Nuclear Data Center Research Articles

Current Status of ACE Format Libraries for MCNP at Nuclear Data Center of KAERI

Current Status of ACE Format Libraries for MCNP at Nuclear Data Center of KAERI

Microscopic description of superallowedα-decay transitions

It was recently found that the formation probabilities of $\ensuremath{\alpha}$ particles in Te isotopes are larger than the corresponding probabilities in Po isotopes. We have done a full microscopic calculation within the framework of the multistep shell model to analyze in detail the formation probabilities and subsequent decays of $\ensuremath{\alpha}$ particles from $^{212}\mathrm{Po}$ and $^{104}\mathrm{Te}$. We have also calculated the spectra of these two decaying nuclei and found that the tentatively assigned spin $({18}^{+})$ at 2.922 MeV in $^{212}\mathrm{Po}$ (National Nuclear Data Center, www.nndc.bnl.gov) is predicted to be a state ${16}^{+}$. We also present for the first time the full energy spectrum of $^{104}\mathrm{Te}$. The evaluated formation amplitudes in both nuclei show that in $^{104}\mathrm{Te}$ there is indeed a superallowed $\ensuremath{\alpha}$-decay transition.

Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources.

AimThe aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters.BackgroundDifferent photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources.Materials and methodsMCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared.ResultsDose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours.ConclusionsDosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems.

Study of charged particle activation analysis (I): determination sensitivity for single element samples

Charged particle activation analysis (CPAA) utilizing an 8 MeV proton beam has been studied for general elemental quantification. We accumulate the reaction cross section and nuclear decay data by referring to nuclear database supplied by National Nuclear Data Center in Brookhaven National Laboratory. By using the database we have derived determination sensitivity of single element samples for each nuclide. The result indicates that, while the determination sensitivity tends to decrease gradually as the target nucleus becomes heavy, the CPAA analysis is possible over the whole elements including the heavy nuclear region. It may be concluded that CPAA can be applied to most of the stable nuclei and is one of the alternative methods to neutron activation analysis.

Reducing uncertainties for short lived cumulative fission product yields

Uncertainties associated with short lived (half-lives less than 1 day) fission product yields listed in databases such as the National Nuclear Data Center’s ENDF/B-VII are large enough for certain isotopes to provide an opportunity for new precision measurements to offer significant uncertainty reductions. A series of experiments has begun where small samples of 235U are irradiated with a pulsed, fission neutron spectrum at the Nevada National Security Site and placed between two broad-energy germanium detectors. The amount of various isotopes present immediately following the irradiation can be determined given the total counts and the calibrated properties of the detector system. The uncertainty on the fission yields for multiple isotopes has been reduced by nearly an order of magnitude.

Progress of Covariance Evaluation at the China Nuclear Data Center

Covariance evaluations at the China Nuclear Data Center focus on the cross sections of structural materials and actinides in the fast neutron energy range. In addition to the well-known Least-squares approach, a method based on the analysis of the sources of experimental uncertainties is especially introduced to generate a covariance matrix for a particular reaction for which multiple measurements are available. The scheme of the covariance evaluation flow is presented, and an example of n+90Zr is given to illuminate the whole procedure. It is proven that the accuracy of measurements can be properly incorporated into the covariance and the long-standing small uncertainty problem can be avoided.

Verification and Validation of the ENDF/B-VII.1–Based Continuous-Energy Data Tables for MCNP6

In December 2011, the National Nuclear Data Center released ENDF/B-VII.1, the “latest recommended evaluated nuclear data file for use in nuclear science and technology applications.” The data were released in the standard Evaluated Nuclear Data Format (ENDF). This release represents the advances made in nuclear data during the 5 years since the release of ENDF/B-VII.0. The Nuclear Data Team at Los Alamos National Laboratory has processed the ENDF/B-VII.1 library and made available a library of ACE data tables at several temperatures for each of the ENDF/B files. The ACE data library is called ENDF71x and is available through the Radiation Safety Information Computational Center with MCNP6. The files can also be used with MCNP5 or other Monte Carlo codes.

B(E2,4→2)/B(E2,2→0)ratio in even-even nuclei: Apparent anomalous behavior of the chromium isotopes

We consider the ratio $\mathrm{RE}4=B(E2,4\ensuremath{\rightarrow}2)/B(E2,2\ensuremath{\rightarrow}0)$ for the lowest ${2}^{+}$ and ${4}^{+}$ states in even-even nuclei. In the rotational and vibrational models and the shell-model calculations considered here, $\mathrm{RE}4$ is greater than 1; however, empirically, using National Nuclear Data Center adopted half-lives and energies for $^{48}\mathrm{Cr}$ and $^{50}\mathrm{Cr}$, this ratio is less than 1.

Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR): International Collaboration Between Nuclear Reaction Data Centres (NRDC)

The International Network of Nuclear Reaction Data Centres (NRDC) coordinated by the IAEA Nuclear Data Section (NDS) successfully collaborates in the maintenance and development of the EXFOR library. As the scope of published data expands (e.g. to higher energy, to heavier projectile) to meet the needs of research and applications, it has become a challenging task to maintain both the completeness and accuracy of the EXFOR library. Evolution of the library highlighting recent developments is described.

Developments of the EXFOR Database: Possible New Formats

The EXFOR database is a collection of experimental nuclear reaction data, maintained by the IAEA on behalf of the International Network of Nuclear Reaction Data Centres (NRDC). The format for the storage of such data was first described in 1969 and while there have been many incremental changes over the years so that the format is now capable of containing a very wide range of measurement results, there is a growing realisation that a major change is required. Consequently the IAEA Nuclear Data Section (NDS) organised a Consultant's Meeting on ‘Further Development of EXFOR’ in 2012. This was an opportunity for a range of international experts to discuss ways of improving EXFOR and while this focused on new formats there was also discussion on ways of storing new data, new output formats and software tools such as editors. This paper will discuss recent and proposed changes to enable new quantities to be stored (such as coincidence measurements and covariances), the range of output formats available (e.g. C4 and X4+) which make interaction with the data more user friendly and the possible use of XML to modernise the database.

Educational Outreach Efforts at the NNDC

Isotopes and nuclides are important in our everyday life. The general public and most students are never exposed to the concepts of stable and radioactive isotopes/nuclides. The National Nuclear Data Center (NNDC) is involved in an international project to develop a Periodic Table of the Isotopes for the educational community to illustrate the importance of isotopes and nuclides in understanding the world around us. This effort should aid teachers in introducing these concepts to students from the high school to the graduate school level.

Nuclear Science References Database

The Nuclear Science References (NSR) database together with its associated Web interface, is the world's only comprehensive source of easily accessible low- and intermediate-energy nuclear physics bibliographic information for more than 210,000 articles since the beginning of nuclear science. The weekly-updated NSR database provides essential support for nuclear data evaluation, compilation and research activities. The principles of the database and Web application development and maintenance are described. Examples of nuclear structure, reaction and decay applications are specifically included. The complete NSR database is freely available at the websites of the National Nuclear Data Center http://www.nndc.bnl.gov/nsr and the International Atomic Energy Agency http://www-nds.iaea.org/nsr.

Recent Developments in the Experimental Nuclear Reaction Data Library EXFOR

The International Network of Nuclear Reaction Data Centres (NRDC) provides nuclear reaction data services to users through collection and compilation of experimental nuclear reaction data in the EXFOR database. The database includes neutron-induced, charged-particle-induced, and photonuclear data for projectile energies up to 1 GeV. Sophisticated search options and user-friendly retrieval interface for downloading data in different formats have been developed at IAEA Nuclear Data Section. Additional output options such as data plotting capabilities are provided as well. The database is constantly revised and extended and at present contains about 20,000 experimental works accumulated in its 40 years of history. The paper will present several recent IAEA NDS activities related to the development of the EXFOR database and retrieval system.

Systematics of low-lying state transition probabilities and excitation energies in the region30≤Z≤38and30≤N≤50

Background: Single-particle and collective modes of nuclear excitation compete in the isotopes of the elements ${}_{30}$Zn, ${}_{32}$Ge, ${}_{34}$Se, ${}_{36}$Kr, and ${}_{38}$Sr.Purpose: To study the factors which determine the onset of collectivity in this region.Methods: Data obtained from National Nuclear Data Center compilations supplemented by recent measurements of excitation energies and $B(E2)$ reduced transition probabilities between the low-lying states in these elements were examined. The data were analyzed as a function of the neutron number $N$ as well as the parameter $P={N}_{p}{N}_{n}/({N}_{p}+{N}_{n})$ related to the number of valence protons and neutrons, ${N}_{p}$ and ${N}_{n}$, in the $28\ensuremath{\le}Z,N\ensuremath{\le}50$ shell.Results: The systematics of the data show variations ranging from mostly single-particle to collective excitations.Conclusions: Collectivity sets in when the number of both protons and neutrons lie near the middle of the shell $30\ensuremath{\le}Z,N\ensuremath{\le}50$. Backbends appear in the data showing that particles and holes in the major shell behave differently. The ${2}_{2}^{+}$ states exhibit single particle behavior. The transition probabilities of the ${2}_{2}^{+}$ states in the Kr isotopes differ significantly from the systematics.

