The 35Cl(n, p)35S reaction plays a key role in neutron dosimetry for Boron Neutron Capture Therapy, in the synthesis of the isotope 36S, whose astrophysical origin remains unresolved, and in the design of next-generation molten-salt reactors. Its relevance has motivated its inclusion in the High Priority Request List (HPRL) of NEA. The goal of this work is to determine the 35Cl(n, p)35S cross-section from thermal energy to 120 keV for the first time ever in a single measurement, thus reducing systematic uncertainties related to the normalization to the thermal value. This had been a subject of concern in previous evaluations of this reaction. We made use of the Time-of-Flight technique with microMEGAS detectors at Experimental Area 2 (EAR-2) of n_TOF facility at CERN. The 10B (n, α ) 7Li and 235U(n, f) reactions were used as references. Rutherford Back-scattering Spectrometry was performed at Centro Nacional de Aceleradores (CNA) in Sevilla, in order to accurately determine the masses of the irradiated samples. We obtained a thermal cross-section of 0.470 ± 0.009 barns. The 1/v energy dependence of the cross-section is observed up to the first resonance at 0.398 keV, the resonances up to 120 keV are analyzed and resonance parameters extracted using SAMMY. Maxwellian Averaged Cross-Section (MACS) was calculated for k_B T from 1 to 100 keV, and lower values compared to estimations from ENDF were found, e.g., 1.07 ± 0.20 mb at k_BT=30 keV. The thermal cross-section and first two resonances are in agreement with the latest evaluation in ENDF/B-VIII.1, while remarkably lower resonance strengths were found for high energy resonances.

Nuclear research reactors ( RR ) are essential facilities in countries implementing nuclear power plants and are used for experiments necessary for commercial reactor development, training and education programs, and many other applications not related to nuclear energy production (e.g., isotope production, neutron sources, materials science). Europe has a broad and very diverse landscape of RRs, many of which have been in operation for 30-60 years, are well maintained and regularly modernized. However, financial pressures caused by a combination of declining interest and the lack of a sound financial model have led to the closure of many of them (e.g. OSIRIS in Saclay, JEEP II research reactor at IFE Kjeller and BER2 in Berlin). These negative trends called for coordinated European action to assess the impact of the declining number of RRs. The Towards Optimized Use of Research Reactors (TOURR) project was a response to this challenge. Its main objective was to assess the status of the EU RR fleet and to develop a strategy for the refurbishment and construction of new RR in Europe. The assessment was based on analysed data obtained through extensive questionnaires sent to all operating European RR. The analysis revealed gaps in terms of lack of long-term funding, lack of manpower and lack of communication between RRs and their customers. It also showed threats of further European RR closures. Regarding the long-term EU RR strategy, the main recommendations of the TOURR project are to build (at least) two RRs, a medium-flux multipurpose reactor and a flexible zero-power facility. Both reactor cores could be part of a single facility built at the European level and accessible to all EU Member States.

Background: The ^35Cl(n, p)^35S reaction is of special interest in three different applications. First, in Boron Neutron Capture Therapy due to the presence of ^35Cl in brain and skin tissue. Second, it is involved in the creation of ^36S, whose astrophysical origin remains unresolved. Third, in the designing of fast nuclear reactors of new generation based on molten salts. Purpose: To measure the ^35Cl(n, p)^35S cross-section from thermal energy to 120 keV, determine the resonance parameters in this range and Maxwellian Averaged Cross-Section (MACS). Method: We made use of the Time-of-Flight technique with microMEGAS detectors at Experimental Area 2 (EAR-2) of n_TOF facility at CERN. The ^10B(n, α)^7Li and ^235U(n, f) reactions were used as references. Rutherford Back-scattering Spectrometry technique was performed at Centro Nacional de Aceleradores (CNA) in Sevilla, in order to accurately determine the masses of the irradiated samples. Results: We obtain a thermal cross-section of 0.470 ± 0.009 barns. The 1/v energy dependence of the cross-section is observed up to the first resonance at 0.398 keV, the resonances up to 120 keV are analyzed and MACS calculated for k_B T from 1 to 100 keV. Conclusions: The ^35Cl(n, p)^35S cross-section has been obtained over a wide energy range for the first time, with high accuracy across the aforementioned range. The thermal cross-section and first two resonances are in agreement with latest evaluation in ENDF/B-VIII.1, while lower resonance strength was found for high energy resonances. These data are used to calculate the MACS for different k_B T.

