99Mo Reaction Research Articles

An analytical approach to optimization of isotope production by bremsstrahlung radiation

Based on analytical description of isotope production by bremsstrahlung (X-ray) radiation, an algorithm is proposed for calculating the optimal dimensions of a cylindrical target of given mass positioned at a given distance from a bremsstrahlung converter to ensure the maximum yield of the isotope product. The expressions are derived for the total activity and its distribution along the target axis. A technique of γ-spectrometric measuring the activity of a thick production target is proposed. The novel approach is validated by the 100Mo(γ,n)99Mo reaction induced in a natural molybdenum target by mass in the range 10-100g with the X-ray photons at an end-point energy of 40 MeV. The analytical predictions are in good agreement with the results of Monte-Carlo simulations and experiment.

Measurement of effective 98Mo(n,γ)99 Mo reaction cross-section in the epi-cadmium neutron flux produced by 10 MeV electron LINAC with Ta-BeO assembly

An experiment was carried out to study the feasibility of 99Mo production using an electron accelerator based epi-cadmium neutron source. The neutrons were produced by the interaction of bremsstrahlung end-point energy of 10 MeV with BeO blocks and the neutrons thus produced were moderated using High Density Polyethylene blocks. Effective cross-section of 98Mo(n,γ)99Mo reaction was measured using foil activation method. An enhancement in the effective cross-section due to resonances in the epi-cadmium region was observed. The photons and neutron production/transport in the experimental set-up were simulated using the FLUKA Monte Carlo code. The simulations were found to be in good agreement with the experimental findings.

Measurement of neutron induced reaction cross-section of 99Mo

In the present work, we have measured 98Mo(n,γ)99Mo reaction cross-section using a 7Li(p,n)7Be neutron source at 1.67 ± 0.14, 2.06 ± 0.14 and 2.66 ± 0.16 MeV neutron energies. We have employed offline γ-ray spectroscopy to measure the induced activity of the sample. The 115In(n,n’γ)115mIn reaction was used as a monitor reaction. Different attributes propagating the uncertainty in the total result, measured cross-sections with their uncertainties and correlation coefficients are given in detail in the present study. The result is compared with the data libraries, EXFOR database and theoretical model outcome from different level density models.

Evaluation of Neutron Cross-Section Data Using Gaussian Mixture Model and Digital Filter

For the accurate estimation of neutron cross-section data, evaluation of nuclear data is mandatory to fulfill the need of nuclear science and technology. In this work, the evaluation of 232Th(n,2n)231Th, 241Am(n,2n)240Am, 100Mo(n,2n)99Mo, and 96Mo(n,p)96Nb reaction cross-section data is carried out using a novel method. This novel method of evaluation employs a cluster-based piecewise evaluation followed by a digital filter for merging the evaluated curves. The clusters in the experimental data and model data are identified using the probabilistic method of the Gaussian Mixture Model. The clustered experimental data are then regressed using the polynomial regression technique. The model data are generated using the Talys 1.9 code, and the model deficiency due to the complex random nature of nuclear reactions is also accounted here using chi-squared analysis. Evaluation in each cluster is then carried out independently using the popular Kalman filter technique. For obtaining a single smooth evaluated curve for the whole energy range, the popular smoothing digital filter, the Savitzky-Golay Filter, is employed for the first time in nuclear data evaluation. The proposed evaluated curves and existing evaluated curves of 232Th(n,2n)231Th, 241Am(n,2n)240Am, 100Mo(n,2n)99Mo, and 96Mo(n,p)96Nb reactions from nuclear data libraries such as ENDF/BVIII.0, JEFF-3.3, JENDL-4.0, CENDL-3.1, and TENDL 2021 are compared and found to be in good agreement. It is also found that generally, evaluation methods are data dependent, and so, a single evaluation method may not be applicable for all reactions of all nuclides. Since piecewise evaluation is cluster dependent, selecting the appropriate cluster makes this method robust for almost all reactions of all nuclides. Also, it is proven that this novel method of evaluation is a promising method demonstrating the potential of this approach for evaluation based on the chi-squared goodness-of-fit test with respect to standard evaluated library ENDF/BVIII.0 and experimental data.

