Search results for "Nuclear fission"
showing 10 items of 44 documents
Theoretical and experimental studies of the neutron rich fission product yields at intermediate energies
2012
A new method to measure the fission product independent yields employing the ion guide technique and a Penning trap as a precision mass filter, which allows an unambiguous identification of the nuclides is presented. The method was used to determine the independent yields in the proton-induced fission of 232 Th and 238 U at 25 MeV. The data were analyzed with the consistent model for description of the fission product formation cross section at the projectile energies up to 100 MeV. Pre-compound nucleon emission is described with the two-component exciton model using Monte Carlo method. Decay of excited compound nuclei is treated within time-dependent statistical model with inclusion of the…
Measurement of the a ratio and (n,¿) cross section of U 235 from 0.2 to 200 eV at n_TOF
2020
We measured the neutron capture-to-fission cross-section ratio (a ratio) and the capture cross section of 235U between 0.2 and 200 eV at the n_TOF facility at CERN. The simultaneous measurement of neutron-induced capture and fission rates was performed by means of the n_TOF BaF2 Total Absorption Calorimeter (TAC), used for detection of ¿ rays, in combination with a set of micromegas detectors used as fission tagging detectors. The energy dependence of the capture cross section was obtained with help of the 6 Li(n,t) standard reaction determining the n_TOF neutron fluence; the well-known integral of the 235U(n, f ) cross section between 7.8 and 11 eV was then used for its absolute normalizat…
Status of independent yield measurements
1996
Recent progress in the measurement of independent yields in low energy nuclear fission is presented. Different experimental approaches are discussed and a survey of the most important experimental results obtained is given. Physical consequences for the understanding of the fission process are briefly referred.
Rapid Synthesis of Radioactive Transition-Metal Carbonyl Complexes at Ambient Conditions
2012
Carbonyl complexes of radioactive transition metals can be easily synthesized with high yields by stopping nuclear fission or fusion products in a gas volume containing CO. Here, we focus on Mo, W, and Os complexes. The reaction takes place at pressures of around 1 bar at room temperature, i.e., at conditions that are easy to accommodate. The formed complexes are highly volatile. They can thus be transported within a gas stream without major losses to setups for their further investigation or direct use. The rapid synthesis holds promise for radiochemical purposes and will be useful for studying, e.g., chemical properties of superheavy elements.
Analysis of a Station Black-Out transient in SMR by using the TRACE and RELAP5 code
2014
The present paper deals with the investigation of the evolution and consequences of a Station Black-Out (SBO) initiating event transient in the SPES3 facility [1]. This facility is an integral simulator of a small modular reactor being built at the SIET laboratories, in the framework of the R&D program on nuclear fission funded by the Italian Ministry of Economic Development and led by ENEA. The SBO transient will be simulated by using the RELAP5 and TRACE nodalizations of the SPES3 facility. Moreover, the analysis will contribute to study the differences on the code predictions considering the different modelling approach with one and/or three-dimensional components and to compare the capa…
Neutron measurements for advanced nuclear systems: The n_TOF project at CERN
2012
A few years ago, the neutron time-of-flight facility n_TOF was built at CERN to address some of the urgent needs of high-accuracy nuclear data for Accelerator Driven Systems and other advanced nuclear energy systems, as well as for nuclear astrophysics and fundamental nuclear physics. Thanks to the characteristics of the neutron beam, and to state-of-the-art detection and acquisition systems, high quality neutron cross-section data have been obtained for a variety of isotopes, many of which radioactive. Following an important upgrade of the spallation target and of the experimental area, a new measurement campaign has started last year. After a brief review of the most important results obt…
The ion-guide isotope separator on-line at the Tohoku University Cyclotron
1987
Abstract The status of the ion-guide isotope separator on-line at the Tohoku University Cyclotron is reported. The optimum ion-guide parameters were determined from test experiments using atomic and molecular ions ionized with an electric discharge inside the target chamber as well as using 64 Ga(T 1 2 = 2.6 m ) ions produced by the 64Zn(p, n) reaction. Using the present system together with a ΔE−E plastic counter telescope and a germanium detector we identified 16 short-lived nuclei including the first mass-separated nuclei 57Cu and 45V. The efficiency of mass separation for 64Ga was ϵ ∼ 1%, where ϵ is defined as the number of atoms collected at the end of the separator divided by that rec…
Rapid Radiochemical Separation Procedures from Aqueous Solutions
1992
The state-of-the-art in the field of rapid radiochemical separation procedures is illustrated by two systems using aqueous solutions as input: ARCA, an apparatus for repetitive separations, and SISAK, a centrifuge system for continuous separations. Applications presented are: Solvent extraction of element 105 investigated with 34-s 262105 using ARCA, and decay scheme studies of the fission product 1.0-s 110Tc by means of SISAK.
Delayed-neutrons from arsenic isotopes 84As, 85As and 86As
1973
Abstract Short-lived arsenic isotopes were produced by thermal-neutron fission of 235U and isolated within 2·5 sec by volatilization of arsenic hydride. The existence of a strong delayed-neutron precursor of 2·05±0·05 sec half-life among the arsenic isotopes is confirmed and its assignment to 85As ascertained by milking of the daughter product 33 sec 85Se and 3·1 min 84Se, which is the final nucleus in the neutron decay branch of 85As. A delayed-neutron yield of 7·8 ± 1·2 neutrons/104 fissions was obtained for 85As. A new isotope, 0·9 ± 0·2 sec 86As, was detected by delayed-neutron counting and by following the decay of its most prominent γ-ray. The mass assignment was verified by milking o…
Advanced model for the prediction of the neutron-rich fission product yields
2013
The consistent models for the description of the independent fission product formation cross sections in the spontaneous fission and in the neutron and proton induced fission at the energies up to 100 MeV is developed. This model is a combination of new version of the two-component exciton model and a time-dependent statistical model for fusion-fission process with inclusion of dynamical effects for accurate calculations of nucleon composition and excitation energy of the fissioning nucleus at the scission point. For each member of the compound nucleus ensemble at the scission point, the primary fission fragment characteristics: kinetic and excitation energies and their yields are calculate…