JP5143277B2 - Reactor control rod - Google Patents

Description

  The present invention relates to a nuclear reactor control rod applied to a boiling water reactor (BWR), and more particularly to a control rod using hafnium (Hf) or an alloy thereof as a neutron absorber.

  The control rod of a boiling water reactor (BWR) is constructed by assembling four blades (wings) having a vertically long cross section into a cross shape, and the reactor core is formed into a quadrilateral cross section so as to sandwich each blade. A large number of fuel assembly array cells are arranged.

  Conventionally, among such control rods, a flux strap type hafnium control rod is known as a long-life control rod. This control rod has a pair of plate-like bodies (hereinafter referred to as “hafnium plates”) made of hafnium (Hf) or an alloy thereof facing each other, and these hafnium plates are used as metals (stainless steel (SUS)) as neutron absorbing elements. ) In the sheath.

  18 to 20 show a hafnium control rod that has been practically used. 18 is a perspective view of a hafnium control rod, FIG. 19 is a cross-sectional view of the main part, and FIG. 20 is a holding member (hereinafter referred to as a spacer part) that holds a distance between two opposing hafnium plates. , Referred to as “frame”) and is a perspective view of a member held inside the sheath.

  As shown in these drawings, the control rod 1 includes a cross-shaped tip structural member 4 including a handle 3, four wings (wings) 2, and a terminal structural member 5, and a central structural member (tie rod) 6. It is formed by being fixed to. The lower structural member 5 is provided with a speed limiting member (speed limiter) 14 that suppresses the speed at which the control rod drops from the core when the coupling member is abnormally separated.

  Each wing 2 is configured by housing an integrated neutron absorbing element in which two hafnium plates 10 are integrated with a holding member 12 in a sheath 7 having a deep U-shaped cross section. Yes. Water passage holes 9 are regularly formed in the sheath 7. Usually, the water passage holes 9 are regularly arranged in the axial direction as a pair of two in the direction perpendicular to the control rod insertion direction (axial direction). Some of the water passage holes 9 are “overlapping holes” that penetrate the sheath 7 and the hafnium plate 10.

  Since the thermal expansion coefficients of hafnium and stainless steel are significantly different, the integrated neutron absorption element is divided into a plurality of parts in the insertion / extraction direction of the control rod and held by the sheath 7 through the shaft 12b of the top 12. The hafnium plate 10 is positioned by the disk 12 a of the frame 12, and a water passage gap 11 is formed between the hafnium plates 10.

  Conventionally, as a control rod configuration to which such a hafnium plate is applied, there have been proposals for improving mechanical properties against impacts such as rapid insertion or improving corrosion problems (for example, Patent Documents 1 and 2). reference).

Japanese Patent Laid-Open No. 10-104382 Japanese Patent Laid-Open No. 11-118972

  In the configuration of the conventional control rod described above, the coma also serves as a configuration for holding the distance between the hafnium plates facing each other and the axial positioning of the hafnium plates. Further, the frame for fixing the hafnium plate is fixed by being welded to the sheath as a whole. Both the top and the sheath are made of stainless steel.

  In such a configuration, it is difficult for water that is a coolant (particularly water directed upward from below) to flow into the sheath, and the welded portion is likely to be corroded, resulting in cracks or further cracks penetrating. There was sex.

  As the corrosion product enters the sheath, the hafnium plate and the sheath are in close contact with each other, and the axial movement is stopped, and when the hafnium plate is irradiated and stretched, the outer sheath is also pulled at the same time. There was a possibility that cracks would become large in the stainless steel sheath due to stress applied to the steel.

  The present invention has been made in view of such circumstances, and does not strongly restrain the hafnium plate, can easily prevent water from flowing into the sheath, can prevent corrosion, etc., and has a movement margin for irradiation elongation of the hafnium plate. An object of the present invention is to provide a nuclear reactor control rod capable of ensuring and improving the soundness of a sheath.

  To achieve the above object, according to the present invention, a plurality of U-shaped sheaths are formed by connecting a tip structure member and a terminal structure member via a tie rod that is a central structure member and forming a wing on the tie rod. And a neutron absorber made of hafnium or a hafnium alloy is loaded into the sheath, and the neutron absorber is divided into a plurality of neutron absorbing elements in the control rod axis direction. In the nuclear reactor control rod determined according to the neutron irradiation amount in the section, the neutron absorbing element is two plate-like members arranged to face each other in a direction perpendicular to the control rod axis direction, The tie rod has a dovetail groove, the neutron absorbing element has a protrusion fitted into the dovetail groove, and the tie rod and the neutron absorbing element are interposed via the dovetail groove and the protrusion. It has a fitting portion for restraining axial movement, and to provide a reactor control rod, characterized in that intermittently welded at a different site as the fitting portion.

