JPH01202692A - Nuclear reactor control rod - Google Patents

Abstract

PURPOSE:To plan the increment of a nuclear reactor stop margin by filling housing holes drilled in a first area of a wing with a high reactivity neutron absorber, and forming a cooling water flowing gap between facing neutron absorbing plates in a second area. CONSTITUTION:A wing 2 of a control rod 1 is partitioned into a first area l1 and a second area l2. Further, a long-lived neutron absorber 6 is provided in a housing hole 5 of a range l4 of the area l1, high reactivity neutron absorber 7 in a range l5, and a long-lived neutron absorber 8 in the range l6 respectively. Further, in the area l2 a pair of facing neutron absorbing plates 13 are provided with a gap 14 therebetween, and a water flowing hole 15 for flowing cooling water is formed. The reactivity value of the whole reactor control rods is heightened while a specially high-reactivity neutron absorber is provided in the area where reactor stop margin tends to stop. Therefore, the reactor stop margin can be enlarged.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a nuclear reactor control rod that adjusts and controls nuclear reactor output, and particularly relates to a long-life type control rod that has a high reactor shutdown margin. Regarding control rods for nuclear reactors.

(Prior technology) As an atomic control rod that controls the output of a nuclear reactor, for example, four stainless steel wings are integrally connected by placing a connecting member in the center, and formed inside the wing in the width direction. A new type of control rod has been developed in which a large number of accommodation holes are filled with powder of a neutron absorbing material such as boron carbide (B4C) at a uniform density.

When this nuclear reactor control rod is inserted into the core of a boiling water reactor, etc., the neutron absorbing material filled in the accommodation hole is irradiated with neutrons and gradually loses its neutron absorption ability, so it is not suitable for operation for a predetermined period of time. It will then be replaced periodically.

(Problem to be Solved by the Invention) By the way, the control rods used in the core of a nuclear reactor are not irradiated with neutrons uniformly over the entire surface of each wing. The lateral edge regions are subjected to intense neutron irradiation. Therefore, the neutron absorbing material filled in that area absorbs a large number of neutrons and is consumed faster than other areas, ending its nuclear life earlier.

Therefore, even though the neutron absorbing material filled in other areas still has sufficient nuclear life remaining, there is an uneconomical need to dispose of the entire reactor control rod as radioactive waste. If the replacement frequency is high, the replacement work will take a long time, which will reduce the operating rate of the reactor and cause a major economic disadvantage. Another problem is that the radiation dose to workers may also increase.

In addition, in conventional control rods for nuclear reactors, the entire wing area is filled with neutron absorbing material at a uniform density, and the neutron absorption capacity, or reactivity, in the axial direction is adjusted to be equal. As such, the unevenness of the neutron irradiation port causes variations in reactivity over time, and there is a possibility that the margin for reactor shutdown may partially decrease at the end of the reactor operating cycle.

In other words, the axial distribution of the reactor shutdown margin (subcriticality) when the reactor is operated for a predetermined period using the above reactor control rods is determined by the design specifications of the fuel assembly or the reactor operating method. Although there are some differences depending on the distribution, the distribution basically becomes as shown in FIG. 7(A). In other words, the reactor shutdown margin is large at the upper and lower ends of the core, while taking a minimum value at a position slightly below the upper end. Possible causes of this are as follows.

If the axial length of the reactor core is L, then 3/3 from the bottom end.
In the upper end region from the 4L position to the upper end, the bubble rate (void rate) during operation is high and the power density of the reactor decreases slightly. The residual amount is relatively large, and the generated bubbles (voids) cause a phenomenon of hardening of the neutron spectrum.

As a result, the plutonium production reaction (neutron absorption reaction) is promoted, so that the concentration of fissile material in the upper part of the reactor core increases after the reactor is in operation, reducing the margin for reactor shutdown in that region.

On the other hand, it is inevitable that future nuclear reactors will shift to higher burn-up of nuclear fuel and longer operating cycles due to demands for improved operational efficiency. As a concrete response to this, the adoption of highly enriched nuclear fuel is progressing, and as a result, there is a strong demand for control rods for nuclear reactors that have a long life and a large margin for reactor shutdown.

