阅读说明：本技术 一种用于源项释放特性研究的实验燃料棒 (Experimental fuel rod for research on source item release characteristics ) 是由 黎阳 宫厚军 昝元锋 李朋洲 杨祖毛 胡钰文 于 2020-05-14 设计创作，主要内容包括：本发明公开了一种用于源项释放特性研究的实验燃料棒,所述实验燃料棒包括上端盖、棒体、燃料和源项；所述棒体为一端开口的中空结构,所述棒体与上端盖可拆卸式连接,所述棒体与上端盖连接后内部形成密封腔体；所述燃料和源项均匀混合装载在棒体内,所述燃料采用非放同位素颗粒,所述源项采用非放同位素元素颗粒。本发明将燃料和源项密封在棒体内,可近似模拟燃料和源项在严重事故后发生的相互反应和释放过程。本实验燃料棒不带放射性,加工方便,易于安装操作,非常适合源项释放特性研究。(The invention discloses an experimental fuel rod for researching the release characteristics of source items, which comprises an upper end cover, a rod body, fuel and source items, wherein the upper end cover is provided with a plurality of through holes; the rod body is of a hollow structure with an opening at one end, the rod body is detachably connected with the upper end cover, and a sealed cavity is formed inside the rod body after the rod body is connected with the upper end cover; the fuel and the source item are uniformly mixed and loaded in the rod body, the fuel adopts non-isotopic element particles, and the source item adopts non-isotopic element particles. The invention seals the fuel and the source item in the rod body, and can approximately simulate the mutual reaction and release process of the fuel and the source item after a serious accident. The experimental fuel rod has no radioactivity, is convenient to process, is easy to install and operate, and is very suitable for research on source item release characteristics.)

1. An experimental fuel rod for source release characteristic research is characterized by comprising an upper end cover (1), a rod body (2), fuel (3) and a source;

the rod body (2) is of a hollow structure with an opening at one end, the rod body (2) is detachably connected with the upper end cover (1), and a sealed cavity is formed inside the rod body (2) after the rod body is connected with the upper end cover (1);

the fuel (3) and the source item are uniformly mixed and loaded in the rod body (2), the fuel (3) adopts non-isotopic particles, and the source item adopts non-isotopic element particles.

2. An experimental fuel rod for research on source release characteristics according to claim 1, characterized in that the material of the upper end cap (1) and the rod body (2) are matched to the cladding material of the stack type under study.

3. An experimental fuel rod for research on source release characteristics according to claim 1, characterized in that the rod body (2) is in threaded connection with the upper end cap (1).

4. An experimental fuel rod for research on source release characteristics according to claim 3, characterized in that the open end of the rod body (2) is provided with a rod body external thread (2-2), and the inner wall of the upper end cover (1) is provided with an upper end cover internal thread (1-2) matched with the rod body external thread (2-2).

5. An experimental fuel rod for research on source and item release characteristics according to claim 3, characterized in that the junction of the upper end cover (1) and the rod body (2) is provided with an upper end cover chamfer (1-3), and the junction of the rod body (2) and the upper end cover (1) is provided with a rod body chamfer (2-1).

6. An experimental fuel rod for research on source release characteristics according to claim 1, characterized in that the outer wall of the upper end cover (1) is provided with an upper end cover positioning groove (1-1).

7. The experimental fuel rod for research on source release characteristics of claim 6, wherein the upper end cover positioning groove (1-1) is provided in plurality, and the plurality of upper end cover positioning grooves (1-1) are uniformly arranged in the circumferential direction.

8. An experimental fuel rod for source release characteristic studies according to any of claims 1 to 7, characterized in that the rod body (2) is of tubular structure.

Technical Field

The invention relates to the technical field of severe accident experimental equipment, in particular to an experimental fuel rod for researching source item release characteristics.

Background

Under normal operating conditions of a nuclear reactor, the source terms resulting from nuclear fission are mainly concentrated in the gaps between the fuel pellets and the cladding, and in the intergranular spaces of the fuel pellets. When a severe accident occurs in a nuclear reactor, as the temperature of a fuel element is continuously increased, volatile source items are separated from the intergranular parts of the pellets in a gas form, exist in the intergranular or intragranular parts in a gas bubble form and move from a radial phase region with lower temperature. The soluble oxide source terms are mainly dissolved in the fuel matrix in a solid mode, a part of oxides in the fuel matrix can reach the limit solubility and are precipitated in the fuel matrix, and some source terms are not easy to oxidize and can be precipitated in the fuel matrix in a metal state. As the temperature increases, the fuel cladding cracks and volatile source elements that accumulate between the fuel pellets and the air gap of the cladding, and source elements that do not readily volatilize/precipitate in the fuel matrix, are released with the fuel matrix. The release characteristics of source items from fuel elements are basic key parameters of a core severe accident mitigation control measure, and accurate research needs to be carried out through experiments. The actual fuel elements have strong radioactivity and the source terms released by them also have strong radioactivity, making experimental development difficult. However, the non-radioactive isotope is adopted to carry out the experiment of the release characteristics of the source item, and the release process of the source item is difficult to simulate. Therefore, there is a need for innovative source release experimental methods to develop new experimental fuel rods for source release characteristic studies.

