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Spark-plasma-sintered lead vanadate iodoapatite Pb9.85(VO4)6I1.7, a promising nuclear waste form for the immobilization of I-129, was irradiated with energetic ions, electrons, and gamma rays, to investigate its radiation stability. In situ TEM observation of the 1 MeV Kr2+ irradiation shows that lead vanadate iodoapatite generally exhibits higher tolerance against ion irradiation-induced amorphization than lead vanadate fluorapatite, and the spark plasma sintering can further enhance its radiation stability attributed to the enhanced crystallinity, reduced defect concentration, and denser microstructure. The critical amorphization dose and critical temperature for the SPS-densified iodoapatite at 700°C are determined to be 0.25 dpa at room temperature and 230°C, respectively. No significant phase transformation or microstructural damage occurred under energetic electron and gamma irradiations. Raman spectra of gamma-ray-irradiated iodoapatite indicate improved V–O bond order at 500 kGy dose. Generally, the spark-plasma-sintered iodoapatite exhibits excellent radiation stability for nuclear waste form applications. The significantly enhanced radiation stability of the SPS-densified iodoapatite suggests that SPS holds great promise for fabricating iodoapatite waste form with minimum iodine loss and optimized radiation tolerance for effective management of highly volatile I-129.

We describe the new ENDF/B-VIII.0 evaluated nuclear reaction data library. ENDF/B-VIII.0 fully incorporates the new IAEA standards, includes improved thermal neutron scattering data and uses new evaluated data from the CIELO project for neutron reactions on 1H, 16O, 56Fe, 235U, 238U and 239Pu described in companion papers in the present issue of Nuclear Data Sheets. The evaluations benefit from recent experimental data obtained in the U.S. and Europe, and improvements in theory and simulation. Notable advances include updated evaluated data for light nuclei, structural materials, actinides, fission energy release, prompt fission neutron and γ-ray spectra, thermal neutron scattering data, and charged-particle reactions. Integral validation testing is shown for a wide range of criticality, reaction rate, and neutron transmission benchmarks. In general, integral validation performance of the library is improved relative to the previous ENDF/B-VII.1 library. Fil: Brown, D.A.. Brookhaven National Laboratory; Estados Unidos Fil: Chadwick, M.B.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Capote, R.. International Atomic Energy Agency, Vienna; Austria Fil: Kahler, A.C.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Trkov, A.. International Atomic Energy Agency, Vienna; Austria Fil: Herman, M.W.. Brookhaven National Laboratory; Estados Unidos Fil: Sonzogni, A.A.. Brookhaven National Laboratory; Estados Unidos Fil: Danon, Y.. Rensselaer Polytechnic Institute; Estados Unidos Fil: Carlson, A.D.. National Institute of Standards and Technology; Estados Unidos Fil: Dunn, M.. Spectra Tech; Estados Unidos Fil: Smith, D.L.. Argonne National Laboratory; Estados Unidos Fil: Hale, G.M.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Arbanas, G.. Oak Ridge National Laboratory; Estados Unidos Fil: Arcilla, R.. Brookhaven National Laboratory; Estados Unidos Fil: Bates, C.R.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Beck, B.. Lawrence Livermore National Laboratory; Fil: Becker, B.. Gesellschaft für Anlagen und Reaktorsicherheit; Alemania Fil: Brown, F.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Casperson, R.J.. Lawrence Livermore National Laboratory; Estados Unidos Fil: Conlin, J.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Cullen, D.E.. Lawrence Livermore National Laboratory; Estados Unidos Fil: Descalle, M.A.. Lawrence Livermore National Laboratory; Estados Unidos Fil: Firestone, R.. Lawrence Berkeley National Laboratory; Estados Unidos Fil: Gaines, T.. AWE plc; Reino Unido Fil: Guber, K.H.. Oak Ridge National Laboratory; Estados Unidos Fil: Hawari, A.I.. University of North Carolina; Estados Unidos Fil: Holmes, J.. Naval Nuclear Laboratory; Estados Unidos Fil: Johnson, T.D.. Brookhaven National Laboratory; Estados Unidos Fil: Kawano, T.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Kiedrowski, B.C.. University of Michigan; Estados Unidos Fil: Koning, A.J.. International Atomic Energy Agency, Vienna; Austria Fil: Kopecky, S.. EC-JRC; Bélgica Fil: Leal, L.. Institut de Radioprotection et de Sûreté Nucléaire; Francia Fil: Lestone, J.P.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Lubitz, C.. Naval Nuclear Laboratory; Estados Unidos Fil: Marquez Damian, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Mattoon, C.M.. Lawrence Livermore National Laboratory; Estados Unidos Fil: McCutchan, E.A.. Brookhaven National Laboratory; Estados Unidos Fil: Mughabghab, S.. Brookhaven National Laboratory; Estados Unidos Fil: Navratil, P.. TRIUMF; Canadá Fil: Neudecker, D.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Nobre, G.P.A.. Brookhaven National Laboratory; Estados Unidos Fil: Noguere, G.. Commissariat A Energie Atomique; Francia Fil: Paris, M.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Pigni, M.T.. Oak Ridge National Laboratory; Estados Unidos Fil: Plompen, A.J.. EC-JRC; Bélgica Fil: Pritychenko, B.. Brookhaven National Laboratory; Estados Unidos Fil: Pronyaev, V.G.. PI Atomstandart at SC Rosatom; Rusia Fil: Roubtsov, D.. Laboratoires Nucleaires Canadiens; Canadá Fil: Rochman, D.. Paul Scherrer Institut; Suiza Fil: Romano, P.. Argonne National Laboratory; Estados Unidos Fil: Schillebeeckx, P.. EC-JRC; Bélgica Fil: Simakov, S.. Karlsruhe Institute of Technology; Alemania Fil: Sin, M.. University of Bucharest; Rumania Fil: Sirakov, I.. Institute For Nuclear Research And Nuclear Energy Bulgarian Academy Of Sciences; Bulgaria Fil: Sleaford, B.. Lawrence Livermore National Laboratory; Estados Unidos Fil: Sobes, V.. Oak Ridge National Laboratory; Estados Unidos Fil: Soukhovitskii, E.S.. Joint Institute for Energy and Nuclear Research; Bielorrusia Fil: Stetcu, I.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Talou, P.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos. Oak Ridge National Laboratory; Estados Unidos Fil: Thompson, I.. Lawrence Livermore National Laboratory; Estados Unidos Fil: van der Marck, S.. NRG; Países Bajos Fil: Welser-Sherrill, L.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Wiarda, D.. Oak Ridge National Laboratory; Estados Unidos Fil: White, M.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Wormald, J.L.. University of North Carolina; Estados Unidos Fil: Wright, R.Q.. Oak Ridge National Laboratory; Estados Unidos Fil: Zerkle, M.. Naval Nuclear Laboratory; Estados Unidos Fil: Zerovnik, G.. EC-JRC; Bélgica Fil: Zhu, Yan. University of North Carolina; Estados Unidos

