JPS62207995A - Fast breeder 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 [Object of the Invention] (Field of Industrial Application) The present invention relates to a fast breeder reactor used in a power generation plant or the like.

(Prior Art) Generally, in a fast breeder reactor, fissile material, which is a fuel, is burned, and fissile material, which is a fuel, is generated from a parent material.

Figure 14 shows an example of a conventional fast breeder reactor core, which is made of plutonium-enriched uranium or enriched uranium oxides, carbides, metals, etc., and has a fuel volume ratio of 40%.
The core 1 is formed into a cylindrical shape with an axial length Ll of 100 CTIl to 120 m, and the core 1 has a plutonium enrichment of about 14%, for example, near the center of the core 1. A region 2 with a low density of fissile material having a plutonium enrichment of about 20% is formed above, below and around the region 2 with a high density of fissile material having a plutonium enrichment of about 20%.

(Problems to be Solved by the Invention) In the conventional fast breeder reactor described above, in order to downsize the reactor core 1, the average power density in the reactor core 1 is set to about 250 W/cc, and the power distribution is made uniform. There is.

For this reason, the stay period of the fuel in the core 1 is set to about 3 to 5 years, and the fuel is replaced several times during this period to suppress fluctuations in the output in the core 1 to a small extent.

However, in such conventional fast breeder reactors, it is necessary to shut down the fast breeder reactor for a long period of time every time the fuel is replaced, and equipment for fuel replacement and fuel storage equipment is required, making it difficult to operate. There are problems such as a decrease in production efficiency and an increase in plant construction costs.

The present invention has been made in response to such conventional circumstances, and aims to provide a fast breeder reactor that does not require fuel exchange for a long period of time or at all, and can improve operating efficiency and reduce construction costs. It is something.

[Structure of the Invention] (Means for Solving the Problems) That is, the fast breeder reactor of the present invention is a fast breeder reactor having a core formed in a cylindrical shape by a fuel consisting of a fissile material and a parent material. The axial length of is 130
CI to 200CTII, and a region having an axial length of 10% to 65% of the axial length of the core and having a lower density of fissile material than the upper, lower, and surrounding regions is formed near the center of the core. and the average power density is 65W/c.
c to 150 W/cc.

(Function) In the fast breeder reactor of the present invention, the axial length of the core is 130 cm.
The reactor core is larger than that of conventional fast breeder reactors, and the average power density is 65 W/cc to 150 W/cc, lower than that of conventional fast breeder reactors, making it possible to vary the power within the core. shall be. By forming a region near the center of the core that has an axial length of 10% to 65% of the axial length of the core and has a lower density of fissile material than the upper, lower, and surrounding regions, operation is improved. By slowing down the accompanying changes in the effective multiplication factor, the core life can be reduced by 2.
It will last from 0 to 300 years.

Here, the axial length of the core is 130 cm to 200 marks, and 10% of the axial length of the core is placed near the center of the core.
The reason for forming a region having an axial length of 65% to 65% and having a lower density of fissile material than the upper, lower and surrounding regions is as follows.

First, the graph in Figure 2 shows the difference in effective multiplication factor due to the difference in core axial length when using oxide fuel with a fuel volume ratio of 50% and a plutonium enrichment of 12%. The vertical axis shows the effective multiplication factor, the horizontal axis shows the number of years of plant operation, and the axial length of each curve A, B, C, and D is 1800.
11. 150 CIll, 120 mark m, 100cm
It shows the change in effective multiplication factor in the case of .

As you can see from this graph, the axial length of the core is 10
For 0CI and 120CIII, the core life is about 200 years or less, so in order to make the core life 20 to 30 years, an axial length of about 130 cm to 200 CTIl is required.

Here, the plutonium enrichment is set to 12% because
The third graph shows the effective multiplication factor on the vertical axis and the number of years of plant operation on the horizontal axis.
As shown in the graph of the figure, in the case of plutonium enrichment of 20% shown by curve E and in the case of plutonium enrichment of 15% shown by curve F, the change in effective multiplication factor is too large, and the change in plutonium enrichment shown by curve G is too large. This is because if the plutonium enrichment is 9%, the core cannot be kept critical, and as shown by curve H, it is preferable to set the plutonium enrichment to about 12%.

