JPH0296687A - Fast breeder reactor nuclear fuel assembly - Google Patents

Abstract

PURPOSE:To originally capture a hunt slug at the time of fuel element burnout by placing particle traps (hollow cylindrical SUS sintered body). CONSTITUTION:Particle traps 16 are arranged multi-column-shapedly and housed in a lump in the outside thereof while a housing part 17 which can easily be attached and detached is integrally formed in an outer shell part. These traps 16 are placed on fuel elements 4 housed in a handling head 1, a wrapper tube 2 and an entrance nozzle 3 for forming the outer shell part to detachably mount on the inner face lower end of the head 1 or forming an upper end part by fixed pins 21 to integrate them. Further, the passage of a coolant 18 is in a condition to open the hole of a particle trap lower end inner face to set a plug cap on the upper end thereof so as to form a passage of the coolant 18 flowing in from the lower inner face thereof to permeating the outer face thereof. Bypass passage holes 22 are drilled on the circumference of a circle on the upper end part of the housing part 17 while several Na drain holes 23 are bored in a circumferential direction to contrive the soundness (heat removal) of the elements 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a nuclear fuel assembly for a fast reactor using a liquid metal coolant.

[Conventional technology] Since fast reactors have higher output per core unit volume than light water reactors, securing M removal capacity with two coolants is extremely important for core safety and operational management, including the integrity of fuel assemblies. be.

In particular, as the size of the reactor core increases, it is essential to develop a damaged fuel detection system that can detect local heat removal abnormalities in the core with high reliability, high sensitivity, and early on.

There is little experience in developing nuclear fuel assemblies for use with these detection systems. Examples of conventional nuclear fuel assemblies are shown in FIGS. 1 and 2, in which a fuel element 4 is supported in a trumpet tube (hexagonal tube) 2 provided between a handling head l and an entrance nozzle 3. It has a structure in which a large number of nozzles are loaded and placed in a regular row on the entrance nozzle 3 via a mechanism 5.

In FIG. 2, the fuel element 4 is formed by connecting a cladding tube 7 between an F end plug 9 and a lower end plug 10 to form an outer shell, and loading a fuel pellet 8 and the like therein.

Further, each fuel element 4 is provided with a wrapping wire 6, which is wrapped around each element in order to maintain a uniform gap between each fuel element 4 and to secure a coolant flow path when forming a pin handle in the assembly.

On the other hand, as shown in Fig. 3, the damaged fuel detection device is equipped with a structural system mounted inside the reactor vessel, which is effective in terms of safety, detection accuracy, manufacturing cost, etc., and has reached the adoption stage.

In such a damaged fuel detection device a, the system main body 20 has a slender cylindrical shape (φ200□), and a detection mechanism such as a diversion ring 11, a flow meter 12, a delayed neutron detector 13, etc. is provided inside. At the same time, it is equipped with various functions and installed on the top surface 14 of the furnace upper mechanism.

In addition, the particle trap 16 for capturing fuel-damaged substances, which is the main detection mechanism, is designed for fuel 1 from the viewpoint of replaceability and handling.
5 (deployed in II.

However, there is no prior precedent in the prior art regarding the research and development and employment results of fuel assemblies in which the particle trap 16, which is the detection mechanism part 21, is incorporated into the nuclear fuel assembly, and future development is urgently needed.

[Problems to be Solved by the Invention] Conventional nuclear fuel assemblies have a structure that does not have an inherent (original) mechanism for capturing fuel damaged substances. Utilization of the damaged fuel detection system main body, etc. that constitutes the detection system excluding the detection part, FM standardization of the replacement method of the particle trap, which is the main detection part, and reuse of the combustion equipment,
The purpose of this study is to construct a nuclear fuel assembly with a built-in particle trap that captures fuel-damaged substances.

[F stage to solve the problem] A particle trap with the necessary Na permeation surface area is installed at the upper end of the fuel element pin bundle (downstream side of the coolant flow) in the nuclear fuel assembly, and the particle trap section is handled and replaced. Considering the nature of the fuel element, it is installed in the storage cylinder that forms the outer shell, and in order to avoid shortening the fuel element, it is formed with a small diameter pin bundle configuration that is a single particle trap.

In addition, the particle trap storage cylinder has a structure that allows it to be easily attached to and removed from the handling head at the top of the nuclear fuel assembly using bolts or fixing pins. In addition, a plurality of coolant bypass passage holes are arranged in the circumferential direction near the upper end of the storage cylinder.

[Effect 1 Conventional nuclear fuel assemblies have a structure that does not have an inherent (original) mechanism to capture fuel-damaged substances.

The particle trap (hollow cylindrical SUS
By deploying a sintered body (sintered body), it is possible to have the function of uniquely capturing damaged materials when a fuel element breaks. Together, these can prevent and suppress the release of phlegm into the reactor vessel.

In a damaged fuel detection system with a built-in particle trap on the fuel side, the particle trap, which is the main detection part, can be installed on the fuel side, which makes the detection system viable, and the main part of the damaged fuel detection system excluding the detection part can be installed on the fuel side. It is possible to reuse such items.

Furthermore, since the particle trap for the main detection part is installed on the nuclear fuel assembly side, particle trap replacement is extremely simple and can be done through the normal fuel exchange route for core components, allowing on-site handling equipment to be used as is. In addition to being able to handle the three damaged fuel detection waves independently, the particle trap can be replaced while the damaged fuel detection device is installed on top of the furnace mechanism.

[Example] Fig. 4 shows a nuclear fuel assembly incorporating a particle trap of the present invention, in which the particle trap 16 (for example, a hollow cylindrical SUS sintered body) was prepared based on the results of a water flow test conducted separately. The pins are arranged in a multi-column arrangement, in this example a 7-pin bundle configuration, and are integrally formed with a storage cylinder 17 as an outer shell that can be stored all at once on the outside and can be easily installed and removed from the nuclear fuel assembly. .