  According to the present invention, the member for positioning the hafnium plate in the axial direction and the separation holding member between the opposing hafnium plates are configured as separate members, and the hafnium plate is strongly restrained by reducing or omitting the welds. Therefore, water can easily flow into the sheath, and the function of preventing corrosion and the like can be enhanced. In addition, a margin for movement of the hafnium plate against irradiation elongation can be secured, and the soundness of the sheath can be improved.

The side view which shows the whole structure of the control rod for nuclear reactors by 1st Embodiment of this invention. AA sectional view taken on the line AA of FIG. The figure which shows the modification in 1st Embodiment. The figure which shows the other modification in 1st Embodiment. FIG. 3 is a sectional view taken along line BB in FIG. 1. The whole figure showing a 2nd embodiment of the present invention. The enlarged view which shows the principal part of 3rd Embodiment of this invention. The DD sectional view taken on the line of FIG. EE sectional view taken on the line of FIG. The enlarged view which shows the principal part of 4th Embodiment of this invention. FF sectional view taken on the line of FIG. GG sectional view taken on the line of FIG. The whole figure showing a 5th embodiment of the present invention. FIG. 14 is a sectional view taken along line HH in FIG. 13. The perspective view of FIG. The whole figure showing a 6th embodiment of the present invention. The II sectional view taken on the line of FIG. The perspective view which shows the conventional hafnium control rod. The cross-sectional view which shows the principal part of the conventional hafnium control rod. The perspective view which shows the frame | top | piece of the conventional hafnium control rod.

  Hereinafter, embodiments of a control rod for a nuclear reactor according to the present invention will be described with reference to the drawings. In the following configuration, portions that are the same as or correspond to those in the conventional configuration will be described with the same reference numerals as in FIGS.

[First Embodiment (FIGS. 1 to 5)]
FIG. 1 is a side view showing the overall configuration of a nuclear reactor control rod according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  As shown in FIG. 1, the control rod 1 of the present embodiment includes a cross-shaped tip structural member 4 including a handle 3, four wings (wings) 2, and a terminal structural member 5. Tie rod) 6 is formed to be fixed. The lower structural member 5 is provided with a speed limiting member (speed limiter) 14 that suppresses the speed at which the control rod falls from the core when the coupling member is abnormally separated.

  Each wing 2 is an integrated neutron absorption element configured by accommodating two hafnium plates 10 inside a sheath 7 having a deep U-shaped cross section. Is drilled.

  Two through holes 9 are regularly arranged in the axial direction as a pair in the direction perpendicular to the control rod insertion direction (axial direction). Some of the water passage holes 9 are “overlapping holes” that penetrate the sheath 7 and the hafnium plate 10.

  The hafnium plate 10 as an integral neutron absorbing element is divided into a plurality of control rod insertion / extraction directions, and a water passage gap 11 is formed between a pair of opposed hafnium plates 10.

  Thus, the tip structural member 4 and the end structural member 5 are connected via the tie rod 6 as the central structural member, and a plurality of U-shaped sheaths 7 forming the wings 2 are connected to the tie rod 6. The sheath 7 is loaded with a hafnium plate 10 as a neutron absorbing element made of hafnium or a hafnium alloy. In the present embodiment, the hafnium plate 10 is divided into, for example, eight parts in the axial direction, and the axial length of each hafnium plate 10 is set to, for example, 40 cm.

  The hafnium plate 10 is divided into a plurality of neutron absorption elements in the axial direction of the control rod 1, and the neutron absorption characteristics of the neutron absorption elements are determined according to the neutron irradiation amount in the division.

  Under this configuration, the positioning member that supports the hafnium plate 10 in the axial direction and the interval holding member that holds the interval between the opposing hafnium plates 10 in each sheath 7 are configured as different structures or parts. Has been.

  As shown in FIG. 2, the positioning member is configured as a positioning pin 21 having a substantially constant diameter, and is provided at the center of one hafnium plate 10. In other words, in the present embodiment, the positioning pin 21 penetrates between the facing portions of each sheath 7, and only one end portion in the axial direction is welded only to the sheath 7 by the welded portion 21a so as to be integrated with the sheath. ing.

  The positioning pin 21 is made of stainless steel and has a pin structure having a constant diameter over the entire length, for example, and the other end portion in the axial direction is not welded to the sheath 7. Only one positioning pin 21 is provided at the center position with respect to the pair of opposed hafnium plates 10.

