Off-line Γ-ray Spectrometric Technique Research Articles

Charge distribution studies in the epi-cadmium neutron induced fission of 238Pu

Studies on charge distribution have been carried out in the epi-cadmium neutron induced fission of 238Pu for the first time. Experimentally fractional cumulative yields (FCY) and independent yields (IY) of various fission products have been measured by using an off-line γ-ray spectrometric technique. From the FCY values, the charge distribution parameters such as the isobaric width parameter (σZ), most probable charge (ZP) and the charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. On the other hand, from the measured IY values, isotopic width parameter (σA), the most probable mass (AP) and the elemental yields (YZ) of Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce and Pr were determined by using a non-linear fit. From the YZ values, the proton even-odd effect (δp) was obtained for the first time. The isobaric and isotopic charge distribution parameters in the 238Pu(nf, f) reaction were compared with the similar data in the thermal neutron induced fission of 238Pu and other actinides to examine the role of excitation energy.

Research on natAg(γ,xn)103-106Ag reaction cross sections with the bremsstrahlung end-point energy of 70 and 75 MeV

The flux-weighted average cross sections of natAg(γ,xn)103-106Ag reactions were measured with the bremsstrahlung end-point energy of 70 and 75 MeV using an activation and off-line γ-ray spectrometric technique. The GEANT4 code was used for the simulation of the bremsstrahlung spectra. The cross sections of natAg(γ,xn) 103-106Ag reactions as a function of mono-energetic photons were theoretically calculated by using the TALYS-1.96 code. The data of the present work and literature at different bremsstrahlung end-point energy are found to be in agreement with the theoretical values within the uncertainty limit. It can be seen that the flux-weighted average cross sections of the natAg(γ,xn)105.106Ag reactions increase with bremsstrahlung energy up to the Giant Dipole Resonance region. Thereafter, a small decrease trend with the bremsstrahlung energy was seen due to the opening of another reaction channel.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 238Pu

In the epi-cadmium neutron induced fission of 238Pu, independent isomeric yield ratios (IR) of 128,130,132Sb, 131,133Te, 134,136I, 135Xe and 138Cs have been measured by using an off-line γ-ray spectrometric technique. The average neutron energy of the epi-cadmium reactor neutron spectrum is 1.9 MeV. From the IR values, root mean square fragment angular momenta (JRMS) were deduced by using spin dependent statistical model analysis. The JRMS values from the present work in the epi-cadmium neutron induced fission of 238Pu were compared with the literature data in the thermal neutron induced fission of 238Pu to examine the role of excitation energy. Effect of nuclear structure on JRMS values was examined.

STUDY THE ISOMERIC RATIOS IN PHOTONUCLEAR EXPERIMENTS ON THE LUE-40 LINAC RDC “ACCELERATOR” NSC KIPT

The results of photoproduction of isomeric pairs from the (γ,xn) and (γ,pxn) reactions on nuclei from Zr up to Ta at the bremsstrahlung end-point energy range 30…100 MeV are systematized. Measurements were performed at the electron beam of the LUE-40 linac RDC “Accelerator” NSC KIPT using the activation method and off-line γ-ray spectrometric technique. The theoretical isomeric ratios IR for the nuclei-products of studied reactions were calculated using the cross-sections σ(E) from the TALYS1.95 code for six different level density models. The data from the international databases were additionally used to compare experimental results and theoretical predictions. The obtained results let us make conclusions about trends of values and energy dependence of IR in studied photonuclear reactions. Further directions of experimental research in the RDC “Accelerator” NSC KIPT are discussed.

Isomeric pair 95 m,g Nb in the photonuclear reactions on natMo at the bremsstrahlung end-point energy of 38–93 MeV

The photonuclear reaction was studied using the electron beam from the NSC KIPT linear accelerator LUE-40. The experiment was performed using the activation and off-line γ-ray spectrometric technique. The experimental isomeric yield ratio (IR) was determined for the reaction products at the bremsstrahlung end-point energy range of 38–93 MeV. The obtained values of IR are in satisfactory agreement with the results of other studies and extend the range of previously known data. The theoretical values of the yields and the IR for the isomeric pair from the reaction were calculated using the partial cross-sections from the TALYS1.95 code for six different level density models. For the investigated range of , the theoretical dependence of IR on energy was confirmed – the IR smoothly increases with increasing energy. The comparison showed a noticeable difference (more than 3.85 times) in the experimental IR relative to all theoretical estimates.