However, when conventional nuclear reactor control rods are employed in a nuclear reactor loaded with aS reduction degree nuclear fuel, the reactor control rods must be frequently replaced every short operating cycle. Replacing nuclear reactor control rods requires the complicated work of shutting down the reactor and removing from the reactor core a large number of fuel assemblies arranged around the control rods to be replaced. Therefore, reactor shutdowns occur frequently to replace control rods, and the extended shutdown period reduces the operating efficiency of the reactor.
Management effort may increase significantly while economics will be significantly reduced.

The present invention has been made to solve the above problems, and it increases the reactivity value of the entire control rod for a nuclear reactor, and also applies it to areas with particularly high reactivity or where the reactor shutdown margin tends to decrease. Provides a long-life nuclear reactor control rod that can inexpensively and effectively increase reactor shutdown margin and prolong nuclear life by partially installing long-life neutron absorbing materials. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) In the nuclear reactor control rod according to the present invention, the inner ends of a plurality of wings are coupled via a plurality of coupling members, and each coupling member is arranged at intervals in the axial direction. The wing consists of a first region and a second region, and the first region has a length L corresponding to the total axial length of the core in the axial direction from the insertion tip of the wing.
The wing is arranged over 4 to 3/4 of the wing, and a large number of accommodation holes are bored in at least a part of the wing in the width direction of the wing,
These accommodation holes are arranged in a large number of rows in the axial direction, and the accommodation holes provided in the parts other than the areas where the neutron irradiation amount is high are filled with a highly reactive neutron absorbing material. On the other hand, the second region is arranged from the end of the first region to the wing insertion end, and a pair of opposing neutron absorption plates are arranged with a gap in the thickness direction of the wing, and the neutron absorption plates is made of a long-life and highly reactive neutron absorbing material, and the gap is formed to allow cooling water to flow therethrough.

(Function) If the axial length of the reactor core is L, then 3/3 from the bottom end.
In the upper end region from the 4L position to the upper end, the void ratio during operation is high and the power density of the reactor is slightly reduced, so the remaining amount of uranium, which is a fissile material, is relatively large.

Furthermore, the void phenomenon causes a hardening phenomenon of the neutron spectrum, which accelerates the plutonium production reaction. Therefore, after a nuclear reactor has been operated for a certain period of time, the concentration of fissile material in the upper part of the reactor core increases, and the margin for reactor shutdown in that area increases.

In the present invention, since the accommodation hole provided in the first region of the wing is filled with a highly reactive neutron absorbing material, the reactivity value of the neutron absorbing material in the first region is maintained even after the reactor is operated for a long time. be done.

Therefore, even after a long period of operation, a sufficient margin for reactor shutdown can be ensured when all reactor control rods are fully inserted.

In addition, in the second region, a gap is formed between a pair of neutron absorption plates that allows cooling water to flow, so neutrons incident from one of the wings are decelerated by the cooling water and then absorbed by one of the neutron absorption plates. .

Therefore, neutrons can be effectively absorbed.

(Example) An example of a control rod for a nuclear reactor according to the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing one embodiment of a control rod for a nuclear reactor according to the present invention. In FIG. 1, the reactor control rod 1 is
The inner ends of the four wings 2 are connected through a plurality of connecting members 3 to form a cross-shaped cross section, and a handle 4 for operation is fixed to the insertion tip.

On the other hand, an end structure member is attached to the insertion end portion (not shown).

Each of the wings 2 is composed of a first region and a second region, and the first region extends from the insertion tip of the wing 2 in the axial direction to 1/4 to 3/4 of the length L corresponding to the total axial length of the core. The second region is arranged from the lower end of the first region to the insertion end of the wing 2. The first area is i in Figure 1.
ll range, which is a region with a long life and particularly high reactivity. The second area is in Figure 1! , which is a region with long life and high reactivity.

The first region 11 is a high irradiation region X where the neutron irradiation amount is extremely high, and a non-high irradiation region
It is divided into Y. Therefore, the neutron absorbing material is effectively disposed in the first region in consideration of the amount of neutron irradiation.

That is, the first area is
As shown in FIGS. (A) to (F), a large number of accommodation holes 5 are bored in the width direction of the wing 2, and these accommodation holes 5 are arranged in multiple rows in the axial direction.

and the first region O forms the Blenheim part 13;
It is divided into a range I4 filled with a long-life neutron absorbing material, a range I5 filled with a highly reactive neutron absorbing material, and a range J6 filled with a long-life neutron absorbing material.

Among the above ranges, J, 1, and 16 correspond to the high irradiation region X, and the range I5 corresponds to the non-high irradiation region Y.

