U-238 fission and Pu-239 production in subcritical assembly

2007

Transmutation at the Nuclotron 2.52 GeV Deuteron Beam in Neutron Field Generated in U/Pb-Assembly ®Energy Plus TransmutationP reliminary results of theˇrst experiment with deuteron beam with energy 2.52 GeV at the electronuclear setup which consists of Pb-target (diameter 8.4 cm, length 45.6 cm) and nat Ublanket (206.4 kg), transmutation samples of 129 I, 237 Np, 238 Pu and 239 Pu (radioecological aspect) are described. Hermetically sealed samples in notable amounts are gathered in atomic reactors and setups of industries which use nuclear materials and nuclear technologies were irradiated in theˇeld of neutrons produced in the Pb-target and propagated in the nat U-blanket. Estimates of transmutations were obtained as result of measurements of gamma activities of the samples. The information about the space and energy distribution of neutrons in the volume of the lead target and the uranium blanket was obtained with help of sets of activation threshold detectors (Al, Co, Y, I, Au, Bi and others), solid-state nuclear track detectors, 3 He neutron detectors and nuclear emulsion. Comparison of the experimental data with the results of simulation with the MCNPX program was performed. The investigation has been performed at the Veksler and Baldin Laboratory of High Energies and at the Dzhelepov Laboratory of Nuclear Problems, JINR.

Cnr '09: Second International Workshop on Compound Nuclear Reactions and Related Topics, 2010

The production cross sections of neutron-rich fission residues produced in reactions induced by a 238 U beam impinging onto Pb and Be targets were investigated at the Fragment Separator (FRS) at GSI using the inverse kinematic technique. These data allowed us to discuss the optimum energies in fission for producing the most neutron-rich residues.

Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile (ENEA),

Bulletin of the American Physical Society, 2020

Precise integral measurement of fast neutron-induced fission product yields for various actinides is of high interest for applied nuclear science. The goal of this effort is to improve uncertainties in fission product yield values of 239 Pu. Fission was induced in a pure 239 Pu (> 99%) target using the Godiva-IV critical assembly in burst mode. The irradiated sample was transferred to a high-resolution γ-ray detector within 45 minutes. γ-ray list mode data was collected from 45 minutes to 1 week after the irradiation. γ-ray spectroscopy was performed to analyze the time dependent γ-ray yields using an automated peak search algorithm to identify isotopes by their decay γ-ray energy and half-life. The initial activity for each isotope identified was used to calculate their fission product yield.

Nuclear Physics A, 2011

The yields of various fission products in the 10 MeV bremsstrahlung-induced fission of 232Th, 238U and 240Pu were determined using a recoil catcher and off-line γ-ray spectrometric techniques. From the yield data, mass yield distributions were obtained using charge distribution corrections. The higher yields of fission products around mass numbers 133–135, 138–140, 143–145 and their complementary products in the neutron and bremsstrahlung-induced fission of 232Th, 238U and 240Pu were interpreted based on nuclear structure effects. From the mass yield distribution, the peak-to-valley (P/VP/V) ratio was also obtained for the above fissioning systems. The present data, along with data from the literature on different bremsstrahlung- and mono-energetic neutron-induced fissions of 232Th and 238U are interpreted to examine the influence of excitation energy on the peak to valley ratio. For the same compound nucleus 240Pu⁎, the data in the 10–30 MeV bremsstrahlung-induced fission of 240Pu were compared with similar data of thermal to 14 MeV neutron-induced fission of 239Pu and the spontaneous fission of 240Pu to examine the role of excitation energy due to bremsstrahlung radiation and mono-energetic neutrons.

