Search results for "Plutonium"
showing 10 items of 38 documents
Fission fragment anisotropy for the 242mAm fission isomer by spin exchange pumping with polarized rubidium vapour
1992
Abstract The foundations of an experiment have been worked out with which, in principle, the spin, hyperfine constants and the isomer shift of the 14 ms fission isomer 242mAm can be measured. Such an experiment would be based on the fission fragment anisotropy signal which has actually been observed in this work after spin exchange pumping with polarized rubidium vapour in an optical buffer gas cell. A decrease of the count rate of (12±4)% has been measured at 90% with respect to the quantization axis. From this result it is concluded that the nuclear spin of the 242mAm fission isomer must be larger than 1. The low-energy fission isomers originating from the 242Pu(d, 2n)242mAm reaction have…
Fast-neutron-induced fission cross section of Pu242 measured at the neutron time-of-flight facility nELBE
2019
The fast-neutron-induced fission cross section of $^{242}\mathrm{Pu}$ was measured at the neutron time-of-flight facility $n$ELBE. A parallel-plate fission ionization chamber with novel, homogeneous, large-area $^{242}\mathrm{Pu}$ deposits on Si-wafer backings was used to determine this quantity relative to the IAEA neutron cross-section standard $^{235}\mathrm{U}(n,f)$ in the energy range of 0.5 to 10 MeV. The number of target nuclei was determined from the measured spontaneous fission rate of $^{242}\mathrm{Pu}$. This helps to reduce the influence of the fission fragment detection efficiency on the cross section. Neutron transport simulations performed with geant4, mcnp6, and fluka2011 ar…
Production of plutonium tracers in 237Np nuclear reactions with 3He-ions in the energy range from 26 to 60 MeV
1998
Cross-sections for the reaction Np-237 + He-3 --> Pu-236,Pu-237,Pu-238 at He-3 bombarding energies from 26 to 60 MeV were measured. Thick-target yields, based on the measured and previously known cross-sections were constructed. The results are discussed and compared with Ether reactions leading to the formation of the same final nuclei. (C) 1998 Elsevier Science S.A.
Resonant laser–SNMS for spatially resolved and element selective ultra-trace analysis of radionuclides
2018
The newly developed resonant laser–SNMS system at the IRS Hannover combines the high spatial and decent mass resolution of a TOF-SIMS instrument with the element-selective process of resonant laser ionization. This setup was characterized by use of synthetic uranium, plutonium and technetium samples to prepare and demonstrate the performance for measurements on environmental samples. The laser–SNMS system will be applied for the detection, visualization and ultra-trace analysis of radionuclide containing nanoparticles in environmental samples with strongly reduced or even completely omitted chemical preparation. The necessary suppression of isobaric contamination was demonstrated as well as…
Contribution of recently measured nuclear data to reactor antineutrino energy spectra predictions
2013
This paper attempts to summarize the actual problematic of reactor antineutrino energy spectra in the frame of fundamental and applied neutrino physics. Nuclear physics is an important ingredient of reactor antineutrino experiments. These experiments are motivated by neutrino oscillations, i.e. the measure of the θ 13 mixing angle. In 2011, after a new computation of the reactor antineutrino energy spectra, based on the conversion of integral data of the beta spectra from 235 U, and 239;241 Pu, a deficit of reactor antineutrinos measured by short baseline experiments was pointed out. This is called the “reactor anomaly”, a new puzzle in the neutrino physics area. Since then, numerous new ex…
Efficiency of dihydroxamic and trihydroxamic siderochelates to extract uranium and plutonium from contaminated soils
2021
International audience; Actinide-based mineral phases occurring in contaminated soils can be solubilized by organic chelators excreted by plants, such as citrate. Herein, the efficiency of citrate towards U and Pu extraction is compared to that of siderophores, whose primary function is the acquisition of iron(III) as an essential nutrient and growth factor for many soil microorganisms. To that end, we selected desferrioxamine B (DFB) as an emblematic bacterial trishydroxamic siderophore and a synthetic analog, abbreviated (LCy,Pr)H2, of the tetradentate rhodotorulic acid (RA) produced by yeasts. Firstly, the uranyl speciation with both ligands was assessed in the pH range 2–11 by potentiom…
Resonance ionization mass spectroscopy for trace determination of plutonium in environmental samples
1997
Resonance ionization mass spectroscopy (RIMS) is a sensitive and isotope selective method and well suited for trace analysis of plutonium in the environment. After the chemical isolation of plutonium from soil, air filters or urine, e.g., it is electrolytically deposited as hydroxide on a tantalum backing and covered with a thin titanium layer. By heating such a sandwich filament in the RIMS-apparatus under vacuum an atomic beam of plutonium is produced. The atoms are ionized by a three-step resonant excitation using pulsed dye lasers, and the ions are mass-selectively detected with a time-of-flight (TOF) spectrometer and a multi channel plate detector. RIMS yields a low detection limit of …
TIVOLI, HADRIAN'S VILLA: THE PLUTONIUM PROJECT (COMUNE DI TIVOLI, PROVINCIA DI ROMA, REGIONE LAZIO)
2021
The Universities of Pavia and Oxford continued their investigations in Villa Adriana, in the area called Plutonium, traditionally interpreted as a reproduction of the Underworld, and located on one of the highest rises of the complex, in the east part of the Villa. The excavations took place from 1 to 21 July 2019. A team of 12 graduate students and postdoctoral researchers took part in the project, both from Oxford and Pavia Universities (S. Andronio, I. Bossolino, E. Casarotti, A. Dalgkitsi, E. Di Virgilio, V. Jukic Buca, A. Poldi Allai, G. Restaino, T. Runeckles, A. Verde). Dr Gilberto Montali, from the University of Palermo, supervised the architectural survey and documentation of the a…
Il progetto Plutonium di Villa Adriana: prime considerazioni a margine del nuovo rilievo e prospettive di ricerca
2020
Nel corso del 2016 e 2017 la missione congiunta delle università di Oxford e Pavia ha condotto una serie di campagne di ricognizione, rilevamento (georadar e geomagnetico) e rilievo architettonico nell'area nota dalla letteratura archeologica come pertinente al Plutonium e Inferi di Villa Adriana. Il complesso, situato nella sona nord-orientale della Villa, in corrispondenza di un rilievo naturale e ai margini della proprietà demaniale è costituito da tre elementi principali: 1) una grotta artificiale/ninfeo, collocata all'estremità di una valletta artificiale, interamente scavata nel tufo (gli Inferi); 2) un grosso edificio costruito su alte sostruzioni concamerate (il Plutonium); 3) una r…
Study of the oxidation mechanisms of Plutonium
2022
Oxidation is a key point when applied to a material such as plutonium. It is essential to understand the oxidation mechanisms in order to predict and prevent catastrophic oxidation, thus managing the reprocessing cost.The originality of this work lies in the coupling of different experimental techniques : in-situ X-ray diffraction, Photo-electron spectroscopy (XPS), FIB-SEM, Raman spectrometry and X-ray absorption (EXAFS) with numerical techniques : CALPHAD and Reverse Monte Carlo, in order to determine the oxidation mechanisms of the studied alloy : -phase stabilised PuGa 1 at%.Study of oxidation of this alloy at different temperatures and oxygen partial pressures showed the oxidation kin…