JP2009058447A - Control rod for reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain soundness in fuel by restraining easiness in the generation of stress corrosion cracks, and electrochemical activity, and suppressing a blade history phenomenon. <P>SOLUTION: A control rod 10A for reactors is composed by connecting the insertion tip side and insertion end side of four wings 15 containing a neutron absorbing material to a tip structure material 16 and an end structure material 17 having a cross-shaped cross section each. The control rod 10A for reactors is composed so that the cross section is in a cross by connecting the four wings 15 by a plurality of tie crosses 18 provided with a prescribed interval axially at the side of the center axis of the control rod. The tip structure material 16 and the tie cross 18 are made of a zirconium alloy, and neutron absorbing materials 20a, 21a for composing the main part of the wing 15 are composed of hafnium or a hafnium alloy. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reactor control rod used in a boiling water reactor (BWR), and more particularly to a long-life reactor control rod using hafnium as a main neutron absorber.

  Some boiling water reactors (BWRs) use long-life reactor control rods, which have a deep U-shaped stainless steel sheath and a cross-shaped tie rod. The control rod tip is fixed to the tip structure material, and the control rod end side is fixed to the end structure material. Further, two neutron absorbers (pairs) are provided in the U-shaped sheath. It is comprised by the four wing | blade (wing) which accommodated and installed the hafnium plate (refer patent document 1 and nonpatent literature 1).

  In such a reactor control rod, the gap between the pair of hafnium plates is filled with reactor water in the reactor, and the neutrons generated in the core are decelerated by the water, so that neutrons are effective for hafnium. Absorbed. This nuclear reactor control rod is called a “flux trap type control rod”. In the case where a gap is formed between the pair of hafnium plates, the weight of the hafnium material is large due to the action of water in the gap, and an expensive hafnium material can be saved.

  Further, since the nuclear reactor control rod is inserted into and removed from the core, hafnium material on the insertion end side of the control rod can be saved. The pair of hafnium plates are divided into a large number in the axial direction, and the paired hafnium plates are held in a U-shaped sheath via a plurality of spacing and load holding members called pieces.

  On the other hand, in the conventional nuclear reactor control rod, when the U-shaped sheath and each piece are fixed by welding, the U-shaped sheath bends toward the hafnium plate due to welding deformation, and there is no gap between them. There was a possibility of restraining each other. In this case, not only the gap formed between the U-shaped sheath and the hafnium plate disappears, but also a structure that does not allow relative displacement due to a difference in thermal expansion or irradiation growth between the U-shaped sheath and the hafnium plate. The U-shaped sheath that is thinner than the hafnium plate may be subjected to excessive stress.

  Further, in the conventional control rod for a nuclear reactor, the pair of hafnium plates are structured to be held by welding through a plurality of frames in a U-shaped sheath. Subject to various loads during operation. When the pair of hafnium plates are fixed in the U-shaped sheath by the top welded portion, various stresses are generated in the vicinity of the welded portion, and therefore stress corrosion cracking may occur in the U-shaped sheath in the vicinity of the welded portion. When stress corrosion cracking occurs in the U-shaped sheath, there is a possibility that the soundness of the nuclear reactor control rod is deteriorated and consequently the life is shortened. However, in the conventional patent document, there is no consideration for stress corrosion cracking of the U-shaped sheath.

  By the way, the stainless steel constituting the U-shaped sheath and the hafnium metal of the neutron absorbing material are dissimilar metals, and conditions that are susceptible to electrochemical corrosion are formed, and corrosion is promoted in a corrosive reactor environment. A clevis problem may occur.

  Patent Document 2 discloses a hafnium control rod that does not use a U-shaped sheath. This reactor control rod has a structure that focuses on the point that hafnium and stainless steel cannot be welded. However, it uses stainless steel as a tie rod, and is basically the same as the reactor control rod of the present invention that does not use a tie rod. Different structure. Furthermore, the nuclear reactor control rod disclosed in Patent Document 2 does not take into consideration the corrosion resistance and the blade history problem.

In addition, the long-life reactor control rod is inserted during the high-power operation for most of the axial length of the control rod, so the neutron flux level in the fuel assembly adjacent to the neutron absorber plate Is significantly reduced, but combustion is delayed and the concentration of the remaining fission material is relatively high. Pulling out the reactor control rod generates high power and threatens the health of the fuel. The problem that adversely affects the soundness of the fuel is called the blade history phenomenon. This blade history phenomenon can be mitigated by suppressing the decrease in neutron flux, but the control rod reactivity value usually decreases and the reactivity is insufficient. May occur.
JP 63-8594 A JP 58-147687 A M. Ueda, T. Tanzawa, R. Yoshioka: "Critical Experiment on a Flux-Trap-Type Hafnium Control Rod for BWRs", Transaction of the American Nuclear Society, vol.55, p.616 (1987).

  Although conventional long-life control rods used for nuclear reactor control rods have been successfully irradiated in boiling water reactors in practical use, nuclear reactor control rods are prone to stress corrosion cracking. It has become clear that the structure is electrochemically activated and may cause a clevis problem.

  However, in conventional control rods for nuclear reactors, no special measures against stress corrosion cracking have been applied to the control rods, and no special measures have been taken to prevent electrochemical activation.

  Furthermore, when reactor control rods are used in boiling water reactors for a long period of time, output is greatly increased when the control rods are pulled out of the fuel (fuel assembly) adjacent to the reactor control rods. Since the rising blade history phenomenon occurs and the fuel suddenly expands, the soundness of the fuel may be impaired.

  The present invention has been made in consideration of the above-mentioned circumstances, and for reactors that effectively prevent the occurrence of stress corrosion cracking and take measures to prevent electrochemical activation, thereby reducing the blade history phenomenon. It aims to provide a control rod.

  Another object of the present invention is to use a long-life type material that significantly reduces stress corrosion cracking and electrochemical activity by using neutron-absorbing material hafnium and zircaloy excellent in coexistence with hafnium as a structural material. It is to provide a control rod for a nuclear reactor.

  Another object of the present invention is to devise the dimensions, layout structure and arrangement of the neutron absorber, and a phenomenon in which a large increase in output occurs even when the control rod is pulled out of the fuel adjacent to the control rod (blade history). It is intended to provide a long-life nuclear reactor control rod that eases the phenomenon (the phenomenon that the phenomenon is large), ensures the soundness of the fuel assembly, and is easy to operate.

  In order to solve the problems of mitigating stress corrosion cracking, electrochemical activity, and blade history, the control rod for a nuclear reactor according to the present invention has four wings containing neutron absorbers at the insertion tip side and the insertion end. In the control rod for a nuclear reactor whose sides are respectively connected to the cross-sectional tip structure material and the end structure material, a plurality of tie cloths provided at predetermined intervals in the axial direction on the control rod central axis side The four wings are combined to form a cross-shaped cross section, the tip structure material and tie cloth are made of a zirconium alloy, and the neutron absorber constituting the main part of the wing is made of hafnium or a hafnium alloy. It is configured.

  In the nuclear reactor control rod according to the present invention, a gap in which reactor water can be interposed is formed in the wing. The hafnium is covered with a hafnium alloy layer obtained by diluting zircaloy or hafnium with zirconium over most or almost the entire outer periphery. The neutron absorber may be a hafnium alloy in which hafnium is diluted with zirconium.

