Patent Number: 043671950
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the apparatus according to the invention uses known heat pipes, it may be worthwhile explaining the operation thereof before describing in greater detail the apparatus according to the invention. Such a heat pipe is shown in FIG. 3 and is in the form of a tight cylinder defined by an envelope A. The cylinder has an end A.sub.1 forming an evaporator and an end A.sub.2 forming a condensor. The inner wall of envelope A is covered by a capillary structure B. The envelope contains a heat transfer fluid. Heat is transported between these two ends A.sub.1 and A.sub.2 by displacement of the heat transfer fluid with change of state. The fluid vaporizes in zone A.sub.1 and the vapour flows towards zone A.sub.2. The return of the fluid after condensation takes place in the capillary structure. In this way, the temperature is homogenized in the immediate vicinity of the heat pipe envelope. The isothermicity of the apparatus is due to the fact that over its entire length, the liquid contained and its vapour are in equilibrium at all times at the saturation temperature. FIG. 4a shows a preferred mode of the fitting of heat pipes on the ferrule for obtaining the apparatus according to the invention. The heat pipes, such as 50 forming rings are fixed to the inner face of ferrule 40a of the component, the heat pipes being positioned in horizontal planes. They are fixed, in accordance with the embodiment shown in FIG. 4a, by bridges 52 welded to the ferrule 14a. Two consecutive heat pipes 51, 52 are separated by a suitable pitch p. As a function of the value of the temperature variations at the different levels, it can be advantageous to vary this pitch over the height of the ferrule. According to the embodiment of FIG. 4b, the heat pipe 50 is supported by an annular container 54 welded by ferrule 14a. It can be of interest to provide a conductive material 46 in said container. According to the embodiment of FIG. 4c, envelope A of heat pipe 40 has a base plate 50" welded to the ferrule 40a. This ensures a better thermal contact between ferrule and heat pipe. Referring now to FIG. 5a, it can be seen that the annular heat pipe can comprise a single cylindrical pipe 50, whose ends A.sub.1 and A.sub.2 are close together. As shown in FIG. 5b, it can be simpler to construct the annular heat pipe by means of three individual heat pipes, e.g. 50a, 50b, 50c, each corresponding to an angle at the centre of approximately 120.degree.. In the case of this constructional variant, it is of interest to realise each homogenization level by means of two rows of three superimposed heat pipes (heat pipes 50a, 50b, 50c and heat pipes 50'a, 50'b and 50'c). Obviously, the two rows of heat pipes belonging to the same homogenization level are displaced relative to one another, as can be seen in FIG. 5c. 5d shows an embodiment of the heat pipes arranged in end to end relationship in the form of a helix. FIG. 6a shows in greater detail another method for the installation of the temperature homogenization apparatus in pump ferrule 14a. According to this embodiment, each assembly or system incorporates two superimposed heat pipes 50 and 50'. These heat pipes are located in an annular space 60 within ferrule 14a and defined by a sealing ferrule 62 welded by its two ends to horizontal ledges 64 and 66. Thus, space 60 is tightly sealed. The heat pipes are held in place against the ferrule 14a by U-shaped vertical angle members 68, which are perforated by small holes 70 in order to hold the heat pipes. A pipe 72 makes it possible to fill space 60 with a metallic material having a low melting point in order to ensure a better thermal contact between heat pipes and ferrule 14a. In order to reduce the liquid mass with a low melting point and to reduce axial conduction, it is possible to use a preshaped ceramic insulant placed between the heat pipes and the sealing ferrule 62. Thus, the liquid volume is reduced. It is also possible to use a loose insulant placed between the sealing ferrule 62 and a holding grating 63 positioned coaxially to the ferrule in space 60. According to the variants shown in FIG. 6b, the sealing ferrules 62' have bulges 62'a to the right of groups of heat pipes. Each group of two heat pipes is located in a guide 74 welded to ferrule 62'. In addition, annular space 60' defined by ferrule 14a and ferrule 62' has a limited volume. Thus, the necessary volume of low melting point material is reduced and vertical thermal conduction limited. It is also pointed out that, bearing in mind the temperatures involved in the apparatus according to the invention, it would appear preferable to use as the heat transfer fluid in the heat pipes either water or mercury. Water has a use range from 60.degree. to 320.degree. C., whilst the range for mercury is 180.degree. to 650.degree. C. The envelope and capillary of the heat pipes are made from stainless steel, for example types AISI304 L, AISI316 or AISI347 L. It is important to note that due to the positioning of the heat pipes within the ferrule of the components, any leaks which may possibly occur in the heat pipes will not lead to the risk of any heat transfer fluid entering the liquid metal for cooling the reactor. As can be gathered from the above description, due to the features of the invention, a reliable and effective homogenization is obtained of the circumferential temperatures of the ferrules of components at the point of passing through the upper slab of the nuclear reactor.