Investigation of the same isomeric pair, produced from different nuclear reactions

The isomeric ratio (IR) of isomeric pair 109m,gPd, produced in 110Pd(γ, n)109m,gCd reaction and 108Pd(n, γ)109m,gPd neutron capture reactions, induced by thermal, epithermal and mixed thermal-epithermal neutrons have been determined. The off-line activation technique using a spectroscopic system consisting of a HPGe semiconductor detector with high energy resolution and a PC based 8192 channel analyzer (CANBERRA) was applied. The investigated samples were prepared from the 99.99 % purity PdO and irradiated at the electron accelerator Microtron MT-25 of the Joint Institute for Nuclear Research Dubna, Russia. The data analysis and necessary corrections were made to upgrade the precision of the experimental method. The obtained results were discussed, compared and combined with those from other authors to point out the role of the reaction channels in nuclear reactions.

Shipborne measurements of methane and carbon dioxide in the Middle East and Mediterranean areas and the contribution from oil and gas emissions

The increase of atmospheric methane (CH4) and carbon dioxide (CO2), two of the main anthropogenic greenhouse gases, is largely driven by fossil sources. Sources and sinks remain insufficiently characterized in the Mediterranean and Middle East areas, where very few in situ measurements are available. We measured the atmospheric mixing ratios of CH4 and CO2 by ship in the region in July and August 2017. High mixing ratios were observed over the Suez Canal, Red Sea and Arabian Gulf, while generally lower mixing ratios were observed over the Gulf of Aden and Gulf of Oman. We probe the origin of the CO2 and CH4 excess mixing ratio by using correlations with light alkanes and through the use of a Lagrangian model coupled to two different emission inventories of anthropogenic sources. We find that the CO2 and especially the CH4 enhancements are mainly linked to nearby oil and gas (OG) activities over the Arabian Gulf and a mixture of other sources over the Red Sea. The isomeric ratio of pentane is shown to be a useful indicator of the OG component of atmospheric CH4 at the regional level. Upstream emissions linked to oil in the northern Arabian Gulf seem to be underestimated, while gas-related emissions in the southern Gulf are overestimated in our simulations. Our results highlight the need for improvement of inventories in the area to better characterize the changes in magnitude and the complex distribution of the OG sources in the Middle East.

Shipborne measurements of methane and carbon dioxide in the Middle East and Mediterranean areas and contribution from oil and gas emissions

The increase of atmospheric methane (CH4) and carbon dioxide (CO2), two main anthropogenic greenhouse gases, is largely driven by fossil sources. Sources and sinks remain insufficiently characterised in the Mediterranean and Middle East areas, where very few in situ measurements area available. We investigated the atmospheric distribution of CH4 and CO2 in the region through shipborne measurement in July and August 2017. High mixing ratios were observed over the Suez Canal, Red Sea and Arabian Gulf, while generally lower mixing ratios were observed over the Gulfs of Aden and Oman. We probe the origin of CO2 and CH4 excess mixing ratio by using correlations with light alkanes and through the use of a Lagrangian model coupled to two different emission inventories of anthropogenic sources. We find that the CO2 and especially the CH4 enhancements are mainly linked to nearby oil and gas (O&G) activities over the Arabian Gulf, and a mixture of other sources over the Red Sea. The isomeric ratio of pentane is shown to be a useful indicator of the O&G component of atmospheric CH4 at the regional level. Upstream emissions linked to oil in the Northern Arabian Gulf seem to be underestimated while gas-related emissions in the Southern Gulf are overestimated in our simulations. Our results highlight the need for improvement of inventories in the area to better characterize the changes in magnitude and the complex distribution of the O&G sources in the Middle East.

Investigation of fission product isomeric ratios and angular momenta of 132Sn populated in the 241Pu(nth,f) reaction

During an experimental campaign performed at the LOHENGRIN recoil spectrometer of the Institut Laue-Langevin (ILL), a kinetic energy dependence of 132Sn fission product isomeric ratio (IR) has been measured by inducing thermal fission of 241Pu. The IRs are deduced using gamma ray spectrometry in coincidence with the ionisation chamber. To interpret these data, we use the FIFRELIN Monte-Carlo code to simulate the de-excitation of the fission fragments. Combining the IRs with the FIFRELIN calculations, the angular momentum distribution with kinetic energy of the doubly magic nucleus of 132Sn was deduced. This will be compared with the angular momentum distribution obtained for the reaction 235U(nth,f) for 132Sn.

The nuclear channel effect in the isomeric ratio of the reaction products

This work presents the experimental study of the isomeric ratio of 115mCd to 115gCd produced in 116Cd(γ, n)115m,gCd photonuclear reaction and 116Cd(n, γ)115m,gCd neutron capture reaction by thermal, epithermal and mixed thermal and epithermal neutrons. The investigated samples were natural cadmium irradiated at the bremsstrahlung photon flux, in the neutron source constructed at the electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The results were analyzed, discussed, compared and combined with those of other authors in the existing literature to examine the role of the nuclear channel effect in the isomeric ratio and provide the nuclear data for theoretical model interpretation of nuclear reactions and applied research.

Status of fission fragment observables measured with the LOHENGRIN spectrometer

Nuclear fission yields are key parameters to evaluate reactor physics observables, such as fuel inventory, decay heat, spent fuel radiotoxicity, criticality but also for understanding the fission process. Despite a significant effort allocated to measure fission yields during the last decades, the recent evaluated libraries still need improvements in particular in the description of the uncertainties with the associated correlations. Additional kinds of measurements provide complementary information in order to test the models used in the nuclear data evaluation. Moreover, some discrepancies between these libraries must be explained. A common effort by the CEA, the LPSC and the ILL aims at tackling these issues by providing precise measurement of isotopic and isobaric fission yields with the related variance-covariance matrices. Nevertheless, the experimental program represents itself a large range of observables requested by the evaluations: isotopic yields, nuclear charge polarization, odd-even effect, isomeric ratio and their dependency with fission fragment kinetic energy as a probe of the nuclear de-excitation path in the (E*, Jπ) representation. Measurements for thermal neutron induced fission of 241Pu have been carried out at the Institut Laue Langevin using the LOHENGRIN mass spectrometer. Experimental program, observables reachable, results and comparison to model calculations are shown.