A fuel assembly channel water-cooled nuclear reactor

 

The invention is used in the designs of fuel assemblies used in ducted water cooled nuclear reactors, especially in nuclear reactors of the RBMK type. A fuel Assembly is supplemented by the elements forming the channel occupancy unmanaged and/or controlled reactor coolant water, and unmanaged orifice configured to provide at the output of the channel steam content close to the optimum, maximum energy release in the tapes with the original concentration of fissile nuclei and almost fully open shutoff valve on the inlet of the channel, and managed - in the same position named valve when changing the energy deposited in the cassettes in the range from the maximum to the minimum allowed, corresponding to a maximum burnup of fissile nuclei. The technical result consists in increasing the coefficient of heat transfer from the fuel elements to the fluid and, consequently, to increase the efficiency of nuclear fuel. 4 C.p. f-crystals, 3 ill.

The invention relates to fuel assemblies (FA) channel water cooled with boiling nuclear reactors, will be two cassettes with the fuel elements and the spacer their grilles fixed to the suspension with protection from gamma radiation tube with helical grooves for the current steam-water mixture or cooling water (coolant). In connection with the constancy of the composition and main characteristics for more than two decades, this FA is only similar and the prototype to the invention.

An important feature of the reactor is operating in mode continuous cyclical replacement of spent, “burned out” FA “fresh” (i.e., fuel assemblies with a relatively low concentration of fissile nuclei on FA with their original concentration). Therefore, when the reactor even at a constant level of the total power of the energy deposition in the fuel assemblies located in different technological channels (TC) and loaded at different times, significantly different. This means that technologically reasonable expenses of cooling water in TC - to maintain their outputs are approximately equal (economical) of the steam quality must be installed different: in the range from the maximum in TC with fresh fuel assemblies to a minimum in TC with almost spent fuel assemblies. During the campaign, as “burnout” FA, in accordance with accepted approaches to the hydraulic profile of the active zone rashedi individual, inputs in TC, shut-off and control valves (AAMS). While the hydraulic resistance of SAMS and the pressure drop across it increases, and the pressure of cooling water in place cassettes in TC (at constant pressure drop across the main coolant pumps reactor) decreases.

The disadvantages of the known FA can be attributed to the fact that the composition and the geometrical parameters that affect the value of the coefficient of heat transfer from the fuel elements to the carrier, not optimal. In particular, they are that technologically reasonable flow of cooling water in TC at any energy in the cassettes can be installed only at the expense of a significant pressure drop on AAMS. The result is the absolute value of the pressure of cooling water in place cassettes in TC, the coefficient of heat transfer from the fuel elements to the carrier and, ultimately, the efficiency of nuclear fuel will always be less possible in principle.

The task of the invention is to improve the performance of the prototype in the given ratio.

The technical result is achieved by the use of the invention is to increase the coefficient of heat transfer from the fuel ele the use of nuclear fuel.

This technical result is achieved by the fact that the known fuel Assembly added elements forming the channel occupancy unmanaged and/or controlled reactor coolant water, and unmanaged orifice configured to provide at the output of the channel steam content close to the optimum, maximum energy release in the tapes with the original concentration of fissile nuclei and almost fully open shutoff valve on the inlet of the channel, and managed - in the same position named valve when changing the energy deposited in the cassettes in the range from the maximum to the minimum allowed, corresponding to a maximum burnup of fissile nuclei.

The following options are proposed FA:

a) FA with elements unmanaged inductor made in the form of reduced cross-section of the spiral grooves in a protective tube or throttling of washers mounted on the plot above cassettes;

b) FA with elements controlled throttle mounted on the plot above cassettes controls made in the form of bellows, a movable part which directly or through a gear connected with moving the meters on the area below cassettes (in the presence of individual elements of unmanaged throttle is not necessary because implicitly they inevitably are part of a managed);

C) FA with elements unmanaged throttle mounted on the plot above cassettes, supplemented by elements managed, secured to the section below cassettes controls made in the form of bellows, a movable part which directly or through a gearbox connected to the movable part of the throttling elements, and the internal cavity through the Central sleeve in suspension with the fluid at the site above cassettes;

g) FA with elements controlled throttle mounted on the plot above cassettes controls made in the form of bellows, a movable part which is connected to the movable part of the throttling element and a mechanism to move them manually, located in the cavities of the bellows and the Central liner suspension with access from the upper end of the Assembly (in the presence of individual elements of unmanaged throttle there is no need for the reason specified for option b)).

