JPS5941557B2 - nuclear fuel assembly - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to nuclear fuel assemblies in nuclear reactors using liquid metal coolant.

The liquid metal coolant used in this type of reactor, which has already been proposed, has a flow rate distribution that takes into account the different calorific values of each nuclear fuel assembly loaded in the reactor vessel. It is configured to make the heat exchange efficiency within the reactor uniform and to improve the efficiency, and to prevent melting of the fuel pins in each nuclear fuel assembly.

That is, in a nuclear reactor that uses a liquid metal coolant that has already been proposed, such as a fast breeder reactor, as shown in FIGS. Coolant supply ports C1y and C2 are provided, the core structure d of the reactor vessel is installed horizontally, and the entrance of each nuclear fuel assembly g is connected to each connecting pipe f having the flow rate adjustment hole e of the reactor core structure d. Insert the nozzle g1 removably,
The curved blade directs the coolant from the high-pressure plenum h, which communicates with the coolant supply port CI+02 of the reactor vessel, through the lower plenum i through the rectifying perforated plate d1 provided at the lower part of the core structure d.
After that, the coolant is injected into each entrance nozzle g1 from the flow rate adjustment hole e, and the coolant flowing into each entrance nozzle g1 is passed through the fuel pin j of each nuclear fuel assembly g. This exchanges heat and supplies it to each outlet of the coolant provided on the upper side wall of the furnace vessel. After that, the coolant flows out from the coolant 2 and performs work by exchanging heat, and then returns to the coolant supply ports C1 and C2.

The liquid metal coolant used in the reactor is determined by the opening aperture and size of the flow rate adjustment hole e of each connecting pipe f,
Since the shape and flow rate are adjusted by each orifice of each entrance nozzle g1, the upper S [junction l] of the upper support plate d2 of the core structure d forms a spherical seat, This is intended to minimize the phenomenon of coolant leakage.

The lower fitting part m of the lower support plate d3 biases the entrance nozzle g1 of the nuclear fuel assembly g due to the fluid pressure of the coolant, which impairs the proper flow rate of the coolant and causes the inside of the reactor vessel to deviate. The flow distribution becomes uneven, reducing the heat exchange efficiency and creating a temperature difference between the nuclear fuel assemblies g, which may cause thermal deformation of the nuclear fuel assemblies g and abnormal heat generation in the fuel pins j. There is.

Therefore, in order to prevent the above-mentioned problem, as shown in Fig. 2, each connecting pipe f leading to the lower fitting part m of the entrance nozzle g1 is lengthened to increase the friction loss when the coolant passes through. It has also been proposed to reduce the gap between the entrance nozzle g1 and the lower fitting part m, as shown in FIG. Not only will this deteriorate, but the lower end of the entrance nozzle g1 may also be thermally deformed, causing each nuclear fuel assembly g
may not be able to be pulled out from the upper and lower fitting parts d and m of the core structure d.

In view of the above-mentioned points, the present invention provides a nuclear reactor using a liquid metal coolant with upper and lower sleeping parts on the upper and lower support plates of the core structure, and a nuclear fuel assembly inserted into the sleeping parts. A leak prevention member slidably fitted into the lower end opening of the entrance nozzle so as not to fall off can be brought into pressure contact with the lower fitting part by the pressure of the liquid metal coolant, and thereby The purpose is to reliably prevent liquid metal coolant from leaking from joints to improve heat exchange efficiency, and to facilitate handling operations such as loading and unloading fuel assemblies. It provides nuclear fuel assemblies.

Hereinafter, the present invention will be described with reference to an illustrated embodiment.

In FIGS. 4 and 5, reference numeral 1 denotes a core structure in a nuclear reactor that uses liquid metal coolant, and upper and lower support plates 2 and 3 of this core structure 1 have flow rate adjustment holes 4. The upper and lower supporting plates 2 and 3 located at the opening of the connecting tube 5 are provided with spherical upper and lower mating portions 6 and 7, respectively.

