Heterogeneous core

On the basis of theoretical calculations by the Physics Division, the Technical Division of Clinton Laboratories submitted a design proposal in May, 1946 for a high-flux thermal reactor of heterogeneous core, light water—cooled and heavy watei moderated and—reflected. The use of light water as a coolant was believed preferable to the use of heavy water because light water increased the operation flexibility of the machine. A brief description of this proposal is given. 

K. Meetz, Exact treatment of heterogeneous core stricture. Proceedings of the Second International Conference on the Peaceful Uses of Atomic Energy, Paper No. 968, (In Press). 

The management of the marked reactivity loss and the optimization of the relative values of the Doppler and sodium void effects appear to be the two major issues to be dealt with so as to ensure the feasibility of Pu burner cores. In this respect, heterogeneous core designs, in which a part of the inert material replacing the fuel in the dilution process is gathered in specific subassemblies, are of particular interest. 

Two design options are considered for the reactor core a conventional homogoteous core and an axial heterogeneous core with an internal fertile slice just below core midplane. Both concepts (see Figio) have three core zones with different plutonium contents and are fully compatible with each other. The core is surrounded by one row of breeder subassemblies and an axial breeder blanket located above and below core. 

One of the main requirements for advanced core development is ensuring of a zero sodium void effect of reactivity. For compensation of an additional positive component of reactivity arising due to higher burn-up a transition to axial heterogeneous core concept was made. Herewith the inner blanket of depleted uranium dioxide is placed in the central part of the core. A size of this blanket is 2/3 of the core radius. 

Characteristic features are a heterogeneous core and a modular structure that allow simplifying the reactor and NPS running tests. 

A heterogeneous core based on thermal neutrons is used. It consists of 55 hexagonal FAs of 144.2 mm width across flats, located in the in-vessel barrel on a 147.5 mm pitch. The FAs are spaced by the lower plate of the core barrel and by an upper plate, which serves to connect with guide tubes, containing orifices into of which FA end fittings are inserted. 

The calculated and measured U fission-rate distributions as a function of the core height are shown in Fig. 1. The measured points were obtained with foils placed next to the slab in the unit cell. In the blanket region the foils were placed on top of the depleted uranium blocks. The accuracy of the relative activities of the foils was 0.5 to 1.0%. The solid line was obtained with the heterogeneous core fluxes using Sn 4 and the anisotropic option foil cross sections were those of the... 

ZPPR-7A Heterogeneous core, no control positions, central blanket and three internal blanket rings... 

Several recent Zero-Power Reactor (ZPR) cores that are suggested for future benchmarks are listed in Table I. these cores have been the subject of detaUed experimental and analytical investigations, tlie last two represent several essential features of a 3S0-MW(e) heterogeneous core and a 700-MW(e) homogeneous core. In addition to their usefulness for testing design-level methods and codes, the latter two cores have indicated problems in prediction of spatially varying parameters that are related to cross-section data. 

The middle range corresponded to the heterogeneous core moiety. The peak at m/z 2293 corresponded to the anhydrododecasaccharide ion followed by its phosphoryl-, pyrophosphoryl-, and pyrophosphoryl-ethanolamine (PPEA) forms appearing at m/z 2373, 2453, and 2496, respectively. The peaks at m/z 3450 and 3257 correspond to m/z 3626 minus the terminal galactosaminuronic acid (GalNA, 175 amu) and the sum GalNA plus the terminal Heptose (Hep, 192 amu). 

Fuel enrichment (TRU/HM) Reference core design radially heterogeneous core... 

The STAR-H2 reactor uses a radially heterogeneous core layout of ductless assemblies. The pin lattice is open with a large coolant volume fraction. 

TABLE XXIV-5. NEUTRONIC DESIGN PARAMETERS AND CALCULATED PERFORMANCE RESULTS FOR THE REFERENCE HETEROGENEOUS CORE LAYOUT (INTERNAL BLANKET CLADDING MATERIAL SiC FUEL RESIDENCE TIME 15 YEARS CAPACITY FACTOR 90%)... 

The radially heterogeneous core layout (i.e. with fertile material blanket assemblies interspersed in the core itself) is used to flatten radial power profile and to enhance internal breeding so as to reduce bum-up reactivity loss. 

The essential feature of the Wigner-Seitz model is that it represents a typical lattice element of a heterogeneous array by an equivalent unit cell. For example, if a heterogeneous core were to be composed of cylindrical fuel rods placed in a square lattice of spacing a, then a reasonable choice of the unit cell would be the circle of radius a/y/r concentric with a rod. In performing a calculation based on this model the usual practice is to specify that the net neutron current at the boundary of the... 

Waltar, A. E. and A. B. Reynolds. 1981. Fast Breeder Reactors. New York Pergamon Press. This book discusses the basic principles and methods as well as design features of fast breeder reactors. Each chapter ends with references and problems to be solved. Appendices include fast reactor data, comparison of homogeneous and heterogeneous core designs, and a list of symbols. 

In addition to these theoretical questions experimental investigations will be needed. The performance of mixed-oxide fuel with plutonium contents up to 45% under irradiation to high bumup will have to be determined. Reactor physics calculation methods suitable for burner cores will have to be validated by comparison with data from critical assemblies. There may also be a need for experimental work on the thermal hydraulic performance of heterogeneous cores containing both fuel and diluent material. 

Here we demonstrate that the reflection noise can be significantly reduced in RoF systems by using GI POFs with a microscopic heterogeneous core. 

We developed a GI POF with an acrylic-polymer-based heterogeneous core, whose attenuation was 200 dB/km at 670 nm. The attenuation produces a radiation loss of around 50 dB/km because of the intrinsic scattering due to microscopic core heterogeneities. The core diameter and NA were 200 pm and 0.3, respectively. Figure 3.17 shows microscopic images of the input beams on the fiber near-end faces and the output beams on the PD for the GI POF under the center launching condition. As shown in Figure 3.17b, the output beam pattern of the GI POF... 

Inoue, A., Sassa, R., Furukawa, X, Makino, K., Kondo, A., and Koike, Y. (2013) Efficient group delay averaging in graded-index plastic optical fiber with microscopic heterogeneous core. Opt Express, 21 (14), 17379-17385. 

Sorbie, K. S., Wat, R. M. S. and Rowe, T. (1987b) Oil displacement experiments in heterogeneous cores. SPE 16706, Proceedings of SPE 62nd Annual Fall Conference, Dallas, TX, September 1987. 

The heterogeneous core arrangement (Fig. XXI-4) provides the following advantages ... 

Sorbie, K.S., Wat, R.M.S., and Rowe, T.C. 1987. Oil Displacement Experiments in Heterogeneous Cores Analysis of Recovery Mechanisms. Paper SPE 16706 presented at the SPE Annual Technical Conference and Exhibition, Dallas, 27-30 September. DPI 10,2118/16706-MS. 

Figure 5.1 Typical homogeneous and heterogeneous sodium-cooled fast reactor core configurations (a) homogeneous core, (h) axial heterogeneous core, and (c) radial heterogeneous core. All rights reserved hy Japan Atomic Energy Agency.

To enhance safety, France made a decision to adopt an innovative core concept with low sodium void reactivity, called Coeur a Faible Vidange (CFV Sciora et al., 2011). The CFV is an axially heterogeneous core with a stepwise core height and a sodium plenum. This configuration exhibits the multiplier effect on the significant reduction... 

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