  The reactor control rod constructed in this way uses zircaloy (zirconium alloy), which is particularly excellent in coexistence with hafnium, a neutron absorber, as a structural material, so stress corrosion cracking and electrochemical activity The degree is greatly eased. And since Zircaloy has a specific gravity smaller than stainless steel, more hafnium can be used as needed, and the neutron absorption effect can be enhanced.

  In the control rod for a nuclear reactor according to the present invention, the four blades are constituted by a Zircaloy sheath whose outer peripheral portion allows the inclusion of hafnium, and contains hafnium which is a neutron absorber inside. In the hafnium, a large number of large-diameter rods having a length that is approximately half the length from the insertion tip toward the insertion end are in direct contact with the inner surface of the sheath, and are thin on the insertion end side. A large number of rods having a diameter are arranged in a row with a gap, and the plurality of hafnium rods on the insertion tip side are within about 3/4 of the blade width from the control rod central axis side. In the range, the hafnium rods having a large diameter and a small diameter are alternately arranged as one or two sets, and the zircaloy sheath of the wing is arranged inside the control rod central axis side. To about 3/4 of the wing span In this range, a large-diameter hafnium rod and a stainless steel tube, a zircaloy hollow metal tube or a weak absorbent material are alternately arranged in one or two sets, and the stainless steel tube or The hollow metal tube is configured such that the reactor water enters the inside.

  In the reactor control rod configured in this way, the sheath and the neutron absorber are not integrally coupled, so if there is a difference in thermal expansion or irradiation growth characteristics between them, the relative position is within the allowable range. Since it can be changed independently, excessive stress is avoided. In addition, because the reactor control rod uses a thin hafnium rod on the insertion end side, unnecessary hafnium on the insertion end side is reduced, and even when the control rod is inserted, the output at the bottom of the core is reduced. It is possible to mitigate, and it is possible to mitigate the increase in output that occurs when the control rod is pulled out. Further, with this nuclear reactor control rod, it is possible to effectively mitigate the increase in power that occurs when the control rod is pulled out while suppressing the degree of decrease in reactivity.

  Furthermore, in the control rod for a nuclear reactor, the hafnium is formed by arranging one or more hafnium flat tubes having a flat cross section, and the hafnium flat tube (flat tube) is inserted. About half the length from the tip, the hafnium is thicker than the insertion end side. On the other hand, in the configuration where multiple hafnium flat tubes are housed in the wing cross section The thickness of the hafnium can be made thinner toward the control rod central axis side. Furthermore, the hafnium has a plurality of flat hafnium tubes with a flat cross section (flattened) in the horizontal direction perpendicular to the control rod insertion / removal direction. The horizontal width of at least the hafnium flat tube on the control rod central axis side is narrower than the insertion tip end side in the half length from the insertion end to the insertion tip side. And it is characterized in that it is configured to position the gap occupied by the reactor water between each flat tube adjacent to.

  The nuclear reactor control rod configured as described above can effectively mitigate the increase in power generated when the control rod is pulled out while suppressing the degree of reduction in the reactivity value.

  Furthermore, the hafnium flat tube is approximately half the length from the insertion end, diluted with zircaloy so that the hafnium concentration is about ½ from the insertion tip side, so that the wall thickness becomes substantially equal to the insertion tip side. It is characterized by being configured.

  Even in a reactor control rod constructed in this way, the thickness of the neutron absorber region is almost uniform in the axial direction of the control rod, so the mechanical and physical strength is uniform in the axial direction, and stress concentration There is a feature that makes it difficult to occur.

  Furthermore, in this control rod for a nuclear reactor, the hafnium flat tube is engaged with the insertion tip structural member at the insertion tip side and with the terminal structure member at the distal end side, and the control rod axial center A fixing arm is provided near the insertion direction in a direction perpendicular to the insertion direction, and the hafnium flat tube on the insertion tip side can be expanded and contracted to the tip side, and the hafnium flat tube on the insertion end side can be expanded and contracted to the end side. It is.

  According to this configuration, the problem of generation of mechanical stress resulting from the dependency of the “irradiation growth” characteristic upon irradiation with neutrons on the hafnium member dependency, the irradiation growth difference between hafnium and the structural material, and the temperature change dependency is solved.

  Furthermore, the hafnium housed in the sheath and inside the sheath is characterized in that the corrosion resistance of hafnium is improved by providing surface polishing or a zircaloy layer on at least the surface facing the sheath inner surface. .

  This reactor control rod has the same overall thickness as hafnium, which is the neutron absorber, and has a width that is narrower than the insertion tip side, with the outer end at the insertion tip, in about half the length from the insertion end to the tip. It is characterized by being aligned to the same side (same span).

  The reactor control rod constructed in this way uses Zircaloy as a structural material, which is particularly excellent in coexistence with hafnium, a neutron absorbing material, as a structural material, so stress corrosion cracking and electrochemical activity Is greatly relaxed.

  Furthermore, due to the device size, structure, and arrangement of the neutron absorber, a phenomenon in which a large increase in output occurs when the control rod is pulled out of the fuel adjacent to the control rod when used in a nuclear reactor for a long time (blade history is The phenomenon of “large” is relieved greatly, the soundness of the fuel assembly is ensured, and the operation is simplified.

  In the control rod for a nuclear reactor according to the present invention, the reactor power can be flattened, and the ease of occurrence of stress corrosion cracking and the electrochemically activated configuration can be remarkably improved to extend the life. it can. In addition, when using control rods for nuclear reactors for a long period of time in the reactor, the blade history phenomenon that causes a large increase in reactor power when the control rods are pulled out in the fuel adjacent to the control rods should be actively mitigated. Can do.

  An embodiment of a control rod for a nuclear reactor according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a plan view showing a configuration example of a critical experiment system in which a reactor control rod is suitably arranged in a core portion (core crack) of a boiling water reactor. Figure 2 is an enlarged view of the A portion of Fig. 1, between the fuel assemblies wide gap G _W and narrow gap G _N are alternately formed.

  In the critical experiment system, a cross-type nuclear reactor control rod 10 equal to the cross section of the actual reactor core is arranged in the center of the core tank of the critical experiment apparatus, and a set of four bodies surrounds the control rod 10. An example in which the fuel assembly 11 is arranged is shown. In the experiment, the fuel assembly 11 is a fuel assembly 11 of a type without a channel box. In this critical experimental boiling water reactor (BWR), all the fuel assemblies 11 have a concentration of 2 wt%, for example, so that the core cross section is square and the outer periphery is targeted until the reactor core becomes critical. Fuel rod 12 was mounted.

In addition, the nuclear reactor control rod 10 inserted and removed between the four fuel assemblies 11 includes, for example, a neutron absorber made of boron carbide (for example, a stainless steel (SUS) pipe having an outer diameter of 4.8 mmφ and an inner diameter of 3.5 mmφ). A neutron absorber rod filled with B ₄ C) powder at a theoretical density of about 70% and a hafnium (Hf) rod which is a neutron absorber with the same outer diameter and almost the same reactivity value were used. In the SUS tube, a water-filled SUS tube partially filled with water is used instead of B ₄ C. In addition, the outer side of the neutron absorber rod used the U-shaped stainless steel sheath with a deep cross section.

