KR920000492B1 - Bundle of nuclear fuel for candu-phwr type - Google Patents

Abstract

The nuclear fuel bundle (1) has 43 circular rods with 2 different diameters. 35 fuel rods (2,2') with a diameter less than the others are positioned on the outer circumference of the bundle. The other 16 rods have the structure in that 15 rods (3,3',4,4') are concentrically assembled in the center of one core rod (1). This geometrical fuel bundle can use low-concentrated nuclear fussion material as well as natural uranium (0.7 wt.% U- 235) and increase the average discharge combustion ratio, the robustness and the stability rather than the conventional nuclear fuel bundle with 37 rods.

Description

High Combustion 43-Double Rod Nuclear Fuel Bundle for CANDU-PHWR Reactor

1 is a 43-binding nuclear fuel bundle arrangement of the present invention.

2 is a schematic drawing of the overall wheel angle, components and fuel of the fuel bundle.

Figure 3 compares the maximum linear powers of the existing 37 rod and 43 rod fuel bundles when using natural uranium.

4 is a comparison of the maximum linear power of the existing 37 rod fuel bundles and 43 rod fuel bundles using 0.9 wt% low enriched uranium.

5 is a comparison of the maximum linear power of the existing 37 rod fuel bundle and 43 rod fuel bundle when using 1.2wt% low enriched uranium.

The present invention is an improved fuel bundle for a CANDU-PHWR reactor, wherein a 43-bi-rod fuel bundle consisting of two fuel rods having different diameters, that is, 35 nuclear fuel rods smaller than the inner ring and the central ring, has 21 outer ring and Located in 14 heavy rings, eight relatively large diameter nuclear fuel rods are divided into seven inner rings and one central rod, making them an ideal arrangement for lowering local peak power as well as flattening fuel bundle radial power and emission burnup. For a high-combustion 43-binding nuclear fuel bundle with structural characteristics.

The 43 binary rod-enhanced nuclear fuel bundles of this geometry can be used not only for natural uranium (0.7 wt% U-235) but also for low enriched fissile material (concentration corresponding to U-235 low enrichment around 1.2 wt%). In this case, the average emission burn rate is more than three times higher than that of the 37 one-way nuclear fuel bundle (natural uranium use, average emission burn rate of 7000MWD / MIU) in Wolsong-ro, which greatly improves the economic efficiency and its soundness and performance even at high combustion. It also improves the reliability of nuclear fuel by improving safety and safety compared to 37 existing fuel bundles. (Note: The existing 37 bundles of Wolsong-type fuels cannot be used for high-combustion fuels.)

Fundamental considerations for the design and safety of high-combustibility fuels for CANDU-PHWR reactors include the integrity of the nuclear fuel cladding so that the fission product is not restricted to the interior of the cladding and is not released into the coolant during the high-burning furnace. It must be maintained.

Due to the nature of the CANDU-PHWR reactor core, most of the fast neutrons produced by nuclear fission are decelerated in moderators located outside the fuel pressure tubes, which become thermal neutrons. Entering the center tends to increase the output of the bundle of foreign exchange fuel rods. In addition, when nuclear fuel rods are burned for a long time in a furnace with high linear power, the release of fission gas is accelerated and the pressure in the nuclear fuel rods is increased, making it impossible to maintain the integrity of the furnace.

Therefore, considering these core and fuel behavior characteristics, 43 types of nuclear fuel rods are divided into two outermost / heavy ring and inner / central rods to form an ideal fuel bundle arrangement, so that the output of the nuclear fuel bundle is not reduced. And lower the linear output of the heavy rod, which in turn lowers the local peak output, which reduces the safety and performance and flexibility of the nuclear fuel rods, thereby flattening the radial output and burnability of the fuel bundle. It has the following structural characteristics.

Hereinafter, the gist of the present invention will be described with reference to the accompanying drawings.

A low-enriched fissile material (concentration corresponding to U-235 low-enrichment (SEU) of about 1.2 wt%) as a high-fuel 43-bin rod fuel bundle (1) for the CANDU-PHWR reactor. In combining two types of fuel rods, 21 and 14 outer ring fuel rods (2) (2 ') having the same diameter are arranged in the concentric ring arrangement in the outer ring and the middle ring of the nuclear fuel bundle, and the inner ring and The central ring consists of seven inner ring fuel rods (3) (3 ') and one central fuel rod (4) that are relatively larger in diameter than the outer ring fuel rods. Combustion degree relates to the structure of the 43-binar nuclear fuel bundle. Reference numeral 5 denotes a sealed laminate.