Nuclear research reactors ( RR ) are essential facilities in countries implementing nuclear power plants and are used for experiments necessary for commercial reactor development, training and education programs, and many other applications not related to nuclear energy production (e.g., isotope production, neutron sources, materials science). Europe has a broad and very diverse landscape of RRs, many of which have been in operation for 30-60 years, are well maintained and regularly modernized. However, financial pressures caused by a combination of declining interest and the lack of a sound financial model have led to the closure of many of them (e.g. OSIRIS in Saclay, JEEP II research reactor at IFE Kjeller and BER2 in Berlin). These negative trends called for coordinated European action to assess the impact of the declining number of RRs. The Towards Optimized Use of Research Reactors (TOURR) project was a response to this challenge. Its main objective was to assess the status of the EU RR fleet and to develop a strategy for the refurbishment and construction of new RR in Europe. The assessment was based on analysed data obtained through extensive questionnaires sent to all operating European RR. The analysis revealed gaps in terms of lack of long-term funding, lack of manpower and lack of communication between RRs and their customers. It also showed threats of further European RR closures. Regarding the long-term EU RR strategy, the main recommendations of the TOURR project are to build (at least) two RRs, a medium-flux multipurpose reactor and a flexible zero-power facility. Both reactor cores could be part of a single facility built at the European level and accessible to all EU Member States.

The design of fast reactors burning MOX fuels requires accurate capture and fission cross sections. For the particular case of neutron capture on 242Pu, the NEA recommends that an accuracy of 8-12 energy region (2 keV-500 keV) compared to their estimation of 35 current uncertainty. Integral irradiation experiments suggest that the evaluated cross section of the JEFF-3.1 library overestimates the 242Pu(n,γ) cross section by 14 addition, the last measurement at LANSCE reported a systematic reduction of 20-30 data sets. In the present work this cross section has been determined up to 600 keV in order to solve the mentioned discrepancies. A 242Pu target of 95(4) mg enriched to 99.959 capture cross section of 242Pu has been obtained between 1 and 600 keV with a systematic uncertainty (dominated by background subtraction) between 8 and 12 reducing the current uncertainties of 35 by the NEA in a large energy range. The shape of the cross section has been analyzed in terms of average resonance parameters using the FITACS code as implemented in SAMMY, yielding results compatible with our recent analysis of the resolved resonance region.The results are in good agreement with the data of Wisshak and Käppeler and on average 10-14 keV, which helps to achieve consistency between integral experiments and cross section data. At higher energies our results show a reasonable agreement within uncertainties with both ENDF/B-VII.1 and JEFF-3.2. Our results indicate that the last experiment from DANCE underestimates the capture cross section of 242Pu by as much as 40

Within the frame of the EU H2020 program SANDA project, sensitivity and uncertainty analyses have been performed for the ESFR, ASTRID and ALFRED reactor concepts and the multi-purpose flexible irradiation facility MYRRHA. Relevant reactor parameters, namely the effective multiplication factor, the effective delayed neutron fraction, the Doppler reactivity coefficient, the void worth and the worth of control rods have been investigated. SCALE, Serpent 2 and MCNP6.2+SUMMON codes together with the covariance data of the JEFF-3.3 nuclear data library have been used for this study. A ranking of the most important isotopes and reactions impacting the mentioned parameters has been derived for all these systems. Uncertainties have been quantified and have been found to be higher than the target accuracies proposed. Therefore, recommendations for improvement of nuclear data are given.

