JPH01210898A - Irradiation assembly with instrumentation - Google Patents

Abstract

PURPOSE:To drastically decrease the leakage of magnetic lines of force and to obviate bending of a welding arc during welding operation by mounting metallic holders consisting of magnetic materials between a pair of permanent magnets constituting a flow meter. CONSTITUTION:The metallic holders 9, 10 consisting of the magnetic material are mounted in the circumferential spacing between a pair of the permanent magnets 2 and 3 of the permanent magnet flow meter 15 provided with a wrapper pipe 12 which has a handling head 11 at one end and an entrance nozzle 13 at the other end, an irradiation sample part 14 provided in the wrapper pipe 12, a flow passage pipe 1 communicating with the aperture of the nozzle 13 and the sample part 14, the magnets 2, 3 which are disposed at both ends of one diameter of the pipe 1 and in which the different poles are opposed to each other, and a pair of electrodes 4, 5 which are mounted to the pipe 1 and are positioned on the diameter perpendicular to one diameter. The leakage of the magnetic lines of force are drastically decreased by this holders 8, 10 by which the bending of the welding arc is obviated and the welding is facilitated at the time of the welding operation.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an instrumented irradiation assembly.

(Prior Art) Instrumented irradiation assemblies capable of online measurement are used to elucidate the behavior of nuclear fuel and structural materials in nuclear reactors. The irradiation assembly is usually equipped with a flow meter to measure the coolant flow rate.

Therefore, the signal line that transmits the measured output of the flowmeter is routed through a high temperature and highly radioactive environment.

For this reason, a permanent magnet type flow meter is often used because it provides a stable output signal.

FIG. 7 is a cross-sectional view of one example. In this diagram,
A pair of permanent magnets 2 and 3, which are located on one diameter of the coolant flow pipe 1 and have different polarities facing each other, are installed at the position where the flow rate measurement of the coolant flow pipe 1 is to be performed. Furthermore, electrodes 4 and 5 are disposed facing each other on a diameter perpendicular to the one diameter. In the figure, 6 is a casing that surrounds and supports the permanent magnet 2.3, and 7 is an electric tf! 4 indicates a signal line connected to the electrode 5, and 8 indicates a signal line connected to the electrode 5, respectively. In addition, each f! The material of the pole 4.5 may be any conductive material, but since it is to be welded to the flow pipe 1, it is preferable that the pole 4.5 be made of the same material. Furthermore, since the signal lines 7 and 8 are used under high temperature and high radiation conditions, they are made of inorganic insulated cables.

The cable core is made of austenitic stainless steel, copper or copper alloy, and the insulation is magnesium oxide,
Aluminum oxide is used. Note that austenitic stainless steel is used for the covering material. Furthermore, the permanent magnets 2 and 3 are usually rare earth magnets with excellent high-temperature properties.
~ (for example, S m Cos ). The core wire of each signal line is connected to each corresponding electrode by welding or brazing, and the covering material is hermetically welded to the flow path pipe 1.

FIG. 8 is a diagram showing the distribution of magnetic lines of force in the permanent magnet flowmeter having the above configuration. As can be seen from this figure, most of the magnetic field lines coming out from the N pole of permanent magnet 3 cross the coolant flow pipe 1, enter the S pole of permanent magnet 2, and exit from the N pole of permanent magnet 2. Most of the magnetic field lines bypass the coolant flow pipe 1 casing 6 and enter the S pole of the permanent magnet 3.

In the flowmeter having the above configuration, when the electromagnetic fluid flows in the flow pipe 1, an electromotive force in a direction perpendicular to the lines of magnetic force is generated in proportion to the flow rate of the electromagnetic fluid. This electromotive force is taken out of the reactor through signal lines connected to the electrodes 4 and 5, and the flow rate is measured.

In order to maintain the insulation properties of the signal lines 4 and 5 and prevent material deterioration, and to prevent the material of the permanent magnet from deteriorating, both of these wires are immersed in inert gas or dry air by a casing 6. Sealed. In order to form this sealed structure, it is necessary to use a welded structure because the flowmeter is installed in a high-temperature, highly radioactive environment. However,
Since the welding arc is a high temperature plasma and a stream of charged particles, it causes electromagnetic interaction with the magnetic field lines from the strong permanent magnet 2.3.