The CIELO collaboration has studied neutron cross sections on nuclides that significantly impact criticality in nuclear technologies - 235,238U, 239Pu, 56Fe, 16O and 1H - with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform Fil: Chadwick, M.B.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Capote, R.. International Atomic Energy Agenc; Austria Fil: Trkov, A.. Brookhaven National Laboratory; Estados Unidos Fil: Herman, M.W.. Brookhaven National Laboratory; Estados Unidos Fil: Brown, D.A.. European Commission, Joint Research Center; Bélgica Fil: Hale, G.M.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Kahler, A.C.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Talou, P.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Plompen, A.J.. European Commission, Joint Research Center; Bélgica Fil: Schillebeeckx, P.. European Commission, Joint Research Center; Bélgica Fil: Pigni, M.T.. Oak Ridge National Laboratory; Estados Unidos Fil: Leal, L.. Institut de Radioprotection et de Surete Nucleaire; Francia Fil: Danon, Y.. Rensselaer Polytechnic Institute; Estados Unidos Fil: Carlson, A.D.. National Institute of Standards and Technology; Estados Unidos Fil: Romain, P.. Commissariat a L'Energie Atomique; Francia Fil: Morillon, B.. Commissariat a L'Energie Atomique; Francia Fil: Bauger, E.. Commissariat a L'Energie Atomique; Francia Fil: Hambsch, F.-J.. European Commission, Joint Research Center; Bélgica Fil: Kopecky, S.. European Commission, Joint Research Center; Bélgica Fil: Giorginis, G.. European Commission, Joint Research Center; Bélgica Fil: Kawano, T.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Lestone, J.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Neudecker, D.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Rising, M.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Paris, M.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Nobre, G.P.A.. Brookhaven National Laboratory; Estados Unidos Fil: Arcilla, R.. Brookhaven National Laboratory; Estados Unidos Fil: Cabellos, O.. Organisation for Economic Co-operation and Development. Nuclear Energy Agency; Francia Fil: Hill, I.. Organisation for Economic Co-operation and Development. Nuclear Energy Agency; Francia Fil: Dupont, E.. Organisation for Economic Co-operation and Development. Nuclear Energy Agency; Francia Fil: Koning, A.J.. International Atomic Energy Agency; Austria Fil: Cano Ott, D.. Centro de Investigaciones Energéticas Medioambientales y Tecnólogicas; España Fil: Mendoza, E.. Centro de Investigaciones Energéticas Medioambientales y Tecnólogicas; España Fil: Balibrea, J.. Centro de Investigaciones Energéticas Medioambientales y Tecnólogicas; España Fil: Paradela, C.. European Commission. Joint Research Center; Bélgica Fil: Durán, I.. Universidad de Santiago de Compostela; España Fil: Qian, J.. China Nuclear Data Center; China Fil: Ge, Z.. China Nuclear Data Center; China Fil: Liu, T.. China Nuclear Data Center; China Fil: Hanlin, L.. China Institute of Atomic Energy; China Fil: Ruan, X.. China Institute of Atomic Energy; China Fil: Haicheng, W.. China Institute of Atomic Energy; China Fil: Sin, M.. Bucharest University; Rumania Fil: Noguere, G.. Commissariat a L'Energie Atomique. Nuclear Energy Division; Francia Fil: Bernard, D.. Commissariat a L'Energie Atomique. Nuclear Energy Division; Francia Fil: Jacqmin, R.. Commissariat a L'Energie Atomique. Nuclear Energy Division; Francia Fil: Bouland, O.. Commissariat a L'Energie Atomique. Nuclear Energy Division; Francia Fil: De Saint Jean, C.. CEA, Nuclear Energy Division; Francia Fil: Pronyaev, V.G.. PI Atomstandart at SC Rosatom; Rusia Fil: Ignatyuk, A.V.. Institute of Physics and Power Engineering; Rusia Fil: Yokoyama, K.. Japan Atomic Energy Agency; Japón Fil: Ishikawa, M.. Japan Atomic Energy Agency; Japón Fil: Fukahori, T.. Japan Atomic Energy Agency; Japón Fil: Iwamoto, N.. Japan Atomic Energy Agency; Japón Fil: Iwamoto, O.. Japan Atomic Energy Agency; Japón Fil: Kunieda, S.. Japan Atomic Energy Agency; Japón Fil: Lubitz, C.R.. Knolls Atomic Power Laboratory; Estados Unidos Fil: Salvatores, M.. Idaho National Laboratory; Estados Unidos Fil: Palmiotti, G.. Idaho National Laboratory; Estados Unidos Fil: Kodeli, I.. Jozef Stefan Institute; Eslovenia Fil: Kiedrowski, B.. University of Michigan; Estados Unidos Fil: Roubtsov, D.. Canadian Nuclear Laboratories; Canadá Fil: Thompson, I.. Lawrence Livermore National Laboratory; Estados Unidos Fil: Quaglioni, S.. Lawrence Livermore National Laboratory; Estados Unidos Fil: Kim, H.I.. Korean Atomic Energy Research Institute; Corea del Sur Fil: Lee, Y.O.. Korean Atomic Energy Research Institute; Corea del Sur Fil: Fischer, U.. Karlsruhe Institute of Technology; Alemania Fil: Simakov, S.. Karlsruhe Institute of Technology; Alemania Fil: Dunn, M.. Oak Ridge National Laboratory; Estados Unidos Fil: Guber, K.. Oak Ridge National Laboratory; Estados Unidos Fil: Marquez Damian, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Cantargi, Florencia Olga. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Sirakov, I.. Institute for Nuclear Research and Nuclear Energy; Bulgaria Fil: Otuka, N.. International Atomic Energy Agency; Austria Fil: Daskalakis, A.. Naval Nuclear Laboratory; Estados Unidos Fil: McDermott, B.J.. Naval Nuclear Laboratory; Estados Unidos Fil: van der Marck, S.C.. Nuclear Research and Consultancy Group; Países Bajos

International audience; A new suite of evaluations for 54,56,57,58 Fe has been developed in the framework of the CIELO international collaboration. New resolved resonance ranges were evaluated for 54 Fe and 57 Fe, while modifications were applied to resonances in 56 Fe. The low energy part of the 56 Fe file is almost totally based on measurements. At higher energies in 56 Fe and in the whole fast neutron range for minor isotopes the evaluation consists of model predictions carefully adjusted to available experimental data. We also make use of the high quality and well experimentally-constrained dosimetry evaluations from the IRDFF library. Special attention was dedicated to the elastic angular distributions, which were found to affect results of the integral benchmarking. The new set of iron evaluations was developed in concert with other CIELO evaluations and they were tested together in the integral experiments before being adopted for the ENDF/B-VIII.0 library.

