JPS61180188A - 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. Enclosed in a long-life reactor control rod.

[Technical day before 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. As shown in FIGS. 5(A) and 5(B), a conventional control rod for a nuclear reactor is constructed by attaching a sheath 2 with a deep U-shaped cross section to each protruding leg of a tie rod 1 having a cross-shaped cross section. A plurality of neutron absorption rods 4 are arranged in a row in each wing 3. The neutron absorption rod 4 is made of stainless steel [1] and boron carbide (84
It is filled with the neutron absorbing material 4b of C). In addition,
Reference numeral 5 denotes a tip structure member to which a handle 6 is attached, and a guide roller 7 for guiding insertion of the control rod is attached to this tip structure member 5.

However, in the conventional control rod for a nuclear reactor, the neutron absorption rod 4 is filled with boron-10 ("B") made of boron carbide.
reacts with neutrons to generate Le gas and lithium, while absorbing neutrons, depleting 10s and lowering the reactivity. In this way, control rods for nuclear reactors are depleted of 10B of boron carbide, which impairs their nuclear lifespan, and the increase in internal pressure caused by the generated T1e gas impairs their mechanical life, so control rods using boron carbide are There were 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 life of a control rod 3 to 6 times longer than a control rod using a boron carbide neutron absorption rod 4.

However, since hafnium is expensive and has large heavy chains, arranging hafnium neutron absorption rods in the wing will significantly increase the weight of the entire control rod, and the impact on the control rod drive mechanism during rapid operation of the control rod will increase significantly. - becomes very large. For this reason, it was physically difficult to backfit control rods that used neutron absorption rods made of hehafnium to existing nuclear reactors.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned circumstances, and it reduces the number of parts to simplify and lighten the structure of the control rod, and provides a long-life nuclear reactor control rod that has a long life despite its lightweight structure. The purpose is to

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 situation, the present invention provides an atomic control rod in which a tip structural member and a bottom structural member are connected to the tip and lower ends of a tie rod having a cross-shaped cross section, in which each protruding leg of the tie rod is provided with a The present invention is characterized in that elongated rectangular metal plates are mounted facing each other to form wings, and the metal plates are made of a long-life neutron absorbing material.

[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 nuclear reactor control rod according to the present invention, and reference numeral 10 in the figure indicates a tie rod of the nuclear reactor control rod. The tie rod 10 has a cross-shaped cross section, and is integrated with a tip structural member 11 at its tip and a lower end structural member (not shown) at its lower end.

The tip structure member 11 is provided with a handle 12 for handling the control rod, and is also provided with guide rollers 13 for guiding insertion and handling of the control rod.

On the other hand, elongated rectangular metal plates 14 are attached to each protruding leg of the tie rod 10 in pairs so as to face each other from both sides, as shown in FIG.

The metal plate 14.14 is fixed by welding or the like to a retaining pin 15 provided on the protruding leg of the tie rod 10, thereby forming four control rod wings 16 arranged in a cross shape as a whole. The metal plate 14° 14 of the wing 16 is, for example, 1.5 to 2
．． It has a wall thickness of about 5s, and its front and rear ends are covered with the tip structure material 1.
1 and the lower end structural member and are integrated.

The metal plate 14 of the wing 16 is made of a long-life metallic neutron absorbing material containing hafnium as a main component, such as hafnium ()-If) or To1f-Zn alloy. Hafnium is a metal material with excellent neutron absorption ability and has a lifespan 3 to 6 times that of boron carbide (84C).

Further, a stiffener 18 as a reinforcing member is interposed in the wing 16 near the attachment portion of the tie rod 10. The stiffener 18 is a rod-shaped member that extends parallel to the tie rod 10 within one internal space of the wing 16, and
4.14 It is made of the same material as the metal material, for example, a metal material whose main component is hafnium, so that it can be welded to the metal material.