Next, the graph in Figure 4 shows that, based on the upper half model, a region with low fissile material density is formed near the center of the core with a total axial length of 150C111 due to fuel with a plutonium enrichment of 9%. , which shows the difference in the effective multiplication factor due to the difference in the axial length of these regions when a region with high fissile material density is formed in the upper and lower regions using fuel with a plutonium enrichment of 15%. Curves I, J,
In each case, L is the axial length of the region with low fissile material density relative to the overall length of 75 cm, 15CTII, 3
The case of 0CTtl, OCT[1145CTtl is shown. Here, for the curve showing the case where the axial length of the region with low fissile material density is Ocm, the distribution of fissile material density in the axial direction is uniform, and the above-mentioned curve H (plutonium enrichment 12% ) plutonium enrichment close to 11.4
It shows the case as %. As you can see in this graph, the axial length of the region with low fissile material density is 4
When the length is about 5 cm, that is, about 60% of the entire axial length, there is little change in the effective multiplication factor during operation, and the core life can be extended. Note that when depleted uranium or natural uranium is used in the region with low density of fissile material, the axial length of the region with low density of fissile material may be 20 CIl to 30 CTIl, that is, approximately 13% to 20%. preferable.

(Example) The details of the present invention will be described below with reference to an example shown in the drawings.

Figure 1 shows the core of a fast breeder reactor according to an embodiment of the present invention. In the fast breeder reactor of this embodiment, the fuel volume ratio is 50%
The axial length L3 is 150 mm due to plutonium oxide fuel of
CTII, a reactor core 11 with a diameter L4 of about 400 cm is formed, and near the center of this core 11, an axial length ' L5 of 90 C1 is formed by fuel with a plutonium enrichment of 9%.
11 regions 12 of low fissile material density are formed, the upper and lower regions 13.14 are filled with fuel with a plutonium enrichment of 15%, the surrounding region 15 is filled with fuel with a plutonium enrichment of 20%, A region with a high density of fissile material is formed, and the average power density is about 100 W/cc.

The reason why the core of the fast breeder reactor of this example was configured as described above is as shown in the graphs of Figures 5 to 7, where the vertical axis is the effective multiplication factor and the horizontal axis is the number of years of plant operation. Due to reasons.

The graph in Figure 5 shows an example of the difference in the effective multiplication factor due to the difference in fuel volume ratio.Curves M, N, O, and P are for oxide fuel with a fuel volume ratio of 40%, respectively. 5
It shows changes in effective multiplication factors for 0% oxide fuel, 40% fuel volume ratio carbide fuel, and 40% fuel volume ratio metal fuel. As can be seen from this graph, when metal fuel or carbide fuel is used, the fuel with a fuel volume ratio of 40%, which is used in conventional fast breeder reactors, can be used to reduce changes in the effective multiplication factor for about 30 years. It is possible to create a long-life reactor core, but in the case of oxide fuel, if the fuel volume ratio is 40%, the change in the effective multiplication factor will be too large, so the fuel volume ratio should be reduced to 4
It needs to be about 5% to 55%.

The graph in Figure 5 shows the case where plutonium from a light water reactor is used as fuel, but as shown by curve Q in the graph in Figure 6, when plutonium from a fast breeder reactor is used as fuel. Because the ratio of isotopes is different,
It can also be used with a fuel volume ratio of 45% or less.

The graph in Figure 7 shows that the plutonium enrichment of the entire core is 1
It shows the change in the effective multiplication factor when the plutonium enrichment in the region 12 with low fissile material density is kept constant at 1.4% and the plutonium enrichment in the regions above and below it is changed, and the curve R, For S, T, and U, (plutonium enrichment in region 12)/(plutonium enrichment in region 13.14) is 11.4%/11.4%, 10%/13.5%, respectively.
The cases of 8%/16.5% and 6%/19.5% are shown. As can be seen from this graph, the plutonium enrichment in region 12 with low fissile material density is reduced to 8% to 10%.
It is preferable that the plutonium enrichment of the regions 13 and 14 above and below it be about 13% to 17%.

That is, in the fast breeder reactor of this embodiment, for the above reasons, the axial length L3 of the core is 150 m, the fuel volume ratio of the oxide fuel is 50%, and the region with low fissile material density is 12 m.
The axial length L5 is 90 cm, the plutonium enrichment of region 12 with low fissile material density is 9%, and region 13.14
The plutonium enrichment in region 15 is 15%, and the plutonium enrichment in region 15 is 20%.

In the fast breeder reactor of this embodiment configured in this way, the effective multiplication factor changes as shown by curve V in the graph of Figure 8, where the vertical axis is the effective multiplication factor and the horizontal axis is the number of years of plant operation. . In other words, there is little change in the effective multiplication factor, resulting in a core life of 30 years or more.