Standard spectrum measurement and simulation of elemental capture spectroscopy log

We have established a set of laboratory measurements which is used for capturing element gammma spectrum. Standard captured gamma ray spectra for ten elements, including Si, Ca, Fe, are obtained using the measurements for the first time in China. We also simulated the capture gamma ray spectra of the ten elements using Monte Carlo methodology with the same parameters of our experimental measurements. Comparing the experiment and simulation results with the data from the International Atomic Energy Agency’s Nuclear Data Center, we obtained the standard captured gamma ray spectra of the ten elements, which, as calibration spectra, are used to calibrate the raw spectrum in data processing. This method solved the key problem during the conversion from the original measuring spectrum to the yield of each element in the data processing. The method can effectively improve the accuracy of the element yield calculation.

On determining dose rate constants spectroscopically

To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of (125)I and (103)Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089-6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated (125)I and (103)Pd sources. Spectra generated by 14 (125)I and 6 (103)Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm(3) voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the (125)I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for (103)Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ≤0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. The ratio of the intensity of the 31 keV line relative to that of the main peak in (125)I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The (103)Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different investigations are in much better agreement with the calculations using the NCRP Report 58 and NNDC(2000) initial spectra with average discrepancies of 0.9% and 1.7% for the (125)I and (103)Pd seeds, respectively. However, there are no differences in the calculated TG-43U1 brachytherapy parameters using either initial spectrum in both cases. Similarly, there were no differences outside the statistical uncertainties of 0.1% or 0.2%, in the average energy, air kerma/history, dose rate/history, and dose rate constant when calculated using either the full photon spectrum or the main-peaks-only spectrum. Our calculated dose rate constants based on using the calculated on-axis spectrum and a line or dual-point source model are in excellent agreement (0.5% on average) with the values of Chen and Nath, verifying the accuracy of their more approximate method of going from the spectrum to the dose rate constant. However, the dose rate constants based on full seed models differ by between +4.6% and -1.5% from those based on the line or dual-point source approximations. These results suggest that the main value of spectroscopic measurements is to verify full Monte Carlo models of the seeds by comparison to the calculated spectra.

Model of individual collisions for description of electron transport in matter

Distributions of electron characteristics are constructed with the use of data of elastic and nonelastic processes of interaction between electrons and matter. The data are taken from the National Nuclear Data Center, http://www.nndc.bnl.gov/. These characteristics are used for developing the technique of modeling the electron transport in matter. The developed model does not use the well-known slowdown approximation and multiple scattering theories. The comparison of some moments of the distributions with the NIST data is carried out. The satisfactory fit of some results computed by using the developed model and MCNP results is obtained.

Studies on p+6Li Fusion Reaction using 3-Parameter Model

The 3-parameter model introduces 3 parame- ters (radius of a square nuclear potential well, the real part and the imaginary part of the nuclear potential depth) to describe the low energy behavior of the fusion cross-sec- tion for light nuclei. It has been justified by the experi- mental data from the National Nuclear Data Center (NNDC) for 3 major fusion reactions (d ? T, d ? D, and d ? 3 He). In the present paper this 3-parameter model has been extended to p? 6 Li fusion reaction. It agrees with the fusion cross-section data from NNDC again. Moreover it is able to calculate the astrophysical S-factor with an electron screening potential for p? 6 Li fusion reaction as well. As a development of the 3-parameter model, the necessary condition for a low energy resonant tunneling through Coulomb barrier is derived. It reveals further the possibility of resonant tunneling at very low energy for p? 6 Li system.

The Role of the Nuclear Reaction Data Centres in Experimental Nuclear Data Knowledge Sharing

The International Network of Nuclear Reaction Data Centres (NRDC) consists of 14 data centers from 10 countries and 2 international organizations, and is collaborating for compilation, exchange and dissemination of various types of nuclear reaction data information. The nuclear data centers common data collection, the EXFOR library today contains experimental information and numerical data from more than 18,000 experiments consisting of more than 134,000 data sets mainly of nuclear reaction data for incident neutrons, charged-particles and photons with incident energy lower than 1 GeV. A brief history and the current status of NRDC collaboration are presented for EXFOR as well as CINDA and ENDF.

System of Covariance Data Evaluation at China Nuclear Data Centre-COVAC

To determine the uncertainty of neutron cross sections for modern nuclear data application, a new evaluation system, COVAC is being developed at China Nuclear Data Centre (CNDC). In COVAC, experimental data were firstly pre-analyzed and handled via processing tools. The sensitivities of theoretical model parameters were analyzed by a special designed subsystem-SEMAW which offers a platform to obtain parameter sensitivities for different nuclear reaction codes. In addition the generalized least-squares method (GLS) and Bayesian method were both contained in COVAC to generate the recommended covariance. The experimental and theoretical uncertain information can be included in the covariance by each of the two methods. The outputs are formatted in ENDF-6. So far, COVAC is suitable to generate the covariance files for structure and fission nuclei in the fast neutron energy range, and n+Ti was taken to illuminate the whole procedure.