The Se-78(n, gamma)Se-79 cross section has a high impact on the abundances of Se-78 produced during the slow neutron capture process (s process) in massive stars. A measurement of the Se-78 radiative neutron capture cross section has been performed at the Neutron Time-of-Flight facility at CERN using a set of liquid scintillation detectors that have been optimized for a low sensitivity to neutrons. We present resonance capture kernels up to 70 keV and cross section from 70 to 600 keV. Maxwellian-averaged cross section (MACS) values were calculated for stellar temperatures between kT = 5 and 100 keV, with uncertainties between 4.6% and 5.8%. The new MACS values result in substantial decreases of 20-30% of Se-78 abundances produced in the s process in massive stars and AGB stars. Massive stars are now predicted to produce subsolar Se-78/Se-76 ratios, which is expected since Se-76 is an s-only isotope, while solar Se-78 abundances have also contributions from other nucleosynthesis processes.

The cross section of the ^89 Y(n, γ ) reaction has important implications in nuclear astrophysics and for advanced nuclear technology. Given its neutron magic number N = 50 and a consequent small neutron capture cross section, ^89 Y represents one of the key nuclides for the stellar s-process. It acts as a bottleneck in the neutron capture chain between the Fe seed and the heavier elements. Moreover, it is located at the overlapping region, where both the weak and main s-process components take place. ^89 Y, the only stable yttrium isotope, is also used in innovative nuclear reactors. Neutron capture and transmission measurements were performed at the time-of-flight facilities n_TOF at CERN and GELINA at JRC-Geel. Resonance parameters of individual resonances were extracted from a resonance analysis of the experimental transmission and capture yields, up to a neutron incident energy of 95 keV. Even though a comparison with results reported in the literature shows differences in resonance parameters, the present data are consistent with the Maxwellian averaged cross section suggested by the astrophysical database KADoNiS.

The ^246 Cm(n, γ ) and ^248 Cm(n, γ ) cross-sections have been measured at the Experimental Area 2 (EAR2) of the n_TOF facility at CERN with three C _6 D _6 detectors. This measurement is part of a collective effort to improve the capture cross-section data for Minor Actinides (MAs), which are required to estimate the production and transmutation rates of these isotopes in light water reactors and innovative reactor systems. In particular, the neutron capture in ^246 Cm and ^248 Cm open the path for the formation of other Cm isotopes and heavier elements such as Bk and Cf and the knowledge of (n, γ ) cross-sections of these Cm isotopes plays an important role in the transport, transmutation and storage of the spent nuclear fuel. The reactions ^246 Cm(n, γ ) and ^248 Cm(n, γ ) have been the two first capture measurements analyzed at n_TOF EAR2. Until this experiment and two recent measurements performed at J-PARC, there was only one set of data of the capture cross-sections of ^246 Cm and ^248 Cm, that was obtained in 1969 in an underground nuclear explosion experiment. In the measurement at n_TOF a total of 13 resonances of ^246 Cm between 4 and 400 eV and 5 of ^248 Cm between 7 and 100 eV have been identified and fitted. The radiative kernels obtained for ^246 Cm are compatible with JENDL-5, but some of them are not with JENDL-4, which has been adopted by JEFF-3.3 and ENDF/B-VIII.0. The radiative kernels obtained for the first three ^248 Cm resonances are compatible with JENDL-5, however, the other two are not compatible with any other evaluation and are 20 and 60

The thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC) has been determined using several 3He proportional counter detectors. Bare and Cd shielded counters were used in a series of long measurements. Pulse shape discrimination techniques were applied to discriminate between neutron and gamma signals as well as other intrinsic contributions. Montecarlo simulations allowed us to estimate the sensitivity of the detectors and calculate values for the background flux of thermal neutrons inside Hall-A of LSC. The obtained value is (3.5±0.8)×10−6 n/cm2s, and is within an order of magnitude compared to similar facilities.

The neutron capture cross section of 241 Am is an important quantity for nuclear energy production and fuel cycle scenarios. Several measurements have been performed in recent years with the aim to reduce existing uncertainties in evaluated data. Two previous measurements, performed at the 185 m flight-path station EAR1 of the neutron time-of-flight facility n_TOF at CERN, have permitted to substantially extend the resolved resonance region, but suffered in the near-thermal energy range from the unfavorable signal-to-background ratio resulting from the combination of the high radioactivity of 241 Am and the rather low thermal neutron flux. The here presented 241 Am(n,γ) measurement, performed with C 6 D 6 liquid scintillator gamma detectors at the 20 m flight-path station EAR2 of the n_TOF facility, took advantage of the much higher neutron flux. The current status of the analysis of the data, focussed on the low-energy region, will be described here.