In the vicinity of the central axis of the control rod 10 for the reactor, a central structure material (tie rod) usually exists in the conventional type control rod. In this critical experiment, in addition to the control rod configuration in which the tie rod 14 exists,
(A) A configuration in which three neutron absorber rods are provided from the side of the tie rod 14 for each wing (wing) 15 of the control rod to form a water-filled SUS tube 12a.
(B) a configuration in which water-filled SUS pipes 12a and Hf rods 12b are alternately arranged from the tie rod 14 side to the vicinity of 2/3 of the blade width;
(C) A configuration in which the tie rod 14 is removed and water is occupied in the portion;
(D) a normal control rod configuration in which a tie rod 14 is present;
4 were used to measure the neutron flux distribution on the control rod surface as the copper foil activation rate. In FIG. 3C, reference numeral 12c is an acrylic square bar equivalent to water.

  The reactor control rod 10 was arranged in a strip shape so that the copper foil was in close contact with the surface of the U-shaped sheath, and water was supplied to the core tank to make the core critical. The reactor core was critically irradiated with neutrons, and after this neutron irradiation, the reactor control rod was removed from the reactor core and cut, and β-rays of the induced radioactivity on the surface of the U-shaped sheath were measured.

  FIG. 4A shows the change in the activation rate distribution on the surface of the control rod. The horizontal axis represents the distance (cm) from the control rod center (water gap center), and the vertical axis represents the relative activation rate. FIG. 4B shows the copper foil activation rate distribution on the surface of the control rod, and the vertical axis shows the activation rate (arbitrary unit).

  FIG. 4A shows a distribution ratio between the control rod configuration of (a) to (c) and the normal control rod configuration of (d). FIG. 4B shows each control rod configuration (a). (D) shows the intensity of radioactive distribution. In FIG. 4 (B), it is normalized and shown at a point (normalization point) that is not affected by changes in the control rod configurations (a) to (d). Since copper activation is caused by neutrons with low energy and thermal energy, it can be regarded as a distribution of almost "thermal neutron flux". The neutron flux distribution is rapidly increased in the outer end of the wing 15, for example, in the range of about 15 mm. In the control rod configuration (d) in FIG. 3, the height is slightly higher in the vicinity of the tie rod 14, and in the control rod configuration (c), the place of the tie rod is occupied by water, so it is very high. Although not shown in the figure, it has been confirmed that in the control rod configuration (a), the side fuel rods are significantly higher in the vicinity of those close to the control rod central axis. In the control rod configuration (b), the neutron flux rises in a wide range. The output of the fuel rods near the control rod does not change as rapidly as these surface neutron flux distributions, but similar changes occur.

  The nuclear reactor control rod of the present invention is intended to flatten the reactor power without using a tie rod, and to increase the neutron flux over a wide range without significantly reducing the reactivity value of the control rod. In the case of the control rod configuration (b) in which a suitable neutron flux distribution was obtained from the measurement results, the reactivity value was the lowest, but the reduction rate was about 8%, which is an acceptable range.

  However, it is not desirable for the reactor control rods to have an 8% drop in reactivity value over the entire length or overall of the control rods, so this control rod configuration is employed only where necessary. It should be noted that in a normal control rod design, a decrease in the reactivity value of the entire control rod exceeds 10%, which is unacceptable. In the control rod configuration (a), the rate of decrease in reactivity value was about 3.5%. Also, the reactivity value increased in the control rod configuration (c). Note that the life of the control rod and the reactivity value can be increased by increasing the number of neutron absorbers as much as possible at the side edge of the blade 15 where the neutron flux distribution is particularly high.

  In the reactor control rod 10 used in an actual machine, the neutron irradiation amount becomes high at both ends of the arranged neutron absorbers in the blades 15. Therefore, when designing a long-life reactor control rod, it is long. This indicates that a life-type neutron absorber should be placed, and that when designing a reactor control rod with high reactivity, a neutron absorber with a high neutron absorption effect should be placed. Conversely, if the central portion of the wing 15 of the nuclear reactor control rod is local, the neutron absorber selection condition is relatively loose.

  In the present invention, a long-life nuclear reactor control rod was developed with the measured values of the reactor control rod used in the critical experiment system in mind.

[First Embodiment]
5 and 6 are views showing a first embodiment of a control rod for a nuclear reactor according to the present invention.

  FIG. 5 is a longitudinal sectional view showing one blade of a long-life reactor control rod 10A configured in a cross-shaped cross section with four blades (wings). 6A is a cross-sectional view taken along line AA in FIG. 6, FIG. 6B is a cross-sectional view taken along line BB in FIG. 5, and FIG. 6C is a vertical cross-sectional view taken along line DD in FIG.

  This long-life reactor control rod 10A is provided so as to be able to be inserted and removed between a set of four fuel assemblies (not shown) mounted on the core of a boiling water reactor (BWR). The nuclear reactor control rod 10A includes four wings 15 in a cross-shaped cross section. The nuclear reactor control rod 10 </ b> A has four rectangular blade-like wings (wings) 15 interposed between a tip structure member 16 and a terminal structure member 17, and has a cross-shaped cross section. The nuclear reactor control rod 10A includes a control rod effective portion whose neutron absorber portion is made of hafnium, a Zircaloy tip structural member 16 fixed to the insertion tip side of the control rod effective portion, and a control rod effective portion. A terminal structure material made of, for example, stainless steel is fixed to the insertion terminal side. The tip structural member 16 is fixed to the wing 15 of the control rod effective portion by welding or the like, and the end structural member 17 is fixed to the wing 15 via a hafnium pin or a zircaloy pin.

  The four wings 15 of the nuclear reactor control rod 10A are fixed by a tie cloth 18 having a cross-shaped block structure at the center, and the tie cloth 18 constitutes a blade local coupling member, and the nuclear reactor control rod 10A. Are disposed in the central part of the first and second parts so as to be appropriately separated in the axial direction. The tie cloth 18 includes arm portions 19 that project radially (cross shape) from the central cross portion, and the wings 15 are fixed to the arm portions 19 by welding. The wing 15 is fixed to a tie cloth 18 made of Zircaloy on the inner side of the wing to constitute a reactor control rod 10A having a cross-shaped cross section. Zircaloy (zirconium alloy) is used as the structural material used for the tip structural member 16 and the tie cloth 18. However, since this zirconium originally contains Hf, the neutron absorption characteristics can be improved.

  The wing 15 constituting one blade of the control rod 10A for the reactor is joined by bending the pair of hafnium plates 20a, 20b: 21a, 21b constituting the neutron absorber at the blade both ends. As shown in FIGS. 6 (A) and 6 (B), the welded structure is formed into a flat tube structure, and a gap (trap) 22 through which water passes is formed. Reactor water penetrates into the trap 22 formed in the wing 15, and the water that has penetrated decelerates the neutrons that have penetrated through the hafnium, trapped as thermal neutrons, and trapped in the hafnium from the inside (trap) Has the function of absorbing neutrons. The reactor water in the trap 22 is taken in and out through the water passage hole 23.

