Nuclear Reaction Code Research Articles

Optimization of 89Zr production using Monte Carlo simulations

Zirconium-89 (89Zr) can be produced in a cyclotron by focusing the proton beam on an yttrium-89 (89Y) foil target. Optimal combination of beam energy and target assembly configuration enables maximum production of 89Zr while minimizing the formation of contaminant nuclides such as 88Zr and 88Y to allow efficient and effective radiopharmaceutical labeling. Accurate modeling of the proton beam and the target is therefore an essential step to assure the best beam and target specification. We used the radiation transport code MCNPX to simulate the transport of protons through the irradiation assembly and the nuclear reaction code TALYS to obtain the production cross sections of various nuclides from proton-89Y reactions. Results from simulating the irradiation of 14 mm diameter targets with aluminum (Al) degrader at 19.8 mA for 1 h suggested that the 0.15 mm thick one would produce 227 MBq while the 0.3 mm thick one would produce 413 MBq of 89Zr with less than 1 % uncertainty. These results show excellent agreement with experimental work in literature. This work provides the basis for further experimental and theoretical assessments of the use of 89Zr as radiopharmaceutical labels.

Experimental excitation functions of deuteron induced reactions on natural thallium up to 50 MeV

Excitation functions of deuteron induced reactions on natural thallium leading to the formation of 204m,203m2+m1+g,202m,201m+g,200Pb and 202,201m+g,200m+gTl isotopes were determined up to 50MeV.The cross sections were measured by an activation technique using stacked foil irradiation. The excitation functions of the investigated reactions are compared with data reported in literature and also with the theoretical results of TALYS nuclear reaction code. From the measured cross section data, the thick target yield for the medical interesting 203Pb isotope is calculated.

Simulation of prompt gamma-ray emission during proton radiotherapy

The measurement of prompt gamma rays emitted from proton-induced nuclear reactions has been proposed as a method to verify in vivo the range of a clinical proton radiotherapy beam. A good understanding of the prompt gamma-ray emission during proton therapy is key to develop a clinically feasible technique, as it can facilitate accurate simulations and uncertainty analysis of gamma detector designs. Also, the gamma production cross-sections may be incorporated as prior knowledge in the reconstruction of the proton range from the measurements. In this work, we performed simulations of proton-induced nuclear reactions with the main elements of human tissue, carbon-12, oxygen-16 and nitrogen-14, using the nuclear reaction models of the GEANT4 and MCNP6 Monte Carlo codes and the dedicated nuclear reaction codes TALYS and EMPIRE. For each code, we made an effort to optimize the input parameters and model selection. The results of the models were compared to available experimental data of discrete gamma line cross-sections. Overall, the dedicated nuclear reaction codes reproduced the experimental data more consistently, while the Monte Carlo codes showed larger discrepancies for a number of gamma lines. The model differences lead to a variation of the total gamma production near the end of the proton range by a factor of about 2. These results indicate a need for additional theoretical and experimental study of proton-induced gamma emission in human tissue.

Partialγ-ray production cross sections for (n,xnγ) reactions in natural argon at 1–30 MeV

Background: Neutron-induced backgrounds are a significant concern for experiments that require extremely low levels of radioactive backgrounds such as direct dark matter searches and neutrinoless double-beta decay experiments. Unmeasured neutron scattering cross sections are often accounted for incorrectly in Monte Carlo simulations. Purpose: Determine partial gamma-ray production cross sections for (n,xng) reactions in natural argon for incident neutron energies between 1 and 30 MeV. Methods: The broad spectrum neutron beam at the Los Alamos Neutron Science Center (LANSCE) was used used for the measurement. Neutron energies were determined using time-of-flight and resulting gamma rays from neutron-induced reactions were detected using the GErmanium Array for Neutron Induced Excitations (GEANIE). Results: Partial gamma-ray cross sections were measured for six excited states in Ar-40 and two excited states in Ar-39. Measured (n,xng) cross sections were compared to the TALYS and CoH3 nuclear reaction codes. Conclusions: These new measurements will help to identify potential backgrounds in neutrinoless double-beta decay and dark matter experiments that use argon as a detection medium or shielding. The measurements will also aid in the identification of neutron interactions in these experiments through the detection of gamma rays produced by (n,xng) reactions.

