JPS6027897A - Method of controlling quantity of neutron absorbed - 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 The present invention relates to a method that makes it possible to adjust the amount of neutron absorption of a neutron absorber.

Neutron absorbing materials can cause elastic scattering, inelastic scattering, (n, γ), (u, p), (''+α) due to interaction with neutrons.
It causes various reactions such as reactions, and as a result, slows down and absorbs neutrons. Applications include control rods and safety rods in nuclear reactors, and shielding materials for neutron flux regulators for research.

Currently, Ag-In-Cd alloy 1 is used as a neutron absorbing material.
BaC, Ta, EllxOv, raw steel, Cd
, 203. H3EC)y.

Many are known, such as borosilicate gafnu, polar, and IaF tiles. In all of these, the constituent elements themselves have a large neutron absorption cross section or neutron scattering cross section, or they are composed of compounds or alloys thereof.

Now, the neutron absorption characteristics of such materials are unique and constant for each material, so in actual use, it is necessary to take this into consideration in the structural design at the equipment design stage. It is necessary to do so, and in some cases, this may even have a significant impact on the overall composition of the synudem. In any case, the fact that the neutron absorption characteristics are fixed is a major constraint in terms of design. In particular, it is necessary to change the neutron absorption efficiency of control rods in nuclear reactors depending on the operating conditions during use. The only way to deal with this problem is to use physical methods, and such methods have problems such as non-uniformity of neutron distribution.

As an effective measure to solve such problems, the present invention aims to reversibly and continuously change the neutron absorption properties of neutron absorption materials.
The aim is to provide a method that allows for control.

That is, the present invention uses a neutron absorbing material that reacts reversibly with hydrogen as a neutron absorbing material, and by placing it in a hydrogen atmosphere and changing either or both of the pressure and temperature of the hydrogen atmosphere, The gist of this invention is a method for controlling the amount of neutron absorption, which is characterized by controlling the amount of neutron absorption by adjusting the hydrogenation rate of a neutron absorbing material.

Metals that can reversibly react with hydrogen and have a large neutron absorption cross section include Hf and Hf alloys (hereinafter referred to as "Hf").

That is, when the Hf powder is brought into contact with hydrogen, it reacts to form hafnium hydride of the form HfHr (1<x<2). In this case, the Hf hydrogenation ratio depends on the pressure and temperature of the hydrogen brought into contact δ, and can be reversibly changed by changing the settings of these two conditions. Figure 1 shows the hydrogenation rate of Hf (hydrogen content M @/
This diagram conceptually shows the tendency of the relationship between Hf i (IV) (denoted as atom ratio-o) and the atmospheric hydrogen pressure (p). The rate changes reversibly depending on the hydrogen pressure history). This hydrogenation rate shows a similar tendency to change even when the temperature conditions of catalytic hydrogen are changed.

On the other hand, it is well known that the above hydrogen has a large cross section regarding so-called elastic scattering (a type of reaction that slows down neutrons)65, so the above Hf powder becomes a hydride that has neutron moderation ability through the hydrogenation. , and the thick δ of the neutron moderating ability of this hydride depends on its hydrogenation rate. For this reason, the neutron absorption cross section of Hf powder changes depending on its hydrogenation rate. Figure 2 conceptually shows the relationship between the hydrogenation rate of Hf <HAA) and its neutron absorption cross section (product).
corresponds to the hydrogenation rate, ](f alone absorption cross section (σ
/] to the absorption cross section of Hf hydride (σ) 17
1] and changes continuously.

Therefore, according to the method of the present invention, the neutron absorption cross section, or in other words, the amount of neutron absorption, can be reversibly and continuously controlled by adjusting the hydrogenation rate of the neutron absorbing material.

FIG. 1 shows a conceptual diagram of a neutron absorbing material hydrogenation apparatus for carrying out the method of the present invention. In the figure, (1) is Hf powder as a neutron absorbing material, which is filled and enclosed in an inner cylinder C21 made of a stainless steel filter.

[3] is an outer cylinder installed outside the inner cylinder (2) containing Hf powder, and the space between it and the inner cylinder (2) is filled with hydrogen.
It is. A pipe (4) is attached to one end of the outer cylinder, through which hydrogen is sent or recovered between the inner and outer cylinders, thereby adjusting the internal hydrogen pressure. Further, a heat exchanger (5) is provided on the outer periphery of the inner cylinder (2).
) is wound around it, which allows the hydrogen temperature between the inner and outer cylinders to be adjusted.

Specifically, the method of the present invention can be applied to, for example, an inner cylinder made of a neutron absorbing material (1) K foam metal in such an apparatus.
2] through which hydrogen is brought into contact and hydrogenated. Then, the pressure and temperature of hydrogen between the inner and outer cylinders (2) and (3) are changed by supplying and discharging hydrogen through the pipe (4) and adjusting the temperature of the heat exchanger (5), and the neutron absorbing material (1) ) The amount of neutron absorption is controlled by adjusting the hydrogenation rate of υ.

The inventors have confirmed through experiments that the hydrogenation rate of Hf (single substance) or various Hf alloy powders and the neutron absorption cross section of the hydride change depending on the hydrogen pressure and temperature conditions. It has been completed.

As is clear from the above explanation, the method for controlling the neutron absorption amount of the present invention allows the neutron absorption amount of the neutron absorbing material to be freely controlled over a fairly wide range. It has the effect of rationalizing various systems by eliminating design constraints, and will soon be applied to items such as control rods in nuclear reactors that require changes in neutron absorption efficiency during use. This eliminates the need to deal with the movement of the neutron absorber as in the past, and provides the advantage of eliminating problems associated with this.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the pressure of hydrogen in contact with the If powder and its hydrogenation rate, and FIG. 2 is a diagram showing the relationship between the hydrogenation rate and its neutron absorption cross section. FIG. 3 is a schematic longitudinal sectional view conceptually showing an example of an apparatus for applying the method of controlling the amount of neutron absorption according to the present invention. In the figure, 1: Neutron absorber, 2: Inner cylinder, 3: Outer cylinder, 4: Tube, 5: Heat exchanger.

Claims (1)

[Claims] (1) By using a neutron absorbing material that reversibly reacts with hydrogen as a neutron absorbing material, placing it in a hydrogen atmosphere, and changing either or both of the pressure and temperature of the hydrogen atmosphere, A method for controlling the amount of neutron absorption, characterized in that the amount of neutron absorption is controlled by adjusting the hydrogenation rate of the neutron absorbing material.