Core configuration

The reactor core ot the BWR is arranged as an upright cylinder containing many tuel assemblies and located within the reactor vessel. The coolant flows upward through the core. Important components ot this arrangement are described in the following sections. 

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Figure 1 Core configuration of the (110) 001 edge dislocation (Ni-core)...

Figure 2 Core configuration and Burgers vector distribution of the (111) 211 edge dislocation display separation into two superpartials.

Figure 3 Core configuration of the (111) screw dislocation. The Burgers vector distribution is calculated for a 211 cut and clearly shows a compact dislocation core.

Two alternate core structures of the ordinary 1/2[110] dislocation, shown schematically in 1 gs. 2a amd b, respectively, were obtained using different starting configurations. The core shown in Fig. 2a is planar, spread into the (111) plame, while the core shown in Fig. 2b is non-plamar, spread concomitcmtly into the (111) amd (111) plames amd thus sessile. The sessile core is energetically favored since when a shear stress parallel to the [110] direction was applied in the (111) plane the planar core transformed into the non-plamar one. However, in a similar study emplo3dng EAM type potentials (Rao, et al. 1991) it was found that the plamar core configuration is favored (Simmons, et al. 1993 Rao, et al. 1995). 

The most stable core configuration for an inner core of one spheron is KM, with an outer core of nine spherons. For icosahedral packing the outer core contains 12 spherons. These structures, which we may take as defining the limits of stability for a one-spheron inner core, have been discussed in the preceding section. 

A neutral chromium atom has 24 electrons, so the corresponding Cr cation has 21 electrons. The first 18 electrons follow the usual filling order to give the argon core configuration ... 

Figure 1.3 The Periodic Table showing the atomic numbers and outer electronic configurations of the elements the core configurations are those of the preceding Group 18 element those that are numbered, but unnamed, have been synthesized in small quantities...

Here Ko stands for all closed and open shells whose electrons do not participate in the transition (passive shells). It is called the core configuration or simply the core. K describes the electrons (usually one or two electrons above the core), one of which performs the transition. Typical patterns of the first sort of transitions are given by the following configurations ... 

X], where X is the symbol of an inert gas element) core configuration. Compare with valence shell. All completely filled shells underneath the valence shell. 

Oxidation state Metal core configuration bond order Example... 

Each atom has an argon inner-core configuration. fCovalent atomic radii. 

This procedure provides a model of the xenon atom which accounts only for the manifold of singly excited states based on the lowest ionic core, P3/2- For all rare gases, a second manifold of states converges to the next spin-orbit component of the ion, the Pi/2 state. For example, these two ionization limits in xenon are separated by 1.3 eV corresponding to different total angular momenta, J, of the 5p configuration. The lower ionization potential is 12.15 eV. We assume that multiphoton excitations into these two manifolds are very weakly coupled so they can be treated separately. This assumption is reasonable because once one of the electrons is excited outside a particular core configuration, transitions... 

GPT is a method of evaluating the effects of cross-section perturbations on quantities that can be formulated as integral responses, such as reactivity and power density. An initial requirement is an exact solution of a reactor physics model for a reference core configuration. In FORMOSA-P the reference neutronics model is a two-dimensional Cartesian [x-y] geometry implementation of the nodal expansion method (NEM) to solve the two-group, steady-state neutron diffusion equation ... 

Successive ionisation potentials that break into a lower closed inert gas core configuration show an exceptional increase and explain why these lower inert gas cores are never broken into in the chemistry of the elements. 

To date, the emphasis has been on the formation of ionic cations or anions, by the formation of inert gas core configurations, which then combine to form purely electrostatic bonds, e.g. Na CP. An alternative type of bond is the covalent bond, which is characterised by the sharing of two electrons by two atoms, in a way that completes the inert gas core of both atoms. Thus, in the case of two hydrogen atoms, both with the same valence shell configuration, ls the formation of a homonuclear diatomic molecule of H2 can be represented, as follows ... 

In this latter reaction, the initial and final oxidation states of the nitrogen atoms differ by the two electrons of the s pseudo inert gas core configuration. 

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