JPS60179687A - Fuel aggregate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel assembly used in a fast breeder reactor.

[7 problems with conventional technology]

In fast breeder reactors, alkaline earth metals such as C1 and liquid sodium are generally used as coolants, F'LC
There is. After C1, such liquid metal coolant is heated in the reactor core inside the reactor vessel, it is guided to the primary cooling system installed outside the vessel, and then returned to the reactor vessel and circulated. .

By the way, in the case of fast breeder reactors, the cladding tubes and core structures of the nuclear fuel elements are usually made of stainless steel.
When these constituent materials receive the sound of neutron irradiation, the iron, cobalt, etc. contained in the above constituent materials undergo a nuclear reaction? and a large number of radionuclides such as manganese-54, cobalt-60, and cobalt-58 are produced. This constituent material is corroded by the above-mentioned alkaline earth gold used as a coolant and released into the coolant. At this time, the aforementioned radioactive nuclei are also released into the coolant, and so-called radioactive 14 edible products are mixed into the coolant.

The radioactive corrosion products mixed into the coolant are carried to the primary cooling system according to the flow of the coolant, and are deposited on the walls of the pipes of primary cooling system equipment such as intermediate heat exchangers.

In this way, the radioactivity of radioactive corrosion products deposited on the walls of the primary cooling system can be removed by maintenance and repair of equipment such as bongs, heat exchangers, valves, flow meters, etc., and the piping connected to these equipment. Give disability money for work. In particular, manganese-54, cobalt-58, cobalt-58, etc. are often produced and have a long half-life, so V has a large influence.

Therefore, in order to solve this problem, recently, nickel has been replaced with manganese in high-temperature liquid metal sodium.
It is considered to install a radioactive corrosion product capture device that utilizes all of the radionuclides of 54, 60 and 4 with high efficiency in the reactor vessel. This radioactive corrosion product capture device has a plurality of elements containing the capture material such as nickel placed above the reactor core, facing one core coolant, and collects all of the coolant flowing out from the core. All radionuclides are captured by direct contact.

When installing a capture device such as the one described above, a space is required above the reactor core. The space is said to be about 30 crn to efficiently capture radioactive corrosion products. Therefore, there is a problem in that the reactor vessel needs to be enlarged in order to install all of the above-mentioned capture devices.

Therefore, in order to avoid the above-mentioned problems, it is considered that a large number of capture devices are installed in the space above the fuel elements of the fuel assembly that form all the main channels of the coolant.However, In this case, there is a problem that the outer circumferential surface of the wrapper tube of the fuel assembly is corroded by the coolant flowing through the gap between the fuel assemblies, making it impossible to capture the radioactive corrosion products released into the cold material C.

[Purpose of the invention]

The present invention has been developed in view of the above circumstances, and its primary purpose is to install a radioactive corrosion product capture device in the space above the fuel elements within the fuel assembly, while at the same time Radioactivity contained in the coolant flowing through the gap1
An object of the present invention is to provide a fuel assembly that can also capture edible products.

[Summary of the invention]

The present invention relates to a trumpet tube, a handling head, and an entrance nozzle each having a regular hexagonal cross-sectional shape.

In a fuel assembly +c consisting of a fuel element, a fuel element support mechanism, and a radioactive corrosion product capture device disposed above the fuel element, the gap between the fuel assemblies flows through the trumpet pipe section V at the bottom of the radioactive corrosion product capture device. A coolant introduction hole is provided for introducing the coolant into the fuel assembly, and the gap between the fuel assemblies is locally
This is a fuel assembly with a collar to make it smaller.

〔Effect of the invention〕

In a fast breeder reactor, most of the coolant flowing into the lower part of the C1 reactor vessel flows into the fuel assembly through the orifice hole C provided in the entrance nozzle of the fuel assembly, and from the trumpet tube V the entire outside is restrained. υ1 is passed through the heated fuel element part to form the top of the C fuel assembly, and is ejected from the no-end ring head section above the core. On the other hand, the coolant that has not flown into the fuel assembly through the orifice holes flows through the gaps between the fuel assemblies arranged in large numbers and flows out to the upper part of the reactor core.

However, with the configuration of the present invention, the gap k between the fuel assemblies
The flow path of the coolant that has reached the handling head becomes locally small due to the collar provided on the outer circumferential surface of the handling head, preventing it from flowing upward into the reactor core. The coolant flows into the fuel assembly through the coolant introduction hole. This inflowing coolant is equal to the coolant inflowing from the orifice hole of the entrance nozzle.
As a result, the radioactive corrosion products are removed and the coolant flows upward through the reactor core from the nozzle nodule.Therefore, the C1 reactor valley The coolant flowing out to the primary cooling system is a coolant from which radioactive corrosion products have been removed, and deposition of radioactive corrosion products into the primary cooling system can be completely prevented.