International audience; Evaluations of nuclear reaction data for the major uranium isotopes 238 U and 235 U were performed within the scope of the CIELO Project on the initiative of the OECD/NEA Data Bank under Working Party on Evaluation Co-operation (WPEC) Subgroup 40 coordinated by the IAEA Nuclear Data Section. Both the mean values and covariances are evaluated from 10 −5 eV up to 30 MeV. The resonance parameters of 238 U and 235 U were re-evaluated with the addition of newly available data to the existing experimental database. The evaluations in the fast neutron range are based on nuclear model calculations with the code EMPIRE–3.2 Malta above the resonance range up to 30 MeV. 235 U( n ,f), 238 U( n ,f), and 238 U( n , γ ) cross sections and 235 U( n th ,f) prompt fission neutron spectrum (PFNS) were evaluated within the Neutron Standards project and are representative of the experimental state-of-the-art measurements. The Standards cross sections were matched in model calculations as closely as possible to guarantee a good predictive power for cross sections of competing neutron scattering channels. 235 U( n , γ ) cross section includes fluctuations observed in recent experiments. 235 U( n ,f) PFNS for incident neutron energies from 500 keV to 20 MeV were measured at Los Alamos Chi-Nu facility and re-evaluated using all available experimental data. While respecting the measured differential data, several compensating errors in previous evaluations were identified and removed so that the performance in integral benchmarks was restored or improved. Covariance matrices for 235 U and 238 U cross sections, angular distributions, spectra and neutron multiplicities were evaluated using the GANDR system that combines experimental data with model uncertainties. Unrecognized systematic uncertainties were considered in the uncertainty quantification for fission and capture cross sections above the thermal range, and for neutron multiplicities. Evaluated files were extensively benchmarked to ensure good performance in reactor calculations and fusion-related systems. New comprehensive evaluations show excellent agreement with available differential data and integral performance better than current evaluated data libraries, and represent a step forward in a quest for better nuclear data for applications.

Improved nondestructive assay of isotopic masses in used nuclear fuel would be valuable for nuclear safeguards operations associated with the transport, storage, and reprocessing of used nuclear fu...

After publication of the paper, the authors realized that the acknowledgements were not correct. Their correct version appears in this erratum.

Neutron capture yields of dysprosium isotopes ( 161Dy, 162Dy, 163Dy, and 164Dy were measured using the time-of-flight method with a 16 segment sodium iodide multiplicity detector. The measurements were made at the 25m flight station at the Gaerttner LINAC Center at Rensselaer Polytechnic Institute. Resonance parameters were obtained using the multilevel R-matrix Bayesian code SAMMY. The neutron capture data for four enriched dysprosium isotopes and one natural dysprosium sample were sequentially fitted. New resonances not listed in ENDF/B-VII.1 were observed. There were 29 and 17 new resonances from 161Dy and 163Dy isotopes, respectively. Six resonances from 161Dy isotope, two resonances from 163Dy, and four resonances from 164Dy were not observed. The capture resonance integrals of each isotope were calculated with the resulting resonance parameters and those of ENDF/B-VII.1 in the energy region from 0.5eV to 20MeV and were compared to the capture resonance integrals with the resonance parameters from ENDF/B-VII.1. A resonance integral value of the natural dysprosium calculated with present resonance parameters was $ 1405 \pm 3.5$ barn. The value is $ \sim 0.3\%$ higher than that obtained with the ENDF/B-VII.1 parameters. The distributions of the present and ENDF/B-VII.1 neutron widths were compared to a Porter-Thomas distribution. Neutron strength functions for 161Dy and 163Dy were calculated with the present resonance parameters and both values were in between the values of “Atlas of Neutron Resonances” and ENDF/B-VII.1. The present radiation width distributions of 161Dy and 163Dy were fitted with the $ \chi^{2}$ distribution by varying the degrees of freedom.

A new array of four Deuterated Benzene (${\mathrm{C}}_{6}{\mathrm{D}}_{6}$) detectors has been installed at the Gaerttner Linear Accelerator Center at Rensselaer Polytechnic Institute for the purpose of measuring neutron capture cross sections in the keV region. Measurements were performed on samples of $^{181}\mathrm{Ta}$ in the unresolved resonance region (URR) using a filtered-beam technique, by which a 30 cm iron filter was placed in a white-spectrum neutron beam to remove all time-dependent $\ensuremath{\gamma}$-ray background and all neutrons except those transmitted through resonance-potential interference ``windows'' in the iron. The resulting filtered beam was effectively a quasimonoenergetic neutron source, which was used for performing measurements on isotopes with narrow level spacings in the URR. The capture cross-section results obtained for two thicknesses of tantalum are in agreement with those documented in the JEFF-3.2 library, as are the average resonance parameters obtained via a fit to the data using the sammy-fitacs code.

Europium is a good absorber of neutrons suitable for use as a nuclear reactor control material. It is also a fission product in the low-yield tail at the high end of the fission fragment mass distribution. Measurements have been made of the stable isotopes with natural and enriched samples. The linear electron accelerator center (LINAC) at the Rensselaer Polytechnic Institute (RPI) was used to explore neutron interactions with europium in the energy region from 0.01 to 200 eV. Neutron capture and transmission measurements were performed by the time-of-flight technique. Two transmission measurements were performed at flight paths of 15 and 25 m with 6Li glass scintillation detectors. The neutron capture measurements were performed at a flight path of 25 m with a 16-segment sodium iodide multiplicity detector. Resonance parameters were extracted from the data using the multilevel R-matrix Bayesian code SAMMY. A table of resonance parameters and their uncertainties is presented. To prevent air oxidation metal samples were sealed in airtight aluminum cans in an inert environment. Metal samples of natural europium, 47.8 atom% 151Eu, 52.2 atom% 153Eu, as well as metal samples enriched to 98.77 atom% 153Eu were measured. The measured neutron capture resonance integral for 153Eu is (9.9 ± 0.4)% larger than ENDF/B-VII.1. The capture resonance integral for 151Eu is (7 ± 1)% larger than ENDF/B-VII.1. Another significant finding from these measurements was a significant increase in thermal total cross section for 151Eu, up (9 ± 3)% from ENDF/B-VII.1. The thermal total cross section for 153Eu is down (8 ± 3)% from ENDF/B-VII.1, but it is larger than that of ENDF/B-VII.0. The resolved resonance region has been extended from 100 eV to 200 eV for both naturally-occurring isotopes. Uncertainties in resonance parameters have been propagated from a number of experimental quantities using a Bayesian analysis. Uncertainties have also been estimated from fitting each Eu sample measurement individually.