  Zircaloy-made arm portions 19 are arranged radially and integrally from the tie cloth 18 of the nuclear reactor control rod 10 </ b> A, and wings 15 are welded to the arm portions 19. Near the center of the wing 15 in the axial direction, a wing fixing arm 25 made of Zircaloy (zirconium alloy) is formed in the wing width direction, and the lower end of the thick hafnium on the insertion tip side and the insertion end side through the wing fixing arm 25 The upper end of the thin hafnium is fixed by welding or the like, and the wing 15 is integrated in the longitudinal direction of the control rod. Hafnium and zirconium have good coexistence and greatly reduce the clevis problem.

  The tie cloth 18 itself provided in the nuclear reactor control rod 10A is appropriately spaced in the axial direction between the tip structural member 16 and the terminal structural member 17 to join the four wings 15 in a cross shape. It is a scattered local thing. The interval between the tie cloths 18 adjacent to each other in the axial direction is significantly longer than the axial length of the tie cloth 18 and is a space occupied by the reactor water in the BWR. This water also decelerates the neutrons and forms a high thermal neutron flux as is apparent from FIG. 4B, so that the output of the nearby fuel rods recovers and combustion due to the presence of the reactor control rod 10A is restored. Delay is alleviated to some extent.

  Further, when the reactor control rod 10A is pulled out from the reactor core, a blade history phenomenon occurs, but the reactor control rod 10A is not provided with a tie rod, and reactor water is present instead of the tie rod. The reactor power can be flattened, and the blade history phenomenon that greatly increases the reactor power when the control rod is pulled out is suppressed, and the rapid expansion of the fuel is mitigated, and as a result, the soundness of the fuel is improved. The axial distance between the tie cloths 18 is usually about 15 to 30 cm, and is determined from the viewpoint of maintaining appropriate mechanical and physical strength of the reactor control rod 10A. The axial length of the tie cloth 18 is, for example, about 25 to 35 mm. The hafnium is provided with a number of water holes in addition to the water holes 23 at the front end, the center, and the end.

  On the other hand, although hafnium used for the nuclear reactor control rod 10A has high corrosion resistance, it has been found that when used for a long time in high temperature water, a corrosion product is generated on the surface and peels off due to some cause. . The exfoliated corrosion products are radioactive. The nuclide is mainly Hf-181 with a relatively short half-life of 43 and emits relatively low energy gamma rays (482, 346, and 133 keV). In addition, Ta-182 with a half-life of 111 days is also generated slightly, and 1.2 MeV gamma rays are emitted.

  In BWR, the water quality of the reactor water was significantly improved compared to the initial level, and the radioactivity level was remarkably lowered. Therefore, it became possible to confirm even the weak radioactivity of Hf-181. Although the half-life is relatively short, there are no problems with the external environment, but it has become clear that it will become a target for reducing radioactivity in the reactor building.

  In the present embodiment, “surface finishing” is performed so as to reduce the fine irregularities on the hafnium surface of the nuclear reactor control rod 10A as much as possible. It is considered that the outer surface of the nuclear reactor control rod 10 </ b> A causes friction with the Zircaloy channel box of the fuel assembly facing the outer surface of the control rod 10 </ b> A when the control rod is driven. The outer surface of the control rod 10A for the nuclear reactor is expected to have an effect of suppressing the peeling of corrosion products by particularly carefully finishing the surface. The corrosion products on the inner surface of the reactor control rod 10A may be peeled off by some vibration such as during a scram or an earthquake, and may be mixed into the reactor cooling water through the water passage hole. Be expected.

  The nuclear reactor control rod 10A aims to achieve a delamination suppression effect that is equal to or higher than the above-mentioned surface finish by covering at least the outer surface of hafnium with the same zircaloy as the channel box instead of the surface finish.

[Second Embodiment]
FIG. 7 is a view showing a second embodiment of the control rod for a nuclear reactor according to the present invention.

  FIGS. 7A and 7B showing the reactor control rod 10B of the second embodiment correspond to FIGS. 6A and 6B, respectively. In describing the reactor control rod 10B of the second embodiment, the same components as those of the reactor control rod 10A shown in the first embodiment are denoted by the same reference numerals, and redundant description and illustration are omitted. To do.

  The reactor control rod 10B shown in FIG. 7 has a configuration in which the zircaloy layer 27 is arranged on the outer surface of the hafnium of the wing 15, that is, most or almost all of the outer periphery. Different from the stick 10A. The outer surfaces of the Hf plates 20a, 20b: 21a, 21b as neutron absorbers constituting the wing 15 of the nuclear reactor control rod 10B are covered with the zircaloy layer 27. Since the weight can be reduced by employing the zircaloy layer 27, the amount of Hf can be increased.

  By disposing the Zircaloy layer 27 on the outer surfaces of the Hf plates 20a and 20b: 21a and 21b of the wing 15, the hafnium corrosion product is not exposed to the outside, and the peeling of the corrosion product can be eliminated. Although peeling of the corrosion product is eliminated, an increase in manufacturing cost is unavoidable, and in order to make the reactivity value the same as the reactor control rod 10A of the first embodiment, it is necessary to increase the amount of hafnium. In the nuclear reactor control rod 10B of the second embodiment, the trap 22 is narrowed and the function of improving the reactivity value is lowered, so it is necessary to increase the reactivity value by increasing the amount of hafnium.

  It should be noted that the inner surfaces of the Hf plates 20a, 20b: 21a, 21b constituting the wings 15 of the nuclear reactor control rod 10B may be provided with a zircoloy layer as necessary. Since the arrangement of the Zircaloy layer on the inner surface of the Hf plate is a trade-off between solving the corrosion product peeling problem and increasing the manufacturing cost, it is arranged in view of cost.

[Third Embodiment]
FIG. 8 shows a third embodiment of a reactor control rod according to the present invention.

  The reactor control rod 10C shown in this embodiment corresponds to the reactor control rod 10A of the first embodiment shown in FIGS. 6A and 6B, and is the same as the reactor control rod 10A. The components are denoted by the same reference numerals, and redundant description or redundant illustration is omitted.

  The nuclear reactor control rod 10C shown in FIGS. 8A and 8B is different from the nuclear reactor control rod 10A of the first embodiment in the structure of the blade structure. The blade structure of the nuclear reactor control rod 10 </ b> C is obtained by mounting a Zircaloy sheet (28) on the outer surface of the hafnium plates 20 a, 20 b: 21 a, 21 b constituting the wing 15 with a covering material. After the zircaloy sheet 28 is brought into close contact with the hafnium plates 20a, 20b: 21a, 21b of the wing (wing) 15 by pressure bonding or the like, the end surfaces of the hafnium plates 20a, 20b: 21a, 21b are welded to form the wing 15. After the cylindrical shape is formed, the cylindrical hafnium plate is crushed into a flat tube to form a wing 15. Other configurations and operations are not different from those of the nuclear reactor control rod 10 shown in the second embodiment, and thus description thereof is omitted.

[Fourth Embodiment]
9 and 10 show a fourth embodiment of a nuclear reactor control rod according to the present invention.