Transmission resonance spectroscopy in the third minimum of232Pa

The fission probability of ${}^{232}$Pa was measured as a function of the excitation energy in order to search for hyperdeformed (HD) transmission resonances using the ($d,pf$) transfer reaction on a radioactive ${}^{231}$Pa target. The experiment was performed at the Tandem accelerator of the Maier-Leibnitz Laboratory (MLL) at Garching using the ${}^{231}$Pa($d,pf$) reaction at a bombarding energy of ${E}_{d}=12$ MeV and with an energy resolution of $\ensuremath{\Delta}E=5.5$ keV. Two groups of transmission resonances have been observed at excitation energies of ${E}^{*}=5.7$ and 5.9 MeV. The fine structure of the resonance group at ${E}^{*}=5.7$ MeV could be interpreted as overlapping rotational bands with a rotational parameter characteristic to a HD nuclear shape (${\ensuremath{\hbar}}^{2}/2\ensuremath{\Theta}=2.10\ifmmode\pm\else\textpm\fi{}0.15$ keV). The fission barrier parameters of ${}^{232}$Pa have been determined by fitting talys 1.2 nuclear reaction code calculations to the overall structure of the fission probability. From the average level spacing of the $J=4$ states, the excitation energy of the ground state of the third minimum has been deduced to be ${E}_{\text{III}}={5.05}_{\ensuremath{-}0.10}^{+0.40}$ MeV.

Nuclear ingredients for cross section calculation of exotic nuclei

The increasing need for cross sections far from the valley of stability, especially for applications such as nuclear astrophysics, poses a challenge for nuclear reaction models. So far, predictions of cross sections have relied on more or less phenomenological approaches, depending on parameters adjusted to available experimental data or deduced from systematic relations. While such predictions are expected to be reliable for nuclei not too far from the experimentally known regions, it is clearly preferable to use more fundamental approaches, based on sound physical bases, when dealing with very exotic nuclei. Thanks to the high computer power available today, all major ingredients required to model a nuclear reaction can now be (and have been) microscopically (or semi-microscopically) determined starting from the information provided by an effective nucleon-nucleon interaction. All these microscopic ingredients have been included in the latest version of the TALYS nuclear reaction code (http://www.talys.eu/).

Validation of Nuclear Reaction Codes for Proton-Induced Radiation Effects: The Case for CEM03

Experimental cross-section data for the interaction of protons with Al, Co, and Au at intermediate energies are compared with the predictions of the nuclear reaction models CEM03, BIC, Bertini INC, and INCL-ABLA. Fission cross-section data for the interaction of protons with W and Au in the energy range 50 MeV-3 GeV are also compared with the considered models. The study reveals that all of the models are satisfactory in limited ranges. However, of these, the CEM03 code from Los Alamos exhibits the broadest applicability for radiation effects computations.

Implementation of New Fission Barrier Model in TALYS Code

This paper is aimed to calculate neutron induced fission cross section using TALYS nuclear reaction code by utilizing new fission barrier model parameter. The new fission barrier model is based on minimization method of action functional of deformed nucleus fission trajectory in configuration of space from ground state to the exit barrier. New fission barrier parameter that obtained from this new model will be fed into the TALYS code to calculate the fission cross section of Th-232 and U-238 through statistical method. The result shows a better agreement with ENDF data compared to that of ETFSI (Extended Thomas-Fermi and Strutinsky Integral) or Mamdouh model of fission barrier for energy between 2 and 10 MeV.

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.

Recent Developments in the Nonelastic Reaction Code BRIEFF

The production of light-mass ion in nucleon induced reactions was lacking in the intranuclear cascade (INC) model of the nuclear reaction code BRIEFF. Deuteron candidates can now be created all along the evolution of the INC stage of reaction ac- cording a quasi-free coalescence process inside the nuclear+Coulomb field of the target nucleus. This process is partly based on the opposite process of the deuteron breakup al- ready implemented. The emission of a deuteron candidate is the result of the competition between the deuteron formation and the deuteron breakup. This development of our INC model allows to calculate the production of deuteron in the full range of outgoing energy in nucleon induced reactions but also in deuteron induced reactions. Preliminary results of deuteron production in continuum in proton (p,xd) and deuteron (d,xd) induced reactions are presented and discussed.

Nuclear cross sections for gamma ray deexcitation line production by secondary neutrons in the Earth's atmosphere

[1] Interactions of galactic cosmic rays and solar energetic particles with nuclei in the Earth's atmosphere produce secondary neutrons. Secondary neutrons with energies greater than a few MeV interact with atmospheric nuclei and produce gamma ray lines. The relative intensities of these lines depend on the shape of the neutron energy spectrum, and so their measurement with satellite detectors provides neutron spectral information complementary to direct observation. Reliable interpretation of such line measurements requires accurate knowledge of the production cross sections. Because the atmospheric neutron spectrum at these energies is very hard (falling by less than a factor of 10 from 10 to 100 MeV), higher-energy neutrons contribute significantly to line production. Knowledge of the cross sections at these higher energies is critical for accurate line yield predictions. In this paper we evaluate and present the most important cross sections for deexcitation line production by neutron interactions with the Earth's atmosphere, with emphasis on extending them to higher neutron energies, using both laboratory measurements and the nuclear reaction code TALYS to obtain the cross sections from a few to >200 MeV. Using these cross sections, we also demonstrate the sensitivity of gamma ray line ratios for providing information about the ∼1–200 MeV atmospheric neutron spectrum.