That is, the welding for sealing the signal lines 7, 8 and the permanent magnets 2.3 inside the casing 6 is done around the casing 6, but while this welding is being done, the welding arc is caused by the lines of magnetic force. It is bent under the influence of distribution. Therefore, the welding line is usually set as far away from the permanent magnets 2 and 3 as possible. However, in this case, the distribution of magnetic lines of force becomes three-dimensional. Moreover, it is still not possible to completely escape the influence of magnetic field lines. Therefore, when performing welding, it is necessary to take into account the bending of the welding arc due to the distribution of magnetic lines of force, making the welding work extremely difficult.

In reality, we try to make several prototypes and gain sufficient proficiency before welding, but we cannot ignore the waste of practice time and practice materials, and the need for sufficient practice. Even after loading, the product yield was low, and an increase in costs was unavoidable.

(Problems to be Solved by the Invention) As described above, in an instrumentation irradiation assembly equipped with a conventional permanent magnet flowmeter, welding arc is generated during welding work to seal the flowmeter signal line and the permanent magnet. Because it bends under the influence of the magnetic field distribution, welding is extremely difficult, which not only increases the manufacturing cost of the flowmeter, but also requires a long period of time to manufacture.

To avoid this, it is necessary to significantly reduce the magnetic field lines at the weld line. The simplest method is to place the welded part sufficiently away from the permanent magnet so that the lines of magnetic force do not reach the welded part. However, since the instrumented irradiation assembly is installed in the reactor core in the same way as the fuel assembly and control rods, its shape and dimensions cannot be set arbitrarily, and the fuel assembly, It is necessary to match the shape and dimensions with the control rod. Therefore, the flowmeter must be configured compactly,
As mentioned above, the welded portion and the permanent magnet cannot be sufficiently spaced apart.

The present invention has been made based on the above circumstances, and has a compact structure and is not affected by the distribution of magnetic lines of force.
It is an object of the present invention to provide an irradiation assembly with instrumentation that allows simple and easy welding for sealing signal lines and permanent magnets.

[Structure of the Invention (Means for Solving the Problems) The instrumented irradiation assembly of the present invention includes a trumpet tube provided with a handling head at one end and an entrance nozzle at the other end, and a trumpet tube provided within the trumpet tube. an irradiation sample section, a channel tube that is connected to the entrance nozzle opening at one end and connected to the irradiation sample section at the other end; A permanent magnet flowmeter comprising a pair of permanent magnets and a pair of electrodes mounted on the flow pipe and located on a diameter perpendicular to the one diameter, wherein a circle between the pair of permanent magnets is provided. It is characterized in that a holding metal fitting made of a magnetic material is attached to the circumferential gap.

(Function) In the irradiation assembly with instrumentation of the present invention having the above configuration, a holding fitting made of a magnetic material is attached between the pair of permanent magnets constituting the flowmeter, so that leakage of magnetic lines of force is drastically reduced. There is no risk of bending of the welding arc during welding work. Therefore, welding for forming a space for sealing permanent magnets, signal lines, etc. and isolating them from the reactor coolant becomes very easy. Further, since the welding site may be a site close to the permanent magnet, the axial dimension of the instrumented irradiation focusing body can be easily matched with other core components.

(Embodiment) Fig. 1 is a longitudinal sectional view of an embodiment of the present invention, and Fig. 2, in which the same parts as in Figs. FIG. 3 is a longitudinal cross-sectional view simultaneously showing a 90° cross section of the flowmeter. First, details of an embodiment of the present invention will be explained with reference to FIG. In this figure, an entrance nozzle 13 into which a coolant flows is provided at the other end of a wrapper tube 12 having a handling head 11 at one end, and a flow connecting the opening of the entrance nozzle 13 and the irradiation sample portion 14 inside the wrapper tube is provided. A permanent magnet flow system 15 is provided surrounding the pipe 1 .

Note that 16 in the figure indicates an orifice provided at the entrance part of the entrance nozzle.

In FIG. 2, a holding metal fitting 9 and a holding metal fitting 10 made of a magnetic material such as pure iron are attached between the permanent magnets 2 and 3. The holding fittings 9 and 10 form a yoke, and leakage of magnetic lines of force to the outside of the casing 6 is almost eliminated. Also,
Since the casing 6 is made of a non-magnetic material such as austenitic stainless steel, such as 5O5316, like other core internal structures, the lines of magnetic force passing through the inside of the casing 6 can be ignored.