The OECD Nuclear Energy Agency (NEA) organizes cooperation between the major nuclear data evaluation projects in the world. The NEA Working Party on International Nuclear Data Evaluation Cooperation (WPEC) was established to promote the exchange of information on nuclear data evaluation, measurement, nuclear model calculation, validation, and related topics, and to provide a framework for cooperative activities between the participating projects. The working party assesses nuclear data improvement needs and addresses these needs by initiating joint activities in the framework of dedicated WPEC subgroups. Studies recently completed comprise a number of works related to nuclear data covariance and associated processing issues, as well as more specific studies related to the resonance parameter representation in the unresolved resonance region, the gamma production from fission product capture reactions, the 235U capture cross section, the EXFOR database, and the improvement of nuclear data for advanced reactor systems. Ongoing activities focus on the evaluation of 239Pu in the resonance region, scattering angular distribution in the fast energy range, and reporting/usage of experimental data for evaluation in the resolved resonance region. New activities include two subgroups on improved fission product yield evaluation methodologies and on modern nuclear database structures. Future activities under discussion include a pilot project for a Collaborative International Evaluated Library Organization (CIELO) and methods to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data. In addition to the above mentioned short-term task-oriented subgroups, WPEC also hosts a longer-term subgroup charged with reviewing and compiling the most important nuclear data requirements in a high priority request list (HPRL)., JRC.D.4-Standards for Nuclear Safety, Security and Safeguards

Recent efforts have been made to improve the prompt fission neutron spectrum and nu-bar measurements for Uranium and Plutonium isotopes particularly in the keV region. A system has been designed at Rensselaer Polytechnic Institute (RPI) utilizing an array of EJ-301 liquid scintillators as well as lithium glass and plastic scintillators to experimentally determine these values. An array of BaF 2 detectors was recently obtained from Oak Ridge National Laboratory to be used in conjunction with the neutron detectors. The system uses a novel gamma tagging method for fission which can offer an improvement over conventional fission chambers due to increased sample mass. A coincidence requirement on the gamma detectors from prompt fission gammas is used as the fission tag for the system as opposed to fission fragments in a conventional fission chamber. The system utilizes pulse digitization using Acqiris 8 bit digitizer boards which allow for gamma/neutron pulse height discrimination on the liquid scintillators during post processing. Additionally, a 252Cf fission chamber was designed and constructed at RPI which allowed for optimization and testing of the system without the need for an external neutron source. The characteristics of the gamma tagging method such as false detection rate and detection efficiency were determined using this fission chamber and verified using MCNP Polimi modeling. Prompt fission neutron spectrum data has been taken using the fission chamber focusing on the minimum detectable neutron energy for each of the various detectors. Plastic scintillators were found to offer a significant improvement over traditional liquid scintillators allowing energy measurements down to 50 keV. Background was also characterized for all detectors and will be discussed.

The latest release of the EMPIRE-3.1 system (codename Rivoli) is being used in the advanced modeling of neutron induced reactions on the 238 U nucleus with the aim of improving our knowledge of neutron scattering. The reaction model includes: (i) a new rotational-vibrational dispersive optical model potential coupling the low-lying collective bands of vibrational character observed in even-even actinides, (ii) the Engelbrecht-Weidenmuller transformation allowing for inclusion of compound-direct interference effects enhanced by a dispersive treatment of the optical model potential, (iii) a multi-humped fission barrier with absorption in the secondary well as described within the optical model for fission, and (iv) a modified Lorentzian model (MLO) of the radiative strength function. Impact of the advanced modeling on elastic and inelastic scattering cross section is being assessed by both comparison with selected microscopic experimental data and integral criticality benchmarks (e.g. FLATTOP, JEMIMA and BIGTEN assemblies). Benchmark calculations provide feedback to improve the reaction modeling and reduce both model and model-parameters uncertainties. Additionally, neutron scattering yields on 238 U measured accurately at RPI by the time-of-flight technique at 29, 60, 112 and 153 degrees have been used as a further constraint on the incident energy dependence of elastic and inelastically scattered neutrons. Improvement of scattering cross sections in existing libraries is discussed.

The use of a lead slowing-down spectrometer (LSDS) is considered as a possible option for nondestructive assay of fissile material of used nuclear fuel. The primary objective is to quantify fissile...

High-energy-neutron-scattering experiments for elemental zirconium were performed at the electron linear accelerator facility at Rensselaer Polytechnic Institute. The scattering experiments were pe...

A new array of C 6 D 6 detectors installed at the RPI LINAC Center has enabled the capability to measure neutron capture cross sections above the 847 keV inelastic scattering threshold of 56 Fe through the use of digital post-processing filters and pulse-integral discriminators, without sacrificing the statistical quality of data at lower incident neutron energies where such filtering is unnecessary. The C 6 D 6 detectors were used to perform time-of-flight capture cross section measurements on a sample 99.87% enriched iron-56. The total-energy method, combined with the pulse height weighting technique, were then applied to the raw data to determine the energy-dependent capture yield. Above the inelastic threshold, the data were analyzed with a pulse-integral filter to reveal the capture signal, extending the the full data set to 2 MeV.

A neutron scattering kernel data evaluation framework for computation of model-dependent predictions and their uncertainties is outlined. In this framework, model parameters are fitted to double-differential cross section measurements and their uncertainties. For convenience, the initial implementation of this framework uses the molecular dynamics model implemented in the GROMACS code. It is applied to light water using the TIP4P/2005f interaction model. These trajectories computed by GROMACS are then processed using nMOLDYN to compute the density of states, which is then used to calculate the scattering kernel using the Gaussian approximation. Double differential cross sections computed from the scattering kernel are then fitted to double-differential scattering data measured at the Spallation Neutron Source detector at Oak Ridge National Laboratory. The fitting procedure is designed to yield optimized model-parameters and their uncertainties in the form of a covariance matrix, from which new evaluations of thermal neutron scattering kernel will be generated. The Unified Monte Carlo method will be used to fit the simulation data to the experimental data.

The CIELO collaboration has studied neutron cross sections on nuclides that significantly impact criticality in nuclear technologies – 16 O, 56 Fe, 235,8 U and 239 Pu – with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality.