An entrance nozzle 10 of a fuel assembly 9 containing a fuel pin 8 is inserted into the upper injection part 6 of the upper support plate 2, and each orifice 11 is inserted in the middle of the entrance nozzle 10. Coolant can flow in from the flow rate adjustment hole 4.

Further, a flange 12 is formed at the lower end opening 10a of the entrance nozzle 10, as shown in an enlarged view in FIG.
The leakage prevention member 13 having 3a is slidably fitted in such a manner that it does not fall out.

Further, the lower part 13b of this leakage prevention member 13 is connected to the lower part 7.
The pressure of the liquid metal coolant flowing in from the orifice 11 presses against the lower injection part 7 to prevent the liquid metal coolant from leaking from the joint surface with the lower injection part 7.

That is, the orifice 11 of the upper self-entrance nostle 10
Since the pressure Pe of the liquid metal coolant flowing from the upper and lower joints 7 is greater than the pressure PL of the coolant against the discharge pressure plenum of the upper and lower joints 7, the above pressures Pe and P
The larger the differential pressure with L, the more effective the leakage prevention effect of the coolant can be.

Next, the embodiment shown in FIGS. 6 and 7 is an embodiment of the music of the present invention, in which the gap 14 between the flange 12 of the entrance nozzle 10 and the stopper 13a is filled with gas. A ring ring 15 is interposed therebetween to prevent the coolant from leaking from the sliding sleeping area.

Next, the embodiment shown in FIG.
An extensible spring 16 is interposed between the stepped portion 10b of No. 0 and the stopper 13a, and the elasticity of the spring 16 and the internal pressure of the coolant press the leakage prevention member 13 downwardly to the joint portion 7. It's just something you get.

Furthermore, in the embodiment of the present invention shown in FIG. 9, a flat step part 13c is provided at the lower part 13b of the leakage prevention member 13, and this makes pressure contact with the flat lower part 7, thereby causing leakage of coolant. It is designed to prevent this.

Furthermore, the embodiment of the song of the present invention shown in FIG.
3 are connected by a metal bellows 17 that expands and contracts, and is substantially the same as the specific example described above.

Furthermore, the embodiment of the song of the present invention shown in FIG.
This is a modification of the embodiment shown in FIG. 10, in which a cylindrical protective cover 18 is provided around the outer periphery of the bellows 17, and is substantially the same as the embodiment described above. be.

As described above, according to the present invention, in a nuclear reactor using a liquid metal coolant, the upper and lower support plates 2 of the core structure 1
, 3 are provided with upper and lower sleeping parts 6, 7, and a lower end opening 10 of the entrance nozzle 10 of the fuel assembly 9 inserted therein.
The leakage prevention member 13, which is slidably fitted in the hole a and not falling, can be pressed to the joint 7 below by the pressure of the liquid metal coolant, so that the appropriate coolant is used. It has excellent effects such as obtaining a good flow rate distribution, eliminating the risk of thermal deformation or abnormal heating, and also being simple in structure and easy to handle.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining nuclear fuel assemblies used in nuclear reactors that have already been proposed, FIG. 4 is a partial sectional view of a nuclear fuel assembly according to the present invention, and FIG. 5 is a diagram illustrating the present invention. FIGS. 6 to 11 are enlarged sectional views showing only the main parts of the music piece, and FIGS. DESCRIPTION OF SYMBOLS 1... Core structure, 2, 3... Upper and lower support plates, 6°7... Upper and lower fitting parts, 9... Fuel assembly, 10...
・Entrance nostle, 13...Leakage prevention member.

Claims (1)

[Claims] 1. In a nuclear reactor that uses liquid metal coolant, upper and lower coupling parts with tapered surfaces are provided on the upper and lower support plates of the core structure of this reactor, and The entrance nozzle of the formed fuel assembly and the lower end opening of this entrance nozzle are fitted so as to be slidable so as not to fall, and are pressed against the lower fitting part by the pressure of the liquid metal coolant. A nuclear fuel assembly comprising a leakage prevention member provided to obtain a leakage prevention member.