Search

The total excitation energy, TXE, as a function of fission fragments, is evaluated for neutron-driven fission of 230-236U using the statistical scission point model. In this model, as the systematic model, the total excitation energy includes the deformation and intrinsic energy. TXE values calculated by the systematic model are compared with the available experimental data for the neutron-induced 233U. Then the total excitation energy as a function of fission fragments is evaluated for neutron-induced fission of 230-236U. The total excitation energy distribution is compared for neutron-induced fission and for photofission of 233U and 238U. There is little difference between the TXE distribution of neutron-induced fission and photofission. The prompt neutron distribution is evaluated by using the obtained total excitation energy. The calculated prompt neutron number has a large variation for even uranium isotopes due to the neutron-separated energy of fission fragments. In addition, the prompt neutron number for heavy fission fragments is less than the experimental neutron number which due to the excess neutron of those fragments. It is due to the evaporation of an excess neutron with lower TXE values in heavy fragments.

The fission fragment total excitation energy, TXE(A), was calculated for neutron-induced fission of 227 - 233 Th using three methods. The first method is the conventional method of calculating TXE by subtracting Q value from total kinetic energy value. The second method is usually used to calculate the number of neutrons emitted and the third method is a systematic method by applying the intrinsic energy within the statistical scission point model. Third method has been modified based on the results of the other two methods and the required parameters have been obtained from neutron-induced fission of 232 Th to calculate TXE distribution for other thorium isotopes. This indicates that for all thorium isotopes, TXE values increase with increasing mass numbers of fission fragments, except for the fission fragments with mass number about 95–100. [ABSTRACT FROM AUTHOR]

Thorium is the primary candidate fuel in Thorium-based Molten Salt Reactor (TMSR) and Accelerator Driven System (ADS). However, to utilize Thorium in the reactor and accelerator systems, nuclear data in the literature are not sufficient for neutron-induced fission reaction process. Therefore, we estimated neutron fission cross-section σ (mb), independent Y (A) and primary fission fragment yield Y I (A) , mass-dependent average neutron multiplicity ν ̄ (A) , energy-dependent average neutron multiplicity ν ̄ (E) and neutron emission multiplicity distribution ν of 2 3 2 Th for different neutron incident energy values, 1 MeV, 1.5 MeV, 3 MeV, 5.5 MeV, 7.7 MeV, 10 MeV, 14.8 MeV and 20 MeV, where the energy region is important for the reactor and accelerator systems used in the industry. The obtained results are compared with experimental data obtained from the literature and are discussed for each energy value. [ABSTRACT FROM AUTHOR]

The mean total kinetic energy as a function of fission fragments, (A), is calculated for neutron-induced fission of 247,249,251,253,255Cf, as well as for spontaneous fission of 248,250,252,254Cf using the scission point model. A comparative analysis is performed between the calculated results and existing experimental data. Investigation into the behavior of (A) is conducted, particularly focusing on intermediate and heavy actinides. While nuclear and Coulomb energy evaluations suffice for estimating values in light actinides, this approximation proves inadequate for evaluating TKE values for intermediate and heavy actinides. Additionally, an evaluation is made of the total excitation energy as a function of fission fragments, (A), concerning spontaneous fission in 247−254Cf. It is found that TXE values sharply increase near the symmetric region across all isotopes and exhibit a gradual increase in heavy fission fragments. Furthermore, an exploration of the total neutron multiplicity as a function of fission fragments, ν T (A) , is conducted for 252Cf fission using two methods. The ν T (A) results obtained through these methods are compared with experimental data, and ν T (A) is estimated for unmeasured californium isotopes. The average neutron emission per fission event, ν ¯ (A i) , is then calculated for spontaneous fission of 251Cf and 253Cf, yielding values of 3.46 and 3.59, respectively. [ABSTRACT FROM AUTHOR]

• Describing experiment was performed in Dubna in QUINTA assembly. • The experimental fission products are measured by activation detectors. • Calculating the fission yield of fission product for proton-induced fissions. • Estimating the measured number of neutron- and proton-induced fissions. • Comparing the experimental data with predicted results from MCNPX code. This work is a next step toward the study of physical properties of the Accelerator Driven System (ADS) in which a deeply subcritical active core (512 kg natural uranium target) is irradiated by a pulsed beam of relativistic particles. The measurement of the total number of fission reactions is a fundamental task in the given research. The estimated method of determining the number of fission reactions based on activation detectors is analyzed. Our interest has been focused on the study of the proton- and neutron-induced fission reaction inside the high-energy particle beam volume. The fission products of fission reactions have been measured employing natural uranium activation detectors and germanium gamma detectors (HPGe). Experimental data are taken from the QUINTA experiment performed at JINR, Dubna, in November 2014. The presented method gives an effective possibility of estimating the measured number of fission reactions induced by neutrons and high-energy protons simultaneously. [ABSTRACT FROM AUTHOR]