Therefore, even if welding is performed at a position close to the permanent magnet 2.3,
There is no influence of magnetic lines of force on the welding arc, and welding can be performed simply and easily in the same way as normal welding. In addition, electrode 4.5 and flow pipe 1° electrode 4.5 and signal lines 7 and 8
It goes without saying that these welds can be easily done since the welding is done before the permanent magnet 2.3 and the flow pipe 1 are assembled.

As mentioned above, since welding can be performed near the permanent magnet to seal it, the permanent magnet flowmeter 15
Since the axial dimension of the irradiation assembly can be reduced and made compact, the instrumentation irradiation assembly of the present invention can be matched in external shape and dimensions with other core equipment such as fuel assemblies.

Furthermore, in the above embodiment, since the two permanent magnets 2.3 are connected by the holding fitting 9.1O, an efficient magnetic circuit is formed, and the permeance coefficient of the magnetic circuit becomes large. The magnetic flux density within the channel tube 1 sandwiched between the permanent magnets 2 and 3 is increased. As a result, when permanent magnets with the same performance are used, the flow signal level obtained is higher than that of conventional flowmeters, the S/N ratio is improved, and a high-performance flowmeter can be obtained.

FIG. 4, in which the same parts as in the previous figures are denoted by the same reference numerals, is a perspective view of the main parts of the second embodiment of the present invention. In this embodiment, the holding fittings 9, 10 are each provided with a window hole (only the window hole 10a of the holding fitting 10 is shown in the figure), and the material of the holding fitting 6 increases the surface area of the holding fitting. If it is selected appropriately, it will exhibit sufficient magnetic properties even if the above-mentioned window hole is provided.

The same functions and effects as in the embodiment described above can be obtained. Furthermore, by increasing the surface area as described above, heat dissipation is improved and temperature rise due to irradiation with neutrons, gamma rays, etc. can be suppressed.

FIG. 5 is a perspective view showing a third embodiment of the present invention. In this embodiment, the holding fittings 9 and 10 are formed by two arc-shaped members (only members 10 and 10□ constituting the holding fitting 10 are shown in the figure) spaced apart in the axial direction. It is configured.

In this embodiment as well, the same functions and effects as in the second embodiment can be obtained.

FIG. 6 is a cross-sectional view of a main part of a fourth embodiment of the present invention.

In this embodiment, a two-part cylindrical magnetic path 2o is attached to the outer periphery of the casing 6 at a position corresponding to the permanent magnet 2.3 only during welding.

In this embodiment as well, leakage of magnetic lines of force is prevented, and the welding arc will not be bent even if welding work is performed near the permanent magnet.

[Effects of the Invention] In the irradiation assembly with instrumentation of the present invention having the above configuration, a holding fitting made of a magnetic material is attached between a pair of permanent magnets constituting the flowmeter, so that leakage of magnetic lines of force is prevented. There is no risk of bending of the welding arc during welding work. Therefore, the parts to be welded to seal the permanent magnets, signal lines, etc. and to form a space to isolate them from the reactor coolant may be in close proximity to the permanent magnets. The axial dimensions of the body can be easily matched to other core components. Furthermore, since the holding metal fittings form a magnetic path between the permanent magnets, the magnetic flux density within the flow pipe can be increased, resulting in an instrumented irradiation assembly with high sensitivity and a good S/N ratio. be able to.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a cross-sectional view of the main part thereof, FIG. 3 is an enlarged cross-sectional view of the main part, and FIG. 4 is a modified example of the main part. FIG. 5 is a perspective view of another modification of the main part, FIG. 6 is a cross-sectional view of still another modification of the main part, and FIG. 7 is a diagram of a conventional permanent magnet flowmeter. The cross-sectional view, FIG. 8, is a schematic diagram showing the distribution of the lines of magnetic force.

Claims (1)

[Claims] A trumpet tube equipped with a handling head at one end and an entrance nozzle at the other end, an irradiation sample section provided within the trumpet tube, and a flow path that connects to the entrance nozzle opening at one end and to the irradiation sample section at the other end. a pair of permanent magnets placed at both ends of one diameter of this channel tube with opposite poles facing each other; and a pair of permanent magnets installed on the channel tube and located on a diameter perpendicular to the one diameter. A permanent magnet flowmeter equipped with an electrode,
An irradiation assembly with instrumentation, characterized in that a holding fitting made of a magnetic material is attached to the circumferential gap between the pair of permanent magnets.