Optimization of target system for the production of 99Mo via 100Mo(γ,n)99Mo reaction

With an increase of stopping operation of nuclear reactors worldwide, the supply of medical 99Mo becomes difficult and thus many efforts have been made to find an alternative. A process based on an electron linear accelerator (linac) system and a100Mo target via the 100Mo (γ,n)99Mo reaction receives a lot of attention due to the relatively low level of co-produced impurities. This process has been recently developed at the Institute of Modern Physics (IMP) and the Monte Carlo simulation was used to optimize the target system before operating pilot irradiation experiments. First, tungsten and tantalum, as mostly used converter materials, were tested. The yield of 99Mo was evaluated with respect to the converter thickness and the electron beam energy by means of Geant4 simulations. Besides, the specific activity of 99Mo produced from one-stage approach (100Mo target without a converter) and two-stage approach (100Mo target with a converter) was compared when varying the testing conditions. The two-stage approach was selected for the experiment due to the higher specific activity of produced 99Mo at all tested conditions. A target consisting of a 10 mm thickness of the 100Mo tablets and a 2.4 mm thick Ta converter was irradiated for 40 h (50 MeV with 0.2 μA). The Geant4-calculated specific activity of generated 99Mo at the end of bombardment agreed well with the experimental value, which proved high level of accuracy of the Geant4 simulation. In future studies, the Geant4 simulation will be used to optimize the production process when using high power linac system.

PHOTONUCLEAR PRODUCTION OF 99Mo/ 99mТс-GENERATOR WITH USING EFFECT SZILARD-CHALMERS AND ELECTROLYSIS METHOD

The possibility of photonuclear production of 99Mo medical radioisotope using recoil nuclei of molybdenite nanoparticles from reaction 100Mo(γ,n)99Mo was investigated. The enrichment of radioactive isotopes is carried out by the effect of Szilard-Chalmers. Molybdenite nanoparticles were irradiated by bremsstrahlung with Emax = 39 MeV. The recoil nuclei of 99Mo are separated by electrolysis. The yield of 99Mo from the extractable phase amounted to ~3%. This technology will allow producing 0.8 GBq/g of 99mTc with high specific activity per day. Key words: linear electron accelerator, photonuclear production, electrolysis, specific activity, recoil nuclei, molybdenite nanoparticles.

Study on (n,p) reactions of 58Ni, 99Tc, 99Ru, 131Xe, 133Cs and 186Os radioisotopes used in medicine

In the last decade, nuclear medicine appears to be a good choice of medicine. 58Co, 99Mo, 99Tc, 99Re, 133Xe and 186Re are very important radionuclides for nuclear medicine. In this study, the excitation functions of 58Ni (n, p) 58Co, 99Tc (n, p) 99Mo, 99Ru (n, p) 99Tc, 131Xe (n, p) 131I, 133Cs (n, p) 133Xe and 186Os (n, p) 186Re nuclear reactions were calculated at neutron energies between 1 and 20 MeV using TALYS 1.95 and EMPIRE 3.2 nuclear codes. Furthermore, the cross sections were calculated with the empirical formula derived in our past study at 14–15 MeV. The obtained results were compared with the measured values in EXFOR library, and with the evaluated data of (JENDL-4.0/HE, JEFF-3.3, TENDL-2019, ENDF/B-VIII.0, IRDFF-II, JENDL/ImPACT-18). The results are in good agreement with those of the evaluated data libraries and experimental results and indicates that these radioisotopes can be produced by smaller cyclotrons.

