JPH0448298A - Nuclear reactor control rod - Google Patents

Abstract

PURPOSE:To reduce the consumption of hafnium by composing a blade of a plate material of hafnium for atomic power and forming plural holes in the hafnium plate in its lateral direction. CONSTITUTION:The blade 1 which has a tie rod 3 in the center is made of the hafnium plate material 4 for atomic power and the holes 2 are formed laterally in the hafnium plate material 4. A cooling material is present in the holes 2 of the hafnium plate material 4, so neutrons which are not absorbed by the external surface of the hafnium plate material 4 are moderated by this cooling material and absorbed in the hafnium plate material 4 to improve the neutron absorbing ability of the control rod. Further, the size and number of the holes 2 in the hafnium plate material 4 provided to the blade 1 can be set properly according to the control ability such as an output distribution requested for the control rod provided in the nuclear reactor.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a nuclear reactor control rod used in a boiling water nuclear reactor, and particularly to a nuclear reactor control rod suitable for extending the life of nuclear performance.

[Prior Art] The configuration of a reactor control rod used in a conventional boiling water reactor is shown in FIGS. 3 and 4. FIG. 3 is an overall perspective view of the reactor control rod, and FIG. 4 is a cross-sectional view thereof.

As shown in these figures, the reactor control rod has a longitudinally extending sheath 6 with a U-shaped cross section fixed to each month of a long tie rod with a cross-shaped cross section in the center. It is composed of a blade 1 having a cross-shaped cross section in which neutron absorption rods 5 are arranged.

The neutron absorption rod 5 has a structure in which boron carbide powder, which is a neutron absorption material, is filled inside a long and thin cladding tube. When boron carbide is irradiated with neutrons, (n
The Nα) reaction generates helium gas and increases the pressure inside the boron carbide cladding tube, resulting in damage to the neutron absorption rods 5 and shortening the life of the reactor control rods.

Therefore, as a reactor control rod with a long service life, a reactor control rod using hafnium for the blade of the control rod has been proposed, for example, as described in Japanese Patent Application Laid-Open No. 59-17192.

[Problems to be Solved by the Invention] Incidentally, in the conventional example described above, since hafnium was used for the blade, there were problems in that it was heavy and very expensive. Also, hafnium is (ns γ)
Since it is a reactive neutron absorption rod, there was a problem in that the hafnium itself became hot due to gamma rays.

The present invention was made in response to these problems, and aims to reduce the amount of hafnium used in a control rod using hafnium, and provide a reactor control rod that is cheaper and has a longer life. This is the purpose.

[Means for Solving the Problems] The present invention provides a nuclear reactor control rod consisting of a cross-shaped blade, in which the blade is made of a plate of nuclear-grade hafnium, and a plurality of perforations are provided in the transverse direction of the hafnium plate. It is characterized by this.

[Function] The reactor control rod of the present invention has multiple perforations in the transverse direction in the hafnium plate material constituting the blade, which reduces the amount of expensive hafnium used, making the reactor control rod lighter and less expensive. can be achieved.

Additionally, the plurality of perforations relatively increases the surface area of hafnium, increasing the neutron absorption capacity of the reactor control rod. Furthermore, since the coolant flows into these perforations, this coolant has the effect of removing the heat generated by the hunium plate.

[Example] An example of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is an overall perspective view of a nuclear reactor control rod according to an embodiment of the present invention, and FIG. 2 is a partially cutaway perspective view of a blade portion of the nuclear reactor control rod shown in FIG.

As shown in these figures, this reactor control rod is composed of a blade having a tie rod 3 in the center, and the blade 1 is composed of a hafnium plate material 4 for nuclear power use, and the hafnium plate material 4 has a A plurality of perforations 2 are provided.

In this example, the hafnium plate material has a diameter of 4mmΦ×100mm.
mm perforations were arranged longitudinally at intervals of 10 mm.

In this case, the amount of hafnium used is reduced to about 20% compared to the conventional case where the blade is formed from a single /%fnium plate, and the weight of hafnium is reduced to about 120 kg per control rod. can do.

The control rod of this example has a lifespan approximately four times longer than that of a conventional boron carbide control rod, even though the hafnium weight has been reduced to approximately 120 kg. Since there is a coolant inside the Fnium plate, neutrons that are not absorbed by the outer surface of the Fnium plate are decelerated by the coolant,
The neutron absorption capacity of the control rod is further improved by being absorbed inside the hafnium plate. Furthermore, the coolant present inside the hafnium plate material acts to remove the 7 heat generated by the (n 1 γ) reaction of hafnium, and has the effect of preventing thermal deformation of the blade due to the 7 heat.

The size and number of perforations in the hafnium plate provided on the blade of the control rod can be selected as appropriate depending on the control capability such as power distribution required of the control rod installed in the reactor. be.

[Effects of the Invention] As explained above, according to the present invention, in a reactor control rod using hafnium as a neutron absorbing material, the amount of expensive hafnium used can be reduced and the surface area of hafnium can be increased. Therefore, neutron absorption capacity can be increased while improving economic efficiency. In addition, the heat generation of hafnium is suppressed by the cooling material present in the perforation,
It is possible to prevent thermal deformation of the blade.

[Brief explanation of the drawing]

Fig. 1 is an overall perspective view of a nuclear reactor control rod according to an embodiment of the present invention, Fig. 2 is a partially cutaway perspective view of the blade portion of the reactor control rod shown in Fig. 1, and Fig. 3 is a conventional nuclear reactor control rod. FIG. 4 is a perspective view of the entire control rod, and FIG. 4 is a cross-sectional view thereof. 1... Blade 2... Perforation 3... Tie rod 4... Hafnium plate material 5... Neutron absorption rod 6... Absorption rod sheath Agent Patent attorney (8733) Yoshiaki Inomata (and 1 other person) ) Mutsu Houkima Hitsuji 4 concave

Claims (1)

[Claims] 1. A nuclear reactor control rod consisting of a cross-shaped blade, characterized in that the blade is made of a nuclear hafnium plate material, and a plurality of perforations are provided in the lateral direction of the hafnium plate material.