Neutron capture and transmission measurements have been performed, and resonance parameter analysis has been completed for dysprosium, Dy, and rhenium, Re. The 60 MeV electron accelerator at RPI Gaerttner LINAC Center produced neutrons in the thermal and epithermal energy regions for these measurements. Transmission measurements were made using 6 Li glass scintillation detectors. The neutron capture measurements were made with a 16-segment NaI multiplicity detector. The detectors for all experiments were located at ≈25 m except for thermal transmission, which was done at ≈15 m. The dysprosium samples included one highly enriched 164 Dy metal, 6 liquid solutions of enriched 164 Dy, two natural Dy metals. The Re samples were natural metals. Their capture yield normalizations were corrected for their high gamma attenuation. The multi-level R-matrix Bayesian computer code SAMMY was used to extract the resonance parameters from the data. 164 Dy resonance data were analyzed up to 550 eV, other Dy isotopes up to 17 eV, and Re resonance data up to 1 keV. Uncertainties due to resolution function, flight path, burst width, sample thickness, normalization, background, and zero time were estimated and propagated using SAMMY. An additional check of sample-to-sample consistency is presented as an estimate of uncertainty. The thermal total cross sections and neutron capture resonance integrals of 164 Dy and Re were determined from the resonance parameters. The NJOY and INTER codes were used to process and integrate the cross sections. Plots of the data, fits, and calculations using ENDF/B-VII.1 resonance parameters are presented.

The development of high-efficiency solid state thermal neutron detectors at low cost is critical for a wide range of civilian and defense applications. The use of present neutron detector system for personal radiation detection is limited by the cost, size, weight and power requirements. Chip scale solid state neutron detectors based on silicon technology would provide significant benefits in terms of cost, volume, and allow for wafer level integration with charge preamplifiers and readout electronics. In this paper, anisotropic wet etching of (110) silicon wafers was used to replace deep reactive ion etching (DRIE) to produce microstructured neutron detectors with lower cost and compatibility with mass production. Deep trenches were etched by 30 wt% KOH at 85°C with a highest etch ratio of (110) to (111). A trench-microstructure thermal neutron detector described by the aforementioned processes was fabricated and characterized. The detector—which has a continuous p+-n junction diode—was filled with enriched boron (99% of 10B) as a neutron converter material. The device showed a leakage current of ~ 6.7 × 10-6 A/cm2 at -1V and thermal neutron detection efficiency of ~16.3%. The detector uses custom built charge pre-amplifier, a shaping amplifier, and an analogto- digital converter (ADC) for data acquisition.

The Gaerttner Laboratory electron linear accelerator at Rensselaer Polytechnic Institute was used in the measurement of the neutron total cross section of natural beryllium and carbon (graphite) in...

The lead slowing-down spectrometer (LSDS) at Rensselaer Polytechnic Institute (RPI) was used to extend previous measurements of the (n,α) cross section on 147Sm and perform measurements on 149Sm over the energy range 0.1 eV–10 keV. A compensated detector based on passivated implanted planar silicon (PIPS) detectors was constructed. Signals from two detectors were combined in opposite polarity and digitized providing a single detector capable of discriminating against capture γ's and “γ-flash” while preserving the discrete signals produced by α events and providing a simultaneous background measurement. Extrapolating the results predicts a 0.3±0.3 mbarn and 11.5±1.1 mbarn thermal neutron (n,α) cross section for 147Sm and 149Sm, respectively. This measurement provides new information on (n,α) reaction cross sections. The method of measuring neutron induced charged particle emission cross sections presented here can be expanded to more isotopes of interest to reactor engineers or astrophysicists, as well as to (n,p) reactions.

The ENDF/B-VII.1 library is our latest recommended evaluated nuclear data file for use in nuclear science and technology applications, and incorporates advances made in the five years since the release of ENDF/B-VII.0. These advances focus on neutron cross sections, covariances, fission product yields and decay data, and represent work by the US Cross Section Evaluation Working Group (CSEWG) in nuclear data evaluation that utilizes developments in nuclear theory, modeling, simulation, and experiment. The principal advances in the new library are: (1) An increase in the breadth of neutron reaction cross section coverage, extending from 393 nuclides to 423 nuclides; (2) Covariance uncertainty data for 190 of the most important nuclides, as documented in companion papers in this edition; (3) R-matrix analyses of neutron reactions on light nuclei, including isotopes of He, Li, and Be; (4) Resonance parameter analyses at lower energies and statistical high energy reactions for isotopes of Cl, K, Ti, V, Mn, Cr, Ni, Zr and W; (5) Modifications to thermal neutron reactions on fission products (isotopes of Mo, Tc, Rh, Ag, Cs, Nd, Sm, Eu) and neutron absorber materials (Cd, Gd); (6) Improved minor actinide evaluations for isotopes of U, Np, Pu, and Am (we are not making changes to the major actinides 235,238U and 239Pu at this point, except for delayed neutron data and covariances, and instead we intend to update them after a further period of research in experiment and theory), and our adoption of JENDL-4.0 evaluations for isotopes of Cm, Bk, Cf, Es, Fm, and some other minor actinides; (7) Fission energy release evaluations; (8) Fission product yield advances for fission-spectrum neutrons and 14 MeV neutrons incident on 239Pu; and (9) A new decay data sublibrary. Integral validation testing of the ENDF/B-VII.1 library is provided for a variety of quantities: For nuclear criticality, the VII.1 library maintains the generally-good performance seen for VII.0 for a wide range of MCNP simulations of criticality benchmarks, with improved performance coming from new structural material evaluations, especially for Ti, Mn, Cr, Zr and W. For Be we see some improvements although the fast assembly data appear to be mutually inconsistent. Actinide cross section updates are also assessed through comparisons of fission and capture reaction rate measurements in critical assemblies and fast reactors, and improvements are evident. Maxwellian-averaged capture cross sections at 30 keV are also provided for astrophysics applications. We describe the cross section evaluations that have been updated for ENDF/B-VII.1 and the measured data and calculations that motivated the changes, and therefore this paper augments the ENDF/B-VII.0 publication [M. B. Chadwick, P. Obložinský, M. Herman, N. M. Greene, R. D. McKnight, D. L. Smith, P. G. Young, R. E. MacFarlane, G. M. Hale, S. C. Frankle, A. C. Kahler, T. Kawano, R. C. Little, D. G. Madland, P. Moller, R. D. Mosteller, P. R. Page, P. Talou, H. Trellue, M. C. White, W. B. Wilson, R. Arcilla, C. L. Dunford, S. F. Mughabghab, B. Pritychenko, D. Rochman, A. A. Sonzogni, C. R. Lubitz, T. H. Trumbull, J. P. Weinman, D. A. Br, D. E. Cullen, D. P. Heinrichs, D. P. McNabb, H. Derrien, M. E. Dunn, N. M. Larson, L. C. Leal, A. D. Carlson, R. C. Block, J. B. Briggs, E. T. Cheng, H. C. Huria, M. L. Zerkle, K. S. Kozier, A. Courcelle, V. Pronyaev, and S. C. van der Marck, “ENDF/B-VII.0: Next Generation Evaluated Nuclear Data Library for Nuclear Science and Technology,” Nuclear Data Sheets 107, 2931 (2006)].