Photofission of Th, U, Np and Pu isotopes are investigated. Modified version of Gorodisskiy approach that is developed to study the neutron-induced fission are employed to simulate fission fragment mass distribution for these isotopes in different energies. The effect of emitted neutron prior to scission point is studied. Peak to valley ratio is also extracted. Obtained results using this approach are compared with original Gorodisskiy model as well as available experimental data. Satisfactory agreement is achieved between theoretical and experimental data especially in medium and low -ray energies than original formalism of Gorodisskiy. [ABSTRACT FROM AUTHOR]

To enhance the capabilities of the DANCE array, a new detector array NEUANCE was developed to enable simultaneous measurements of prompt fission neutrons and γ rays. NEUANCE was designed and constructed using 21 stilbene organic scintillator crystals. It was installed in the central cavity of the DANCE array. Signals from the 160 BaF 2 detectors of DANCE and the 21 detectors of NEUANCE were merged into a newly designed high-density high-throughput data acquisition system. The excellent pulse shape discrimination properties of stilbene enabled detection of neutrons with energy thresholds as low as 30–40 keVee. A fission reaction tagging method was developed using a NEUANCE γ -ray or neutron signal. The probability of detecting a neutron from the spontaneous fission of 252 Cf using NEUANCE is ∼ 47%. New correlated data for prompt fission neutrons and prompt fission γ rays were obtained for 252 Cf using this high detection efficiency experimental setup. Average properties of prompt fission neutron emission as a function of prompt fission γ -ray quantities were also obtained, suggesting that neutron and γ -ray emission in fission are correlated. [ABSTRACT FROM AUTHOR]

Fission and capture reactions were simultaneously measured in the neutron-induced reactions of 241 Am at the spallation neutron facility of the Japan Proton Accelerator Research Complex (J-PARC). Data for the neutron energy range of E n =0.1–20 eV were taken with the TOF method. The fission events were observed by detecting prompt neutrons accompanied by fission using liquid organic scintillators. The capture reaction was measured by detecting γ rays emitted in the deexcitation of the compound nuclei using the same detectors, where the prompt fission neutrons and capture γ rays were separated by a pulse shape analysis. The cross sections were obtained by normalizing the relative yields at the first resonance to evaluations or other experimental data. The ratio of the fission to capture cross sections at each resonance is compared with those from an evaluated nuclear data library and other experimental data. Some differences were found between the present values and the library/literature values at several resonances. [ABSTRACT FROM AUTHOR]

At the IGISOL-4 facility, neutron-rich, medium mass nuclei have usually been produced via charged particle-induced fission of natural uranium and thorium. Neutron-induced fission is expected to have a higher production cross section of the most neutron-rich species. Development of a neutron source along with a new ion guide continues to be one of the major goals since the commissioning of IGISOL-4. Neutron intensities at different angles from a beryllium neutron source have been measured in an on-line experiment with a 30 MeV proton beam. Recently, the new ion guide coupled to the neutron source has been tested as well. Details of the neutron source and ion guide design together with preliminary results from the first neutron-induced fission experiment at IGISOL-4 are presented in this report. [ABSTRACT FROM AUTHOR]

A fission-fragment detector based on thin scintillating films has been built to serve as a trigger/veto detector in neutron-induced fission measurements at DANCE. The fissile material is surrounded by scintillating films providing 4 π detection of the fission fragments. The scintillation photons were registered with silicon photomultipliers. A measurement of the 235 U ( n , f ) reaction with this detector at DANCE revealed a correct time-of-flight spectrum and provided an estimate for the efficiency of the prototype detector of 11.6(7)%. Design and test measurements with the detector are described. [ABSTRACT FROM AUTHOR]

Measurements of neutron-induced fission cross-sections and light-ion production are planned in the energy range 1–40 MeV at the upcoming Neutrons For Science (NFS) facility. In order to prepare our detector setup for the neutron beam with continuous energy spectrum, a simulation software was written using the Geant4 toolkit for both measurement situations. The neutron energy range around 20 MeV is troublesome when it comes to the cross-sections used by Geant4 since data-driven cross-sections are only available below 20 MeV but not above, where they are based on semi-empirical models. Several customisations were made to the standard classes in Geant4 in order to produce consistent results over the whole simulated energy range. Expected uncertainties are reported for both types of measurements. The simulations have shown that a simultaneous precision measurement of the three standard cross-sections H(n,n), 235 U(n,f) and 238 U(n,f) relative to each other is feasible using a triple layered target. As high resolution timing detectors for fission fragments we plan to use Parallel Plate Avalanche Counters (PPACs). The simulation results have put some restrictions on the design of these detectors as well as on the target design. This study suggests a fissile target no thicker than 2 μ m (1.7 mg/cm 2 ) and a PPAC foil thickness preferably less than 1 μ m . We also comment on the usability of Geant4 for simulation studies of neutron reactions in this energy range. [ABSTRACT FROM AUTHOR]

A combination of germanium detectors was installed at the PF1B neutron guide of the ILL to perform prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of U and Pu. In addition, LaBr detectors from the FATIMA Collaboration were installed to complement with the EXOGAM clovers to measure lifetimes of low-lying excited states. The measured characteristics and online spectra indicate very good performances of the overall set-up. [ABSTRACT FROM AUTHOR]