d) FA with elements unmanaged throttle mounted on the plot above cassettes, supplemented by elements managed, secured to the section below cassettes controls performed according to the reference pressure in the shopping center on the site of placement of the cartridges through the creation of additional hydraulic resistance at the site above cassettes; this will achieve the desired increase in the value of the coefficient of heat transfer from the fuel elements to the coolant. Mutual difference of these options due to the difference in the degree of possible approaches the maximum of this increase on average for the campaign, i.e. the time from loading in channel “fresh” fuel assemblies to discharge the exhaust, and the source and nature of control actions to maintain the steam quality at the outlet of the channel within the specified limits. So:

option a) design provides maximum heat transfer coefficient for the fluid only from the “fresh” fuel assemblies, and over time, as “burnout” of fissile nuclei and reduce the power density in the fuel Assembly, its value decreases. The reason is the reduction of pressure on the area cassettes with increasing differential pressure on ADMS and lower consumption of cooling water to restore the output TC of the original steam content in the course of works on the hydraulic profile of the active zone. The change in the flow rate of water in TC with such fuel assemblies using ADMS manually;

option b) design provides maximum heat transfer coefficient of the coolant FA with any concentration of fissile nuclei, from the highest to the controlled throttle to maintain the output TC of the steam quality, close to optimal. The change in the flow rate of water in TC with such a fuel Assembly is carried out by means of controlled throttle automatically;

C) design provides maximum heat transfer coefficient for the fluid only from the “fresh” fuel assemblies, and over time, as “burnout” of fissile nuclei and reduce the power density in the fuel Assembly, its value decreases. The reason is the reduction of pressure on the area cassettes with increasing differential pressure controlled throttle to maintain the output of the LC steam content close to the optimum. The change in the flow rate of water in TC with this FA is in principle the same as using ADMS, but automatically;

option g) structure on the effectiveness of the heat transfer coefficient and the steam content is similar to option b) with the difference that the change in the flow rate of water in TC with such fuel assemblies is controlled by the throttle periodically, manually (like using ADMS, but with access from the upper end of the Assembly opening in the Central hall of the reactor);

option d) design on the effectiveness of the heat transfer coefficient and the steam content is similar to option a) with the difference that the change in the flow rate of water in TC with this FA is not in the Yomi other - in the ease of implementation, variant b) in the maximum efficiency achieved, however, due to the substantial complexity (increasing cost) of the throttle and the Assembly as a whole. FA option), you may prefer FA option a) because of the ability to automatically maintain a predetermined steam quality at the outlet of the channel. FA options g), d) is proposed for a complete examination of the problem, because of the availability of the manual drive is somewhat more complicated FA variant b), and performance inferior to him. However, the best option proposed FA can be carried out, at least, only the results of mathematical modeling of teplogidravlike in a separate TC and TC with such fuel assemblies in the reactor as a whole, and especially there is a question about the provision of thermal-hydraulic stability, reliability, escribiente heat from the fuel assemblies at random fluctuations of energy in them and flow rate of cooling water.

Design FA variant (a) is almost identical to the design of fuel assemblies, described in /1/, the principle of unmanaged throttle known principles of hydraulic profiling of the active zone and throttling costs of cooling water in TC is described in detail in /the th environment within the parameters of the reactor coolant type RBMK - in /3/. Therefore, to explain the principle of the FA option a) you can do without special sketch and limited only by the following remark.