Measurements of nuclearγ-ray line emission in interactions of protons andαparticles with N, O, Ne, and Si

$\gamma$-ray production cross sections have been measured in proton irradiations of N, Ne and Si and $\alpha$-particle irradiations of N and Ne. In the same experiment we extracted also line shapes for strong $\gamma$-ray lines of $^{16}$O produced in proton and $\alpha$-particle irradiations of O. For the measurements gas targets were used for N, O and Ne and a thick foil was used for Si. All targets were of natural isotopic composition. Beams in the energy range up to 26 MeV for protons and 39 MeV for $\alpha$-particles have been delivered by the IPN-Orsay tandem accelerator. The $\gamma$ rays have been detected with four HP-Ge detectors in the angular range 30$^{\circ}$ to 135$^{\circ}$. We extracted 36 cross section excitation functions for proton reactions and 14 for $\alpha$-particle reactions. For the majority of the excitation functions no other data exist to our knowledge. Where comparison with existing data was possible usually a very good agreement was found. It is shown that these data are very interesting for constraining nuclear reaction models. In particular the agreement of cross section calculations in the nuclear reaction code TALYS with the measured data could be improved by adjusting the coupling schemes of collective levels in the target nuclei $^{14}$N, $^{20,22}$Ne and $^{28}$Si. The importance of these results for the modeling of nuclear $\gamma$-ray line emission in astrophysical sites is discussed.

Experimental studies on deuteron-induced activation reactions in IFMIF accelerator structural elements

In order to improve the quality of deuteron-induced activation data required for the safety design of the IFMIF (International Fusion Materials Irradiation Facility), we have measured (1) the activation cross-section of natLi(d,x)7Be in the deuteron-energy range from 7 to 39MeV and (2) the production rates of radioactive nuclides in thick targets for natLi(d,x)7Be, natC(d,x)7Be, and 27Al(d,x)7Be, 22Na, 24Na reactions at 40MeV using the AVF cyclotron of Tohoku University. We have also estimated the production rates of these nuclides in the thick targets below 40MeV using the cross-sections obtained in this study.The present data compared favorably with other experimental data, IAEA-recommended data, and the data obtained using the recent nuclear reaction code TALYS and the activation code IRACM, which is based on the ALICE-F code. Some calculation results showed marked disagreement with the experimental data.

Fission properties of actinide nuclei from proton-induced fission at 26.5 and 62.9 MeV incident proton energies

Fission properties of proton-induced fission on {sup 232}Th, {sup 237}Np, {sup 238}U, {sup 239}Pu, and {sup 241}Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code talys. The code couples the multimodal random neck-rupture model with the pre-equilibrium exciton and statistical models to predict fission fragment mass yields, pre- and post-scission neutron multiplicities, and total fission cross sections in a consistent approach. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed in detail.

Directional distribution of the ambient neutron dose equivalent from 145-MeV 19F projectiles incident on thick Al target

The directional distribution of the ambient neutron dose equivalent from 145-MeV (19)F projectiles bombarding a thick aluminium target is measured and analysed. The measurements are carried out with a commercially available dose equivalent meter at 0°, 30°, 60° and 90° with respect to the beam direction. The experimental results are compared with calculated doses from EMPIRE nuclear reaction code and different empirical formulations proposed by others. The results are also compared with the measured data obtained from an earlier experiment at a lower projectile energy of 110 MeV for the same target-projectile combination.

Calculation of Prompt Fission Product Average Cross Sections for Neutron-Induced Fission of 235U and 239Pu

Yield-weighted average cross sections of neutron radiative capture, (n,2n), and (n,3n) reactions over prompt fission products (FPs) from 235U and 239Pu are calculated. The prompt fission production yields are taken from the ENDF/B-VII.0 library. The FPs for each fissile material exist over a range of approximately 1000 neutron-rich nuclides. Several nuclear reaction codes are utilized for calculating the cross sections on each individual fission product—EMPIRE-2.19, TALYS-1.0, GNASH, and CoH. The influence of the FP isomers on the average cross sections is examined with TALYS. We investigate the dependence of the average cross sections on the number of FPs taken for averaging. It is shown that the average capture cross section is much more sensitive to the number of FPs included, compared with the (n,2n) and (n,3n) reactions. An intercomparison of the calculated cross sections with the different reaction codes is carried out. In the capture reaction, EMPIRE predicted lower cross section than TALYS and CoH owing to different default assumptions used in the γ-ray strength function modeling. Moreover, the preequilibrium models implemented in each code give different predictions for the neutron-emission reactions, although the differences are relatively small. We also discuss a difference between the macroscopic and microscopic calculation options in TALYS for the pre-equilibrium model, optical potential model, and γ-ray strength function. The predictive capability of the reaction codes for the capture reaction is examined by comparing their calculations with the ENDF data, which are based on measurements. Compared with the historic Foster and Arthur's evaluation, our new (n,2n) predictions are similar, although our capture predictions are almost an order of magnitude higher. Recommended cross sections for use in applications have been tabulated in ENDF-formatted files.