Post-Neutron Mass Yield Distribution in the Epi-Cadmium Neutron–Induced Fission of 238Pu

The cumulative and independent yields of various fission products within the mass range of 78 to 157 have been measured in the epi-cadmium neutron–induced fission of 238Pu by using an off-line γ-ray spectrometric technique. The lower yield of 136I than the usual trend indicates the formation of delayed neutron emitter 137I. From the cumulative yields, post-neutron mass chain yields were obtained by using the charge distribution correction. From the mass yield data, the peak-to-valley (P/V) ratio, the full-width at tenth-maximum of light and heavy mass wings, the average light mass <AL> and heavy mass <AH> as well as the average number of neutrons <ν> emitted were obtained. The mass chain yield data in the 238Pu(n,f) reaction were compared with similar data of the 238Pu(nth,f) reaction to examine the role of excitation energy on the nuclear structure effect and P/V ratio.

Excitation functions of the 197Au(p,pxn) and 197Au(p,xn) reactions

Abstract The cross-sections for the 197Au(p,pxn)196-193Au and 197Au(p,xn)197,195,193Hg reactions within the proton energy range of 49.8–65.5 MeV were measured at the high-intensity proton linac facility (KOMAC) in Korea using the stacked-foil activation and off-line γ-ray spectrometric technique The proton beam intensity was determined based on the natCu(p,x)62Zn monitor reaction with the recommended cross-section accessed from the IAEA database library. The data gathered in the present work are compared with the available data from the literature, which agreed well with each other. In this study, the 197Au(p,p5n)193Au reaction cross-section was measured for the first time. The data from the present work and existing literature were compared with the TALYS-1.9-based data taken from the TENDL-2019 library, which generally agreed well.

Post-Neutron Mass Yield Distribution in the Epi-Cadmium Neutron-Induced Fission of 241Pu

The cumulative and independent yields of various fission products within the mass range of 83 to 117 and 123 to 157 have been measured in the epi-cadmium neutron–induced fission of 241Pu using an off-line γ-ray spectrometric technique. From the cumulative yields, post-neutron mass yields were obtained using the charge distribution correction. The full-width at tenth maximum of the light and heavy mass wings and the average light mass <AL> and heavy mass <AH>, as well as the average number of neutrons <ν>, were obtained. The mass yields in the epi-cadmium– and thermal neutron–induced fission of 241Pu were compared to examine the role of excitation energy on the nuclear structure effect.

Charge distribution of light mass fission products in the thermal neutron induced fission of 233U, 235U and 239Pu

Fractional cumulative yields (FCY) of various light mass fission products in the 233U(nth, f), 235U(nth, f) and 239Pu(nth, f) reactions were measured by using an off-line γ-ray spectrometric technique. The values of most probable charge (ZP) were obtained by using the width of isobaric charge distribution (σZ) of nearby fissioning systems with proper apportion. From the ZP values, the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were also deduced. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show an oscillating nature in the interval of five mass units due to even-odd staggering. A local effect around the shell region and a systematic decreasing trend with the approach of symmetric split was also observed. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which shows no oscillation but only a systematic decreasing trend with the approach of symmetric split due to the assumption of liquid drop behaviour of the fissioning nucleus.

Cross-section measurements of the 81Br(n,2n)80mBr reaction via secondary nuclear decay

The secondary nuclear decay method was applied for the cross-section measurement of the 81Br(n,2n)80mBr reaction. As a result, the cross-sections of the 81Br(n,2n)80m,gBr reactions with a detailed uncertainty propagation and their isomeric cross-section ratios σm/σg were obtained at four neutron energies within the range from 13 to 15 MeV by applying an activation and off-line γ-ray spectrometric technique. The Br-based samples and Nb-based monitor foils were activated together to determine both the reaction cross-sections and the incident neutron flux. The neutron beam was formed via the 3H(d,n)4He reaction. The cross-sections were also calculated by using a theoretical nuclear model code TALYS-1.95 with different options of level density at neutron energies varying from the reaction threshold to 20 MeV. The extracted results were analytically discussed and compared with the corresponding theoretical and evaluated data from the published works in the literature.