The above-mentioned range l is provided at the insertion tip of the first region O, and the accommodation hole 5 in this range O is filled with helium gas (He gas) generated when the neutron absorbing material 7 etc. filled in the range 15 reacts with neutrons. ) serves as a blennium for This is because this range 13 does not require a high degree of reactivity when the nuclear reactor is shut down, so it is not necessarily necessary to provide a neutron absorbing material.

This is especially true when the wing base material 12 is made of hafnium (Hf) or a hafnium alloy. Hafnium alloys include, for example, hafnium-zirconium (Hf-Zr
) alloy, octium-titanium (Hi-Ti) alloy, etc. are used.

Range J! 3, as shown in FIG. 2(B), a pair of opposing long-life neutron absorption plates 9 may be arranged with a gap 10 in the thickness direction of the wing 2. The neutron absorption plate 9 is provided with a water passage hole 11 through which cooling water flows through the gap 10 . If you configure it like this, it will be a while! Since the cold W water that occupies 1110 has a moderating effect, the irradiated neutrons can be slowed down by the cooling water, and the slowed epithermal neutrons and thermal neutrons can be effectively absorbed by the neutron absorption plate 9.

Range 4 is provided between range J3 and range O, and since it is a position where the neutron irradiation amount is high and the reactivity value should not be small, it accommodates a long-life neutron absorbing material 6 such as hafnium. Hole 5 is filled. In addition to hafnium, the long-life neutron absorbing material 6 may include hafnium alloys such as hafnium-zirconium (Hf-Zr) alloy, silver-indium-cadmium (AG-I n-Cd) alloy, europium oxide (Eu203), and oxide. Dysprosium (Dy203) or the like is used. The reason why the long-life neutron absorbing material 6 is provided in the range I4 is that small neutron flux spikes are likely to occur in this area. For example, one or two of the accommodation holes 5 are filled with the long-life neutron absorbing material 6 .

The range J15 is located on the insertion end side of the first region 11,
This is a range corresponding to the non-high irradiation area Y, and is also a part where the degree of subcriticality becomes shallow when the reactor is shut down after long-term operation. The accommodation hole 5 in this range J5 is filled with a highly reactive neutron absorbing material 7. As the neutron absorbing material 7 with high reactivity,
For example, natural boron (B), a boron compound obtained by concentrating boron 10 (10B), etc. are used. Boron compounds include boron carbide (B4C) and europium hexaboride (
EuB) is included. When filling the accommodation hole 5 in the range 15 with boron carbide, it is preferable to set the filling density to about 30 to 65% of the theoretical density from the viewpoint of preventing swelling and economical efficiency.

The range l is a portion of the first region O that is provided at the outer edge of the wing 2 and is included in the high irradiation region X. range 1
6 is provided with a long-life neutron absorbing material 8 such as hafnium. Range o. If it is clear that the control rods are only used for reactor shutdown, there is no need to install them. 1-2α due to irradiation
It is necessary to install long-life neutron absorbing material with a width of

In general, long-life neutron absorbers such as hafnium have a slightly lower reactivity value than high-reactivity neutron absorbers such as boron carbide, so expanding range 16 does not match the purpose of increasing reactivity. .

Therefore, the width of the range 16 is preferably about 1 to 2α. Also, if it is unclear whether or not the control rods will be used during reactor operation, the range j! It is preferable to set the width of 6 to about 0.5 to 1α. Set the width of range i6 to 0.5 to 1α
Even to a certain extent, it has a significant effect on extending the life of control rods.

Between the long-life absorbing material 8 in range 16 and the neutron absorbing material 6.7 filled in each accommodation hole 5, a neutron absorption material 7 such as boron carbide filled in accommodation hole 5 in range 15 absorbs neutrons. In order to discharge gas such as helium generated by the reaction with the gas into the gas plenum in the range i3, a minute gap is formed to allow the gas to communicate. This minute RWJ can reduce the pressure caused by helium generation, suppress swelling, and increase the mechanical life of the control rod.

For example, when disposing hafnium in range 16, first fill each accommodation hole 5 with neutron absorbing materials 6 and 7, and place a hafnium rod with a semicircular cross section into the accommodation hole to prevent boron carbide, etc. in range 15 from leaking. 5, the hafnium rod is wrapped in the wing base material 12, and welded from the outside.

First area j! 1 has a high reactivity because the accommodation hole 5 is filled with multi-port neutron absorbers 6 and 7 as described above. Various modifications are possible as shown in the following.