Nuclear Physics A

The cumulative yields of various fission products in the 6. 35, 8.53, 9.35 and 12.52 MeV quasi-monoenergetic neutron induced fission of 238 U have been determined by using the off-line γ -ray spectrometric technique. The mass chain yields were obtained from the fission product yields by using charge distribution correction. From the mass yield data, the peak-to-valley (P/V) ratio, the average value of light mass ( A L ), heavy mass ( A H ) and thus the average number of neutrons ( υ expt ) were obtained in the 238 U(n, f ) reaction for the above mentioned four neutron energies. The present and literature data in the 238 U(n, f ) and 238 U (γ, f ) reactions at various energies were compared to arrive at the following conclusions. (i) The yields of fission products for A = 133-134, A = 138-140, and A = 143-144 and their complementary products in the 238 U(n, f ) and 238 U(γ, f ) reactions are higher than other fission products, which has been explained from the point of even-odd effect and standard I and standard II asymmetric mode of fission. (ii) The yields of symmetric products increase and thus the peak-to-valley (P/V) ratios decrease with excitation energy, whereas the ν expt values increase with excitation energy. (iii) The variation of A L , A H and υ expt values with excitation energy behave differently in between 238 U(n, f ) and 238 U(γ, f ) reactions, which may be due to the different types of reaction mechanism for the neutron and photon with 238 U. = 6. 35, 8.53, 9.35 and 12.52 MeV; measured fission product yields, mass yield distributions, off-line γ -ray spectrometric technique, peak-to-valley (P/V) ratio, average number of neutrons ( υ expt ), average light mass ( A L ), average heavy mass ( A H )

Nuclear Physics A, 2011

Fission of 238 U and 234 U induced by bremsstrahlung of 6.5-9.0 MeV endpoint energy has been investigated at the superconducting Darmstadt electron linear accelerator S-DALINAC. Using a twin Frisch grid ionization chamber, fission-fragment energy and mass distributions have been determined by means of the double kinetic-energy technique. Results on the fission-fragment characteristics from 238 U(γ , f ) are in agreement with results from the literature. In addition fission-fragment mass and energy distributions from 234 U(γ , f ) are presented for the first time in this energy region. An analysis of fission modes within the Brosa model has been performed. The relative yield of the S1 mode was found to be (13 ± 3)% in 234 U and (35 ± 2)% in 238 U.

Radiation Measurements, 1997

One of the main advantages of using dielectric track detectors in the study of heavy ion interactions is the possibility of observing each multi-prong event individually with complete kinematical details. It is thus possible to analyze even those reaction channels that have very low branching ratios. In the study of reactions induced by 16.7 MeV/u uranium ions incident on natural gold targets, we have observed 18 four-pronged events in a total detector area of 24 cm 2. Using a polynomial range-energy relationship, empirically fitted to the observed data of binary and ternary events, it was possible to perform kinematical analysis of 10 out of 18 events. The masses and relative velocities of the reaction products, determined in this analysis were compared with theoretical prediction based on double sequential fission process. An agreement within one standard deviation with respect to theoretical values has been found for eight analysed events.

Proceedings of XXII International Baldin Seminar on High Energy Physics Problems — PoS(Baldin ISHEPP XXII), 2015

The ratios of the average 239 Pu and 237 Np fission cross-sections to the average 235 U fission crosssection were determined experimentally. Experiments with U-assembly QUINTA were carried out using the accelerator complex "Nuclotron" of the Veksler and Baldin Laboratory of High Energy Physics (VBHEP) of the Joint Institute for Nuclear Research (JINR) (Dubna, Russia). Experiments were conducted in the frame of the project "E&T RAW". It is based on so called Relativistic Nuclear Technology (RNT) proposed recently [1] by one of the institutions (CPTP "Atomenergomash", Moscow) participating in "E&T RAW" collaboration. The assembly was irradiated by deuterons and carbon ions with energies 2 and 4 GeV/A. Comparison between experimental results and MCNPX calculations are presented. Accumulation and burning of plutonium, neptunium and others isotopes influences the neutron balance of the assembly that attracts an interest in such measurements.

The High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) is a versatile 85 MW{sub th}, pressurized, light water-cooled and -moderated research reactor. The core consists of two fuel elements, an inner fuel element (IFE) and an outer fuel element (OFE), each constructed of involute fuel plates containing high-enriched-uranium (HEU) fuel (93 wt% ²³U/U) in the form of UO in an Al matrix and encapsulated in Al-6061 clad. An over-moderated flux trap is located in the center of the core, a large beryllium reflector is located on the outside of the core, and two control elements (CE) are located between the fuel and the reflector. The flux trap and reflector house numerous experimental facilities which are used for isotope production, material irradiation, and cold/thermal neutron scattering. Over the past five decades, the US Department of Energy (DOE) and its agencies have been producing radioisotope power systems used by the National Aeronautics and Space Administrat...

2008

We have measured the neutron capture and fission cross section of 233 U at the neutron time-of-flight facility n TOF at CERN in the energy range from 1 eV to 1 MeV with high accuracy by using a high performance 4π BaF 2 Total Absorption Calorimeter (TAC) as a detection device. The method, based on the TAC energy response study, allowing to disentangle between γ's originating from fission and capture will be presented as well as the first very preliminary results.

