Tvel for integral fuel cartridge nuclear reactor (rbmk)

 

The invention relates to nuclear energy, in particular for fuel Rods for the fuel cartridges of nuclear RBMK-type reactor consisting of two fuel assemblies (FA), and can be used in Fuel elements and other assemblies, in which it is necessary to reduce a local burst of neutrons, causing increased energy. The technical result - the reduction of energy release at the ends of the fuel Rods in the center of the active zone, which will provide a more uniform deep the burn-in length and, consequently, improve the safety of a nuclear reactor. In a fuel rod for a composite fuel cartridges of nuclear RBMK-type reactor consisting of a cylindrical zirconium shell, sealed at one end by a plug, and the other with the tip inside the fuel pellet of uranium dioxide and the spring retainer of the fuel column, between the end plugs and the adjacent fuel pellets placed absorber of excess neutrons, which is a washer made of a material containing hafnium. 2 C.p. f-crystals, 2 ill., 1 PL.

The invention relates to nuclear energy, in particular for fuel Rods for the fuel cartridges of nuclear RES, in which it is necessary to reduce a local burst of neutrons, causing increased energy.

A known design of a fuel rod [1], consisting of filled fuel tablets sealed shell, which is used in the fuel cartridge, consisting of a single fuel Assembly. The power control in such FA spend the vertical movement of the absorbing rods in the guide channels. In Fuel elements such TVs release height is nearly constant except for the ends where it is lowered. This energy deposition in the fuel Rods is characteristic only for fuel cartridges, consisting of a single fuel Assembly and enables the adjustment of the power absorbing rods.

In the fuel Rods of such cassettes fuel burn is almost uniform in height, and their efficiency is high. However, the use of such fuel cassettes, consisting of a single fuel Assembly, is limited by the height of the active zone of the nuclear reactor.

Known TVEL taken by the authors for the prototype [2], consisting of a cylindrical zirconium shell, sealed at one end by a plug, and the other tip, inside which are preloaded spring retainer fuel pellets of enriched uranium dioxide. This is The Central pipe. Structurally, the cartridge is made so that the area of intersection of two fuel assemblies in the center of the active zone is the gap on the fuel pole due to the presence of a water gap height of 30 mm between the ends of the fuel Rods and two plugs 9.5mm height of zirconium alloy with cross-capture of thermal neutrons is not more than 0.2 barn.

The disadvantage of the prototype is the increased energy at the ends of the fuel Rods in the center of the active zone of the nuclear reactor caused a local outbreak of the neutron field due to a rupture in the fuel height fuel cartridge. When in the fuel Rods of the fuel with an enrichment of 2.6% uranium-235, the amount of non-uniformity of energy deposition at the ends of the fuel Rods can reach up to 1.34. The main change of the energy release occurs at a distance of 20-30 mm from the extreme ends of tablets. The result is a substantial increase in the power density at the ends of the fuel Rods decreases their health (depressurization of the fuel Rods occurs mainly in the center of the active zone, until the separation of the plugs, safety in emergency situations and the deterioration of the economic performance of nuclear power plants, including due to the inability of the operation of the fuel Rods with a 100% power for the entire length (there is a limitation of the proposed invention, is to reduce the power density at the ends of the fuel Rods in the center of the active zone, which will provide a more uniform deep the burn-in length, increase efficiency of FA and security of a nuclear reactor, including in emergency situations.

The solution of the technical problem is achieved by the fact that a fuel rod for a composite fuel cartridges of nuclear RBMK-type reactor consisting of a cylindrical zirconium shell, sealed at one end by a plug, and the other tip is inside the fuel pellet of uranium dioxide and the spring retainer of the fuel column, between the end plugs and the adjacent fuel tablet placed absorber of excess neutrons, which is a washer made of a material containing hafnium.

In the private embodiment, the washer is made from an alloy of hafnium to zirconium in the zirconium content of 0.1 to 50 wt.%.

In another private embodiment, the washer is made from an alloy of hafnium and titanium in the titanium content is from 0.1 to 50 wt.%.

In another private version in the cylindrical shell are fuel pellets of uranium dioxide only staff enrichment.

Hafnium is compatible with the materials of the shell, end caps and teachinig conditions above, than that of zirconium alloys. The cross-section capture the hafnium 105 barn, during operation ability hafnium changes slightly.

The influence of the thickness of the washer to reduce the power density in the center of the active zone at the ends of the fuel Rods in the outer row of cassettes RBMK-1000 fuel enrichment 2.8% and the content of erbium 0.6% in the area of juncture of the two beams in the center of the active zone are shown in table 1.