Through research, the experimental fuel rod for researching the release characteristic of the serious accident source item internationally at present adopts a spent fuel rod as a research object. The spent fuel rod has very strong radioactivity, is difficult to obtain, is difficult to perform the experiment process, and causes the experiment research to be greatly limited.

Disclosure of Invention

The invention aims to provide an experimental fuel rod for source release characteristic research, which has no radioactivity, is close to a real source release process, and can be used for researching various source release characteristics of different reactor types and different burning severe accidents.

The invention is realized by the following technical scheme:

an experimental fuel rod for researching the release characteristics of source items comprises an upper end cover, a rod body, fuel and source items;

the rod body is of a hollow structure with an opening at one end, the rod body is detachably connected with the upper end cover, and a sealed cavity is formed inside the rod body after the rod body is connected with the upper end cover;

the fuel and the source item are uniformly mixed and loaded in the rod body, the fuel adopts non-isotopic element particles, and the source item adopts non-isotopic element particles.

The rod body is of a hollow structure with an opening at one end and is used for containing the fuel and the source items, the rod body is detachably connected with the upper end cover and is used for disassembling and assembling experimental fuel rods, the required fuel and source items are loaded in the experimental process, and the fuel and source items are all non-radioactive isotopes, such as UO₂Pellet fuel element, fuel using UO₂、ZrO₂The source items of the Zr mixture are I, Cs, Mo, Ru, La, Ce, Sr, Ba and the like, the mixing proportion is determined according to the research of the burnup, so that the experimental process has no radioactivity, and the proportion of fuel and the source items can be selected according to the research of the pile type and the burnup, so that the release characteristic research of various source items with different pile types and different burnups is realized.

The experimental fuel rod can realize cold-state charging, can accurately load volatile source items (I, Cs and the like) and non-volatile source items (Mo, Ru, La, Ce, Sr, Ba and the like) under the inert condition at normal temperature, can be filled as much as possible according to the research requirement proportion, and can simultaneously research the release characteristics of various normal-temperature solid or liquid source items.

This real situation is: in severe accident conditions, the fission product source items released in the gaps between the fuel pellets and the cladding, and the intergranular fission product source items of the fuel pellets interact in the cladding, and the source items are released after the cladding is damaged.

According to the invention, non-discharge fuel and source items are sealed in the experimental fuel rod, the outer part of the experimental fuel rod is heated during the experiment, the fuel and the source items interact in the rod body, and the source items are released after the experimental fuel rod is damaged.

Therefore, the experimental fuel rod source item release process is close to the real source item release process.

According to the invention, the non-discharge fuel and the source item are sealed in the fuel rod, so that the mutual reaction and release processes of the fuel and the source item after a serious accident can be simulated approximately; the experimental fuel rod has no radioactivity, is convenient to process, is easy to install and operate, is very suitable for research on release characteristics of source items, and can be used for researching various source item release characteristics of different reactor types and different serious burnup accidents.

Further, the materials of the upper end cap and the rod are matched to the cladding material of the stack type under study.

The upper end cover and the rod body are made of the same material, deformation is synchronous in the heating process, source items are not prone to being leaked in advance, the materials of the upper end cover and the rod body are matched with a cladding material of a researched stack type, and the effect that the experimental fuel rod source item releasing process is close to the real source item releasing process is further achieved.

Further, the rod body is in threaded connection with the upper end cover.

The threaded connection has the advantage of convenient disassembly and assembly.

Furthermore, the open end of the rod is provided with a rod external thread, and the inner wall of the upper end cover is provided with an upper end cover internal thread matched with the rod external thread.

Furthermore, an upper end cover chamfer is arranged at the joint of the upper end cover and the rod body, and a rod body chamfer is arranged at the joint of the rod body and the upper end cover.

The arrangement of the chamfer can ensure that the thread is not damaged in the process of inserting the rod body into the upper end cover.

Further, the outer wall of upper end cover is provided with the upper end cover constant head tank.

The positioning groove is used for being connected with an external driving mechanism and can accurately position the insertion time and the insertion temperature of the experimental fuel rod.

Further, the upper end cover positioning grooves are provided with a plurality of grooves which are evenly distributed in the circumferential direction.

Further, the rod body is of a tubular structure.

Compared with the prior art, the invention has the following advantages and beneficial effects:

according to the invention, the non-discharge fuel and the source item are sealed in the fuel rod, so that the mutual reaction and release processes of the fuel and the source item after a serious accident can be simulated approximately; the experimental fuel rod has no radioactivity, is convenient to process, is easy to install and operate, is very suitable for research on release characteristics of source items, and can be used for researching various source item release characteristics of different reactor types and different serious burnup accidents.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a general schematic of an experimental fuel rod;

FIG. 2 is a schematic view of the connection of the upper end cap and the rod;

FIG. 3 is a schematic view of the connection between the rod and the upper end cap.

Reference numbers and corresponding part names in the drawings:

1-upper end cover, 2-rod body, 3-fuel, 1-1-upper end cover positioning groove, 1-2-upper end cover internal thread, 1-3-upper end cover chamfer, 2-1-rod body chamfer and 2-2-rod body external thread.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.