In the first region 11 shown in FIG. 2(A), the receiving holes 5 have a constant diameter and are arranged at regular intervals in the axial direction, but as shown in FIG. 4(A), In particular, narrow the spacing between the accommodation holes 5 in the area H where you want to increase the reactivity,
More neutron absorbing material may be filled.

FIG. 4(B) shows the accommodation hole 5 in the high reactivity region H, h2
...ho, the wings are divided into small groups, and the thickness of the wing base 111112 between each group is ensured to maintain strength.

In FIG. 4(C), a plurality of holes in the high reactivity region H are connected to form accommodation holes 5A, and a wing base material 12 is inserted between each accommodation hole 5A.
The thickness is ensured and the strength is maintained.

Figure 4 (D) shows the range. A small-diameter accommodation hole 5C is formed in the high-irradiation region (tip high irradiation region), a large-diameter accommodation hole 5 is formed in the range J4 (high irradiation region), and a long-hole-shaped accommodation hole is formed in the high reactivity region H of the range 15. 5B, and a housing hole 5Bfl.
The thickness of the wing base material 12 is ensured to maintain strength.

FIG. 4(E) is a modification of FIG. 4(D), in which a small-diameter accommodation hole 5D is provided between the accommodation holes 5B, and more neutron absorbing material is filled.

FIG. 4(F) is a modification of FIG. 4(D), in which the accommodation hole 5B is a rectangular accommodation hole.

Furthermore, Fig. 4 (G) is a modification of Fig. 4 (D) as well,
This is a combination of a modified rectangular housing hole 5F and a triangular housing hole 5G.

In addition, in FIG. 2, range 13 is the Blenheim part,
It was decided to fill range 14 with a long-life neutron absorbing material 6 such as hafnium, but in Figs. It may be filled with a highly reactive neutron absorbing material such as.

The sheath base material 12 in the first region J1 may be made of any one of stainless steel, hafnium, and hafnium alloy. In the present invention, since the accommodation hole 5 of the first region 11 is filled with a large amount of neutron absorbing material 6.7, the neutron absorption rate of the neutron absorbing material 6, 7 does not decrease even after long mri+ operation.
Even when stainless steel is used as the wing base material 12, a sufficiently long life can be achieved.

When using hafnium or a hafnium alloy as a long-life neutron absorber for the wing base material 12 in the first region l, a long-life neutron absorber such as hafnium and a highly reactive neutron absorber such as boron carbide are used. absorbs neutrons, reducing the burden on boron carbide in absorbing neutrons and extending its life accordingly.

For example, a hafnium alloy is used for the wing base material 12 in the first region O, and the range j! When filling the accommodation hole 5 of 5 with boron carbide, hafnium and boron carbide do not simply share a certain neutron absorption rate, but as described later, each neutron absorption rate is the same as that contained in the hafnium alloy. The combined neutron absorption rate of hafnium and boron carbide increases with hafnium concentration. That is, as the hafnium turbidity of the wing base material 12 in the first region 11 increases, the reactivity value of the first region increases. Therefore, if a hafnium yafnium alloy is used as the wing base material 12 of the first region 11, it will have a long life and a particularly low reactivity 1iIli11.
It is possible to construct a control rod having:

Regarding the relationship between the change in neutron absorption rate between hafnium alloy and boron carbide, as shown in FIG.
The accommodation hole 5 is filled with boron carbide, and the wing base material 1 is
When the diameter d and pitch p of the accommodation holes 5 are set to appropriate values and the hafnium concentration in the hafnium-zirconium alloy is changed, the relationship between the hafnium concentration and the neutron absorption rate is shown in Figure 5 (B). It comes to show.

That is, when the hafnium concentration is O, neutrons are absorbed only by boron carbide, but as the hafnium concentration increases, the absorption rate of boron carbide gradually decreases,
Meanwhile, the neutron absorption rate of hafnium gradually increases. Then, the total absorption rate of boron carbide and hafnium tends to increase slightly. However, if the hafnium content is 30
From around flffi% onwards, the total absorption rate does not increase much and exhibits saturation characteristics.

Therefore, in areas where the amount of neutron irradiation is not so large and only the reactivity value needs to be increased, there is no need to increase the hafnium content as a long-life neutron absorber due to increased weight and cost. . On the other hand, in areas where long life is required, it is necessary to increase the hafnium/boron carbide neutron absorption rate ratio, so a higher hafnium concentration is better, but even a high concentration of 90% by weight or more is not effective. small. Practically speaking, it is preferably about 70% by weight.

