Fission yields at different fission-product kinetic energies for thermal-neutron-induced fission of 239Pu

At the recoil spectrometer “Lohengrin” of the Institut Laue-Langevin in Grenoble, the yields of the light fission products from the thermal-neutron-induced fission of ²³⁹Pu were measured as a function of A, Z, the kinetic energy E and the ionic charge states q. The nuclear charge and mass distributions summed over all ionic charge states were determined for different light fissionproduct kinetic energies between 93 and 112 MeV. The proton odd-even effect which was measured to be (11.6 ± 0.6)% causes considerable fine structure in the yields. The average kinetic energy of even-Z elements in the light fission-product group is 0.3 ± 0.1 MeV larger than for odd-Z elements. The neutron odd-even effect is (6.5 ± 0.7)%. The comparison with previously published data ¹) for thermal-neutron-induced fission of ²³⁵U reveals a correlation between the proton odd-even effect in the yield and in the kinetic energy of the elements. The dependence of the proton odd-even effect on the fragmentation is very similar for ²³⁵U and ²³⁹Pu when it is considered as a function of the nuclear charge of the heavy fission products. The isobaric variances σ_z². for thermal-neutron fission of ²³⁵U and ²³⁹Pu coincide at all kinetic energies if the influence of the proton odd-even effect is averaged out. This supports the hypothesis that the magnitude of σ_z² is determined only by quantum-mechanical zero-point fluctuations. The influence of the spherical shells Z = 50 and N = 82 on the fragmentation is discussed.     

High-Order Analytical Nodal Method for the Multigroup Diffusion Equations

We develop a high-order analytical nodal method for the multigroup diffusion equations. Based on the transverse integration procedure, the discrete 1D equations are analytically approximated using the combined direct algebraic evaluation of trigonometric functions of multigroup matrices, and the truncated Legendre series. The remaining Legendre coefficients of the transverse leakage moments are determined exactly in terms of the different neutron flux moments order. The self-consistent is guaranteed. In the weighted balance equations, the transverse leakage moments are linearly written in terms of the partial currents, facial and centered fluxes moments. Furthermore, as the order increases, the neutron balance in each node and the coupling between the adjacent cell are reinforced. The efficacy of the method is shown for 2D-PWR and 2D-LMFBR benchmark problems.     

Order of convergence for polynomial and analytical nodal methods

In [6] we analyzed the direct analytical nodal methods (ANM) of indexl and show that the corresponding mathematical methods are equivalent to the physical ones when the components of the matrices are calculated by generalized Radau reduced integration. In this article we extend the theorem 8 of [7] to the polynomial nodal methods (PNM) (exact calculation of moments) which are thus the order ofO(h ^l+3?δ _l0. We also show that the analytical nodal methods are only the order ofO(h ^l+2). Forl = 0 our numerical results confirm our theoretical results.     

The assessment of radiological risks associated with the ingestion of 210Po, 210Pb,and 137Cs in marine organisms collected from the local fish market of Kenitra,Morocco

Journal of Radioanalytical and Nuclear Chemistry - 210Po, 210Pb, and 137Cs activities were measured using gamma and alpha spectrometry in commonly consumed seafood collected from the local fish...     

Recursive two-levelILU preconditioner for nonsymmetric M-matrices

We develop in this paper some preconditioners for sparse non-symmetric M-matrices, which combine a recursive two-level blockILU factorization with multigrid method, we compare these preconditioners on matrices arising from discretized convection-diffusion equations using upwind finite difference schemes and multigrid orderings, some comparison theorems and experiment results are demonstrated.     

Un dienophile chiral tres reactif : le Z-(R)S p-tolylsulfinyl-3 propenoate de methyle

Methyl Z-(R)_S 3-p-tolylsulfinyl propenoate reacts under mild conditions with cyclopentadiene. A high stereoselectivity and diastereospecificity were observed. The structure and absolute stereochemistry were established by N.M.R.     

Neutron activation analysis applied to the study of heavy metal marine pollution observed through bioaccumulation in macroscopic algae near El Jadida,Morocco

The heavy metals bio-accumulation ability of algae was studied along the North Atlantic Morrocan coast. Instrumental neutron activation analysis was used, to determine concentrations of various elements. The k ₀ standardization method was used. Some interferences corrections, particularly due to high concentrations of uranium were applied. The quality of the method was checked by using the CRM 140, a Fucus provided by IAEA. Important pollutions appear for several heavy metals from the Morrocan phosphate industry, with respect to the natural background environment.     

The effect of block red-black ordering on blockILU preconditioner for sparse matrices

It is well known that the ordering of the unknowns can have a significant effect on the convergence of a preconditioned iterative method and on its implementation on a parallel computer. To do so, we introduce a block red-black coloring to increase the degree of parallelism in the application of the blockILU preconditioner for solving sparse matrices, arising from convection-diffusion equations discretized using the finite difference scheme (five-point operator). We study the preconditioned PGMRES iterative method for solving these linear systems.