Primary Core Parameters

Length of the lower grid plate pin flow orifices (m) N/A 

The XY plane section of a pin shows a close-up of the radial layout of a single pin. The innermost volume of the fuel pin is UN. Then there is a small gas gap followed by a layer of Rhenium. Next is the NblZr cladding and then the gas flow channel. Finally there is the matrix that the fuel pins are suspended in. A rhenium wire wrap is used to keep the fuel pins centered in the flow channels. 

As a result of the desire for a pressure vessel material compatible with the Martian environment at the desired temperatures Hastx was chosen for the pressure vessel. HastX is known for being extremely insensitive to corrosion and carburization [Brown, W., 1992]. Theoretically, the relatively small neutronic penalty associated with Hastelloy means that any comparably transparent material (from a neutronic standpoint) could be substituted, which may be necessary if HastX and NblZr are incompatible. 

To examine its viability, a variety of parametric scans were performed using MCNP-5 [LANL, 2003] on a model of the proposed core. The core was designed with sufficient reactivity to ensure 10 years of full-power operation even when including such negative feedback coefficients as temperature, temperature based expansion, and bumup. The neutronics runs done include  

This section will cover some simple calculations related to the reactor. The reactor had a cold, beginning of life, neutron multiplication factor of 1.037 0.001, which corresponds to an excess positive reactivity of 5.7 based on a delayed neutron fraction of 0.0065. The burnup for the reactor was determined using a fairly simple set of equations. The consumption over 10 years at a power level of 200 kWth was 0.8 kgs of and at 400 kWth, 1.6 kgs of would be consumed. Given that the fuel loading is 186 kgs of the burnup is -0.86% for the upper end of the uranium consumed. This burnup results in a loss of 1 reactivity. 

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A Reference Design for the primary circuit of a 60 MWt experimental fast reactor is completed. Some parameters and characteristics have been selected mostly based on the Integral Fast Reactor (IFR) concept. Fuel pin dimensions and other data were used for calculations which lead to a general core configuration. Some calculations were also independently performed at lEN, and the differences in methodologies are being evaluated. Table 1 shows the main primary circuit parameters. 

The primary coolant parameters have been chosen from the well-proven range of working pressures and temperatures typical of light water reactors. Consideration has been also made of experience in the operation of nuclear propulsion power plants in the modes of natural circulation of the primary coolant. The maximum primary coolant temperature at the core outlet (data averaged over the cross-section) can be taken equal to 330°C. Considering the above mentioned decrease of temperature due to fuel bum-up, this value would amount to 320°C at the end of life prior to maintenance shutdown. Under natural circulation of the primary coolant, the temperature difference between the core outlet and inlet will be no less than 70°C. Thus, the minimum temperature of the primary coolant will be 250°C. 

Primary coolant parameters - sodium temperature at core inlet, °C 382 377... 

The first step is to determine the number of turns needed for the primary winding. For this, the parameters from the core data sheet of the particular core and core material are used. Also, the minimum level of flux density already should have been determined (refer to Appendix D). The equation for determining the number of turns for the primary winding in the CGS System (U.S.) is... 

In all above mentioned applications, the surface properties of group IIIA elements based solids are of primary importance in governing the thermodynamics of the adsorption, reaction, and desorption steps, which represent the core of a catalytic process. The method often used to clarify the mechanism of catalytic action is to search for correlations between the catalyst activity and selectivity and some other properties of its surface as, for instance, surface composition and surface acidity and basicity [58-60]. Also, since contact catalysis involves the adsorption of at least one of the reactants as a step of the reaction mechanism, the correlation of quantities related to the reactant chemisorption with the catalytic activity is necessary. The magnitude of the bonds between reactants and catalysts is obviously a relevant parameter. It has been quantitatively confirmed that only a fraction of the surface sites is active during catalysis, the more reactive sites being inhibited by strongly adsorbed species and the less reactive sites not allowing the formation of active species [61]. 