As described above, the present invention shows the difference in the maximum linear power of the existing 37 rod nuclear fuel bundle and the 43 rod nuclear fuel bundle when using natural uranium as shown in FIG. It can be seen that the maximum linear power of the 43-pack nuclear fuel bundle is about 17% lower than that of the 37-pack nuclear fuel bundle, and even when the 0 / 9wt% and 1.2wt% low enriched uranium is used in Figs. It shows the difference in maximum line power between the fuel bundle and the 43 rod fuel bundle. It can be seen that the maximum linear power of the 43-pack nuclear fuel bundle is about 17% lower than that of the 37-pack nuclear fuel bundle at the maximum initial power output of combustion.

The main point of the present invention in the nuclear configuration for the design of high-combustion fuel is compatible with existing overmolded reactors, and considers to improve the in-house performance, economy and safety than the existing 37 nuclear fuel bundles. Nuclear design considerations for compatibility with Wolsong reactors currently in operation include:

High-combustion fuels should be designed to prevent loss of control of the Zone Control System (ZCU). That is, the excess reactivity of the new fuel injected during the fuel replacement should be within the control function of the ZCU. It is designed to form neutron flux distribution that can support the responsiveness of the adjusting rod so that the adjusting rod function of the adjusting rod system is not lost. In order to prevent tripping by the local ROP system, the output difference at the same location after the fuel replacement should not be large.

In order to increase the economics of the new nuclear fuel, the direction of increasing the fuel emission rate and reducing the frequency of use of the nuclear fuel solid equipment was set. To this end, the nuclear fuel core management system should be optimized and the nuclear fuel itself will be sound at high combustion levels. Critical heat flux by minimizing fuel bundle output and maximum channel output and minimizing maximum peak output of nuclear fuel rods by flattening radial output in nuclear fuel bundle. Flux) and critical channel power.

In accordance with the above conceptual requirements, in the configuration of 43 binary rod fuels, during the combustion of the fuel furnace with increased combustion, the pressure is maintained at a low pressure so that the fuel rod integrity is maintained by increasing the internal pressure of the rod. In order to minimize material change and geometric specification change, and to maintain the soundness and safety during high combustion residence in the furnace, the following main technical ideas / perspectives were considered. Lowering the maximum linear power of a nuclear fuel rod added to one fuel rod in the fuel bundle suppresses the release of fission gas and reduces the maximum temperature of the fuel rod core.

Thus, by increasing the number of fuel rods in the fuel bundle, the output load of one fuel rod is reduced. Lowering the local maximum linear power of the fuel rods by flattening the relative power ratio of the radial bundles of the fuel bundles. In other words, by using a relatively large output density of the outer ring rod nuclear fuel is smaller than the inner ring rod radius size, the linear output of the outer ring is reduced. When the high-combustion fuel bundle is irradiated with high combustion furnace, it creates a bundle arrangement and a sealing plate of nuclear fuel rods that can maintain the mechanical integrity even under mechanical changes due to deformation and irradiation growth of the fuel structure. .

Considering the mechanical compatibility between the high-combustion fuel bundle and the existing fuel loader in Wolseong-ro, it has mechanical compatibility between the outer specifications of the fuel bundle (outer ring and end junction plate) and the side stop of the loader. (See Figure 2.) Fuel rod types used for high-combustion fuel bundles were allowed to be dualized, considering economics / processability.

Therefore, the 43-Double Rod Fuel Bundle designed according to the above design requirements and methodology has 43 binary fuel rods with the ideal geometric fuel bundle arrangement as shown in Fig. 1, and the average emission burnup is about 21,000MWD / MTU. High fuel for Wolseong-ro, which improves the reliability of nuclear fuel by improving economic efficiency, processability, furnace performance and safety as a nuclear fuel, is also a nuclear fuel.

Claims (1)

43 binary fuel bundles (1) for high-combustion for CANDU-PHWR reactors, using natural uranium or low enriched fissile material (concentration corresponding to U-235 low enrichment of about 1.2 wt%) Two types of nuclear fuel rods are used for the bundle, and the outer and middle rings of the nuclear fuel bundle have 21 concentric rings and 14 outer ring fuel rods (2) (2 ') of the same diameter in concentric ring arrangement. The inner ring and central ring have a geometrically structured concentric arrangement of seven inner ring fuel rods (3) (3 ') and one central fuel rod (4) that are relatively larger in diameter than the outer ring (outer ring and heavy ring) fuel rods. A high-combustion 43- binary fuel bundle for a CANDU-PHWR reactor.

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