  Thus, the positioning pin 21 has a fixed diameter dedicated for fixing the hafnium plate 10, and the entire circumference of only one end located outside the wing 2 is welded to the sheath 7, and the role of the spacer is I don't have it.

  FIG. 3 shows a second example of the positioning pin 21 made of stainless steel. The positioning pin 21 is configured as a pair of opposing screw members 22 and 23 each including a male member and a female member, and is configured as a pair of screw-type pins.

  FIG. 4 shows a third example of the positioning pin 21 made of stainless steel. The positioning pin 21 is also composed of a pair of members each having a male member 24 and a female member 25 that can be fitted to each other, and the fitting portion of the male member 24 has a larger diameter than the female member 25. By cooling the fitting portion of the male member 24 and fitting it into the female member 25, a pair of cold fitting pins are formed.

  On the other hand, in this embodiment, as shown in FIG. 5, an interval holding member that holds an interval between the hafnium plates 10 facing each other in each sheath 7 is provided as a dedicated spacer 26. The spacer 26 is a pin-like spacer 26 which is arranged differently from the positioning pin 21 and is not welded between the opposing hafnium plates 10 in each sheath 7. For example, the spacer 26 is located at the center of the hafnium plate 10. One is provided.

  More specifically, FIG. 5A shows the configuration of the dedicated spacer 26, and FIG. 5B shows an enlarged part of the spacer 26 (C portion in FIG. 5A). The spacers 26 are made of hafnium. For example, a total of four spacers 26 are provided on the hafnium plate 10 in a vertical arrangement. This spacer 26 is a pin-shaped member having a function of exclusively securing a space between the hafnium plates 10, and has a large diameter portion 27 at one end side in the axial direction. The large-diameter portion 27 is fitted in a recess 20 provided on the outer surface side of the hafnium plate 10. The thickness of the large-diameter portion 27 of the spacer 26 is larger than the depth of the recess 20 of the hafnium plate 10, and a gap 28 is formed between the hafnium plate 10 and the sheath 7 due to the gap of this size. Is generated. Water that is a coolant flows into the gap 28. Therefore, unlike the conventional case where the top is welded and fixed, the corrosion product does not accumulate.

  According to such a configuration of the present embodiment, the axial positioning member of the hafnium plate 10 and the separation holding member between the opposing hafnium plates 10 are configured as separate members, and the welded part is partially welded. As a result, the hafnium plate 10 is not strongly restrained, water can easily flow into the sheath 7, and corrosion or the like can be prevented. In addition, it is possible to secure a movement margin for the irradiation elongation of the hafnium plate 10 and improve the soundness of the sheath 7.

[Second Embodiment (FIG. 6)]
FIG. 6 is an overall configuration diagram showing a second embodiment of the control rod according to the present invention. In addition, since this embodiment is the structure substantially the same as 1st Embodiment fundamentally, about the same component, the same code | symbol as FIG. 1 is attached | subjected to FIG. 6, and description is abbreviate | omitted.

  This embodiment is different from the first embodiment in that the number of divisions of the hafnium plate 10 is changed. That is, in this embodiment, the hafnium plate 10 is divided into 16 parts, which is twice that of the first embodiment. The axial length L of the hafnium plate 10 is one half of the length of the first embodiment, that is, approximately 20 cm. One hafnium plate 10 has one positioning pin 21 and four spacers 26, which are arranged in the same manner as in the first embodiment.

  Also in the present embodiment, the axial positioning member of the hafnium plate 10 and the separation holding member between the opposing hafnium plates 10 are configured as separate members, and the welded portion is reduced by partially welding the welded portion. Thus, the hafnium plate 10 is not strongly restrained, water can easily flow into the sheath 7, corrosion and the like can be prevented, and a movement margin with respect to the irradiation elongation of the hafnium plate 10 is secured and the soundness of the sheath 7 is improved. Etc. can be achieved.

[Third Embodiment (FIGS. 7 to 9)]
FIG. 7 is an enlarged view showing a main part of the control rod 1 according to the third embodiment of the present invention, and FIGS. 8 and 9 are a DD sectional view and an EE sectional view of FIG. Since this embodiment also has basically the same configuration as that of the first embodiment, the same components as those of the first embodiment are not shown, and the same or corresponding parts are denoted by the same reference numerals as those in FIG. A description thereof will be omitted.