  The nuclear reactor control rod 10D shown in this embodiment corresponds to the nuclear reactor control rod 10A shown in FIGS. The same components as those in the reactor control rod 10A of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The nuclear reactor control rod 10D of the fourth embodiment is similar to the nuclear reactor control rods 10B and 10C shown in FIGS. 7 and 8 in that the zircaloy layer 29 is disposed on the outer surface of the wing 15. is there. The zircaloy layer 29 is mounted so as to cover the outer surfaces of the Hf plates 20a, 20b: 21a, 21b constituting the wing 15. The difference from the nuclear reactor control rod 10A shown in the first embodiment is that when the reactivity value may be lowered on the insertion end side, the neutron absorber (hafnium plates 20a, 20b: 21a) of the blade (wing) 15 is used. , 21b) instead of reducing the thickness of the wing (wing) 15 and the deep U-shaped hafnium plates 20a, 20b: 21a, 21b with the tie cloth 18 side in FIG. 8 released. And hafnium plates 20a, 20b: the open ends of 21a, 21b are sandwiched between the arm portions 19a of the tie cloth 18 and fixed.

  In the nuclear reactor control rod 10D of the fourth embodiment, the neutron absorbing material is excluded in a range in which approximately half of the insertion end side of the wing 15 is wider than the insertion tip side, and a space occupied by the reactor water is widely provided. In the region on the insertion end side of the wing 15, a water space 30 is formed in which no neutron absorber (hafnium plates 21 a and 21 b) exists in the width direction of the wing 15 from the central axis of the control rod.

  The reactor control rod 10D is about half of the insertion end side of the wing 15 and has a water space (gap) 30 occupied by reactor water without providing a neutron absorber on the control rod central axis side. When the control rod 10D is inserted, it is possible to suppress a decrease in power output on the center side of the control rod, in which the decrease in furnace power is particularly large, and the output of the fuel rod located on the side surface increases. Even during insertion of the nuclear reactor control rod 10D, fuel combustion can be advanced to some extent on the insertion end side. The increase in reactor power when the reactor control rod 10D is pulled out is alleviated, and the soundness of the fuel is improved.

[Fifth Embodiment]
FIG. 11 shows a fifth embodiment of a control rod for a nuclear reactor according to the present invention.

  In the nuclear reactor control rod 10E shown in FIG. 11, (A) is a vertical side view and longitudinal sectional view of the nuclear reactor control rod 10E, and (B) is a wing 15 along the line BB in FIG. (C) is an axial sectional view of one neutron absorber rod provided in the wing 15.

  In this nuclear reactor control rod 10E, four wings 15 having a cross-shaped cross section are provided between a tip structural member 16 on the control rod insertion tip side and a terminal structure member 17 on the insertion end side. No tie rods with four wings 15 having a cross-shaped cross section are provided, and the wing central part side of each wing 15 is formed by zirconium tie cloths 18 that are discretely provided at appropriate intervals in the axial direction. Combined and integrated.

  Further, a zircaloy (zirconium alloy) sheath 32 constituting the wing 15 is fixed to the arm portion 19 of the tie cloth 18 by welding or the like. The zircaloy sheath 32 is formed by forming a zircaloy plate into a cylindrical shape and crushing this cylindrical shape into a flat tube to form a wing 15.

  As shown in FIG. 11B, rod-shaped neutron absorbers (Hf neutron absorber rods) 33 made of hafnium (Hf) are arranged in a row on the flat tube or flat tube wing 15 of the reactor control rod 10E. Each of the Hf neutron absorbing rods 33 accommodated in this manner has different diameters on the insertion tip side and the insertion end side, which are about half of the total length. As shown in FIG. 11C, the Hf neutron absorber rod 33 has a diameter that is in contact with the inner surface of the sheath 32 up to about half the total length on the insertion tip side. Then, the trap 22 through which water passes is formed in the sheath 32 having a reduced diameter.

  In order to correct the arrangement of the small diameter portions of the Hf neutron absorbing rod 33 in which the nuclear reactor control rod 10 is housed in the wing 15, the nut-shaped hafnium or zircaloy shown in FIG. A spacer positioning member 34 is attached. In the adjacent Hf neutron absorber rod 33, the axial position of the positioning member 34 is set to the same position, so that the same positioning as that of the large diameter portion Hf neutron absorber rod 33 can be performed. The surface of each Hf neutron absorbing bar 33 is polished to reduce irregularities, so that the substantial surface area can be reduced and the amount of corrosion products generated can be suppressed.

  Even if the diameter of about half of the insertion end side of the control rod 10E for the reactor is reduced in diameter, the reactivity value on the insertion end side may be lowered, and the density is large considering that the neutron flux is low, The amount of expensive hafnium material can be reduced.

  The nuclear reactor control rod shown in the fifth embodiment eliminates the need to provide a tie rod on the blade central portion side of the four wings 15, and the wings 15 are replaced with Zircaloy instead of the conventional stainless steel sheath. A sheath 32 is used. Since the Zircaloy sheath 32 is lighter than the stainless steel sheath, it is possible to increase the amount of Hf of the neutron absorbing material as a whole, thereby extending the life.

[Modification of Fifth Embodiment]
12 (A) and 12 (B) show a modification of the fifth embodiment of the reactor control rod, and the reactor control rod 10E ₁ shown in this modification includes a tie cloth 18 and While improving the mechanical and physical strength in the coupling with the wing (blade) 15, by using the neutron absorber 35 made of Zircaloy instead of the neutron absorber on the control rod central axis side, by eliminating the neutron absorber, The blade history effect is mitigated. Note that the reactivity value slightly decreases, for example, by about 2%.

The reactor control rod 10E ₁ shown in FIG. 12B shows a wing 15 corresponding to the reactor control rod 11E in FIG. 11B, and in the wing 15, the central axis of the control rod A bar-shaped neutron reinforcing material 35 made of Zircaloy is arranged on the side, and the arm portion 19 of the tie cloth 18 is fixed to and integrated with the Zircaloy rod of the neutron reinforcing material 35.

  Since there is no guarantee that the irradiation growth accompanying neutron irradiation is the same as the zircaloy rod 35 that constitutes the sheath 32, the zircaloy rod 35 is usually divided into a plurality of parts in the axial direction and is designed not to bend or break due to the irradiation growth of neutron irradiation. Has been.

[Sixth Embodiment]
FIG. 13 shows a sixth embodiment of a reactor control rod according to the present invention.

  In the wing 15 of the reactor control rod 10F shown in the sixth embodiment, a small neutron absorber rod 37 made of Hf is alternately placed in the spacer 36 on the Hf neutron absorber rod 33 and the inner wing side of the wing 15. The “concept of the configuration (b) in FIG. 3” is taken into the insertion tip side.

  The wing 15 of the reactor control rod 10F accommodates a solid neutron absorber rod (Hf absorber rod) 37 made of Hf and having a small diameter through a spacer 36 in a sheath 32 on the insertion tip side. A space 38 of water is secured around the neutron flux, and a neutron flux distribution with an increased neutron flux is obtained without significantly reducing the reactivity value of the control rod.

