maria , Tamagno Pierre , Billebaud Annick , Lecolley François-René , Soldner Torsten , Köster Ulli , Mutti Paolo , Pepino Alexandra , Méplan Olivier , Kessedjian Grégoire , Lecouey Jean-Luc , Mathieu Ludovic , Marie-Nourry Nathalie
Published: September 2020

Delayed-neutron (DN) data is essential in inherent reactor safety and reactor control since it is needed for the estimation of the reactivity. Nowadays, discrepancies among the data in various international databases (JEFF, ENDF, JENDL) are large and bring excessive conservatism in the safety margins. The ALDEN (Average Lifetime of DElayed Neutrons) experiment, built in a collaboration between CEA and CNRS, aimed at re-measuring the DN data associated with several fissioning systems (average delayed-neutron yield and kinetic parameters). The first experimental campaign consisted in the integral measurement of the DN activity after the irradiation of an 235U target. It took place under the cold neutron flux of ILL (Institut Laue-Langevin) at the beginning of September 2018, in the PF1b experimental zone (doi:10.1016/j.nima.2006.03.020). The data analysis gave an average DN yield of 1.631E-02(2) DN/fiss and a mean precursors’ half-life of 8.93(9) s. The results are consistent with the literature, but they are affected by one third of the uncertainty.
The High-Energy Intra-Nuclear Cascade Liège-based Residual (HEIR) nuclear data library
Authors: Fleming M. , David J-C. , Rodríguez-Sánchez J.L. , Fiorito L. , Gilbert M. , Stainer T.
Published: September 2020

It is standard practice for nuclear data files to include tabulated data for distinct reaction channels for incident energies up to 20-30 MeV. Above these energies, the assumptions implicit in the definition of individual channels break down and event generators are typically used within codes that simulate nuclear observables in applications. These offer robust simulation of the physics but increase the computational burden. So-called ‘high-energy’ nuclear data files have been produced, but the well-known libraries are more than a decade old and rely upon models developed many years before their release. This presentation describes a modern library with a high level of production automation that offers regular updates as the models it is based upon are improved.

The most recent versions of the intra-nuclear cascade and de-excitation models available within Geant4 were used to generate tabulated data of residual nuclide production. For the first released library, the INCL++5.3 and ABLA version within Geant4 v10.3 were used to calculate over 1012 incident protons over 2095 target isotopes with incident energies up to 1 GeV. These were collated into tabulated data in the international-standard ENDF-6 format. The resulting files were provided as group-wise files and were distributed as HEIR-0.1 with the FISPACT-II version 4.0 release.

A second library, HEIR-0.2, has been generated using the new INCL++6.0 and C++ translation of the ABLA07 model available within Geant4 v10.4. Simulations were performed using incident protons, neutrons, deuterons and π±. An improved agreement is observed in the comparison to experimental data not only between the two versions, but against the other well-known high-energy nuclear data files and models available within Geant4. This benchmark includes mass and isotopic distributions, as well as incident-energy dependent cumulative and independent cross sections from the EXFOR database.
Peak neutron production from the 7Li(p,n) reaction in the 20-35 MeV range
Authors: Majerle Mitja , Prokofiev Alexander V. , Ansorge Martin , Bém Pavel , Hladík David , Mrázek Jaromir , Novák Jan , Šimečková Eva , Štefánik Milan
Published: September 2020

New experimental data on the peak neutron production in the 7Li(p,n) reaction were collected during several irradiation campaigns at the NPI CAS. Time-of-flight method was used to measure the number of the peak neutrons in the forward direction, and the number of produced 7Be nuclei was determined using γ-spectrometry. The new measurement results are compared with experimental data from the literature and used for the validation of several different systematics and nuclear data libraries developed over the years.
Comparative survey of evaluated nuclear data libraries for fusion-relevant neutron activation spectrometry
Authors: Raj Prasoon , Fischer Ulrich , Klix Axel , Contributors JET
Published: September 2020

The neutron flux-spectrum in a fusion device is frequently determined with activation foils and adjustment of a guess-spectrum in unfolding codes. Spectral-adjustment being a rather complex and uncertain procedure, we are carefully streamlining and evaluating it for upcoming experiments. Input nuclear cross-section data holds a vital position in this. This paper presents a survey of common dosimetry reactions and available data files relevant for fusion applications. While the IRDFF v1.05 library is the recommended source, many reactions of our interest are found missing in this. We investigated other standard sources: ENDF/B-VIII.0, EAF-2010, TENDL-2017, JENDL-4.0 etc. And, we analysed two experiments to ascertain the sensitivity of the spectral adjustment to the choice of nuclear data. One was performed with D-D (approx. 2.5 MeV peak) neutrons at the Joint European Torus (JET) machine and another with a white neutron field (approx. 33 MeV endpoint energy) at Nuclear Physics Institute (NPI) of Řež. Choice of cross-section source has affected the integral fluxes (<5%), reaction rates (<10%), total fluxes in some sensitive energy-regions (>20%) and individual group fluxes (<30%). Based on this experience, essential qualitative conclusions are made to improve the fusion activation-spectrometry.
On the impact of nuclear data uncertainties on LWR neutron dosimetry assessments
Authors: Vasiliev Alexander , Pecchia Marco , Rochman Dimitri , Ferroukhi Hakim , Alhassan Erwin
Published: September 2020

In this work, an overview on the relevance of the nuclear data (ND) uncertainties with respect to the Light Water Reactors (LWR) neutron dosimetry is presented. The paper summarizes results of several studies realized at the LRT laboratory of the Paul Scherrer Institute over the past decade. The studies were done using the base LRT calculation methodology for dosimetry assessments, which involves the neutron source distribution representation, obtained based on validated CASMO/SIMULATE core follow calculation models, and the subsequent neutron transport simulations with the MCNP® software. The methodology was validated using as reference data results of numerous measurement programs fulfilled at Swiss NPPs. Namely, the following experimental programs are considered in the given overview: PWR “gradient probes” and BWR fast neutron fluence (FNF) monitors post irradiation examination (PIE). For the both cases, assessments of the nuclear data related uncertainties were performed. When appropriate, a cross-verification of the deterministic and stochastic based uncertainty propagation techniques is provided. Furthermore, the observations on which particular neutron induced reactions contribute dominantly to the overall ND-related uncertainties are demonstrated. The presented results should help with assessing the overall impact of the various nuclear data uncertainties with respect to dosimetry applications and provide relevant feedback to the nuclear data evaluators.
Benchmarking the new ENDF/B-VIII.0 nuclear data library for the first core of Indonesian multipurpose research reactor (RSG GAS)
Authors: Hartanto Donny , Gillette Victor , Sembiring Tagor Malem , Liem Peng Hong
Published: September 2020

The Indonesian Multipurpose Research Reactor namely Reaktor Serba Guna G.A. Siwabessy (RSG GAS) is a 30 MWth (max.) pool-type reactor loaded with plate-type low-enriched uranium fuel, using light water as coolant and moderator, and beryllium as reflector. The benchmark of the 1st criticality core of RSG GAS using different nuclear data libraries such as JENDL-4.0, JENDL-3.3, ENDF/B-VII.0, and JEFF-3.1 have been performed in the previous work and compared with the experiment result. In this work, the newly released ENDF/B-VIII.0 neutron reaction and thermal neutron scattering libraries will be used and the important neu-tronics parameters such as multiplication factor, kinetics parameters, and fission reaction rate will be calculated using Monte Carlo code MCNP6.2 and compared against the previous work and the experiment result.