Background: The $^{14}\mathrm{N}(n,p)^{14}\mathrm{C}$ reaction is of interest in neutron capture therapy, where nitrogen-related dose is the main component due to low-energy neutrons, and in astrophysics, where $^{14}\mathrm{N}$ acts as a neutron poison in the $s$ process. Several discrepancies remain between the existing data obtained in partial energy ranges: thermal energy, keV region, and resonance region.Purpose: We aim to measure the $^{14}\mathrm{N}(n,p)^{14}\mathrm{C}$ cross section from thermal to the resonance region in a single measurement for the first time, including characterization of the first resonances, and provide calculations of Maxwellian averaged cross sections (MACS).Method: We apply the time-of-flight technique at Experimental Area 2 (EAR-2) of the neutron time-of-flight (n_TOF) facility at CERN. $^{10}\mathrm{B}(\mathrm{n},\ensuremath{\alpha})^{7}\mathrm{Li}$ and $^{235}\mathrm{U}(n,f)$ reactions are used as references. Two detection systems are run simultaneously, one on beam and another off beam. Resonances are described with the $R$-matrix code sammy.Results: The cross section was measured from subthermal energy to 800 keV, resolving the first two resonances (at 492.7 and 644 keV). A thermal cross section was obtained ($1.809\ifmmode\pm\else\textpm\fi{}0.045$ b) that is lower than the two most recent measurements by slightly more than one standard deviation, but in line with the ENDF/B-VIII.0 and JEFF-3.3 evaluations. A 1/$v$ energy dependence of the cross section was confirmed up to tens of keV neutron energy. The low energy tail of the first resonance at 492.7 keV is lower than suggested by evaluated values, while the overall resonance strength agrees with evaluations.Conclusions: Our measurement has allowed determination of the $^{14}\mathrm{N}(n,p)$ cross section over a wide energy range for the first time. We have obtained cross sections with high accuracy (2.5%) from subthermal energy to 800 keV and used these data to calculate the MACS for $kT=5$ to $kT=100$ keV.

We report on the thermal neutron flux measurements carried out at the Laboratorio Subterráneo de Canfranc (LSC) with two commercial 2^''× 2^'' CLYC detectors. The measurements were performed as part of an experimental campaign at LSC with ^3 He detectors, for establishing the sensitivity limits and use of CLYCs in low background conditions. A careful characterization of the intrinsic α and γ -ray background in the detectors was required and done with dedicated measurements. It was found that the α activities in the two CLYC crystals differ by a factor of three, and the use of Monte Carlo simulations and a Bayesian unfolding method allowed us to determine the specific α activities from the ^238 U and ^232 Th decay chains. The simulations and unfolding also revealed that the γ -ray background registered in the detectors is dominated by the intrinsic activity of the components of the detector such as the aluminum housing and photo-multiplier and that the activity within the crystal is low in comparison. The data from the neutron flux measurements with the two detectors were analyzed with different methodologies: one based on an innovative α /neutron pulse shape discrimination method and one based on the subtraction of the intrinsic α background that masks the neutron signals in the region of interest. The neutron sensitivity of the CLYCs was calculated by Monte Carlo simulations with MCNP6 and GEANT4. The resulting thermal neutron fluxes are in good agreement with complementary flux measurement performed with ^3 He detectors, but close to the detection limit imposed by the intrinsic α activity.

The 77Se(n, & gamma;) reaction is of importance for 77Se abundance during the slow neutron capture process in massive stars. We have performed a new measurement of the 77Se radiative neutron capture cross section at the Neutron Time-of-Flight facility at CERN. Resonance capture kernels were derived up to 51 keV and cross sections up to 200 keV. Maxwellian-averaged cross sections were calculated for stellar temperatures between kT = 5 keV and kT = 100 keV, with uncertainties between 4.2% and 5.7%. Our results lead to substantial decreases of 14% and 19% in 77Se abundances produced through the slow neutron capture process in selected stellar models of 15M0 and 2M0, respectively, compared to using previous recommendation of the cross section.