  The positioning member of the present embodiment is a stay 29 that has one end supported by the tie rod 6 and the other end fitted and inserted into each hafnium plate 10. As shown in FIG. 9, the stay 29 is provided with a frame-shaped fixing pin 32 at the tip of a plate-like base 31 joined to the tie rod 6 via a welded portion 30, and a hole 33 is formed in the frame-shaped fixing pin 32. It has a perforated structure. The thickness of the plate-like base 31 corresponds to the distance between the pair of hafnium plates 10.

  Further, the thickness of the fixing pin 32 is substantially the same as the arrangement width between both outer surfaces of the pair of hafnium plates 10. Further, a tip plate portion 34 having the same thickness as the plate-like base portion 31 is integrally formed at the tip of the fixing pin 32. The axial position of the hafnium plate 10 is determined by fitting and inserting the fixing pin 32 of the stay 29 into the hole 33 formed in the hafnium plate 10.

  Further, as shown in FIGS. 8 and 9, both end portions 10a and 10b of the pair of hafnium plates 10 and 10 in the direction perpendicular to the axis are partially bent in a direction away from each other (outward direction). The bent end portions 10 a and 10 b abut against the inner surface of the sheath 7, whereby a gap 36 is formed between the sheath 7 other than the end portions 10 a and 10 b and the hafnium plate 10.

  That is, the inner surface of each sheath 7 and both ends 10a, 10b of the hafnium plate 10 inserted into the sheath 7 are in a state where convex portions are formed outward, thereby the hafnium plate 10 excluding both ends 10a, 10b. A gap 36 is formed between the sheath 7 and substantially the entire axial direction.

  As described above, in this embodiment, a part of the outer surface of the hafnium plate 10 is partially covered with the gap 36 so that a convex portion for contacting the sheath 7 and the hafnium plate 10 is formed.

  On the other hand, as shown in FIG. 9, the spacer 26 as the spacing member is configured as a pin-like member similar to the conventional spacer in shape, but is not welded to the sheath 7 and is mutually connected. It is inserted into a hole 37 formed in the opposing surface of the opposing hafnium plate 10 and is disposed with a gap between the opposing surfaces of the sheath 7.

  Thus, the stay 29 is connected to the tie rod 6 by welding, the hole 37 is formed at the tip of the stay 29, and the fixing pin 32 is further provided. The fixing pin 32 has a configuration similar to that of the spacer 26, and has a hole 33 in that portion so that water as a coolant can be passed therethrough. The hole 37 penetrates the outside and communicates with the gap.

  The sheath 7 is formed with a plurality of holes (oval holes) 38 only for the sheath 7 and a small number of whole through holes (perfect circle holes) 39 penetrating the sheath 7 and the entire hafnium plate 10. Has been. A notch 40 is intermittently formed in the contact portion of the sheath 7 with the tie rod 6.

  Also according to the present embodiment, the axially positioning member of the hafnium plate 10 and the separation holding member between the opposing hafnium plates 10 are configured as separate members, and the welded portion 30 is reduced or omitted, thereby reducing the hafnium plate. 10 is not strongly restrained, water can easily flow into the sheath 7, corrosion and the like can be prevented, a movement margin for irradiation elongation of the hafnium plate 10 is secured, and the soundness of the sheath 7 is improved. Can do.

[Fourth Embodiment (FIGS. 10 to 12)]
FIG. 10 is an enlarged view showing a main part of the fourth embodiment of the present invention, and FIGS. 11 and 12 are a cross-sectional view taken along a line FF and a line GG in FIG.

  As shown in these drawings, the configuration of the present embodiment is substantially the same as that of the third embodiment. Therefore, the same parts as those in the third embodiment are denoted by the same reference numerals and the description thereof is omitted.

  The present embodiment is different from the third embodiment in that a gap 36 is formed between the sheath 7 and the hafnium plate 10 by adding dimples 41 to the inner surface rather than bending both ends of the sheath 7. . The dimple 41 has a configuration in which, for example, both ends of the sheath 7 are pressed and deformed inward. As a result, a gap 36 is formed between the inner surface of each sheath 7 and the hafnium plate 10 inserted into the sheath 7 over substantially the entire axial direction. In other words, this embodiment also has a configuration in which a convex portion is formed on a part of the inner surface of the sheath 7 so as to close a part of the gap 36 and bring the sheath 7 and the hafnium plate 10 into contact with each other.

  Also according to the present embodiment, the hafnium plate 10 is configured by configuring the axial positioning member of the hafnium plate 10 and the separation holding member between the opposing hafnium plates 10 as separate members, and reducing or omitting the welds. Can prevent water from flowing into the sheath 7, prevent corrosion, etc., ensure a movement margin for irradiation elongation of the hafnium plate 10, and improve the soundness of the sheath 7. it can.