  Since the other configuration of the nuclear reactor control rod 10F of the sixth embodiment is not different from the nuclear reactor control rod 10E shown in FIG. 11, the same components are denoted by the same reference numerals, and redundant description is omitted. The reactor control rod 10F shown in FIG. 13 adopts the “concept of the configuration (b) of FIG. 3” on the insertion tip side, and arranges the small-diameter neutron absorber rods 37 alternately to increase the neutron absorption rate. Although it is decreased alternately, practical use is easy because the rate of decrease in reactivity value is small. Further, the configuration of the small-diameter neutron absorber rod 37 on the insertion tip side is the same as that on the insertion end side shown in FIG.

  Also in the reactor control rod 10F of the sixth embodiment, a zircloy sheath is used instead of a stainless steel sheath for the wing 15 without providing a tie rod using a tie cloth 18 on the wing center side of the wing 15. It is characterized by the point of adoption.

[Modification of Sixth Embodiment]
FIG. 14 shows a modification of the sixth embodiment of the reactor control rod.

The nuclear reactor control rod 10F ₁ shown in this modification improves the physical and mechanical strength in the connection between the tie cloth 18 and the wing 15, and is a rod-shaped reinforcing material made of Zircaloy on the central axis side of the control rod. 40 is arranged to reduce the blade history effect.

  Since the other configuration is not different from the reactor control rod 10F shown in FIG. 13, the same components are denoted by the same reference numerals, and redundant description is omitted.

[Seventh Embodiment]
FIG. 15 shows a seventh embodiment of a control rod for a nuclear reactor.

  The reactor control rod 10G shown in this embodiment shows an example in which the “concept of the configuration (b) in FIG. 3” is implemented entirely, and the “concept of the configuration (b) in FIG. Although it differs from the reactor control rod 10F of the sixth embodiment introduced in FIG. 1, since the other configurations are not different, the same components are denoted by the same reference numerals, and redundant description is omitted.

  A nuclear reactor control rod 10G shown in the seventh embodiment replaces the small-diameter Hf-made neutron absorber rod 37 shown in FIG. 13 with a plurality of water-containing stainless steel tubes 43 from the control rod central axis side with a wing 15 The neutron absorbing rod 33 made of Hf is alternately arranged up to a region around 2/3. As shown in FIG. 15B, the water-containing stainless steel pipe 43 forms a water space 44 inside the pipe, and a plurality of water introduction holes 45 are formed in the pipe wall (side face). The arrangement of the stainless steel pipes 43 with water has a large rate of decrease in reactivity value, so it is not preferable to arrange them continuously. The arrangement of the stainless steel tube 43 with water, the arrangement combination with the neutron absorber rod 33 made of Hf, and the like are adjusted and set in light of the design conditions of the reactor core.

  A reactor control rod 10G shown in FIGS. 15 (A) and 15 (B) is a neutron made of Hf made of a stainless steel tube 43 filled with water in a predetermined blade region, for example, 3/4 region, on the control rod central axis side of the wing 15. Since they are arranged alternately with the absorbing rods 33, it is possible to take measures against blade history without significantly reducing the reactivity value. The configuration of the stainless steel pipe 43 with water is conceptually shown in FIG. 15B, and the reactor water can freely flow through the stainless steel pipe 43. Although the stainless steel pipe 43 is held in the spacer 36 for stability, a hollow pipe or a weak absorbent material such as a solid Zircaloy rod may be used instead of the stainless steel pipe 43.

  Also in the reactor control rod 10G of the seventh embodiment, a tie rod is not used on the control rod central axis side, and the wing 15 is not a conventional U-shaped sheath made of stainless steel but a sheath 32 made of Zircaloy. It has a feature in the configuration. Instead of the tie rod, a tie cloth 18 made of Zircaloy is used.

[Modification of the seventh embodiment]
FIG. 16 shows a modification of the seventh embodiment of the control rod for a nuclear reactor.

Reactor control rod 10G ₁ shown in this modification, in order to improve the bond strength between the wing 15 and the tie cross 18, the control rod center axis side of the neutron absorber, for example, instead of Hf neutron absorber rods A rod-shaped reinforcing member 40 is interposed to reduce the blade history effect. For the reinforcing member 40, for example, a reinforcing rod made of Zircaloy is used.

  Since other configurations and operations are not different from the reactor control rod 10G shown in FIG. 15, the same components are denoted by the same reference numerals, and redundant description is omitted.

[Eighth Embodiment]
17 and 18 show an eighth embodiment of a nuclear reactor control rod according to the present invention.

  In describing the nuclear reactor control rod 10H shown in this embodiment, the same components as those in the nuclear reactor control rods 10A and 10D shown in the first and fourth embodiments are denoted by the same reference numerals. Therefore, duplicate explanation is omitted. 17 is a longitudinal sectional view showing one blade of the wing 15 of the nuclear reactor control rod 10H, FIG. 18A is a plan sectional view of the wing 15 taken along the line AA in FIG. 17, and FIG. These are the plane sectional views of the wing 15 which follow the BB line of FIG.

  The reactor control rod 10H shown in the eighth embodiment is an arrangement in which two hafnium flat tubes 47 and 48 in which a hafnium tube is crushed into a flat plate shape are arranged in a Zircaloy sheath 32 constituting the wing 15. is there. The hafnium flat tubes 47 and 48 are called “flat tubes” or “flat tubes” of hafnium tubes. The hafnium flat tubes 47 and 48 are surface-finished at least on the outer surface in order to suppress corrosion.

  In this nuclear reactor control rod 10H, the horizontal width of the hafnium flat tubes 47, 48 constituting the wing 15 is such that the insertion end side is closer to the insertion tip side than shown in FIGS. 17 and 18A, 18B. It is narrowed to save hafnium material. Further, the nuclear reactor control rod 10H is narrowed in the blade width of the hafnium flat tube 48 on the insertion end side, and is housed and held in the wing 15 on the insertion end side via the spacer 49. On the insertion end side of the wing 15, when the blade width of the hafnium flat tube 48 is reduced, a water gap 50 in the wing 15 is formed, while a trap 51 is also formed in the hafnium flat tube 48. In addition, the reactor water is freely guided into the hafnium flat tube 48.

  Further, two wide hafnium flat tubes 47 are accommodated on the insertion tip side of the wing 15. The hafnium flat tube 47 is locked and held in engagement with the tongue piece 52 of the tip structural member 16, while a trap 51 is also formed in the hafnium flat tube 47, and reactor water is free in the trap 51. It is supposed to flow through. In this embodiment, an example in which the hafnium flat tubes 47 and 48 are accommodated in the wing 15 and the two hafnium flat tubes 47 and 48 are divided into two in the blade width direction is shown. However, the hafnium flat tubes 47 and 48 have a blade width. It may be composed of a plurality of sheets in the direction or a single sheet.

  The reactor control rod shown in FIG. 17 and FIGS. 18A and 18B saves hafnium material by reducing the horizontal width of the hafnium flat tube 48 from the insertion tip side at the insertion end side. A part of the reactivity value is recovered by providing a gap (gap 50) between the two hafnium flat tubes 48 while suitably providing a water gap (trap 51) to measure the output recovery on the tie cloth 18 side. Is. The formation of the water gap 50 between the two hafnium flat tubes 48 raises the neutron flux, and the neutron absorption rate rises at a part of the hafnium flat tube 48 adjacent to the water gap 50. This also improves the blade history effect.

