RU2453936C1 - Shell-type nuclear once-through reactor cooled with water of supercritical pressure with steam superheating and method of its operation - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: invention relates to the field of nuclear engineering and may be used in development of light-water reactors of supercritical pressure with steam superheating. The method to operate a reactor includes placement of fuel assemblies in the reactor core, their usage for a certain period of time, implementation of the fuel assembly handling programme. At the same time as fresh fuel assemblies loaded into the central subzone burn out, the fuel assemblies are serially shifted from the central subzone into the middle subzone and then as they burn out to the peripheral subzone. The shell-type nuclear once-through reactor cooled with water of supercritical pressure with steam superheating comprises a reactor vessel, facilities for water supply and steam discharge connected with appropriate headers formed under the support plate and in the upper part of the reactor core, fuel assemblies distributed in the reactor core. There are three radial subzones formed in the reactor core. Headers formed under the support plate and in the upper part of the reactor core are arranged in the form of sections providing for serial passage of the supplied water flow along three formed subzones from fuel assemblies of the peripheral subzone to the fuel assemblies of the central subzone.

EFFECT: reduced temperature of fuel assembly shells, reduced density of coolant to compensate for reactivity margin for burning.

2 cl, 1 dwg

Description

The invention relates to the field of nuclear energy and can be used in the development of light-water supercritical pressure reactors with superheating of steam.

The design of a light-water reactor of the VVER-1000 type is known (see, for example, F.Ya. Ovchinnikov, L.V. Golubev, V.D.Dobrynin “Operational modes of water-cooled nuclear power reactors”, Atomizdat, 1979). Reactors of this type are widely used at nuclear power plants in Russia and abroad.

The disadvantage of this reactor is very low for modern energy efficiency.

Also, a technical solution is known - an analogue according to the patent of the Russian Federation 2128864, IPC6 G21C 7/30, G21C 3/32, METHOD FOR OVERLOADING OF THE HEAT-DIVING ASSEMBLIES OF A WATER-WATER REACTOR.

The invention relates to the field of nuclear energy and can be used in the operation of pressurized water reactors such as VVER-1000 reactors. The technical result consists in the simultaneous placement in the active zone of a water-water reactor of dissimilar fuel assemblies that differ when they are in the active zone by the neutron spectrum while maintaining unchanged or slightly reduced compensation ability of the absorbers of the CPS. A method of overloading fuel assemblies (FAs) in a water-water reactor containing two or more types of FAs that differ in the softness of the neutron spectrum when they are in the active zone involves extracting spent fuel, moving the remaining fuel assemblies in the core and loading fresh FAs with the soft spectrum among the CPS cells has established more than the fraction of these fuel assemblies in the core and is equal to unity in the limit.

However, in this solution there is an increased sensitivity to uneven heating medium coolant, which leads to overheating of the coolant and the cladding of the fuel elements. The high temperature of the cladding of the fuel elements requires the use of heat-resistant and heat-resistant alloys, for example, nickel-based alloys. In this case, in particular, the fuel cycle characteristics are radically deteriorating.

Also known is the design of a direct-flow supercritical pressure vessel reactor (see, for example, Oka Y. Review of temperature water and steam cooled reactor concept-In 4-th Int / Symp. On SCWR, Japan, Nov.6-9, 2000, Rep / 104, p. 37-56) is a prototype.

Known direct-flow reactor includes a robust housing, a base plate, a block of protective pipes and an active zone formed from fuel assemblies (FA).

In a known reactor, the supercritical pressure coolant is heated, evaporated and overheated in the core in one pass. Moreover, most of the moderator is placed in separate tubes in the fuel assembly, which is not involved in heat transfer, and rod fuel elements (fuel elements) are placed in a tight lattice. This is due to the fact that the coolant of a once-through reactor has a 12-fold increase in enthalpy increase and, correspondingly, a 12-fold lower coolant consumption in comparison with the well-known VVER-1000 type reactor. The use of a tight lattice is due to the need to provide a sufficiently high speed for cooling fuel rods and the need to place a moderator in separate tubes to provide the necessary water-uranium ratio.

A disadvantage of the known once-through reactor is an extremely high sensitivity (12 times compared with VVER-1000) to the uneven heating of the coolant, which leads to overheating of the coolant and cladding of fuel rods to a level of 900-1000 ° C. The high temperature of the cladding of the fuel elements requires the use of heat-resistant and heat-resistant alloys, for example, nickel-based alloys. In this case, the characteristics of the fuel cycle are radically worsening.

Evaporation and even more overheating of the moderator are unnatural (undesirable), as they adversely affect the burnup of the fuel.

Therefore, it is necessary to use a decrease in the density of the coolant due to boiling and superheating of steam to compensate for the reactivity margin for burnout.

In connection with the stated technical objective of the invention is to reduce the temperature level of the cladding of fuel rods and increase the characteristics of the fuel cycle, as well as the use of reducing the density of the coolant due to boiling and overheating of steam to compensate for the reactivity margin for burnout.

The specified technical problem is provided by the fact that the proposed:

a method for operating a case direct-flow nuclear reactor cooled by supercritical pressure water with superheating of steam, including placing fuel assemblies in the core, using them for a certain time, moreover, they will overload the fuel assemblies, in which, as the fuel assemblies are loaded into the central subzone, they produce “fresh” fuel rearrangement of fuel assemblies from the central subzone to the middle subzone and then, as it burns out, to the peripheral subzone;

- it is also proposed:

a nuclear reactor direct-flow reactor vessel cooled by supercritical pressure water with steam superheating, including a reactor vessel, means for supplying water and removing steam associated with respective collectors formed under the base plate and in the upper part of the core, fuel assemblies (FAs) distributed in the core, moreover

three radial subzones are formed in the active zone, the collectors formed under the base plate and in the upper part of the active zone are made in the form of sections providing a sequential passage of the supplied water flow through three formed subzones from the fuel assemblies of the peripheral subzone to the fuel assemblies of the central subzone.

