Geometrical buckling

The geometrical buckling depends on the neutron flux distribution in the reactor. This distribution in turn dep ds on the g ieral geometry of the assembly, including boundary... 

Geometrical Buckling vs. Degree of Clustering for the Moderator to Fuel Ratio of a Uniform 3/4-in.-Triangular Lattice. 

The fuel elements while in storage on the walls of the charging area can be represented if flooded as isolated slabs, approximately one fuel element diameter thick and five fuel element diameters wide. Ihe geometrical buckling for ouch a slab is so large that it is a certainty that a critical mass is precluded as long as the fuel remains in this... 

It should be noted that the reflector augmentation as defined by the geometrical buckling is extremely sensitive to the total pile reactivity an error of only 0.2 per cent a>k/k in the determination of k can result in an error of over 60 centimeters in the estimate of S, the reflector savings. 

Increase the reactivity by cutting down on the leakage and this can be done by making the reactor bigger. This effect is described by what we call the geometric buckling. 

It depends only on the size of the reactor, and as the geometric buckling Increases, the leakage Increases. 

Bjn (material buckling) - (geometric buckling) = excess reactivity... 

Cold Clean Reactivity - (Which nay also be noted as CCp y Rqq) The excess. reactivity that a cold, xenon-free pile would have if there were no control or safety rods inserted, no poison eolumns, and no flattening material. The value, as commonly used, includes the enrichment in the pile at the time and assumes that all other columns are charged with (Irradiated) natural uranium. The initial cold clean reactivity is the excess available when the pile was first completely loaded with every tube containing natural uranium. It is the differenc b iveen the material and geometrical bucklings. 

From equation (9.5), the geometric characteristics of the core are called geometric buckling, Bg. 

In a critical reactor, the geometric buckling and the material buckling must be equal. 

This equation may be used to calculate an effective geometric buckling for a heterogeneous reflected reactor if the various parameters are known. 

Multl group calculations by Bowers indicate an effective multiplication for the fully-loaded green reactor of/v l.061 at room temperature Independent calculations by Gumprecht Indicate keff 1.059.. The effective geometrical buckling may be determined from a rearrangement... 

Assuming beat values of the parameters are given in Section 1.2.2, and a k ff for the fully loaded reactor of 1.060, the total geometrical buckling is 22.1 micro-bucks (1 /th 10 cm ) ... 

The effects of temperature on the factors of Eq. (1) arise mainly from the neutron-energy dependence of the microscopic absorption (and to a lesser extent scattering) cross sections, and from the variation of the macroscopic cross sections due to variations in core density. Also, the effect of volume changes on the geometrical buckling can be an important effect. With increasing temperature, some factors increase, some decrease, and some hardly change, so that overall coefficient depends on which factors dominate. 

What is the geometrical buckling for the system described in Question 7 What is the minimum critical volume for the reactor as a function of the buckling ... 

Associated with each mode generated is a value of the geometric buckling, B . For higher modes (larger values of i) the value of B increases, and the value of the decay constant, aj, increases. Thus the higher modes will decay more rapidly than the lowest or fundamental mode. 

E. Plot each set of data on a semilog plot, and determine the decay constant for each geometric buckling. 

F. Plot the decay constant versus geometric buckling, and determine the diffusion parameters of water from this plot by means of Eqs. (12) and (14) in Section II. 

In this method, the time dependence of the thermal-neutron flux in a source-free pure water system is compared with that of a dilute solution having the Seime geometric buckling. In the limiting case of very dilute solutions, the difference between the two decay rates will be due to the added absorption of the solute. In the case of more concentrated solutions, corrections must be made for the cheinge in diffusion coefficient auid macroscopic absorption cross section of the water due to displacement by the s olute. 

B. Place a known amount of distilled water in an aluminum tank, and determine the dimensions and geometric buckling of the sample by use of the appropriate extrapolation length. The extrapolation length may be determined from a previous experiment or from the published diffusion parameters for water. 

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