Search results for "M-23"
showing 10 items of 18 documents
Ultratrace analysis and isotope ratio measurements of long-lived radioisotopes by resonance ionization mass spectrometry (RIMS).
2003
Resonance Ionization Mass Spectrometry (RIMS) is a sensitive and selective method for ultratrace analysis of long-lived radioisotopes and isotope ratio measurements. It provides extremely high isobaric suppression and good overall efficiency. The experimental limits of detection are as low as 10(6) atoms per sample and isotopic selectivities of 5x10(12) have been obtained. The widespread potential of RIMS, using different experimental arrangements, is demonstrated for the determination of the radiotoxic isotopes Pu-238 to Pu-244 and Sr-89/Sr-90 in various environmental samples as well as for Ca-41 in nuclear reactor components and biomedical samples.
New measurement of the 242Pu(n,γ) cross section at n_TOF
2016
The use of MOX fuel (mixed-oxide fuel made of UO2 and PuO2 ) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. With the use of such new fuel composition rich in Pu, a better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. For the case of 242 Pu, the two only neutron capture time-of-flight measurements available, from 1973 and 1976, are not consistent with each other, which calls for a new time-of flight captu…
(Supplement Table S2) Results of 230Th/U-dating
2016
We compared the suitability of two skeletal materials of the Atlantic brain coral Diploria strigosa for 230Th/U-dating: the commonly used bulk material comprising all skeletal elements and the denser theca wall material. Eight fossil corals of presumably Last Interglacial age from Bonaire, southern Caribbean Sea, were investigated, and several sub-samples were dated from each coral. For four corals, both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty. Three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232Th content and (230Th/238U) ratios. The bulk material sam…
Approaching the precursor nuclei of the third r-process peak with RIBs
2013
The rapid neutron nucleosynthesis process involves an enormous amount of very exotic neutron-rich nuclei, which represent a theoretical and experimental challenge. Two of the main decay properties that affect the final abundance distribution the most are half-lives and neutron branching ratios. Using fragmentation of a primary $^{238}$U beam at GSI we were able to measure such properties for several neutron-rich nuclei from $^{208}$Hg to $^{218}$Pb. This contribution provides a short update on the status of the data analysis of this experiment, together with a compilation of the latest results published in this mass region, both experimental and theoretical. The impact of the uncertainties …
Uranium from German Nuclear Power Projects of the 1940s— A Nuclear Forensic Investigation
2015
Here we present a nuclear forensic study of uranium from German nuclear projects which used different geometries of metallic uranium fuel. Through measurement of the (230)Th/(234)U ratio, we could determine that the material had been produced in the period from 1940 to 1943. To determine the geographical origin of the uranium, the rare-earth-element content and the (87)Sr/(86)Sr ratio were measured. The results provide evidence that the uranium was mined in the Czech Republic. Trace amounts of (236)U and (239)Pu were detected at the level of their natural abundance, which indicates that the uranium fuel was not exposed to any major neutron fluence.
Kongo Demokrātiskās Republikas loma starptautiskajās attiecībās. 2005-2013
2016
Maģistra darba tēma ir “Kongo Demokrātiskās Republikas loma starptautiskajās attiecībās 2005-2013” Kongo Demokrātiskās Republikas iekšpolitiskie un ārpolitiskie procesi Latvijā ir nepietiekami pētīti. Darbā skatīts kā procesi lielākajā valstī Subsahāras reģionā skar starptautisko organizāciju-ANO un ES, kā arī atsevišķu lielvalstu-Lielbritānijas,Francijas, ASV,Ķīnas politiku. Pētijumā svarīga loma ir iekšpolitiskajiem procesiem-paramilitāru grupu aktivitātēm,korupcijai,jo tie ir saistīti ar ārvalstu-gan reģionālu,gan pasaules mēroga darbībām. Kongo Demokrātiskās Republikas problemātika skaidri parāda ģeopolitisko interešu sadursmi gan starp Eiropas, gan pasaules lielvalstīm,kuras atbalsta d…
Variable masses in fission and heavy-ion collisions
1972
With the use of the cranking formula, the coordinate-dependent mass parameters of the kinetic-energy operator in fission processes and heavy-ion collisions are calculated in the two-center oscillator model. It is shown that the reduced mass and also the classical moment of inertia are obtained for large separations of the fragments. For small separations, however, the mass parameter for the motion of the centers of mass of the fragments is larger than the reduced mass by an order of magnitude.
Fission in238U+238U collisions below the Coulomb barrier
1988
Integral fission cross sections in the system238U+238U were measured at beam energies below the interaction barrierVC. Scattering angle dependent probabilities and integral cross sections for Coulomb fission were calculated. It is concluded that earlier observed discrepancies between measured and calculated angular distributions for the one-neutron transfer product239U cannot be explained by sequential fission. Multi-nucleon transfer induced fission is observed down to energies (0.90±0.02)×VC.
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.
Nuclear structure “southeast” ofPb208: Isomeric states inHg208andTl209
2009
The nuclear structure of neutron-rich N>126 nuclei has been investigated following their production via relativistic projectile fragmentation of a E/A=1 GeV U-238 beam. Metastable states in the N=128 isotones Hg-208 and Tl-209 have been identified. Delayed gamma-ray transitions are interpreted as arising from the decay of I-pi=(8(+)) and (17/2(+)) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers Z 126.