JPS61180187A - Control rod for nuclear reactor - 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 control rod for a nuclear reactor that is inserted into and removed from the core of a nuclear reactor such as a boiling water reactor, and particularly relates to a control rod for a nuclear reactor that is inserted into and removed from the core of a nuclear reactor such as a boiling water reactor. Concerning long-life nuclear reactor control rods.

[Technical background of the invention and its problems]

Generally, this type of nuclear reactor control rod is inserted into and removed from the core of a boiling water reactor or the like to control the operation of the reactor. In conventional nuclear reactor control rods, as shown in FIGS. 4(A) and 4(B), a sheath 2 with a deep U-shaped cross section is attached to each protruding leg of a tie rod 1 with a cross-shaped cross section. A plurality of neutron absorption rods 4 are arranged in a row within each wing 3. The neutron absorbing rod 4 has a stainless steel cladding tube 5 filled with a neutron absorbing material 6 made of Bonn Carpide (84C). Reference numeral 7 is a tip structure member to which a handle 8 is attached, and this tip structure member 7 has a guide roller 9a that guides the insertion of the i and lJ control rods.
is installed (). Reference numeral 9b indicates a coolant water passage hole.

Therefore, in the conventional nuclear reactor control rod, the neutron absorption rod 4 is filled with boron-10 (10B
) reacts with neutrons to generate He gas and lithium, while absorbing neutrons and depleting 10s, reducing the reactivity. In this way, control rods for nuclear reactors are depleted of 10 seconds of boron carbide, which impairs their nuclear lifespan, and the mechanical life is impaired due to an increase in internal pressure due to e-gas generated. had problems such as a relatively short lifespan.

From this point of view, consideration has been given to using hafnium (Hf) metal rods as neutron absorption rods loaded into nuclear reactor control rods. It is known that hafnium can extend the lifespan by 318 to 6 times that of control rods using boron carbide neutron absorption rods 4.

However, hafnium is expensive and heavy, so
When hafnium neutron absorption rods are arranged in a wing, the overall weight of the control rod for a nuclear reactor increases significantly, and the impact on the control rod drive mechanism during rapid operation of the control rod becomes extremely large. For this reason, it has been difficult to backfit control rods that use neutron absorption rods made of hehafnium to existing nuclear reactors.

[Purpose of the invention]

The present invention was made in consideration of the above-mentioned circumstances, and its main purpose is to simplify the structure of the control rod, reduce the number of parts, and provide a long-life control rod for a nuclear reactor that has a long life despite its lightweight structure. purpose.

Another object of the present invention is to provide a nuclear reactor control rod that can be smoothly backfitted into an existing nuclear reactor.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides a control rod for a nuclear reactor in which a tie rod tip structure member and a lower end structure member having a cross-shaped cross section are combined, and each projecting leg of the tie rod has a deep U-shaped cross section. The wing is formed by attaching an opening in a metal plate having a metal plate having an opening, and the metal plate is made of a metal neutron absorbing material containing hafnium as a main component.

(Embodiments of the Invention) Hereinafter, preferred embodiments of the control rod for a nuclear reactor according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a control rod for a nuclear reactor according to the present invention, and reference numeral 10 in the figure indicates a tie rod of the control rod. The tie rod 10 has a cross-shaped cross section, and is integrated with a tip structure member 11 at its tip and a lower end structure member (not shown) at its lower end. The lower end structural material is control rod drive 1Fl1
It is tied to a mechanism. The tip structure member 11 is provided with guide rollers 12 that guide insertion and extraction of the control rod. Reference numeral 13 does not indicate an operating handle attached to the tip structure member 11.

On the other hand, a metal plate 15 having a deep U-shaped cross section is attached to each protruding leg of the tie rod 10. The metal plate 15 is fixed by welding or the like to a stopper 16 provided on each projecting leg of the tie rod 10, thereby forming a wing 17 of the control rod. The metal plate 15 of the wing 17 is made of hafnium (1-(f') or l
It is composed of a long-life metallic neutron absorbing material whose main component is hafnium, such as -1f-Zn alloy. Hafnium is a metal material with excellent neutron absorption ability, and is similar to boron carbide (
B4C) has a lifespan 3 to 6 times longer than that of B4C).

In addition, since the wing 17 is composed of a thin metal plate with a thickness of about 1.5 to 2.5#I#I, it has a light 4 structure. A stiffener 18 as a reinforcing member is interposed near the attachment portion of the tie rod 10.

The stiffener 18 extends in the interior space 19 of the wing 17 in parallel to the axial direction of the tie rod 10.

The stiffener 18 is made of a metal material that can be welded to the wing 17, preferably a metal material mainly containing hafnium,
It is welded to the wing 17.

Further, the wing 17 is bulged out except in the vicinity of the attachment portion to the tie rod 10, and the width W of the wing 17 is widened outside the stiffener 18.