According to the indicated, the active zone is made of at least three radial subzones connected in series along the heat carrier with the help of collectors made under the base plate and in the block of protective pipes, the external radial subzone being cooled mainly by the aqueous phase, the middle one is cooled by a boiling coolant, and the internal the subzone is cooled by superheated steam.

During reactor operation, the following overload mode is carried out. “Fresh” fuel assemblies (FAs) are loaded into the central radial subband, which implements a hard neutron spectrum due to the low density of water vapor and high enrichment of uranium in “fresh” FAs. At the same time, the excess breeding capacity of “fresh” fuel assemblies is compensated for due to increased neutron absorption in the resonances of uranium-238 with the formation of plutonium-239.

After reaching about 33% of the design burnup, the fuel assemblies from the central subband are rearranged into the middle subband, in which the intermediate neutron spectrum is realized.

After reaching about 67% of the design burnup, these fuel assemblies (from the middle subzone) move to the periphery of the core (to the peripheral subzone), in which the thermal neutron spectrum is realized, which ensures the achievement of the design burnup (100%). With such an overload scheme, spectral regulation is implemented, which allows one to practically abandon burn-out absorbers and, accordingly, achieve increased burnup. This will significantly reduce the negative effect of the use of steel cladding of fuel elements. At the same time, the proposed design allows to reduce the enthalpy increment (steam overheating) in the central zone to an acceptable level of 300 kJ / kg (120 ° C). This will provide an acceptable level of coolant temperature in hot jets and an acceptable temperature of the fuel claddings below 700 ° C.

The invention is illustrated in the drawing, which shows a vertical section of the reactor, a General view.

In the drawing, the positions indicated:

1 - reactor vessel;

2 - collecting collector;

3 - supply of feed water;

4 - steam output;

5 - upper intermediate manifold;

6 - peripheral part of the core;

7 - middle subzone (middle part of the core);

8 - the inner part of the core;

9 - separator;

10 - lower intermediate manifold;

11 - thermal insulation.

Description of the proposed solution

The nuclear reactor shown in the drawing includes a robust casing 1, collecting collector (protective tube unit) 2, feed water supply (feed water pipe) 3, steam outlet (superheated steam pipe) 4, upper intermediate collector 5, peripheral part of the core ( peripheral subzone} 6 fuel assembly placement, middle core (middle subzone) 7 fuel assembly, inner core (central subzone) 8 fuel assembly, splitter 9, lower intermediate manifold 10 and thermal insulation 11.

The reactor operates as follows.

Cold coolant is supplied to the durable housing 1 through the nozzle 3. Then it flows along the housing and enters the input of the peripheral subzone 6, which it cools, moving from bottom to top.

Heated to a mixed temperature of about 385 ° C, the coolant from the fuel assembly of the peripheral subzone 6 with different temperatures enters the upper intermediate manifold 5, in which the unevenly heated coolant is mixed and distributed to the fuel assembly of the middle subzone 7, in which the supercritical pressure coolant is heated to a mixed temperature of 410 -420 ° C. In this case, a significant change in the density of the coolant occurs. In turn, this implements an intermediate neutron spectrum in the middle subband 7.

The coolant from the fuel assemblies of the middle subzone 7 with different temperatures enters the lower collecting manifold 10, in which the coolant with different temperatures is mixed and distributed to the fuel assemblies of the central subzone 8. In it, the coolant is heated to an average mixed temperature of about 540 ° C. Next, superheated steam is discharged from the reactor vessel through the cavity of the block of protective pipes (2 - collecting manifold) 2 and the steam pipe 4.

Moreover, the heating medium in the central zone is only 120-130 ° C. This provides an acceptable level of the temperature of the cladding of the fuel rods at 650 ° C.

That is, the organization of the coolant circulation in the core of the nuclear reactor, including the design study, the selection and installation of the parameters of the coolant flow rate and heat dissipation, are implemented in such a way that the formed external (peripheral) subzone is cooled mainly by the aqueous phase of the coolant, the middle subzone is cooled by a boiling coolant, and the inner subzone is cooled with superheated steam.

The claimed technical solution allows the implementation of a supercritical pressure reactor with superheating of steam to 540 ° C at a fuel cladding temperature of 650 ° C. This provides an increase in the efficiency of the steam turbine plant above 45%. The proposed method of operation allows for spectral regulation of the margin of reactivity to burnout. This provides an increase in uranium burnup by about 25%.

Claims (2)

1. The method of operation of a nuclear reactor direct-flow reactor cooled by supercritical pressure water with steam overheating, including the placement of fuel assemblies in the active zone, their use for a certain time, characterized in that they carry out a program of overloading fuel assemblies, in which, as they burn up, they are loaded into the central subzone " fresh ”fuel assemblies sequentially rearrange fuel assemblies from the central subzone to the middle subzone and then, as it burns out, to the peripheral subzone. 2. A nuclear direct-flow reactor vessel cooled by supercritical water with superheating of steam, including a reactor vessel, means for supplying water and removing steam associated with the corresponding collectors formed under the base plate and in the upper part of the core, fuel assemblies distributed in the core (fuel assemblies) ), characterized in that in the active zone three radial subzones are formed, the collectors formed under the base plate and in the upper part of the active zone are made in the form of sections providing the apparent passage of the supplied water flow through three formed subzones from the fuel assemblies of the peripheral subzone to the fuel assemblies of the central subzone.