  Further, the distance between the opposite sides of the two hafnium flat tubes 48, that is, the span of the neutron absorbing material portion is expanded, and the reactivity value is restored. In this embodiment, the hafnium flat tube 47 on the insertion tip side and the hafnium flat tube 48 on the insertion end side have the same cross section on the control rod central axis side and the outside, but there is no necessity and they may be different. .

  The distal end portion of the insertion end side hafnium flat tube 47 is engaged with a “tongue-like” engaging portion 52 extending from the Zircaloy tip structure material 16 toward the insertion end side, so that the insertion end side hafnium flat tube is provided. The end of 48 is fixed to the end (lower end) structural member 17 via a pin made of hafnium or Zircaloy (which can be welded to the sheath). Since the terminal structure material itself has almost no corrosion problem from the past results, stainless steel can be used, but zircaloy can also be used. When zircaloy is used, since the sheath is also made of zircaloy, it can be fixed directly to the end structure material by welding.

[Ninth Embodiment]
FIG. 19 shows a ninth embodiment of a reactor control rod according to the present invention.

  The nuclear reactor control rod 10I shown in this embodiment has a plurality of, for example, three hafnium flat tubes 55a, 55b, 55c accommodated in the wing width direction of the wing 15, and the other configuration is shown in FIG. , Because it is not different from the reactor control rod 10H shown in FIG.

  The three hafnium flat tubes 55a to 55c accommodated in the wing 15 of the nuclear reactor control rod 10I have a thinner hafnium plate thickness (tube thickness) toward the control rod central axis side and the opposite side. It is configured to be thick.

  Further, this nuclear reactor control rod 10I is provided with a rod-shaped reinforcing material 40, for example, a zircaloy reinforcing material, in the sheath 32 on the central axis side of the control rod, thereby improving the bonding strength between the tie cloth 18 and the wing 15. On the other hand, the blade history effect is alleviated by eliminating a part of the neutron absorber on the control rod central axis side. Moreover, the neutron irradiation of the nuclear reactor control rod 10I is large outside the wing 15 and the irradiation growth accompanying the neutron irradiation is not uniform over the entire blade surface of the wing 15. For this reason, a plurality of hafnium flat tubes 55a to 55c are accommodated in different thicknesses in the wing direction of the wing 15 to prevent generation of bending and strength accompanying irradiation growth of neutron irradiation.

[Tenth embodiment]
20 and 21 show a tenth embodiment of a control rod for a nuclear reactor according to the present invention.

  The reactor control rod 10J shown in this embodiment is similar to the reactor control rods 10A, 10C, and 10D shown in the first embodiment, the third embodiment, and the fourth embodiment. The same components as those of the nuclear reactor control rods 10A, 10C, and 10D are denoted by the same reference numerals, and redundant description is omitted.

  The nuclear reactor control rod 10J shown in the tenth embodiment is provided with a tie cloth 18 instead of a tie rod on the central axis of the control rod, while the tip structural member 16 is made of Zircaloy and the terminal structural member 17 is made of stainless steel. Then, the Zircaloy reinforcing material 40 accommodated in the wing 15 is pinned with the pin 56 made of zirconium or hafnium from the end structure material 17 and fixed.

  The cross-shaped cross-shaped wings 15 of the control rod 10J for the nuclear reactor are coupled to each other by a tie cloth 18 on the central axis side of the control rod, and a rod-shaped reinforcing member 40 made of Zircaloy is provided to reinforce the coupling portion. The wing 15 uses a Zircaloy sheath 32 that is excellent in coexistence with hafnium, and an Hf plate 57 is installed oppositely in the sheath 32, and a water gap (trap) 22 is formed in the Hf plate 57. The Hf plate 57 may be formed by opposing two plates or by bending one plate inside the blade. The Hf plate 57 is configured such that the tip structural member 16 side is thick and the terminal structural member 17 side is thin.

  Further, a plate-like elongated hafnium bar 58 is disposed on the blade tip side of the reactor control rod 10J to reinforce the blade tip side while receiving strong neutron irradiation and having an activation rate (approximately proportional to the thermal neutron flux). Efficiently placed neutron absorbers in the high part increase plate life and increase reactivity value.

  In this nuclear reactor control rod 10J, the Zircaloy bar 40 on the central axis side of the control rod is used for securing the strength of the wing 15 and improving the coupling strength of the tie cloth 18. In this part, Zircaloy, which has almost no neutron absorption or moderation effect, is disposed to slightly reduce the neutron absorption effect in this coupling part, to slightly recover the thermal neutron flux, and to improve the blade history slightly.

  Further, the hafnium (hafnium plate 57) on the insertion tip side that receives large neutron irradiation is thick, the insertion end side is thinned, and one end thereof is fixed to the “wing fixing arm 25” that is the wing fixing arm 25, and the other side is fixed to the opposite side. Has a structure that allows relative expansion and contraction by irradiation growth.

  In this nuclear reactor control rod 10J, there is no guarantee that the hafnium bar 58 at the blade side end is subjected to strong neutron irradiation, and the irradiation growth accompanying the neutron irradiation is the same as that of the main absorber hafnium plate 57 constituting the sheath position. Therefore, it is divided into a plurality of parts in the normal axial direction. When a member having the same thickness rolled at the same time as the hafnium plate 57 of the main absorbent is overlapped with the hafnium bar 58, the difference in irradiation growth is almost eliminated. However, for safety, in this embodiment, the hafnium bar 58 is shortened. It has become. In order to prevent the reactor water from entering the gap due to the overlap of the hafnium plate 57, it is desirable to seal the side ends of the overlap by welding.