AN ESTIMATE OF CROSS-SECTION OF PHOTO-PROTON REACTIONS ON 47-50Ti ISOTOPES

Development of technology of isotope production at an electron accelerator, in particular 47Sc by the 48Ti(γ,p)47Sc reaction, requires accurate data on cross-sections of this and other photo-proton reactions on the titanium isotopes, as the available data are characterized by considerable scatter. A simple technique for estimating maximum and width of the excitation function of a reaction with dominating giant dipole resonance was proposed and validated earlier. The method is based on measurement of normalized reaction yield in a thin target, overlapping completely a flux of X-rays, and processing of data obtained with the use of a developed analytical model. The joint activation of foils from natural nickel, molybdenum and titanium by bremsstrahlung radiation with end-point photon energy in the range 40…95 MeV was carried out. The characteristics of the reactions 48Тi(γ,p)47Sc, 49Ti(γ,p)48Sc, 50Ti(γ,np)48Sc, 47Ti(γ,p)46Sc, and 48Ti(γ,np)46Sc are studied by new technique. For verifying results, the wellexamined 58Ni(γ,n)57Ni and 100Mo(γ,n)99Mo reactions, taking place in the nickel and molybdenum foils, are used.

Risk Management of a Fusion Facility: Radiation Protection and Safety Integrated Approach for the Sorgentina-RF Project

The Sorgentina-RF project will use fusion neutrons to produce 99Mo, a precursor of 99mTc, by irradiating natural molybdenum. 99Mo is produced by means of the inelastic reaction 100Mo(n, 2n)99Mo on 100Mo, which is an isotope of natural Mo. From a functional point of view, the project consists of two parts: an irradiation neutron source at 14 MeV and a radiochemistry facility dedicated to the extraction of 99Mo from the solid sample irradiated by the neutron source. Given the degree of complexity of such a facility, the risk management strategy is based on an integrated approach that combines the engineering method of safety with that of radiation protection. Therefore, design issues were studied and systems were planned according to both radiation protection and safety criteria already in the preliminary phase, allowing a general strengthening of the safety of the plant. This work discusses the preventive analysis and the related activities to identify the ways in which potential exposures to radiation may occur. In particular, the preliminary safety analysis is presented for the innovative rotating target, developed for the project, and, accordingly, some specific technical solutions are given to refine the initial design of the facility.

Experimental cross-sections for proton induced reactions on natural molybdenum

The experimental cross-sections of the natMo(p,xn)93m+g,94g,95m,95g,96m+gTc, 100Mo(p,x)99Mo and 100Mo(p,2n)99mTc nuclear reactions were measured up to 18.3MeV, by the stacked-foil activation technique at the superconducting linear accelerator of the Institute of Modern Physics, Chinese Academy of Sciences. And the proton beam current was monitored by the independent natCu(p,x)65Zn and natTi(p,x)48V reactions. The experimental results were compared with the literature data taken from EXFOR database, evaluation data of the charged-particle cross section database and theoretical values by using TALYS-1.95 code with six level density models. The obtained results for most of the radionuclides show good agreement with the available literature data. Besides, the theoretical calculations predicted by the TALYS-1.95 code demonstrate similar trends with experimental data. Although in some cases, cross-sections results are sensitive to the nuclear level densities. Evaluated nuclear values of the charged-particle cross section database correspond well with our measurements for 96m+g,99mTcand 99Mo.

Application of Kalman filtering technique for evaluation of neutron cross section data of [formula omitted]Mo (n, 2n) [formula omitted]Mo reaction

In this paper, for the first time, evaluation of neutron cross section data of 100Mo (n, 2n) 99Mo reaction is performed using experimental data available in IAEA-EXFOR database library and nuclear model-based data generated using Talys 1.9 code by applying a novel method of combining Kalman filtering technique with Machine Learning (ML) regression algorithms. The neutron cross section data evaluation has been performed after a detailed study of all the EXFOR papers corresponding to 100Mo (n, 2n) 99Mo reaction and nuclear model based cross section generation by executing T6 random input files using Talys 1.9 code. The evaluated curve generated is then compared with the existing evaluated curve of 100Mo (n, 2n) 99Mo reaction from nuclear data libraries such as ENDF/B-VIII.0, JEFF-3.3, JENDL-4.0, CENDL-3.1 and TENDL 2017 and found to be in good agreement with them. Chi-square and generalized Chi-square tests were employed to assess the proposed evaluation techniques and found them to be good in estimating evaluated mean values and evaluated uncertainties of cross section.