The P,T-parity nonconservation parameters and hyperfine constants have been calculated for the particular heavy-atom molecules which are of primary interest for modern experiments to search for PNC effects. It is found that a high level of accounting for electron correlations is necessary for reliable calculation of these properties with the required accuracy. The applied two-step (GRECP/NOCR) scheme of calculation of the properties described by the operators heavily concentrated in atomic cores and on nuclei has proved to be a very efficient way to take account of these correlations with moderate efforts. The results of the two-step calculations for hyperfine constants differ by less than 10% from the corresponding exper-... 

The lines of primary interest in an xps spectrum are those reflecting photoelectrons from core electron energy levels of the surface atoms. These are labeled in Figure 8 for the Ag 3s, 3p, and 3d electrons. The sensitivity of xps toward certain elements, and hence the surface sensitivity attainable for these elements, is dependent upon intrinsic properties of the photoelectron lines observed. The parameter governing the relative intensities of these core level peaks is the photoionization cross-section, q. This parameter describes the relative efficiency of the photoionization process for each core electron as a function of element atomic number. Obviously, the photoionization efficiency is not the same for electrons from the same core level of all elements. This difference results in variable surface sensitivity for elements even though the same core level electrons may be monitored. 

Other formulation parameters that may be used to modulate the release include the ratio (relative concentrations) of polymers in the case of incorporation of a mix of two or more polymers as primary coating material, the properties of the core material, and the amount of plasticizers used, which affects the strength of the coat. Plasticizers with low water solubility such as dibutyl sebacate, diethyl phthalate, tri-acetin, triethyl citrate, and acetylated monoglyceride result in delaying... 

A considerable amount is known about details of the primary events in electronic excitation. Electronic excitation cross sections are dependent on the charge and velocity of the incident primary ion. Both of these parameters have been confirmed to be the important variables in the emission of secondary molecular ions under bombardment by ions in the 50-100 MeV regime (1 MeV/u) (5-6). The excitation promotes electrons within atoms and molecules to very high energies resulting in ionization and emission of secondary electrons (up to 50 per incident ion) (7). The excitation of electrons in core... 

Planets, satellites, and small bodies provide a wide range of dynamical and chemical constraints on the building of the Solar System from planetesimals. In addition to the primary parameters of planets, the planet mass and semi-major axis distributions, the relative masses of the cores (exceptionally large for Mercury and low for the Moon) provide further constraints. In addition, the Asteroid Belt seems to be depleted in mass by three to four orders of magnitude and its medium- to small-sized... 

Detailed kinetic schemes also consist of several hundreds of species involved in thousands of reactions. Once efficient tools for handling the correspondingly large numerical systems are available, the extension of existing kinetic models to handle heavier and new species becomes quite a viable task. The definition of the core mechanism always remains the most difficult and fundamental step. Thus, the interactions of small unsaturated species with stable radicals are critical for the proper characterization of conversion and selectivity in pyrolysis processes. Parallel to this, the classification of the different primary reactions involved in the scheme, the definition of their intrinsic kinetic parameters, the automatic generation of the detailed primary reactions and the proper simplification rules are the important steps in the successive extension of the core mechanism. These assumptions are more relevant when the interest lies in the pyrolysis of hydrocarbon mixtures, such as naphtha, gasoil and heavy residue, where a huge number of isomers are involved as reactant, intermediate and final products. Proper rules for feedstock characterizations are then required for a detailed kinetic analysis. 

Fig. 6.26 Variations in proxy measurements for various climatic parameters in the Southern Ocean during the last glacial-interglacial cycle.MSA (methane sulphonic acid, a proxy for DMS) and 5lsO (proxy for temperature) in an eastern Antarctic ice core estimated iron concentration (Fe) and C02 trapped in air in another Antarctic ice core (Vostok) Corg = organic carbon (proxy for primary productivity) in an eastern tropical Pacific sediment core (after Turner et al. 1996).

Analysis of parameters changes showed that carbon and hydrogen contaira ng substances penetrated into the primary sodium and deposited on the walls of SA feet and core diagrid. This was the cause of the flow rate decrease through SA in some sections of the reactor core. 

The changes in process parameters resulting in decrease in core inlet temperature causing reactivity transient were studied. The required inlet temperature change to cause the two transients were estimated to be -3.1 and -4.9 C respectively. Extensive tests on the influence of changes in primary, secondary and feed water flow and steam pressure were studied at 9.5 MWt power and the results are given in Table 1. 

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