First area! Of these, the range l, ゛ and the range 1゜1
When changing the hafnium concentration of the wing base material 12 in 3^4, since range 1.14 is the irradiation area X, range 1.
．． The hafnium concentration on the J14 side may be 70% by weight or more, and the hafnium concentration on the J5 side may be significantly lower than 70% by weight.

FIG. 5(C) is a characteristic diagram showing the relationship between the specific gravity and hafnium concentration of a hafnium alloy. The specific gravity of the hafnium alloy changes approximately linearly as the hafnium concentration changes.

When a hafnium-titanium (Hf-Ti) alloy is used, the specific gravity of titanium (4,5) is smaller than that of zirconium (6°5), so it is effective in terms of weight reduction.

Changes in neutron absorption rate shown in Figure 5(B) and Figure 5(C)
) The hafnium concentration that meets the usage conditions can be determined from the relationship between the changes in the specific gravity of the hafnium alloy.

In the second region, a pair of opposing neutron absorption plates 13 are disposed with a gap 14 in the thickness direction of the wing 2 . The gap 14 is formed to allow cooling water to flow therethrough, and the neutron absorption plate 13 has water holes 1 that allow the cooling water to flow through the gap 14.
5 is formed.

As the neutron absorbing plate 13, a long-life neutron absorbing material such as hafnium or hafnium alloy is used.

Other examples of long-life neutron absorbing materials include those exemplified in the explanation of the first region (1).

FIG. 6 shows a comparison of the cross section of the first region J2 and the cross section of the second region J2, and FIG. 6A shows a cross section of the first region J2.
A cross section of range 15 is shown. In the first region (e), the neutrons irradiated onto the wing 2 are directly absorbed by the neutron absorbing material 7, such as boron carbide, filled in the wing 2. Further, when hafnium or a hafnium alloy is used for the wing base material 12, neutrons are directly absorbed by both boron carbide and hafnium.

On the other hand, FIG. 6(B) shows a cross section of the second region 12, in which a gap 14 is formed between the neutron absorption plates 13 made of hafnium or a hafnium alloy, and cooling water flows through and occupies this gap 14. . In this second area No. 2, wing 2
Neutrons incident from either side are decelerated by the deceleration effect of the cooling water occupying the gap 14, and then become epithermal neutrons and thermal neutrons and are absorbed by one of the neutron absorption plates 13. In this case, the wider the gap 14 occupied by the cooling water, the more linearly the reactivity value increases. This means that the wider the gap 14 is, the smaller the amount of hafnium in the neutron absorption plate 13 is required. However, the width of the gap 14 is 3α
If this is the case, there is no change in the reactivity value, and the actual )ll! In control rods for flood-water reactors, it is difficult to make the width of the gap 11i14 wider than the 7 ends, so the width of the gap 14 is set to 7 m or less, and the necessary amount of hafnium is provided in the neutron absorption plate 13. preferable.

Note that when Zircaloy is used for the tip structure material 16 and the end structure material 17 as shown in FIG. The structural member 16 can be welded, and the terminal structural member 17 and the neutron absorbing plate 13 can also be welded. On the other hand, as shown in FIG. 2(B), when stainless steel is used for the tip structure material 16A and the end structure material 17A, stainless steel and hafnium or hafnium alloy cannot be welded, so the stainless steel bottle 18 is Use to combine.

FIG. 7(A) is a characteristic diagram showing a reactor shutdown margin when a conventional reactor control rod is used to shut down a reactor core after a long period of operation. As shown in this figure, when shutting down a nuclear reactor using conventional control rods that have negative neutron absorption characteristics in the axial direction, the margin for shutting down the reactor is especially severe in the upper part.

On the other hand, in the above embodiment, as shown in FIG. 7(B), range 14 and j! of the first region Flt7 are included. 5's neutron absorption characteristics in range 13 and second region j! It has a configuration that is particularly enhanced compared to 2.

Therefore, if the reactor control rod 1 of the above embodiment is used, the distribution of the reactor shutdown margin when shutting down the reactor after long-term operation is as shown in FIG. 7(C). In the axial direction, it can be shaped like a bow over almost the entire area.