Study of Proton Induced Reactions on Molybdenum Using TALYS and EMPIRE

Direct production of 99Mo and 99mTc with accelerator has a good development prospect in the field of nuclear medicine. Accurate and reliable nuclear reaction data is of great significance for isotope production. In this paper, the cross sections for natMo(p, x)96m+gTc, 100Mo(p, x)99Mo and 100Mo(p, 2n)99mTc reactions being taken from EXFOR database have been analyzed, and the experimental data were fitted by polynomial fit method. The excitation functions of natMo(p, x)96m+gTc、100Mo(p, x)99Mo and 100Mo(p, 2n)99mTc reactions were calculated up to 40 MeV by using TALYS-1.95 and EMPIRE-3.2.3 code with different energy level density and pre-equilibrium emission models. For the natMo(p, x)96m+gTc reaction, the calculation results predicted by preeqmode 1, 2 models are in good agreement with the experimental data when the input parameter ldmodel 6 of level density is used in TALYS-1.95 code. For the 100Mo(p, x)99Mo reaction, the calculation results predicted by preeqmode 4 models are in good agreement with the experimental data when the input parameter ldmodel 6 of level density is used in TALYS-1.95 code. For the 100Mo(p, 2n)99mTc reaction, the calculated results predicted by LEVDEN 2 in EMPIRE-3.2.3 code are in good agreement with the experimental data.

Low-energy Measurement of the 96Zr(α,n)99Mo Reaction Cross Section and Its Impact on Weak r-process Nucleosynthesis

Abstract Lighter heavy elements beyond iron and up to around silver can form in neutrino-driven ejecta in core-collapse supernovae and neutron star mergers. Slightly neutron-rich conditions favor a weak r-process that follows a path close to stability. Therefore, the beta decays are slow compared to the expansion timescales, and (α,n) reactions become critical to move matter toward heavier nuclei. The rates of these reactions are calculated with the statistical model and their main uncertainty, at energies relevant for the weak r-process, is the α+nucleus optical potential. There are several sets of parameters to calculate the α+nucleus optical potential leading to large deviations for the reaction rates, exceeding even one order of magnitude. Recently the 96Zr(α,n)99Mo reaction has been identified as a key reaction that impacts the production of elements from Ru to Cd. Here, we present the first cross section measurement of this reaction at energies (6.22 MeV ≤ Ec.m. ≤ 12.47 MeV) relevant for the weak r-process. The new data provide a stringent test of various model predictions which is necessary to improve the precision of the weak r-process network calculations. The strongly reduced reaction rate uncertainty leads to very well-constrained nucleosynthesis yields for Z = 44–48 isotopes under different neutrino-driven wind conditions.

Production cross-sections of Mo-isotopes induced by fast neutrons based on the 9Be(p, n) reaction

We measured the flux-weighted average cross-sections of the 100Mo(n, 2n)99Mo and 92Mo(n, 3n)90Mo reactions with the average neutron energies between 14.0- and 31.8-MeV by using an activation and off-line γ-ray spectrometric technique. The fast neutrons were generated based on the 9Be(p, n) reaction with the proton energies of 25-, 35- and 45-MeV from the MC-50 Cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). The neutron flux was measured by using the 27Al(n, α)24Na monitor reaction, whereas the neutron spectra were simulated by using the MCNPX 2.6.0 code. The theoretical cross-sections of the 100Mo(n, 2n)99Mo and 92Mo(n, xn)91.90,89Mo reactions as a function of mono-energetic neutron were calculated by using the TALYS-1.9 code. The present results for the 100Mo(n, 2n)99Mo and 92Mo(n, 3n)90Mo reactions are compared with the calculated neutron flux-weighted average values based on the literature data and theoretical cross-sections as a function of mono-energetic neutron energy, and show a good agreement.