In the present invention, the radioactive corrosion product gold contained in the coolant flowing through the gap between the fuel assemblies can also be captured with just the radioactive corrosion product capture device installed between the fuel assemblies. There is no need to install a radioactive corrosion product capture device on the surrounding surface, and there is no need to increase the size of the fuel assembly itself.
+/- In addition, it can help prevent the price increase of nuclear reactor plants.

[Embodiments of the invention]

FIG. 1 is a perspective view showing a schematic structure of a fuel assembly according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view showing a schematic structure of an upper part of this fuel assembly. This fuel assembly includes a handling head 1, a fuel element 2, a fuel element support mechanism (not shown), a trumpet tube 3 with a regular hexagonal cross section that functions to restrain the outside of these components, and a coolant inside the fuel assembly. The radioactive corrosion product trapping device 5 consists of an entrance nozzle 4 with a functional metal introduced into the fuel element 2, and a radioactive corrosion product capture device 5 made of a nickel wire mesh installed in the space above the fuel element 2. A spacer pad 6 is attached to the outer peripheral surface of the wrapper tube to maintain the entire gap between the fuel assemblies, and an orifice hole 7 is provided in the entrance nozzle 4 to introduce all the coolant into the fuel assemblies. It is provided. Further, on the outer circumferential surface of the handling head 1, barbs 8 are attached around the entire circumference so that when the fuel assemblies are installed in the reactor core, the gap between adjacent fuel assemblies is 1 mm or more.

Furthermore, two circular coolant introduction holes 9 are provided on each surface of the wrapper tube wall in the space between the fuel element 2 and the radioactive corrosion product capture device 5 for introducing the coolant into the fuel assembly.

When a large number of fuel assemblies are arranged in the reactor core, the coolant that does not flow into the fuel assemblies through the orifice hole 7 of the entrance nozzle 4 flows through the gaps between the fuel assemblies. At this time, the outer peripheral surface of the activated trumpet tube corrodes, and radioactive corrosion products mix into the C coolant. When this coolant passes through the handling head 1 and is about to flow out into the upper part of the reactor core, the flow path is extremely narrowed due to the collar 8 attached to the outer peripheral surface of the handling head 1. resistance increases. As a result of U, the coolant flows into the fuel assembly through the coolant introduction hole 9 provided in the wrapper tube wall of the F section of the radioactive corrosion product capture device 5. The coolant flowing in through this coolant introduction hole is combined with the coolant flowing into the fuel assembly through the orifice hole 7 of the entrance nozzle 4 into a radioactive corrosion product capture device. Ls
*It flows through and flows out from the handling head 1 to the upper part of the reactor core. The radioactive corrosion products drawn into the coolant are captured when flowing through the radioactive corrosion product capture device 5, and the effect described in Ai1 is obtained.

[Other embodiments of the invention]

The present invention is not limited to the embodiments described above.

In the embodiment, the shape of the coolant introduction hole was circular, but other shapes such as a rectangle may also be used. Further, the number is not limited to two on each surface.

Although gold 711 rock made of nickel is used for the radioactive corrosion product capture device, the capture device may be made of wire or plate, and the material may be nickel alloy or nickel-plated stainless steel.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic structure of a fuel assembly according to an embodiment of the present invention, and FIG. 2 is a partially omitted longitudinal sectional view. 1... Handling head, 2...・Fuel element. 3...Trumpet pipe, 4...Entrance nozzle. 5...Radioactive corrosion product capture device. 6...Spacer pad, 7...Orifice hole. 8...Brim, 9 ...Coolant introduction hole. L...Coolant. Agent: Patent attorney Noriyuki Chika (and one other person) Figure 1 Figure 2

Claims (1)

[Claims] A trumpet tube having a regular hexagonal cross-sectional shape, a handling head, an entrance nozzle, and a fuel element. A fuel assembly consisting of a fuel element support mechanism and a radioactive corrosion product capture device disposed on the upper part of the fuel element is provided, and a collar is provided on the outer peripheral surface of the handling head to close the gap between the fuel bundle assembly. A fuel assembly characterized in that each of the trumpet tubes at the bottom of the radionuclide capture device is provided with coolant introduction holes for introducing coolant into the fuel assembly.