Nuclear Data Sheets, 2016

has performed a set of absolute Fission Product Yield (FPY) measurements. Using monoenergetic neutron at energies between 0.5 and 14.8 MeV, the excitation functions of a number of fission products from 235 U, 238 U and 239 Pu have begun to be mapped out. This work has practical applications for the determination of weapon yields and the rate of burn-up in nuclear reactors, while also providing important insight into the fission process. Combining the use of a dual-fission ionization chamber and-ray spectroscopy, absolute FPYs have been determined for approximately 15 di↵erent fission products. The dual-fission chamber is a back-to-back ionization chamber system with a 'thin' actinide foil in each chamber as a monitor or reference foil. The chamber holds a 'thick' target in the center of the system such that the target and reference foils are of the same actinide isotope. This allows for simple mass scaling between the recorded number of fissions in the individual chambers and the number of fissions in the center thick target, eliminating the need for the knowledge of the absolute fission cross section and its uncertainty. The 'thick' target was removed after activation and-rays counted with well shielded High Purity Germanium (HPGe) detectors for a period of 1.5-2 months.

Physica Scripta, 2012

Accurate neutron induced fission cross section of 240 Pu and 242 Pu are required in view of making nuclear technology safer and more efficient to meet the upcoming needs for the future generation of nuclear power plants (GEN-IV). The probability for a neutron to induce such reactions figures in the NEA Nuclear Data High Priority Request List [1]. A measurement campaign to determine neutron induced fission cross sections of 240 Pu and 242 Pu at 2.51 MeV and 14.83 MeV has been carried out at the 3.7 MV Van De Graaff linear accelerator at Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. Two identical Frisch Grid fission chambers, housing back to back a 238 U and a A Pu target (A = 240 or A = 242), were employed to detect the total fission yield. The targets were molecular plated on 0.25 mm aluminium foils kept at ground potential and the employed gas was P10. The neutron fluence was measured with the proton recoil telescope (T1), which is the German primary standard for neutron fluence measurements. The two measurements were related using a De Pangher long counter and the charge as monitors. The experimental results have an average uncertainty of 3-4% at 2.51 MeV and for 6-8% at 14.81 MeV and have been compared to the data available in literature.

Nuclear Instruments and …, 2001

The primary fission fragment mass and kinetic energy distributions, and neutron multiplicities as function of fragment mass have been measured in the proton-induced fission of 238 U at energies E p ¼ 20, 35, 50 and 60 MeV using time-of-flight technique. Pre-scission and post-scission neutron multiplicities have been extracted from double differential distributions. The fragment mass dependence of the post-scission neutron multiplicities reveals the gross nuclear shell structure effect even at the higher proton energies we measured. The yields of neutron-rich fission products in the fission of 238 U by 25 MeV protons were measured using an ion guide-based isotope separator technique. The results indicate enhancement for superasymmetric mass division at intermediate excitation energy of the fissioning nucleus. The experimental results have been analysed in the framework of a time-dependent statistical model with inclusion of nuclear friction effects in the fission process.

2016

Transmutation at the Nuclotron 2.52 GeV Deuteron Beam in Neutron Field Generated in U/Pb-Assembly ®Energy Plus TransmutationP reliminary results of theˇrst experiment with deuteron beam with energy 2.52 GeV at the electronuclear setup which consists of Pb-target (diameter 8.4 cm, length 45.6 cm) and nat Ublanket (206.4 kg), transmutation samples of 129 I, 237 Np, 238 Pu and 239 Pu (radioecological aspect) are described. Hermetically sealed samples in notable amounts are gathered in atomic reactors and setups of industries which use nuclear materials and nuclear technologies were irradiated in theˇeld of neutrons produced in the Pb-target and propagated in the nat U-blanket. Estimates of transmutations were obtained as result of measurements of gamma activities of the samples. The information about the space and energy distribution of neutrons in the volume of the lead target and the uranium blanket was obtained with help of sets of activation threshold detectors (Al, Co, Y, I, Au, Bi and others), solid-state nuclear track detectors, 3 He neutron detectors and nuclear emulsion. Comparison of the experimental data with the results of simulation with the MCNPX program was performed. The investigation has been performed at the Veksler and Baldin Laboratory of High Energies and at the Dzhelepov Laboratory of Nuclear Problems, JINR.