A dedicated digital data acquisition (DAQ) system has been developed for innovative nuclear data measurements, from time-of-flight to irradiation experiments as well as other basic nuclear physics experiments. The DAQ system is based on fast digitizers with 14 bits resolution and 1 GS/s sampling rate for reliable pulse shape discrimination, energy and timing resolution measurements. Thanks to the high throughput provided by the PCIe bus, data can be processed at CPU or co-processor level, thus allowing great flexibility and reliability. The use of an external clock system and a dedicated triggering system guarantee a very precise synchronization with other possible subsystems in any experimental setup. Finally, its modularity allows to build a flexible and scalable system.

An error was discovered in the neutron flux used to normalize the Ge-70(n, gamma) data. The same error affects data in Ref. [1] and a separate correction will be published. Updated resonance kernels are printed in Tables I and II. Systematic uncertainties in the capture kernels are 3.2% below and 5.1% above 10 keV neutron energy. Analysis of the (updated) resonance parameters under the same assumptions as in Ref. [1] yield the average resonance parameters <Gamma(gamma)> = 200(12) meV with sigma Gamma(gamma) = 62( 8) and D-0 = 1400(200) eV, where <Gamma(gamma), sigma Gamma(gamma) and D-0 are expectation value of s-wave radiation width, standard deviation of the distribution of Gamma(gamma). and s-wave resonance spacing, respectively. The difference in D-0 does not come from use of correct flux. We found a bug in the code used for determination of D-0 of Ge-70. The corrected unresolved cross section from 25-300 keV is shown in Fig. 1. The correction of the flux mainly affects the data at high neutron energy above 100 keV where now our data are in better agreement with the ENDF/B-VIII evaluation [3] and previous results from Walter and Beer [2]. Systematic uncertainties of the unresolved cross section are 6.7%. The Maxwellian averaged cross sections (MACS) are shown in Table III. Above the experimental limit of 300 keV, we used the ENDF/B-VIII cross section for our MACS calculations, assuming a 20% uncertainty. Changes in the MACS values remain below 6%, therefore, our astrophysical considerations remain largely unchanged. It should be noted that the agreement between our results and Kadonis-1.0 [4] is now excellent. We apologize for any inconvenience this caused. The corrected results will be provided to the EXFOR database.

Accurate neutron capture cross section data for minor actinides (MAs) are required to estimate the production and transmutation rates of MAs in light water reactors, critical fast reactors like Gen-IV systems, and other innovative reactor systems such as accelerator driven systems (ADS). In particular, 244 Cm, 246 Cm and 248 Cm play a role in the transport, storage and transmutation of the nuclear waste of the current nuclear reactors, due to the contribution of these isotopes to the radiotoxicity, neutron emission, and decay heat in the spent nuclear fuel. Also, capture reactions in these Cm isotopes open the path for the formation of heavier elements. In this work, the results of the capture cross section measurement on 244 Cm, 246 Cm and 248 Cm performed at the CERN n_TOF facility are presented. It is important to notice that the Cm samples used in the experiment at n_TOF have been used previously in an experiment at J-PARC, this experiment and the previous one done in the 70s with a nuclear explosion were the only previous capture experiments for these isotopes. At n_TOF, the capture cross section measurements of 244 Cm, 246 Cm and 248 Cm were performed at the 20 m vertical flight path (EAR2) with three C 6 D 6 total energy detectors. In addition, the cross section of 244Cm was measured at the 185 m flight path (EAR1) with a Total Absorption Calorimeter (TAC). The combination of measurements in EAR1 and EAR2 has contributed to controlling and reducing the systematic uncertainties in the results. The compatibility of the different measurements performed and the techniques to obtain the results are presented in this paper as well as the procedure to obtain the resonance parameters.

73 Ge(n, γ ) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV.Results indicate that the stellar cross section at kT = 30 keV is 1.5 to 1.7 times higher than most theoretical predictions.The new cross sections result in a substantial decrease of 73 Ge produced in stars, which would explain the low isotopic abundance of 73 Ge in the solar system.