Calculation of Prompt Fission Product Average Cross Sections for Neutron-Induced Fission of 235U and 239Pu

Yield-weighted average cross sections of neutron radiative capture, (n,2n), and (n,3n) reactions over prompt fission products (FPs) from 235U and 239Pu are calculated. The prompt fission production yields are taken from the ENDF/B-VII.0 library. The FPs for each fissile material exist over a range of approximately 1000 neutron-rich nuclides. Several nuclear reaction codes are utilized for calculating the cross sections on each individual fission product—EMPIRE-2.19, TALYS-1.0, GNASH, and CoH. The influence of the FP isomers on the average cross sections is examined with TALYS. We investigate the dependence of the average cross sections on the number of FPs taken for averaging. It is shown that the average capture cross section is much more sensitive to the number of FPs included, compared with the (n,2n) and (n,3n) reactions. An intercomparison of the calculated cross sections with the different reaction codes is carried out. In the capture reaction, EMPIRE predicted lower cross section than TALYS and CoH owing to different default assumptions used in the γ-ray strength function modeling. Moreover, the preequilibrium models implemented in each code give different predictions for the neutron-emission reactions, although the differences are relatively small. We also discuss a difference between the macroscopic and microscopic calculation options in TALYS for the pre-equilibrium model, optical potential model, and γ-ray strength function. The predictive capability of the reaction codes for the capture reaction is examined by comparing their calculations with the ENDF data, which are based on measurements. Compared with the historic Foster and Arthur's evaluation, our new (n,2n) predictions are similar, although our capture predictions are almost an order of magnitude higher. Recommended cross sections for use in applications have been tabulated in ENDF-formatted files.

Microscopic cross sections: An utopia?

The increasing need for cross sections far from the valley of stability poses a challenge for nuclear reaction models. So far, predictions of cross sections have relied on more or less phenomenological approaches, depending on parameters adjusted to available experimental data or deduced from systematical relations. While such predictions are expected to be reliable for nuclei not too far from the experimentally known regions, it is clearly preferable to use more fundamental approaches, based on sound physical bases, when dealing with very exotic nuclei. Thanks to the high computer power available today, all major ingredients required to model a nuclear reaction can now be (and have been) microscopically (or semi-microscopically) determined starting from the information provided by a nucleon-nucleon effective interaction. We have implemented all these microscopic ingredients in the TALYS nuclear reaction code, and we are now almost able to perform fully microscopic cross section calculations. The quality of these ingredients and the impact of using them instead of the usually adopted phenomenological parameters will be discussed.

Recent developments in the nonelastic reaction code BRIEFF

The production of light-mass ion in nucleon induced reactions was lacking in the intranuclear cascade (INC) model of the nuclear reaction code BRIEFF. Deuteron candidates can now be created all along the evolution of the INC stage of reaction ac- cording a quasi-free coalescence process inside the nuclear+Coulomb field of the target nucleus. This process is partly based on the opposite process of the deuteron breakup al- ready implemented. The emission of a deuteron candidate is the result of the competition between the deuteron formation and the deuteron breakup. This development of our INC model allows to calculate the production of deuteron in the full range of outgoing energy in nucleon induced reactions but also in deuteron induced reactions. Preliminary results of deuteron production in continuum in proton (p,xd) and deuteron (d,xd) induced reactions are presented and discussed.

Simultaneous Evaluation of Fission Cross Sections for Cm Isotopes

Fission Cross Sections for a complete set of Cm-isotopes, 240 250 Cm, have been calculated in the incident energy range from above resonance region to 20 MeV. This work aims at providing the fission cross sections with consistent set of model parameters for Cm isotopes, as a part of a complete evaluation including covariance files for several minor actinides which play a great role in the Advanced Fuel Cycle (AFC) design and applications as well as the design of new generation of nuclear reactors (GEN-IV). This was accomplished by means of computational analyses carried out with the nuclear model code EMPIRE-2.19 which is the modular system of nuclear reaction codes. A Fission model of this work took into account transmission derived in the WKB approximation within an optical model through a double-humped fission barrier.