As described above, according to the above embodiment, the reactivity value of the entire reactor control rod 1 is increased, and neutron absorption with particularly high reactivity or long life is provided in the region where the reactor shutdown margin tends to decrease. By arranging the material, it is possible to provide a long-life nuclear reactor control rod 1 that can inexpensively and effectively increase the reactor shutdown margin and prolong the nuclear life.

〔Effect of the invention〕

In the nuclear reactor control rod according to the present invention, the inner ends of the plurality of wings are coupled via the plurality of coupling members, each coupling member is arranged at intervals in the axial direction, and the wing is connected to the first region. The first region has a length L corresponding to the total axial length of the core in the axial direction from the insertion tip of the wing.
The wing is arranged over 4 to 3/4 of the wing, and a large number of accommodation holes are bored in at least a part of the wing in the width direction of the wing,
These accommodation holes are arranged in multiple rows in the axial direction, and a highly reactive neutron absorbing material is filled in the accommodation holes provided in the parts other than the parts where the neutron irradiation is high. On the other hand, the second region is arranged from the end of the first region to the wing insertion end, and a pair of opposing neutron absorption plates are arranged with a gap in the thickness direction of the wing, and the neutron absorption plates The rod is made of a long-life and highly reactive neutron absorbing material, and the gap is formed to allow cooling water to flow through it, increasing the reactivity value of the entire reactor control rod and reducing the reactor's shutdown margin, which tends to stop the reactor. By disposing a neutron absorbing material with particularly high reactivity in the region, it is possible to inexpensively and effectively increase the reactor shutdown margin, and to extend the nuclear lifetime.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of a control rod for a nuclear reactor according to the present invention, and FIG. 2(A) is a sectional view taken along line II-I in FIG. B) is a sectional view showing a modification of Fig. 2(A), Fig. 3(A) is an enlarged view showing the ■ part in Fig. 1, and Fig. 3(B) is a cross-sectional view showing a modification of Fig. 2(A). 3(C) is a sectional view taken along line C-C in FIG. 3(A), and FIG. 3(D) is a sectional view taken along line C-C in FIG. 3(A). 3(E) is a sectional view taken along line EE in FIG. 3(A), and FIG. 3(F) is a sectional view taken along line EE in FIG. 3(A). A sectional view taken along F-Fll in A), FIG. 4 (A)
~(G) is a sectional view showing a modified example of the first region in the above embodiment, FIG. 5(A) is a sectional view showing the configuration of each part of the first region in the above embodiment, and FIG. A characteristic diagram showing the relationship between hafnium concentration and neutron absorption rate in the above example, Figure 5 (C) is a characteristic diagram showing the relationship between hafnium weight percent and specific gravity of hafnium alloy, and Figure 6 (A) is the above A sectional view showing the range 15 in the example taken along the line A-A in FIG. 1, and FIG. 6(B) shows the second region in the above example taken along the line B-B in FIG. 1. Cross-sectional view, Figure 7 (A) is a characteristic diagram showing the distribution of reactor shutdown margin when conventional atomic control rods are used, and Figure 7 (B) is a characteristic diagram showing the distribution of neutron absorption characteristics in the above example. The characteristic diagram shown in FIG. 7(C) is a characteristic diagram showing the distribution of the reactor shutdown margin in the above embodiment. 1... Reactor control rod, 2... Wing, 3...
Coupling member, 5... Accommodation hole, 6.7.8... Neutron absorbing material, 13... Neutron absorbing plate, 14... Gap, 11
...first area, 12...second area. Jin f Gate (,4) (B) Certain 22 Stone 3 Figure (,4) (B) (C) Certain 5 Figure

Claims (1)

[Claims] The inner ends of the plurality of wings are coupled via a plurality of coupling members, each coupling member is arranged at intervals in the axial direction, the wing is composed of a first region and a second region, and the first region is It is arranged in the axial direction from the insertion tip of the wing over 1/4 to 3/4 of the length L corresponding to the total axial length of the core, and at least a part thereof has a large number of accommodation holes in the width direction of the wing. These accommodation holes are arranged in multiple rows in the axial direction, and the accommodation holes that are arranged in the areas except for the areas where the neutron irradiation amount is high are neutron absorbing holes with high reactivity. While the material is being filled, the second region is arranged from the end of the first region to the wing insertion end, and a pair of opposing neutron absorption plates are arranged with a gap in the thickness direction of the wing. A control rod for a nuclear reactor, characterized in that the neutron absorption plate is made of a neutron absorption material with a long life and high reactivity, and the gap is formed to allow cooling water to flow therethrough.