Roughly speaking, the metal plate 14゜14 that forms the pair of the wing 16 is,
The free end (outer end) side area except for the vicinity of the attachment part to the tie rod 10 is widened in the direction of separating from each other, and the outer pad 21 that can be engaged with the channel box surface 20 of the fuel assembly is attached to this widened part. is installed. A plurality of outer pads 21 are provided at appropriate intervals in the axial direction of the tie rod 10,
slidably engages an outer surface 20 of the channel box;
It guides the insertion and withdrawal of control rods. The metal plate 14
．． The free end sides of 14 are curved toward each other and narrowed in width. This ensures smooth insertion and withdrawal of the control rod.

An inner pad 22 is attached to correspond to the outer pad 21 attached to the metal plate 14.14 of the wing 16. The inner pad 22 may be constructed integrally with the outer pad 21. The inner pads 22 are provided on both sides (may be on one side) of the inner space 19 of the wing 16 to maintain the interval between the inner spaces 19 of the wings 16 and are set so that the inner spaces 19 do not fall below a certain value.

Therefore, since the wing 16 has a bulging widened part except for the vicinity of the attachment part to the tie rod 10, the gold gFi 14, 14 of the wing 16 located in the widened part is on the surface 20 of the channel box of the fuel assembly. Moreover, since the inner space 19 of the wing 16 is filled with a coolant as a moderator, it has a high reactivity.

In addition, the inner part of the wing 16, that is, the tie rod 10
The side wing width (thickness)/W is formed to be as narrow as a conventional wing. This is because the output in the bundle located near the tie rod is particularly low, so the width of the wing 16 is narrowed and the distance between the metal plate 14, 14 of the wing 16 and the dial box surface 20 is set to be large. . Thereby, local reduction in output can be suppressed. Since the output near the tie rod is increased by narrowing the width of the wing 16, it is possible to effectively prevent an abnormal increase in output when the control rod is withdrawn, and the output distribution within the handle is also flattened and made uniform.

On the other hand, ruled lines 24 are formed on the wings 16 of the nuclear reactor control rods in a direction substantially perpendicular to the axial direction of the tie rods 10. A plurality of ruled lines 24 are formed at appropriate intervals in the axial direction of the tie rod 1o, and a small hole 25 is bored in the middle of the ruled lines 24. The ruled line 24 of the wing 16 is recessed on the outside of the wing 16 with the small hole 25 as a boundary, and is preferably stepped on the inside. It is not necessarily necessary to form the ruled lines 24 inside the wings 16. Metal plate 1 of the wing 16
By providing the ruled lines 24 on 4.14, the control rod is given flexibility and elastic deformation is facilitated, so that insertion and withdrawal of the control rod can be performed smoothly.

Next, the operation of the present invention will be explained.

The metal plates 14.14 attached to each protruding leg of the tie rod 10 of the reactor control rod are installed facing each other, and the wings 16
Since the outer ends of the wings 16 are not connected, the outer pad 21 slides and is guided by the channel box surface 20 during insertion and withdrawal of the control rod, and the outer end opening of the wing 16 is narrowed, so that the control rod can be smoothly inserted and withdrawn. Inserted and pulled out.・After the control rod is inserted, the outer pad 21 expands until it comes into close contact with the channel box surface 20, and the metal neutron absorbing material (metal plate 1
4.14> is close to the surface of the fuel assembly, and the internal space 19 of the wing 16 is filled with coolant, so the reactivity is improved and the reactivity of the control rods can be increased. Therefore, the metal plates 14, 14 of the control rod can be made thinner, and the structure can be made lighter by that much. Since the metal plates 14 and 14 of the control rods can be made thinner and lighter, the impact on the control rod drive mechanism during withdrawal or emergency insertion of the control rods will be reduced, and the impact on the control rod drive mechanism will be reduced. Can be backfitted.

In addition, the inner pad 22A attached to the metal plate 14.14 of the reactor control rod is configured as a coolant flow control fin, as shown in FIG. 4, and a narrow passage 26 is formed between the fins. A water passage hole 27 may be provided in the metal plate 14.14 on the distal end side of the inner pad 22Δ.

The inner pad 22A has the function of a spacer that maintains the distance between the opposing metal plates 14 and 14 above a certain level, and also functions as a coolant flow control fin, so it acts as a brake in the event of a control rod fall accident. , during emergency insertion during a scram, it has the effect of releasing the brake action, allowing emergency insertion.