The top view in the core tank of the critical experiment system explaining the control rod for reactors which concerns on this invention. The elements on larger scale of the A section of FIG. (A)-(d) is a figure which respectively shows the example of a control rod structure of the wing | wing using 4 types of simulation control rods. (A) is a figure which shows the activation rate distribution change of the control-rod surface, (B) is a figure which shows copper foil activation-rate distribution on the control-rod surface. BRIEF DESCRIPTION OF THE DRAWINGS The longitudinal cross-sectional view which shows 1st Embodiment of the control rod for nuclear reactors which concerns on this invention. 5A is a cross-sectional view taken along line AA in FIG. 5, FIG. 5B is a cross-sectional view taken along line BB in FIG. 5, and FIG. 5C is a partial view taken along line CC in FIG. FIG. (A) And (B) is a plane sectional view of the wing which shows 2nd Embodiment of the control rod for nuclear reactors which concerns on this invention. (A) And (B) is a plane sectional view of the wing which shows 3rd Embodiment of the control rod for reactors which concerns on this invention. The longitudinal cross-sectional view of the wing which shows 4th Embodiment of the control rod for nuclear reactors which concerns on this invention. 9A is a plan sectional view taken along line AA in FIG. 9, FIG. 9B is a plan sectional view taken along line BB in FIG. 9, and FIG. 9C is a partial sectional view taken along line CC in FIG. FIG. (A) is a figure which shows 5th Embodiment of the control rod for reactors which concerns on this invention, (B) is a plane sectional view which shows the wing of the control rod for reactors of FIG. 11, (C) is FIG. The figure which shows the neutron absorber rod which accommodates the wing of). (A) is a partial longitudinal sectional view of a wing showing a modification of the fifth embodiment of the reactor control rod according to the present invention, and (B) is a diagram of the reactor control rod shown in FIG. The plane sectional view of a wing. The plane sectional view of the wing which shows a 6th embodiment of the control rod for nuclear reactors concerning the present invention. The plane sectional view of the wing which shows the modification of 6th Embodiment of the control rod for nuclear reactors which concerns on this invention. (A) is a plane sectional view of a wing showing a modification of the seventh embodiment of the control rod for a nuclear reactor according to the present invention, and (B) is a longitudinal sectional view showing a stainless steel pipe provided in the wing of FIG. 15 (A). . The plane sectional view of the wing which shows the modification of 7th Embodiment of the control rod for nuclear reactors which concerns on this invention. The longitudinal cross-sectional view of the wing which shows 8th Embodiment of the control rod for nuclear reactors which concerns on this invention. (A) is a plane sectional view which follows the AA line of FIG. 17, (B) is a plane sectional view which follows the BB line of FIG. The plane sectional view of the wing which shows a 9th embodiment of the control rod for nuclear reactors concerning the present invention. The figure which shows 10th Embodiment of the control rod for nuclear reactors which concerns on this invention in part longitudinal cross-section. (A) is a plane sectional view of the wing along the AA line of FIG. 20, (B) is a figure which expands and shows the B section of FIG.

Explanation of symbols

10, 10A Reactor control rod 11 Fuel assembly 12 Fuel rod 12a Water-filled stainless steel tube 12b Hf rod 12c Acrylic square rod 15 Wing (wing)
16 End structure material 17 End structure material 18 Tie cloth 19 Arm part 20a, 20b, 21a, 21b Hf board (neutron absorber)
22 Trap (gap)
23 Water passage hole 25 Wing fixation arm (wing local coupling member)
27, 29 Zircaloy layer 28 Zircaloy sheet 30 Water space 32 Zircaloy sheath 33 Rod-like neutron absorber (Hf neutron absorber rod)
34 Positioning member 35 Zircaloy neutron reinforcement 36 Spacer 37 Thin Hf neutron absorber rod 38 Water space 40 Rod-shaped reinforcement 43 Water-filled stainless steel tube 44 Water space 45 Water introduction holes 47 and 48 Hafnium flat tube 49 Spacer 50 Water gap 51 Trap 52 Tongue piece (engagement part)
55a, 55b, 55c Hafnium flat tube 56 pin 57 Hf plate 58 hafnium bar (hafnium bar)

Claims (18)

In a control rod for a reactor in which the insertion tip side and the insertion end side of four wings containing neutron absorbers are respectively connected to a tip structure material and a terminal structure material having a cross-section in cross section,
Combining the four wings with a plurality of tie cloths provided at predetermined intervals in the axial direction on the control rod central axis side to form a cross-shaped cross section,
The tip structural material and the tie cloth are made of a zirconium alloy,
A control rod for a nuclear reactor, wherein the neutron absorber constituting the main part of the wing is made of hafnium or a hafnium alloy. The reactor control rod according to claim 1, wherein the hafnium-made neutron absorbing material has a gap formed therein for guiding reactor water. 3. The nuclear reactor according to claim 2, wherein the hafnium-made neutron absorber is covered with a layer of a zirconium alloy or a hafnium alloy at most or almost all of the outer periphery, and the hafnium alloy has hafnium diluted with zirconium. Control rod. 4. The nuclear reactor control rod according to claim 1, wherein the neutron absorber is made of a hafnium alloy obtained by diluting hafnium with zirconium. 5. 2. The nuclear reactor according to claim 1, wherein each of the four wings includes a sheath made of zircaloy containing hafnium and having hafnium as a neutron absorbing material housed inside the sheath. Control rod for. In the hafnium, a large number of large-diameter rods that are approximately half the length from the insertion tip toward the insertion end are in contact with the inner surface of the sheath. The nuclear reactor control rod according to claim 5, wherein a large number are arranged in a row. The large number of hafnium rods on the insertion tip side are alternately arranged as one or two large-diameter hafnium rods within a range of about 3/4 of the blade width from the control rod central axis side. The nuclear reactor control rod according to claim 6, wherein the control rod is a nuclear reactor. Within the wing Zircaloy sheath, a large hafnium rod, a stainless steel tube, a Zircaloy hollow metal tube, or a weak absorbent material within a range of about 3/4 of the blade width from the control rod central axis side is 1 The control rod for a nuclear reactor according to claim 6 arranged alternately as a book or a set of two. The reactor control rod according to claim 8, wherein the stainless steel tube or the hollow metal tube is configured such that reactor water enters the tube. The reactor control rod according to claim 5, wherein the hafnium is configured by arranging one or a plurality of flat hafnium tubes having a flat cross section. 11. The control rod for a nuclear reactor according to claim 10, wherein the hafnium flat tube is configured so that the thickness of hafnium is thicker than the insertion end side in a length that is approximately half from the insertion tip to the insertion end side. 11. The nuclear reactor control rod according to claim 10, wherein a plurality of hafnium flat tubes are housed in a wing cross section of the wing, and the hafnium flat tube is formed such that the thickness of the hafnium is thinner toward the control rod central axis side. A plurality of hafnium flat tubes having a flat cross section are arranged in the horizontal direction perpendicular to the control rod insertion / extraction direction,
At about half the length from the insertion end to the insertion tip side, the horizontal width of the hafnium flat tube at least on the control rod central axis side is narrower than that of the insertion tip end side, and between the adjacent hafnium flat tubes in the horizontal direction. The reactor control rod according to claim 10, wherein the control rod is configured to arrange a gap occupied by the reactor water. The hafnium flat tube is configured to be approximately half the length from the insertion tip side by diluting with a zircaloy so that the hafnium concentration is about ½ from the insertion tip side, about half the length from the insertion end. The control rod for a nuclear reactor according to claim 10. 11. The control rod for a nuclear reactor according to claim 10, wherein the hafnium flat tube is engaged with a distal end structural member on an insertion distal end side and an end structural member on an insertion distal end side. A fixing arm is provided near the center of the control rod axis direction in a direction perpendicular to the insertion direction, and the hafnium flat tube on the insertion tip side can be expanded and contracted to the tip side, and the hafnium flat tube on the insertion end side can be expanded and contracted to the insertion end side. The control rod for a nuclear reactor according to claim 10. The control rod for a nuclear reactor according to any one of claims 5 to 16, wherein at least a surface facing the inner surface of the sheath is provided with a surface polishing or a Zircaloy layer on the inner surface of the sheath of the wing and inside the sheath. Hafnium, which constitutes the neutron absorber, has the same overall length, is approximately half the length from the insertion end to the insertion tip side, has a smaller width than the insertion tip side, and the wing blade outer end is the insertion tip side. The control rod for a nuclear reactor according to any one of claims 1 to 3, wherein the control rod is the same as the above.

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