From the presented results it follows that in the fuel Rods of the RBMK-1000 without washer-scavenger of excess neutrons at the ends in the center of the active area is increased power density to a value of 1.34. Washer thickness of 0.6 mm reduces the initial burst to 1.11, and washer thickness 1,0 mm eliminates surge energy almost completely.

The invention is illustrated by drawings.

In Fig.1 shows a longitudinal section of a fuel rod, comprising a shell 1, the stub 2, tip 3, the fuel pellets 4, the spring retainer 5. Additional absorber of excess neutrons 6 in the form of a washer made of hafnium or an alloy of hafnium to zirconium is located inside the fuel rod between the inner end of the stub and the adjacent tablet of uranium dioxide.

In Fig.2 shows the plug 2 washer 6.

TV is moderator and coolant distilled water is used, and as a nuclear fuel is enriched uranium dioxide. During operation of a nuclear reactor in the center of the active area of the junction of the two bundles of fuel Rods due to the presence in this area of water gap height of 30 mm and two zirconium plugs (G,5 mm) with a cross-section of capture of thermal neutrons is not more than 0.2 barn, formed a local burst of energy neutron field, which causes increased up to the value of 1.34 was initiated at the ends of the fuel Rods. Placed between the inner end of the stub and the adjacent fuel tablet washer, made of hafnium or an alloy of hafnium from zirconium, with a cross-section of the grip 105 barn absorbs some of the neutrons and thereby aligns the energy deposition along the length of a fuel rod. In addition, the replacement of two on-screen tablets from depleted uranium washer from hafnium allows to increase the load of the fuel in the fuel rod, which will give an opportunity to improve the economic performance of nuclear power plants.

The larger the mass of hafnium in the fuel rod, the larger value decreases the energy deposition at the end of the fuel element.

More energonaprjazhenie fuel cartridges of nuclear reactor RBMK-1500 (similar in design RBMK-1000), in which high local energy deposition in the Oia at the ends of the fuel Rods in the center of the active zone in the fuel pole plugs put two screen tablet height 30 mm dioxide uranium of low enrichment [3], in the result, the amount of non-uniformity of energy deposition along the length of the fuel rod is reduced to 1.25 to 1.34. Hafnium more efficient and to a lesser extent, in comparison with depleted uranium dioxide, levels of energy along the length of a fuel rod. So, two screen tablet with a total height of 30 mm from the uranium dioxide enrichment 0.7% uranium-235 in the fuel Rods of the RBMK-1500 reduce the surge of energy at the ends of the fuel Rods in the center of the active zone of 1.34 to 1.25, while for obtaining the similar effect of reducing the energy deposited in the fuel Rods at the ends enough washers from hafnium thickness of only 0.2 mm

This loss in fuel burnup using the two screen tablets from depleted uranium dioxide is 1.8%, and the use of washers of hafnium thickness of only 0.2 mm 0,42%. In the present invention are fuel pellets only staff enrichment.

A new technical result of the invention is that when used in a fuel cartridge of the fuel Rods washers from hafnium or an alloy of hafnium from zirconium, or hafnium alloy with titanium, which is located between the inner end of zirconium plugs and fuel tablet, provides high performance TVs, reduces the number of permeti cost of generated electricity. Use in RBMK-1500 tablets regular enrichment will increase the energy deposition along the entire length of a fuel rod, which will enhance the economic performance of nuclear power plants.

Sources of information

1. Emelianov, I. E. nuclear Power reactors. - M.: Energoatomizdat, 1984, S. 18-30.

2. Dollezhal N. A. Channel nuclear power reactor. - M.: Atomizdat, 1980, S. 54-55, 95-97.

3. K. Almenas, A. Kaliatka, E. Uepuras. Ignalina RBMK-1500. A Sourse Book. - Lithuanian Energy Institute, 1998, p. 62-64.

Claims

1. TVEL for the composite fuel cartridges of nuclear RBMK-type reactor consisting of a cylindrical shell, sealed at one end by a plug and the other end in which is located the fuel pellet of uranium dioxide and the spring retainer of the fuel column, characterized in that between the end plugs and the adjacent fuel tablet placed absorber of excess neutrons, which is a washer made of a material containing hafnium.

2. TVEL under item 1, wherein the washer is made of an alloy of hafnium to zirconium in the zirconium content of 0.1 to 50 wt.%.

3. TVEL under item 1, wherein the washer is made of an alloy of hafnium and titanium in the titanium content is from 0.1 to

 

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