As a result, the metal plate 15 of the wing 17 is positioned close to the channel box 20 of the fuel assembly, and the coolant (water) as a moderator is present in the internal space 19 of the wing 17. The degree of reactivity can be increased. That is, by widening and retracting the wing 17 except for the vicinity of the attachment portion to the tie rod 10, the metal plate 15 of the wing 17 approaches the surface of the fuel assembly, and the reactivity can be increased accordingly. At this time, in order to further avoid increasing the reactivity of the control rod, a neutron absorption rod containing hafnium as a main component may be accommodated in the internal space near the side end of the wing 17.

Incidentally, outer pads 22 are provided on the widened portion of the wing 17 at appropriate distances in the axial direction of the tie rod 10, and the outer pads 22 allow the control rods to be inserted and withdrawn by sliding against the channel box 20. Gi is guided. An inner pad 23 is attached to a position corresponding to the outer pad 22. The inner pad 23 covers the inner space 1 of the wing 17.
They are provided on both sides (or on one side) of the wing 9 and function as a spacer υ to prevent the internal space 19 of the sheath-like wing 17 from becoming excessively narrow.

The inner pad 23 and the outer pad 22 may be an integral structure.

Further, the inner side of the wing 17, that is, the wing width W on the tie rod 10 side, is formed to be as narrow as a conventional wing. This is because the output in the bundle near the tie rods is particularly low. - The width of the wing 17 is narrowed, and the distance between the surface of the metal plate 15 of the wing 17 and the channel box surface 20 is set to be large. This suppresses the decrease in output. wing 1
By narrowing the width W1 of the control rod 7, the output near the tie rod increases, so an abnormal increase in output when the control rod is pulled out can be effectively prevented. Furthermore, the power distribution within the bundle when the control rods are inserted is further flattened and made uniform.

On the wing 17 of the nuclear reactor control rod, ruled lines 25 are carved at appropriate intervals in the axial direction of the tie rod 10. W
? ', il 25 +j Extends in a direction substantially perpendicular to the axial direction of the tie rod 10, and has a small hole 2 in the middle of the ruled line 25.
6 is drilled. The ruled line 25 of the wing 17 is preferably concave on the outside of the wing 17 with the small hole 26 as a boundary, and is preferably stepped on the inside.

By forming the ruled lines 25 on the wing 17, the control rod is given elasticity and deformation is facilitated, so that insertion and withdrawal of the control rod can be performed smoothly.

Note that the metal plate 15 of the wing 17 is appropriately provided with water passage holes for the coolant.

〔Effect of the invention〕

As described above, in the atomic control rod according to the present invention, an opening in a metal plate having a deep U-shaped cross section is attached to each protruding leg of the tie rod to form a wing, and the metal plate Since it is made of long-life metal neutron absorbing material, there is no need to arrange a large number of neutron absorbing rods in the wing, which greatly reduces the number of parts and simplifies the structure. For this reason, the control rod can have a lightweight structure even if a large metal neutron absorbing material is used. Therefore, the control rod of the present invention can be made to have the same weight as the conventional control rod using B4C by adjusting the thickness of the metal plate. This has the effect that the impact acting on the control rod can be suppressed to a small level, that it can be smoothly backfitted into an existing nuclear reactor, and that the life of the control rod can be extended.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of a control rod for a nuclear reactor according to the present invention, Fig. 2 is a plan cross-sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a diagram showing an embodiment of the control rod for a nuclear reactor according to the present invention. 4(A) is a diagram showing a conventional nuclear reactor control rod, and FIG. 4(B) is a longitudinal sectional view taken along the line.
It is a plane cross-sectional view along the B-8 line of A). 10... Tie rod, 1... Tip structure material, 15...
・Metal plate, 17...Wing, 18...Stiffener, 19.19a...Wing width, 20...Channel box surface, 22...Outer pad, 23...Inner pad, 25... - Ruled line, 26...small hole. Applicant's agent Hisashi Hatano Figure 3 Figure 4

Claims (1)

[Claims] 1. In a control rod for a nuclear reactor in which a tip structure member and a bottom structure member are connected to the tip and bottom ends of a tie rod having a cross-shaped cross section, each protruding leg of the tie rod has a deep U-shape. A control rod for a nuclear reactor, characterized in that a wing is formed by attaching an open side of a metal plate having a cross section, and the metal plate is made of a metal neutron absorbing material containing hafnium as a main component. 2. The control rod for a nuclear reactor according to claim 1, wherein the metal plate is a thin plate-shaped metal neutron absorbing material containing hafnium as a main component. 3. The metal plate is bulged out except near the tie rod attachment area,
A control rod for a nuclear reactor according to claim 1, wherein the width of the wing is increased. 4. The control rod for a nuclear reactor according to claim 1, wherein the metal plate is provided with ruled lines substantially perpendicular to the axial direction of the tie rod at appropriate intervals in the axial direction of the tie rod.