energy range for the LSDS is 0.1 eV to 10 keV with energy resolution of about 35%. Two new LSDS applications were recently developed at RPI; the rst enables simultaneous measurements of the ssion cross section and ssion fragment mass and energy distributions as a function of the incident neutron energy. The second enables measurements of the (n, ) and (n;p) cross sections for materials with a positive Q value for these reactions. Fission measurements of 252 Cf, 235 U, and 239 Pu were completed and provide information on ssion fragment and energy distributions in resonance clusters. Measurements of the (n, ) cross section for 147;149 Sm were completed and compared to previously measured data. The new data indicate that the existing evaluations need to be adjusted.

The Boltzmann Transport equation is the governing formalism upon which simulations of nuclear reactors are performed, in particular when strong absorption or anisotropic scattering are significant. On the left (loss) hand side of the balance equation one finds the absorption and the scattering cross section Σa(E′), Σs(E′) respectively. Those cross sections are energy and temperature dependent i.e. Doppler Broadened. The scattering cross section appears explicitly again on the right (production) hand side of the equation in its differential form ∫∫0 ∞Σ(E → E′); Ω → Ω′)dE dΩ. However, this term is commonly evaluated at 0 K and it does not account for the existing resonances which are the underlying characteristic for Doppler Broadening. Evidently one gets an inherent inconsistency between the integral and differential scattering cross section within the transport solver codes. In this study this missing Doppler Broadened formalism for the differential scattering cross section is introduced in its stochastic and deterministic form. The impact on core criticality is shown to be up to 600 pcm and the change in the nuclides' inventory significant, in particular the 239PU content can be changed by several percents.

A series of new total cross section measurements for the stable molybdenum isotopes of 92,94,95,96,98,100 Mo covering the energy range between 1 keV and 620 keV was performed at the Gaerttner LINAC Center at Rensselaer Polytechnic Institute. New high-accuracy resonance parameters were extracted from an analysis of the data using the multilevel R-matrix Bayesian code SAMMY. In the unresolved resonance region, average resonance parameters and fits to the total cross sections were obtained using the Bayesian Hauser-Feshbach statistical model code FITACS.

The electron linear accelerator facility at the Rensselaer Polytechnic Institute was used to measure neutron capture yields of dysprosium with the time-of-flight method in the neutron energy region from 10 eV to 1 keV. The neutron capture experiments were made at a flight path length of 25.5 m with a 16-section NaI multiplicity detector. High purity isotopic samples of 161Dy, 162Dy, 163Dy, 164Dy as well as one natural dysprosium sample with thickness of 0.508 mm were used in this measurement. Resonance parameters were extracted from the data using simultaneous fit with the multilevel R-matrix Bayesian code SAMMY 8.0. New resonances are proposed, and other resonances previously identified in the literature have been revised. The present results are compared with other evaluated values of ENDF/B-VII.1 and JENDL 4.0.

Different target materials were investigated to determine which ones are favorable to increasing the theoretical neutron yield using pyroelectric crystal D–D nuclear fusion. Calculations show that deuterated polyethylene (CD2) will potentially yield the highest number of neutrons compared to the other targets investigated. However, deuterated plastic targets have been found to erode over the course of experiments.

In order to aid in the improvement of the high energy neutron differential scattering cross-section data, scattering experiments were performed using a collimated source of pulsed neutrons with energies up to 20 MeV from the Rensselaer Polytechnic Institute Linear Accelerator. An array of proton recoil detectors surrounding a sample placed at 30.1 m from the source measures the scattered flux using time-of-flight (TOF) methods. A state of the art digital data acquisition system is used to collect the data from the detector array and stream the digitized data to disk. Software was developed to perform pulse shape analysis, multi-channel analyzer functions, and to generate TOF spectra and angular dependent scattered neutron distributions. Scattering measurements were performed on carbon and molybdenum and compared to the Monte Carlo simulation using various nuclear data libraries.

The electron linear accelerator facility at the Rensselaer Polytechnic Institute was used to explore neutron interactions with molybdenum in the energy region from 10 eV to 2 keV. Neutron capture and transmission measurements were performed by the time-of-flight technique. Resonance parameters were extracted from the data using the multilevel R-matrix Bayesian code SAMMY. A table of resonance parameters and their uncertainties is presented. Two transmission measurements were performed at a flight path of 25 m with a 6 Li glass scintillation detector. The neutron capture measurements were per- formed at a flight path of 25 m with a 16-segment sodium iodide multiplicity detector. Nine different thicknesses of elemental molybdenum metal samples ranging from 0.051 mm (0.002 in.) to 6.35 mm (0.250 in.) were measured in either capture or transmission. Reductions in resonance integrals were observed when compared to ENDF/B-VII.0 for six of the seven stable isotopes. The largest reductions were 9% in 97 Mo and 11% in 100 Mo. The one measured increase in resonance integral relative to ENDF/B-VII.0 occurred in 95 Mo, and it was significant (10%). The measured distribution of neutron widths for 95 Mo and 97 Mo are a better match to a Porter-Thomas distribution than those of ENDF/B-VII.0. Neutron strength functions for 95 Mo and 97 Mo were measured and compared to ENDF/B-VII.0. The strength of 95 Mo and 97 Mo are within uncertainties of each other. The measured radiation width distribution for 95 Mo and 97 Mo are compared to those of ENDF/B-VII.0 and to x 2 distributions. Significant aspects of this analysis are the assignment of radiation widths, the determination of the transmission resolution function, and the propa- gation of experimental uncertainties into resonance parameter uncertainties.

Summary Thin films of vertically aligned tungsten nanorods were used to enhance field ionization in pyroelectric crystal D–D fusion experiments resulting in increased neutron production. The tungsten nanorods were deposited on a single LiTaO3 crystal using sputter deposition at glancing angles. The combination of a single tungsten tip with a thin film of nanorods on the face of the crystal yielded about four times the number of neutrons than did either a single tip or nanorods alone.