Cumulative fission yield measurements with 14.7 MeV neutrons on 238U* *Supported by the National Natural Science Foundation of China (11975113)

The fission yield data in the 14 MeV energy neutron induced fission of 238U play an important role in decay heat calculations and generation-IV reactor designs. In order to accurately measure fission product yields (FPYs) of 238U induced by 14 MeV neutrons, the cumulative yields of fission products ranging from 92Sr to 147Nd in the 238U(n, f) reaction with a 14.7 MeV neutron were determined using an off-line γ-ray spectrometric technique. The 14.7 MeV quasi-monoenergetic neutron beam was provided by the K-400 D-T neutron generator at China Academy of Engineering Physics (CAEP). Fission products were measured by a low background high purity germanium gamma spectrometer. The neutron flux was obtained from the 93Nb (n, 2n)92mNb reaction, and the mean neutron energy was calculated using the cross-section ratios for the 90Zr(n, 2n)89Zr and 93Nb(n, 2n)92mNb reactions. With a series of corrections, high precision cumulative yields of 20 fission products were obtained. Our FPYs for the 238U(n, f) reaction at 14.7 MeV were compared with the existing experimental nuclear reaction data and evaluated nuclear data, respectively. The results will be helpful in the design of a generation-IV reactor and the construction of evaluated fission yield databases.

Photonuclear reactions natNi(γ,xn)57Ni and natNi(γ,xn)56Ni in the energy range Eγmax = 35–94 MeV

The total bremsstrahlung flux-averaged cross-sections 〈σ(Eγmax)〉 for the photonuclear reactions natNi(γ,xn)57Ni and natNi(γ,xn)56Ni have been measured in the range of end-point energies Eγmax = 35–94 MeV. The experiments were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 with the use of the activation and off-line γ-ray spectrometric technique. The calculation of the flux-average cross-sections 〈σ(Eγmax)〉th was carried out using the partial cross-section values σ(E) computed with the TALYS1.95 code for the level density models LD1-6 and bremsstrahlung γ-flux calculated by GEANT4.9.2. The obtained experimental results are compared both with the theoretical calculation 〈σ(Eγmax)〉th and with the data available in the literature. The obtained 〈σ(Eγmax)〉 values expand the energy range of previously known experimental data.

Post-Neutron Fission Product Yield Distribution in the Spontaneous Fission of 244Cm

The cumulative yield of fission products within the mass range of 85 to 115 and 127 to 156, as well as the independent yield of some of the fission products, have been measured in the spontaneous fission of 244Cm by using an off-line γ-ray spectrometric technique. From the cumulative yield of the fission products, their mass chain yields were obtained by applying the charge distribution correction. Mass yield distribution parameters like full width at tenth maximum of light and heavy mass wing and the average light mass <AL> and heavy mass <AH>, as well as the total average neutron multiplicity <ν>expt were obtained. The fission yield data in the 244Cm(SF) reaction were compared with similar data in the neutron-induced fission and spontaneous fission of other actinides to examine the role of excitation energy. The effect of nuclear structure on the excitation energy deficit spontaneous systems has been clearly observed.

Charge distribution of heavy mass fission products in the thermal neutron induced fission of 233U, 235U and 239Pu

Isobaric charge distribution has been carried out in the thermal neutron induced fission of 233U, 235U and 239Pu by measuring the fractional cumulative yields (FCY) of various heavy mass fission products within the range of 127–149. An off-line γ-ray spectrometric technique was used for the measurement of fission product activities. The width of the isobaric charge distribution (σZ), most probable charge (ZP) and thus the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. It was found that the σZ values around the mass number 127–129 and 132–136 are lower due to the presence of spherical 50p and 82n shells. The ΔΖEXPT values show an oscillating nature in the interval of five mass units due to even-odd effect. The ΔΖEXPT values also show a decreasing trend with the approach of symmetric split besides an oscillating nature. The most probable charge (ZMPE) and thus the ΔΖMPE values based on the minimum potential energy surface were theoretically calculated, which show a systematic decreasing trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

Charge distribution of light mass fission products in the fast neutron induced fission of 237Np, 241Am and 243Am

In the fast neutron induced fission of 237Np, 241Am and 243Am, fractional cumulative yields (FCY) of various light mass fission products have been measured for the first time by using an off-line γ-ray spectrometric technique. The most probable charge (ZP) and the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show a decreasing trend towards symmetric split with fluctuations for some of the mass chains due to the effect of shell closure proximity. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which also shows a systematic decrease trend with the approach of symmetric split without any fluctuation due to the liquid drop behaviour of the fissioning nucleus.