That is, in the event of a control rod fall accident, the flow below the coolant flow control fins 22A becomes as shown by the solid line arrow,
The flow path resistance by the fins acts to widen the gap between the metal plates 14, 14, pressing the outer pad 21 against the channel box surface 20 and acting as a brake. The set flow (jet flow) passing through the passages 26 of the coolant flow control fins 22A is guided upward so as to entrain the coolant sucked in from the water passage ports 27.

In addition, when rapidly inserting a control rod such as during a scram, the coolant flows in the opposite direction to that when the control rod falls, and an inward force in the opposite direction to that when the control rod falls is applied to the opposing metal plate 14. .1
4 and connect the outer pad 21 to the channel box 20.
Since the control rod is separated from the control rod, the control rod can be inserted smoothly.

〔Effect of the invention〕

As described above, in the nuclear reactor control rod according to the present invention, elongated rectangular metal plates are attached to each protruding leg of the tie rod so as to face each other to form wings, and the metal plates are used for long-life neutron Since the control rod is only made of absorbing material, there is no need to arrange many neutron absorption rods in the wing, and the number of parts of the control rod can be greatly reduced, simplifying the structure. can avoid weight reduction. Even if the weight of the control rod is avoided, the metal plate is made of a long-life neutron absorbing material, and the space between all the opposing bending plates of the wing is filled with coolant as a moderator, so it has a high reactivity. We can provide control rods with a long life.

In addition, the nuclear reactor control rod of the present invention can be made to have the same weight as a conventional control rod using B4C by adjusting the thickness of the metal plate, so it can be smoothly backfitted into an existing nuclear reactor. can be done.

[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 line II-II in FIG. 1, and FIG. 4 is a diagram showing a modification of the inner pad attached to the metal plate of a nuclear reactor control rod; FIG. 5 (A) is a diagram showing a conventional nuclear reactor control rod; FIG. 5(B) is a plan cross-sectional view taken along line BB in FIG. 5(A). 10... Tie rod, 11... Tip structure material, 14.
・・Metal plate (long-life metal neutron absorber), 16・・
・Wing, 18... Sudifuna, 19... Inner space of wing, 20... Channel box surface, 2
1...Outer pad, 22...Inner pad, 22A・
...Inner pad (coolant flow control fin), 24...Ruled line, 27...Water hole. Applicant's agent Hisashi Hatano Figure 3 Figure 5

Claims (1)

[Scope of Claims] 1. In a nuclear reactor control rod 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 projecting leg of the tie rod is provided with an elongated rectangular metal plate. A control rod for a nuclear reactor, characterized in that the metal plates are attached to face each other to form wings, and the metal plate is made of a long-life neutron absorbing material. 2. The control rod for a nuclear reactor according to claim 1, wherein the metal plate is formed into a thin plate shape and is a metal neutron absorbing material containing hafnium as a main component. 3. The nuclear reactor according to claim 1, wherein the front end and the lower end of the metal plate are respectively connected to the front end structural member and the lower end structural member, and an internal space of a wing is formed between the opposing metal plates. control rod. 4. The free end side area of the metal plate excluding the tie rod side attachment part of the wing is widened in the direction of separating from each other, and in this widened part, an outer pad that can engage with the channel box surface of the fuel assembly is attached to the tie rod axis. The nuclear reactor control rods according to claim 1, which are provided at appropriate distances in the direction. 5. The widened portion of the wing is provided with an inner pad at a position opposite to the outer pad, and the inner pad maintains the gap in the inner space of the wing to a certain value or more. Control rods for nuclear reactors. 6. The nuclear reactor according to claim 5, wherein the inner pad is configured as a coolant flow control fin passing through the internal space, and a water passage hole is provided in the metal plate on the control rod insertion side of the control fin. control rod. 7. The control rod for a nuclear reactor according to claim 1, wherein the wings are curved in a direction in which the free end sides of the metal plates approach each other. 8. 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.