Pyroelectric crystals are being used to ionize and accelerate D 2 gas into a deuterated target to achieve D–D fusion at Rensselaer Polytechnic Institute (RPI). Previous results from RPI yielded up to 5.9×10 4 neutrons over one thermal cycle; however, these results were not reproducible from one experiment to another. A portable prototype vacuum system has been developed that enhances reproducibility of results. A thermal management system consisting of two thermoelectric module temperature controllers was developed to improve the reproducibility of the thermal cycle. Twenty-eight experiments were conducted over a period of three days to determine the optimum ambient gas operating pressure of the vacuum system. The optimum operating pressure was found to be 26 mTorr which is much higher than operating pressures that have been previously reported. Reproducibility of the results has been improved. At optimum pressure, five consecutive experiments yielded an average of 9×10 3 neutrons with a standard deviation of 14% for each thermal cycle. While the neutron yield is lower than previous results, increased reproducibility in a more stable vacuum environment may allow for an increase in neutron yield in the future.

This paper presents new measurements of the carbon and beryllium neutron total cross section in the energy range of 24 to 950 keV. The measurements were done using a pulsed neutron source driven by an electron LINAC. The neutron beam passed through a 30-cm-thick iron filter, which results in neutron transmission only in energies where resonance scattering and potential interference exist. The neutron filter removes most of the neutrons at other energies and significantly attenuates the gamma background resulting in 20 energy windows and a high signal-to-background ratio. The filtered beam was used for transmission measurements through graphite that results in ;1% accurate total cross sections that are in excellent agreement with current evaluations. The carbon measurement provides a verification of the accuracy of the filtered beam method. Measurements of three samples of different thicknesses of beryllium resulted in accurate total cross-section values that agree with one previous measurement and show dis- crepancies from current evaluations. The high accuracy of the new measurements can be used for improve- ment of future total cross-section evaluations of beryllium.

The focus of this work is to determine the resonance parameters for stable hafnium isotopes in the 0.005- to 200-eV region, with special emphasis on the overlapping 176Hf and 178Hf resonances near ...

This paper reports on the device processing and characterization of hexagonal boron nitride (hBN) based solid-state thermal neutron detectors, where hBN thickness varied from 2.5 to 15 microns. These natural hBN epilayers (with 19.9% B-10) were grown by a low pressure chemical vapor deposition process. Complete dry processing was adopted for the fabrication of these metal-semiconductor-metal (MSM) configuration detectors. These detectors showed intrinsic thermal neutron detection efficiency values of 0.86%, 2.4%, 3.15%, and 4.71% for natural hBN thickness values of 2.5, 7.5, 10, and 15 microns, respectively. Measured efficiencies are very close (more than 92%) to the theoretical maximum efficiencies for corresponding hBN thickness values for these detectors. This clearly shows the hBN thickness scalability of these detectors. A 15-micron thick hBN based MSM detector is expected to yield an efficiency of 21.4%, if enriched hBN (with ~100% B-10) is used instead of natural hBN. These results demonstrate that the fabrication of hBN thickness scalable highly efficient thermal neutron detectors is possible.

This paper reports on the growth and characterization of hexagonal boron nitride (hBN) and its use for solid-state thermal neutron detection. The hBN epilayers were grown by metalorganic chemical vapor deposition on sapphire substrates at a temperature of 1350 °C. X-ray diffraction peak from the (002) hBN plane at a 2θ angle of 26.7° exhibited the c-lattice constant of 6.66 A for these films. A strong peak corresponding to the high frequency Raman active mode of hBN was found for the films at 1370.5 cm -1 hBN-based solid-state neutron detectors were fabricated and tested with a metal-semiconductor-metal configuration with an electrode spacing of 1 mm and hBN thickness of 2.5 μm. Fabricated detectors showed strong response to deep UV light as well. An intrinsic thermal neutron detection efficiency of 0.86% was measured, which is close to the theoretically expected efficiency of 0.87%. These results demonstrate that epitaxial hBN films are promising for thermal neutron detection applications.

The Gaerttner LINAC Center at RPI uses a 60 MeV electron linear accelerator to produce short pulses of neutrons with duration of 5-5000 ns. The main research thrust at the Center is nuclear data for nuclear reactors and criticality safety applications. The Center includes several setups for time-of-flight measurements including neutron transmission, capture and scattering detectors, and a lead slowing-down spectrometer. Experiments were designed to produce neutron interaction cross sections that cover the energy range of 0.01 eV to 20 MeV. Recently added experiments include: setups for keV and fast neutron transmission, a C 6 D 6 detector array for keV neutron capture measurements, and a fast neutron scattering system. Results discussed here include fast neutron scattering and angular distributions for nat Fe, iron capture measurements for incident neutrons from 1 keV to 2 MeV, fast neutron transmission through W and H 2 O samples, and keV transmission through Mo isotopes.

The Collaborative International Evaluated Library Organisation (CIELO) aims to provide revised and updated evaluations for Pu-239, U-238,U-235, Fe-56, O-16, and H-1 through international collaboration. This work, which is part of the CIELO project, presents the initial results for the evaluation of the Fe-56 isotope, with neutron-incident energy ranging from 0 to 20 MeV. The Fe-56(n,p) cross sections were fitted to reproduce the ones from IRDFF dosimetry file. Our preliminary file provides good cross-section agreements for the main angle-integrated reactions, as well as a reasonable overall agreement for angular distributions and double-differential spectra, when compared to previous evaluations.

The discovery of pyroelectric X-ray generation in 1992 by Brownridge has led to a recent surge of interest in the use of the pyroelectric effect as a means of producing useful radiation. By heating or cooling a pyroelectric crystal such as lithium tantalate (LiTaO3) in a vacuum, a potential on the order of 100 kV can be generated. This potential is great enough to eject electrons from the crystal for the production of characteristic or bremsstrahlung X-rays, or to cause field ionization near a tip mounted to the crystal. By using the combined fields of two polarized crystals, the acceleration potential can be doubled, with one crystal acting as a particle emitter and the other crystal serving as a target. Such a paired-crystal system was used to generate X-rays with energies of greater than 200 keV, and can be used to fluoresce the K shell of thorium (Z = 92). An alternative use of pyroelectric sources is the field ionization of a dilute gas. If the positively-charged crystal is used to ionize a deuterium gas, and the target crystal is coated with deuterated target, the deuterium ions can be accelerated into the target at high enough energy to cause D–D fusion. Results verifying the production of D–D fusion neutrons from a pyroelectric source will be presented. Future applications of pyroelectric accelerator technology, such as the use of the electron beam for materials testing, will also be discussed.