Measurements of natCd(γ, x) reaction cross sections and isomer ratio of 115m,gCd with the bremsstrahlung end-point energies of 50 and 60 MeV * *Supported by the National Research Foundation of Korea (NRF) through a grant provided by the Ministry of Science and ICT (NRF-2017R1D1A1B03030484, NRF-2013M7A1A1075764, NRF-2018R1A6A1A06024970)

The flux-weighted average cross sections of natCd(γ, xn)115g,m,111m,109,107,105,104Cd and natCd(γ, x)113g,112,111g,110mAg reactions were measured at the bremsstrahlung end-point energies of 50 and 60 MeV. The activation and off-line γ-ray spectrometric technique was carried out using the 100 MeV electron linear accelerator at the Pohang Accelerator Laboratory, Korea. The natCd(γ, xn) reaction cross sections as a function of photon energy were theoretically calculated using the TALYS-1.95 and the EMPIRE-3.2 Malta codes. Then, the flux-weighted average cross sections were obtained from the theoretical values of mono-energetic photons. These values were compared with the flux-weighted values from the present study and were found to be in general agreement. The measured experimental reaction cross-sections and integral yields were described for cadmium and silver isotopes in the natCd(γ, xn)115g,m,111m,109,107,105,104Cd and natCd(γ, x)113g,112,111g,110mAg reactions. The isomeric yield ratio (IR) of 115g,mCd in the natCd(γ, xn) reaction was determined for the two bremsstrahlung end-point energies. The measured isomeric yield ratios of 115g,mCd in the natCd(γ, xn) reaction were also compared with the theoretical values of the nuclear model codes and previously published literature data of the 116Cd(γ, n) and 116Cd(n, 2n) reactions. It was found that the IR value increases with increasing projectile energy, which demonstrates the characteristic of excitation energy. However, the higher IR value of 115g,mCd in the 116Cd(n, 2n) reaction compared to that in the 116Cd(γ, n) reaction indicates the role of compound nuclear spin alongside excitation energy.

Post-neutron mass yield distribution in the thermal neutron induced fission of 238Pu

The cumulative and independent yields of various fission products within the mass range of 83–155 have been measured in the thermal neutron induced fission of 238Pu by using an off-line γ-ray spectrometric technique. From the cumulative yields, post-neutron mass chain yields were obtained by using the charge distribution correction. From the mass yields data, the full width at tenth maximum (FWTM) of light and heavy mass wing, the average light mass (<AL > ) and heavy mass (<AH > ) as well as the average number of neutrons (<ν > ) emitted were obtained. The mass yield data in the 238Pu(nth, f) reaction was compared with the similar data of 241Pu(nth, f) reaction to examine the nuclear structure effect.

Charge distribution of light mass fission products in the 232U(nth, f), 238Pu(nth, f) and 244Cm(SF) reactions

Fractional cumulative yields (FCY) of various light mass fission products in the 232U (nth, f), 238Pu(nth, f) and 244Cm(SF) reactions were measured by using an off-line γ-ray spectrometric technique. The values of most probable charge (ZP) were obtained by using the width of isobaric charge distribution (σZ) of nearby fissioning systems with proper apportion. From the ZP values, the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were also deduced. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show an oscillating nature in the interval of five mass units, which is due to even-odd effect. A local effect around the shell region for some mass chains and a systematic decreasing trend with the approach of symmetric split was also observed. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which also shows a systematic decreasing trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

Measurement of 59Co(n, x) reaction cross sections with the fast neutrons based on the 9Be(p, n) reaction * *Partly supported by the National Research Foundation of Korea (NRF) through a grant provided by the Ministry of Science and ICT (NRF-2017R1D1A1B03030484, NRF-2013M7A1A1075764, NRF-2018R1A6A1A06024970)

The cross sections of the 59Co(n, x) reaction in the average energy range of 15.2-37.2 MeV were measured using activation and an off-line γ-ray spectrometric technique. The neutrons were generated from the 9Be(p, n) reaction with proton beam energies of 25-45 MeV at the MC-50 Cyclotron facility of the Korean Institute of Radiological and Medical Sciences (KIRAMS). Theoretical calculations of neutron–induced reactions on 59Co were performed using the nuclear model code TALYS-1.9. The results for the 59Co(n, x) reactions were compared with the theoretical values obtained using TALYS-1.9 and the literature data provided in EXFOR and the TENDL 2019 nuclear data library. The theoretical values obtained using TALYS-1.9 with adjusted parameters are comparable to the experimental data. The measured reaction cross sections of a few radionuclides are new, and the others are comparable to the literature data, and thus, they can strengthen the database. The present study on cross sections leads to useful insight into the mechanisms of 59Co(n, x) reactions.

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.