Cross-sections for , and reactions on molybdenum isotopes in the neutron energy range of 13 to 15 MeV * * Supported by the National Natural Science Foundation of China (11875016, 11565012, 11165007)

Given the insufficient cross-sectional data regarding the 14-MeV-neutron experiment of molybdenum, the vital fusion reactor structural material, and the significant heterogeneities among the reported values, this study examined the (n,2n), (n,α), (n,p), (n,d), and (n,t) reaction cross sections in molybdenum isotopes based on the neutrons produced via a T(d,n)4He reaction carried out in the Pd-300 Neutron Generator at the China Academy of Engineering Physics (CAEP). A high-resolution gamma-ray spectrometer, which was equipped with a coaxial high-purity germanium detector, was used to measure the product nuclear gamma activities. In addition, 27Al(n,α)24Na and 93Nb(n,2n)92mNb reactions were utilized as the neutron fluence standards. The experimental 92Mo(n,2n)91Mo, 94Mo(n,2n)93mMo, 100Mo(n,2n)99Mo, 98Mo(n,α)95Zr, 100Mo(n,α)97Zr, 92Mo(n,p)92mNb, 96Mo(n,p)96Nb, 97Mo(n,p)97Nb, 98Mo(n,p)98mNb, 92Mo(n,d)91mNb, and 92Mo(n,t)90Nb reaction cross sections were acquired within the 13–15 MeV neutron energy range. Thereafter, we compared and analyzed these obtained cross sections based on the existing IAEA-EXFOR database-derived experimental data, together with evaluation results corresponding to ENDF/B-VIII.0, JEFF-3.3, BROND-3.1, and CENDL-3.1 and the theoretical outcomes acquired through TALYS-1.95 and EMPIRE-3.2.3 (nuclear-reaction modeling tools).

Side-reaction products identified for photo-nuclear production of99Mo

Production of 99Mo by the 100Mo (γ, n)99Mo reaction through the bremsstrahlung process using an electron accelerator is one of the feasible options currently pursued by several countries. Here we report experimental results on identification of side-reaction products after the irradiation of natural and enriched 100Mo targets. Side-reaction products identified include various Mo, Nb and Zr isotopes. Comparison of experimentally determined reaction production rates with those determined based on theoretical cross-sections will be presented. Moreover, activation products formed due to presence of impurities introduced during the manufacturing of the Mo targets will also be discussed.

Cross section of the 96Zr(α,n)99Mo reaction induced by α-particles beams on natZr targets

The excitation function of the 96Zr (α,n)99Mo reaction was determined using the stacked-foil activation technique. For the experiments, two stacks with metal foils of Cu, Ti and Zr of natural isotopic composition were irradiated independently with a 27.2 MeV α-particle beam. The characteristics of the primary beam and its verification along each stack were determined according to the well-known natCu(α,x)65Zn, natCu(α,x)66,67Ga, and natTi (α,x)51Cr monitor reactions. It was deduced that the expected production yield from 99Mo by irradiating 96Zr targets with a 23.8 MeV alpha particle beam for 1 h is 1.77 MBq/μA. According to the results, irradiation characteristics are proposed to produce 99Mo with high specific activity.