Figures 9 to 13 show modified examples of the fast breeder reactor of this embodiment. In these modified examples, the shape of the region with low fissile material density is changed in order to average the output in the reactor core. The fast breeder reactor has a different shape from the fast breeder reactor of the previous embodiment.

In the core of the fast breeder reactor shown in FIG.
It is placed at a position as low as 10C111.

In the core of the fast breeder reactor shown in FIG. 10, a region 12b of the core 11b with a low density of fissile material is not rectangular in longitudinal section, but has a convex shape on the side.

In the core 11C of the fast breeder reactor shown in FIG. 11, the region 12C with low fissile material density is divided into a plurality of regions in the radial direction, and the plutonium enrichment is uniform above, below, and around it. It is surrounded by a region 13G.

In the core lid of the fast breeder reactor shown in FIG. 12, similar to the core ILG shown in FIG.
A region 12d surrounded by d and having a low density of fissile material
is divided into multiple parts in the axial direction.

In the core 11e of the fast breeder reactor shown in FIG. 13, similarly to the core 11C1 and the core 11d shown in FIGS. 11 and 12, a region 12e with a low fissile material density is surrounded by a region with uniform plutonium enrichment. 13e, and the region 12e with low fissile material density has an axial cross section of
It has a shape different from a rectangular shape.

As in these modified examples, in order to flatten the power distribution within the core, the region with low density of fissile material may have any shape; This can be done in any way, such as making the plutonium enrichment in the region with high density of fissile material vertically asymmetrical or giving the plutonium enrichment distribution in the radial direction, to obtain the same effect as in the above embodiment. I can do it.

Further, instead of plutonium fuel, enriched uranium fuel may be used, and in this case, the enrichment level is 14% or less in the region 12 with low density of fissile material, and the enrichment level is 14% or less in the region 12 with low density of fissile material, and the region 13.14 with high density of fissile material above, below, and around the region 12. .15 is 15% or 2
It is preferable to set it to about 2%.

Moreover, instead of oxide fuel, carbide fuel, metal fuel, etc. can also be used, and in this case, the fuel volume ratio may be set to 40%.

[Effects of the Invention] As described above, in the fast breeder reactor of the present invention, the axial length of the core is 130cm to 200C! II, 10% to 65% of the axial length of the core near the center of the core.
It has an axial length of It can last for about a year,
Fuel exchange becomes unnecessary for a long time or again, and it is possible to improve the operating rate and downsize or reduce the number of fuel storage and handling systems, thereby reducing plant construction costs.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing the core of a fast breeder reactor according to an embodiment of the present invention, FIGS. 2 to 7 are graphs showing differences in effective multiplication factor over time due to differences in core configuration, and FIG. Figure 1 is a graph showing the change in effective multiplication factor of the fast breeder reactor over time, Figures 9 to 13 are configuration diagrams showing modifications of the fast breeder reactor shown in Figure 1, and Figure 14 is the conventional fast breeder FIG. 1 is a configuration diagram showing the core of a breeder reactor. 11......Reactor core 12......Regions with low fissile material density 13-15...Region L2 with high fissile material density
・・・・・・・・・・・・Axial length of core Figure 1 Figure 3 Wax urine! ! IIl@A Togen! ! Figure 7 Figure 8 Figure 9 Figure 10

Claims (5)

[Claims] (1) In a fast breeder reactor having a core formed in a cylindrical shape with fuel made of fissile material and parent material, the axial length of the core is 130 cm to 200 cm, and the core is located near the center of the core. axial length 10
% to 65% of the axial length and having a lower density of fissile material than the upper, lower and surrounding regions;
A fast breeder reactor having an average power density of 65 W/cc to 150 W/cc. (2) The fast breeder reactor according to claim 1, wherein the fuel is an oxide fuel having a fuel volume ratio of 45% to 55%. (3) The fast breeder reactor according to claim 1, wherein the fuel is composed of a metal fuel. (4) The region with low fissile material density consisted of plutonium fuel with a plutonium enrichment of 11% or less, and the upper, lower, and surrounding regions had a plutonium enrichment of 13% to 20%. A fast breeder reactor according to any one of claims 1 to 3, comprising plutonium fuel. (5) The region with low fissile material density is composed of uranium fuel with an enrichment of 13% or less, and the upper, lower, and surrounding regions are composed of uranium fuel with an enrichment of 15% to 22%. A fast breeder reactor according to claims 1 to 3.