These particle traps 16 include a handling head 1, a wrapper tube (hexagonal tube) 2.
The fuel element 4 is disposed on the fuel element 4 housed in the entrance nozzle 3, and is easily attached to and integrated with the lower end of the inner surface of the handling end 1 forming the upper end of the fuel element 4 with a fixing pin 21.

In addition, the flow path for the coolant 18 is made open on the inner surface of the lower end of the single particle trap, and a blind plug is provided at the upper end to form a flow path in the IN→OUT direction through which the coolant 18 flowing from the lower inner surface permeates to the outer surface. These are N at the time of withdrawal and replacement,
It has a structure that prevents leakage. In addition, a bypass passage hole 22 is provided at the upper end of the storage cylinder 17 to ensure the integrity (heat removal) of the fuel element 4. In this example, as shown in Figure 5, six locations are arranged on the circumference, and the bottom end is N and two train holes are arranged.
3 are arranged in several places in the circumferential direction.

FIG. 5 shows a cross section taken along the line AA in FIG. 4, and shows the arrangement of the coolant passage holes near the upper end of the storage tube 17 of the particle trap 16.

FIG. 6 shows a cross section taken along the line B-B in FIG. 4, showing the particle trap 16, storage tube 17. It shows the arrangement of the wrapper tube 2, the coolant flow path 18, and the like.

7 to 10 show different structural examples of the particle trap 16, in which FIG. 7 is a branched flow path type, FIG. 8 is a double cylindrical type, and FIG.
The figure shows example 1 of the type equipped with a partition plate 19. FIG. 1O is a sectional view of part Jl of the loading structure showing Example 2 of the partition plate 19 device il type.

The nuclear fuel assembly configured in this manner can satisfy the system configuration of the damaged fuel detection device loaded inside the reactor vessel shown in Fig. 3, and also has the ability to independently capture damaged materials when a fuel element breaks. At the same time, it is possible to prevent and suppress the release of damaged materials into the reactor vessel.

In addition, when replacing a single particle trap, it is possible to replace the fuel by using the normal core component fuel exchange route regardless of the damaged fuel detection device itself, making the handling extremely simple and allowing the on-site handling equipment to be used as is. Can be done. This can prevent the complexity and increase of fuel handling equipment, including on-site handling operations, and can also improve plant operating efficiency.

The two-particle trap 16 is not only installed on the top side of the fuel element, but also on the bottom (lower end) side, that is, it is loaded on the top end of the entrance nozzle 3 to capture coolant impurities flowing into the reactor and nuclear fuel assembly. It is also possible to have a structure where

In addition to the above-mentioned nuclear fuel assembly incorporating the particle trap 16, as an alternative, a Jll structure may be used in which a stainless steel sintered body having a hollow cylindrical shape is directly used as a particle trap in the cladding section of the fuel element. can.

[Effects of the Invention] As explained above, conventional nuclear fuel assemblies do not have a structure that uniquely (inherently) captures fuel-damaged substances, but the present invention provides particle traps to It can have the ability to uniquely capture damaged materials in the event of fuel element failure.

In addition, these are effective in preventing and suppressing the release of damaged materials into the A reactor vessel and improving the safety of the reactor.Furthermore, when replacing particle traps and nuclear fuel assemblies,
Regardless of the main body of the damaged fuel detection system, it can be handled through the normal refueling route for core components, making its handling extremely simple and allowing on-site handling equipment to be used as is. These can prevent the complexity and expansion of fuel handling equipment, including buildings, during on-site handling operations.

[Brief explanation of drawings]

Figure 1 is a perspective view showing an example of a conventional nuclear fuel assembly;
The figure is a perspective view showing details of the fuel element portion in Figure F;
Figure 3 shows the detection of damaged fuel loaded inside the reactor vessel! FIG. 4 is a vertical cross-sectional view showing an example of the specific structure of It22, FIG. 4 is a vertical cross-sectional view of a nuclear fuel assembly incorporating the particle trap of the present invention, and FIG.
The figure is a cross section taken along line A-A in Figure 4, and shows the layout of the coolant passage holes near the upper end of the particle trap storage cylinder. Figure i6 is a cross section taken along line B-B in Figure 4, showing the particle trap and cooling. Figures 7, 8, 9, and 10 showing the arrangement of material flow paths, etc. are nuclear fuel assemblies of the present invention, and show structures different from the particle trap structure shown in Figure 4. It is a partial vertical cross-sectional view. In the figure. l: Handling head 2 Niratsuba tube 3: Entrance nozzle 4: Fuel element 16: Particle trap 17: Storage tube 18: Coolant 19: Partition plate agent Patent attorney 1) Haru Kitatake

Claims (3)

[Claims] (1) In order to avoid shortening of fuel element pins, particle traps made of hollow cylindrical stainless steel sintered bodies are arranged in regular rows in a multi-column configuration to form a pin bundle structure. A nuclear fuel assembly characterized by intervening equipment above a fuel element and below a handling head. (2) A nuclear fuel assembly for a fast reactor according to claim (1), which is equipped with a particle trap at the upper end of the entrance nozzle. (3) In the nuclear fuel assembly according to claim (1), a storage cylinder for collectively storing the particle trap is provided on the outer periphery of the particle trap, and a flow path for the coolant is secured and an N_a reservoir is provided at the upper and lower ends of the particle trap. A nuclear fuel assembly for a fast reactor, characterized in that a plurality of coolant flow passage holes are provided on the circumference in consideration of the above.