Measurement and covariance analysis of 100Mo (n, 2n) 99Mo and 96Mo (n, p) 96Nb reaction cross sections at the incident neutron energy of 14.54 MeV

The 100Mo (n, 2n) 99Mo and 96Mo (n,p) 96Nb reactions have been studied relative to the 197Au (n, 2n) 196Au monitor reaction, at the neutron energy of 14.54 MeV, based on an experiment performed using Purnima neutron generator. Extended unscented transformation technique has been applied for computing the contribution of uncertainty of each attribute, which is then propagated, for the measurement and covariance analysis of the cross section of 100Mo (n, 2n) 99Mo and 96Mo (n, p) 96Nb reactions. The results obtained agree closely with the experimental data, model data and data in various evaluated nuclear data libraries.

High-power electron accelerator for the production of neutrons and radioisotopes

The purpose of the work is to study the possible use of existing high-power electron accelerators for neutron therapy and the production of radioisotopes. Calculations were performed for both applications and the results were normalized to the characteristics of the existing MEVEX accelerator (average electron current 4 mA at a monoenergetic electron beam of 35 MeV). A unifying problem for the applications is the task of cooling the target: at a beam energy of about 140 kW, almost half of this energy is released directly in the target. For this reason, a liquid heavy metal was chosen as a target in order to combine the high quality of thermohydraulics with the maximum performance of both bremsstrahlung radiation and photoneutrons. The targets were optimized using precision codes for radiation transfer and thermal-hydraulic applications. Optimization was also carried out on the installation as a whole: (1) on the composition of the material and the configuration of the photoneutron extraction unit for neutron capture therapy (NCT) and (2) on the bremsstrahlung generation scheme for producing radioisotopes. The photoneutron unit provides an acceptable beam quality for NCT with a large neutron flux density at the output: ~ 2·1010 cm–2s–1, which is an order of magnitude higher than the output values of existing and planned reactor beams. Such intensity at the beam output will make it possible in many cases to abandon fractionated irradiation. As for the production of radioisotopes, in the calculations for the (γ, n) reaction, 43 radionuclides in five groups were obtained. For example, using the Mo100(γ, n)99Mo reaction, it is possible to obtain the 99Mo precursor of the main diagnostic isotope 99mTc with a specific activity of ~ 6 Ci/g and a total target activity of 1.8 kCi after irradiation for 24 hours. The proposed schemes for generating and outputting photoneutrons and bremsstrahlung have a number of obvious advantages over traditional methods, including: (a) the use of electron accelerators for producing neutrons is much safer and cheaper than the use of reactor beams; (b) the accelerator with the target and the beam extraction unit with the necessary equipment and tooling can be easily placed in a clinical setting; and (c) the proposed liquid gallium target for NCT, which also serves as a coolant, is an “environmentally friendly” material: its activation is relatively small and drops quickly (after about four days) to the background level.

Measurement of 100Mo (n, 2n) 99Mo reaction cross section and covariance analysis using extended unscented transformation technique at the incident neutron energy of 13.9 MeV

In this paper, the measurement and covariance analysis of the cross section of 100 Mo (n, 2n) 99 Mo reaction, with the 197 Au (n, 2n) 196 Au reaction being used as the monitor, at the incident neutron energy of 13.9 MeV is reported. The 3 H (d, n) 4 He nuclear reaction is used as the neutron source. The experiment was performed at the Purnima neutron facility, BARC. The method of activation with off-line -ray spectrometry is used. The covariance analysis of the 100 Mo (n, 2n) 99 Mo reaction is also performed, for the first time, using the extended unscented transformation (EUT) technique 1 , which is an extension of unscented transformation (UT) technique 2 , for the determination of partial uncertainties arising due to attributes in combination with the micro-correlation technique of Geraldo and Smith 3 . The present results obtained for 100 Mo (n, 2n) 99 Mo reaction cross section are found to be in good agreement with EXFOR data and the theoretically calculated value using the TALYS 1. 8 code. Comparisons with the data in the available basic evaluated nuclear data libraries, such as ENDF/B-VIII.0, JEFF-3.3, JENDL-4.0, ROSFOND-2010, CENDL-3.1 and TENDL 2017 are also presented and discussed.