[Fifth Embodiment (FIGS. 13 to 15)]
FIG. 13 is an overall view showing a fifth embodiment of the present invention. It is the HH sectional view taken on the line of FIG. 14 is a cross-sectional view taken along line HH in FIG. 13, and FIG. 15 is a perspective view.

  Also in the control rod of this embodiment, as in the first embodiment, the tip structural member 4 and the end structural member 5 are connected via a tie rod 6 that is a central structural member, and a wing 2 is formed on the tie rod 6. A plurality of U-shaped sheaths 7 are connected. A hafnium plate 10 is loaded in the sheath 7.

  The hafnium plate 10 is divided into a plurality of neutron absorption elements in the control rod axis direction, and is configured as a nuclear reactor control rod in which the neutron absorption characteristics of each hafnium plate 10 are determined according to the neutron irradiation amount in the division.

  The tie rod 6 and the hafnium plate 10 are connected to each other by a fitting portion that restricts movement in the axial direction via a dovetail groove 42 and a tab 43 at adjacent portions. The tie rod 6 and the hafnium plate 10 are joined by a welded portion intermittently at a portion different from the fitting portion formed by the dovetail groove 42 and the tab 43.

  Thus, the tie rod 6 is formed with a dovetail groove 42, and the hafnium plate 10 is formed with a tab 43, which is a protrusion fitted into the dovetail groove 42. As a result, a fitting portion that restrains the movement in the axial direction is formed, and these fitting portions are arranged one by one with respect to each hafnium plate 10.

  Also according to the present embodiment, the hafnium plate 10 is configured by configuring the axial positioning member of the hafnium plate 10 and the separation holding member between the opposing hafnium plates 10 as separate members, and reducing or omitting the welds. Can prevent water from flowing into the sheath 7, prevent corrosion, etc., ensure a movement margin for irradiation elongation of the hafnium plate 10, and improve the soundness of the sheath 7. it can.

[Sixth Embodiment (FIGS. 16 and 17)]
FIG. 16 is an overall view showing a sixth embodiment of the present invention. 17 is a cross-sectional view taken along the line II of FIG.

  In the present embodiment, the tie rod 6 and the hafnium plate 10 are connected to each other through the dovetail groove 42 and the tab 43 in substantially the same manner as in the fifth embodiment. The description is omitted.

  This embodiment is different from the fifth embodiment in that fitting portions including dovetail grooves 42 and tabs 43 for restraining movement in the axial direction are arranged at two positions close to each hafnium plate 10. It is. Other configurations are the same as those of the fifth embodiment.

  Also according to the present embodiment, the hafnium plate 10 is configured by configuring the axial positioning member of the hafnium plate 10 and the separation holding member between the opposing hafnium plates 10 as separate members, and reducing or omitting the welds. Can prevent water from flowing into the sheath 7, prevent corrosion, etc., ensure a movement margin for irradiation elongation of the hafnium plate 10, and improve the soundness of the sheath 7. it can.

DESCRIPTION OF SYMBOLS 1 Control rod 2 Wing 3 Handle 4 End structure material 5 End structure material 6 Tie rod 7 Sheath 9 Water passage hole 10 Hafnium plate 14 Speed limiter 21 Positioning pin 22, 23 Screw member 24 Male member 25 Female member 26 Spacer 27 Large diameter part 28 Clearance 29 Stay 30 Welded portion 32 Fixing pin 33 Hole 37 Hole 38 Hole (Oval hole)
39 hole (hole of perfect circle)
40 Notch 41 Dimple 42 Dovetail 43 Tab

Claims (2)

The tip structure material and the end structure material are connected via a tie rod that is a central structure material, and a plurality of U-shaped sheaths that form wings are connected to the tie rod, and hafnium or a hafnium alloy is connected to the sheath. The neutron absorber is made of, and the neutron absorber is divided into a plurality of neutron absorption elements in the control rod axis direction, and the neutron absorption characteristics of each neutron absorption element are determined according to the neutron irradiation amount in the classification. In furnace control rods,
The neutron absorbing element is two plate-like members arranged facing the direction perpendicular to the control rod axis direction,
The tie rod has a dovetail,
The neutron absorbing element has a protrusion fitted into the dovetail groove,
The tie rod and the neutron absorbing element have a fitting portion that restrains axial movement through the dovetail groove and the protrusion, and are intermittently welded at a portion different from the fitting portion. A control rod for a nuclear reactor. 2. The nuclear reactor control rod according to claim 1, wherein the fitting portion is disposed one by one or two adjacent to each of the neutron absorbing elements.

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