JPS5855888A - Control rod of reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A conventional shaving rod for a boiling water nuclear reactor is constructed as follows.

That is, a thin U-shaped cross-section sheath is attached to each leg of the tie rod, which is the central structural member, to form a wing, and dozens of neutron-absorbing rods are loaded inside each wing. One drug is required. Therefore, the neutron absorption rod is placed inside a break tube made of SUS (4: B which is a neutron absorption member).
The structure is filled with 4c powder.

13 in B4C absorbs neutrons and reacts with them to generate lIe gas and increase the gas pressure inside the cladding tube. In addition, the neutron absorption rate of substances produced by absorbing neutrons is low. Due to the above two reasons, control rods using B4C powder as a neutron absorbing material reach the end of their mechanical and nuclear IC life early.

In response, there is a desire to extend the life of control rods from the viewpoints of simplifying reactor operation, improving core characteristics, reducing the number of radioactive waste generation chambers, and improving reactor availability.

In order to meet the above requirements, we have developed long-life neutron absorbing materials such as Eu203, Ilr, Ag-In-
C (1st grade is the part that receives strong neutron irradiation from the control rod, and the part that receives the neutron irradiation from the control rod is 141
One shot was fired.

However, all of the long-life neutron absorption rods mentioned above have a high density, and therefore the control rods are vertical or thick.

If the control rod is heavy, it is disadvantageous in terms of measures such as one-rod falling accident and the margin of control rod drive device.
In extreme cases, the existing control rod drive system cannot be used.

The present invention was made based on the above-mentioned circumstances, and an object of the present invention is to obtain a long-life and lightweight control rod for a nuclear reactor.

In the present invention, hafnium is used in whole or in part as a neutron absorption effect, and part or all of the structural material is composed of zircaloy or an alloy containing zirconium as a main component to achieve the above object.

The invention will now be described in detail with reference to the drawings. Each leg of the tie rod, which has a cross-shaped cross section in Figures 1 to 3, has
Cross-shaped wings 2 are formed by attaching elongated U-shaped cross-section sheaths at their openings. In addition, each wing 2 is loaded with a large number of neutron absorbers S3, a lower structural member 5 having a speed limiter 4 at the lower end is fixed to the lower end of the wing 2, and a handle 6 is provided at the upper end of the wing. A superstructure member 7 is fixed thereto.

Among the above, except for the neutron absorption rod, all structural materials of the control rod are composed of Zircaloy or an alloy whose main component is zirconium.

Furthermore, the neutron absorption rod has a cladding tube 3 made of hafnium 3b and zircaloy or an alloy whose main component is zirconium.
It is constructed by filling inside a.

In the control rod of the present invention having the above configuration, all structural members such as the sheath constituting the wing 2, the tie rod which is the central structural member, the tip structural member 7, the handle 6, the lower structural member 5, and the speed limiter 4 are made of Zircaloy or It is composed of an alloy whose main component is zirconium.

The density of the above-mentioned structural material is considerably lower than that of SUS, which is the construction material of the conventional JLT control rod, so (11η
The total 1ift of construction material can be reduced by about 20% compared to the conventional method.

Therefore, as in the above example, even if the inside of the wing (all the neutron absorption rods loaded) is made of funium as the absorbing material, the weight of the entire control rod will increase by 7+ compared to the weight of the conventional control rod. In addition, only the parts that receive particularly strong neutron irradiation, such as the tip of the wing of the control rod and the edge of the wink, are filled with hafnium-filled neutron absorption rods, and the other parts are filled with 134C. In the case of a packed neutron absorption rod, it can be made lighter than a normal control rod.

In addition, when using the above-mentioned 134C-filled neutron absorption rod and hafnium-filled neutron absorption rod together, if the weight 4 is equal to that of a normal type control rod, the number of hafnium-filled neutron absorption rods can be increased by the amount that the structural material is lighter. It can improve the reactivity effect and extend the life span.

On the other hand, the neutron absorbing rod 3 used in the present invention uses hafnium as the neutron absorbing material and zircaloy or an alloy containing zirconium as the main component as the cladding tube. Zirconium and hafnium have very similar physical and chemical properties, so even if mutual diffusion of atoms occurs between the neutron absorbing material and the cladding, there is no risk of damaging the integrity of both, and they are compatible. Excellent.

Note that zirconium and hafnium naturally coexist, and separating and removing hafnium in the process of zirconium purification is quite troublesome and requires considerable cost. However, the amount of hafnium contained in naturally occurring zirconium is approximately 2%, and this amount of hafnium contained in zirconium significantly increases the neutron absorption effect1. Accordingly, there is no need to separate and remove zirconium into hafnium, which takes a lot of effort and costs a lot of money.

Therefore, it is possible to reduce the cost.

Structural materials that receive large amounts of neutron irradiation are likely to become brittle due to irradiation scratches, such as handles and tip structural materials, to be constructed of zirconium alloy, etc., to prevent strength loss due to irradiation. (・7) Note that the present invention is not limited to the above embodiments only.

For example, if the weight limit of the control rod is not too severe, it is not necessary to make all the structural members of Zircaloy or an alloy containing zirconium as a main component, and only the particularly heavy ones may be made of such material.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of an embodiment of the present invention;
FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a front view thereof. ]... Tie rod, 2... Wing, 3... Neutron absorption outside, 4... Speed limiter, 5... Lower structure material, 6... Handle, 7... Tip structure material. Application agent Patent attorney Gobe Kikuchi

Claims (1)

[Claims] Neutron absorbing rods made of hafnium filled in a tube made of an alloy whose main component is zirconium are placed in the parts of the wing that receive at least intense neutron irradiation, and at least heavy structural materials are made of zirconium as the main component. A control rod for a nuclear reactor, characterized in that it is made of a V# alloy as a component.