The 60-MeV electron linear accelerator at Rensselaer Polytechnic Institute (RPI) is used to produce parametric X-rays (PXR). PXR is an intense, quasi-monochromatic, energy-tunable, and polarized X-ray source derived from the interaction of relativistic electrons with the periodic structure of crystal materials. Experiments were performed using highly oriented pyrolytic graphite (HOPG), LiF, Si, Ge, Cu, and W target crystal radiators. Smooth X-ray energy tunability is achieved by rotating the crystal with respect to the electron beam direction. Measured energy linewidths consistently agreed with predicted values except in cases using lower quality HOPG. When the predicted energy linewidth was narrower than our Si X-ray detector resolution (350 eV at 17.5 KeV), a near-absorption edge transmission technique that takes advantage of the PXR energy tunabilty was used to measure the PXR energy linewidth for example, Si(4 0 0) FWHM of 134 eV at 9.0 keV (2%). Per electron, the photon production efficiency of PXR is comparable to synchrotron radiation sources. A theoretical model that considers electron multiple scattering, electron divergence, and crystal mosaicity was used to broaden the PXR photon distribution in order to calculate the predicted PXR photon yield. Comparing measurements and calculations resulted in a typical relative error below 50%. In some cases with LiF, the differences between predicted and measured values were as low as 2% for LiF(4 0 0). Finally, this work reports for the first-time PXR imaging. This was achieved using LiF(2 2 0) interacting with 56 MeV electrons with electron beam currents up to 6 lA. The LiF and graphite PXR target crystals were compared for use in soft tissue imaging, e.g. mammography using energies 17–20 keV. Low Z materials like graphite and LiF were most suitable for PXR production because of their low Bremsstrahlung production, electron scattering, and photon absorption. Graphite was more efficient at producing PXR photons while the LiF energy line width was narrower. � 2007 Elsevier B.V. All rights reserved. PACS: 41.60.� m; 87.59.� e; 41.75.Fr

Accurate isotopic molybdenum nuclear data are important because molybdenum can exist in nuclear reactor components including fuel, cladding, or as a high yield fission product. High-resolution time-of-flight neutron transmission measurements on highly enriched isotopic metallic samples of $^{95}\mathrm{Mo}$, $^{96}\mathrm{Mo}$, $^{98}\mathrm{Mo}$, and $^{100}\mathrm{Mo}$ were performed in the resonance energy range from 1 to $620\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$. The measurements were taken with the newly developed modular $^{6}\mathrm{Li}$-glass transmission detector positioned at the 100-m experimental flight station. In the unresolved energy region (URR), new comprehensive methods of analysis were developed and validated in order to obtain accurate neutron total cross-section data from the measurement by correcting for background and transmission enhancement effects. Average parameters and fits to the total cross section for $^{95}\mathrm{Mo}$ were obtained using the Hauser-Feshbach statistical model code fitacs, which is currently incorporated into the sammy code. The fits to the experimental data deviate from the current evaluated nuclear data file/B-VII.1 isotopic Mo evaluations by several percent in the URR.

Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute linac facility using metallic and liquid Gd samples. The liquid ...

The purpose of the present work is to accurately measure the neutron cross sections of samarium. The most significant isotope is {sup 149}Sm, which has a large neutron absorption cross section at thermal energies and is a {sup 235}U fission product with a 1% yield. Its cross sections are thus of concern to reactor neutronics. Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic institute (RPI) LINAC facility using metallic and liquid Sm samples. The capture measurements were made at the 25 meter flight station with a multiplicity-type capture detector, and the transmission total cross-section measurements were performed at 15- and 25-meter flight stations with {sup 6}Li glass scintillation detectors. Resonance parameters were determined by a combined analysis of six experiments (three capture and three transmission) using the multi-level R-matrix Bayesian code SAMMY version M2. The significant features of this work are as follows. Dilute samples of samarium nitrate in deuterated water (D{sub 2}O) were prepared to measure the strong resonances at 0.1 and 8 eV without saturation. Disk-shaped spectroscopic quartz cells were obtained with parallel inner surfaces to provide a uniform thickness of solution. The diluent feature of the SAMMY program was usedmore » to analyze these data. The SAMMY program also includes multiple scattering corrections to capture yield data and resolution functions specific to the RPI facility. Resonance parameters for all stable isotopes of samarium were deduced for all resonances up to 30 eV. Thermal capture cross-section and capture resonance integral calculations were made using the resultant resonance parameters and were compared to results obtained using resonance parameters from ENDF/B-VI updated through release 3. Extending the definition of the capture resonance integral to include the strong 0.1 eV resonance in {sup 149}Sm, present measurements agree within estimated uncertainties with EnDF/B-VI release 3. The thermal capture cross-section was calculated from the present measurements of the resonance parameters and also agrees with ENDF within estimated uncertainties. The present measurements reduce the statistical uncertainties in resonance parameters compared to prior measurements.« less

A neutron source having ∼30 discrete energy lines in the range 34–6200 eV is produced by using a 238U filter in conjunction with an electron linear accelerator. The characteristics of this neutron source are discussed and possible uses and applications are given.

Neodymium is a 235 U fission product and is important for reactor neutronic calculations. The aim of the present work is to improve upon the existing neutron cross-section data of neodymium. Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute (RPI) linear accelerator (LINAC) laboratory using metallic neodym- ium samples. The capture measurements were made at the 25-m flight station with a 16-segment NaI multiplicity detector, and the transmission measurements were performed at 15- and 25-m flight stations, respectively, with 6 Li glass scintillation detectors. After the data were collected and reduced, resonance parameters were determined by combined fitting of the transmission and capture data with the SAMMY multilevel R-matrix Bayesian code. The resonance parameters for all naturally occurring neodymium isotopes were deduced within the energy range of 1 to 500 eV. The resulting resonance parameters were used to calculate the capture resonance integrals from this energy. The RPI parameters gave a resonance integral value of 32 61 b that is ;7% lower than that obtained with the ENDF/B-VI parameters. The current measurements significantly reduce the uncertainties of the resonance parameters when compared with previously published parameters.

X-ray imaging produced by parametric X-rays (PXR) is reported. The PXR are generated using an electron beam with energy of 56 MeV and currents up to 6.4 μA, that interacted with a 1.5-mm thick lithium fluoride (LiF) crystal target in Laue geometry. The LiF (2 2 0) crystallographic plane was used with a Bragg angle (θB) near 15° to produce PXR with energy 16.6 keV and FWHM of 3%. This intense, directional, and tunable X-ray source was then used to image a small fish, an integrated circuit, and an electrical switch with an intensified CCD camera. The bremsstrahlung from the target crystal is characterized as a source of noise and compared to the PXR.