By itself, the method of adjusting the flow rate of cooling water in TC with FA variant (a) remains the same as in TC with known assemblies, and is carried out by stepwise decreasing the degree of opening of the AAMS as “burnout” of fissile nuclei. The difference is only that the initial value of the cooling water consumption, i.e. consumption in TC with the “fresh” fuel assemblies with a maximum permitted power in cartridges installed when fully or almost fully open ADMS, when the differential pressure on it is minimal and unmanaged throttle - maximum. The word “almost "fully open" SAM” means that the actual value of the flow of water in a particular TC with fresh fuel assemblies in the fully open ADMS can be a little more technologically sound (because of the natural variation in size of the LC and FA) and then to reduce it to the required level, you may need some cover-up for the ADMS. The estimated increase in the “initial” heat transfer coefficient from FA option a) to the coolant during typical for RBMK values paraserianthes b), C) consider the sketches of Fig.1-3. The first depicted a well-known FA (RBMK) showing the locations of possible placement of items controlled throttles flow on the second - these items with on-site suspension above the cassette, the third similar items by placing lower cassettes. In Fig.1-3 are marked: 1 - shut-off tube TVs with shank 2; 3 - bearing rod with protective charms (from gamma radiation) tube 4 with helical grooves for current carrier 5 is fixed to the suspension cartridge fuel elements with spacers 6 and end - 7 bars; 8 - lug suspension with the fastening nut 9; 10 - LC reactor pipes 11, 12 to drain water mixture and cooling water, respectively; 13, 14 - the area of possible locations of the elements, forming in TC managed chokes the flow rate of cooling water (area 13 are elements and unmanaged throttle); 15-19 elements controlled throttle with accommodation in the area 13 of the suspension above cassettes; 15 - fixed throttle valve with side holes 16; 17 is movable flap of the throttle partial overlap of the holes 16; 18 - bellows, movable (upper) part of which is connected with ASDs charms - with the coolant below cassettes; 20-24 elements controlled throttle with accommodation in region 14 of the suspension below cassettes; 20 is a fixed throttle valve with side holes 21; 22 is movable flap of the throttle with the front holes 23 and partially overlapping holes 21; 24 - bellows, movable (upper) part of which is connected to the valve 22, a fixed - valve 20 and the rod 3 and the inner cavity through the Central sleeve 25 in terminal 3 of the suspension and the holes 26 with fluid above cassettes; assume (to simplify the drawings), the bellows against axial displacements of the movable part has spring characteristics; the direction of flow of water and steam-water mixture in TC is shown by arrows; cartridge fuel assemblies within the reactor core.

FA variant b) works as follows. Suppose that TC is “fresh” fuel assemblies, reactor has a capacity close to the maximum permitted, and the flow rate of cooling water in the pipe 12 (channel 10) in the fully open ADMS installed using a configured appropriately managed inductor formed by elements 15-19 and walls of the channel 10, so that the steam quality steam-water mixture in the pipe 11 (in AspectJ such a gap between the stationary valve 15 and the inner wall of the channel 10, such spring properties of the bellows 18, the overlap of the holes 16 valve 17 and, ultimately, such a hydraulic resistance region 13, which achieves the desired steam quality. Moreover, the position of the movable valve 17 relative to the holes 16 is ensured by the balance of two forces acting on the movable portion of the bellows 18, one of which is caused by the pressure drop in the coolant between the regions 13 and 14, the tensile corrugations of the bellows 18, and the other elastic force of the compression ratio of the corrugation of the bellows.

Over time, as “burnout” of fissile nuclei and reduce the energy deposited in the fuel assemblies, the intensity of generation of steam in the area of placement of the cassette begins to decrease. In the result, start to decrease the hydraulic resistance of the LC on the area of the tapes, the pressure differential between the areas 13, 14, and strength, tensile corrugations of the bellows 18. The latter causes a slight compression of the corrugation of the bellows 18 and the movement of the movable valve 17 in the direction of increasing the degree of overlap of the holes 16 (Fig.2 - down) to a new state of equilibrium of the forces acting on the movable portion of the bellows 18, when due to the increase in hydraulic resistance controlled throttle the values. The increase in the energy release in cassettes leads, on the contrary, to increase the pressure differential between the areas 13, 14 and moving the movable valve 17 in the direction of reducing the degree of overlap of the holes 16 (Fig.2 - up) to a new state of equilibrium of the forces acting on the movable portion of the bellows 18, when by reducing the hydraulic resistance controlled throttle the water flow in the TC increases so that the steam quality at the outlet of the LC is reduced to approximately the previous values. So is automatic stabilization of the steam quality at the outlet of the LC within fairly narrow limits. The value of the coefficient of heat transfer from the fuel elements to the coolant remains close to the maximum.

The principle of the FA option) similar to that described with the difference that the reduction of the energy deposited in the tapes and the resulting decrease in the pressure differential between the areas 13, 14 moves the movable valve 22 (Fig. 3) upwards, and the increase in the energy release in the tapes and the resulting increase in pressure differential between the regions 13, 14 to move the movable valve 22 down (in the direction of decreasing and increasing the degree of overlap of the holes is thus close to the value of the coefficient of heat transfer from FA option a) under continuous maintenance of the given steam quality at the outlet of the LC by gradually cover AAMS.

The principle of FA options g), d) is similar to the principle of the FA options b), C) with the difference that the movement of the movable flaps 17 or 22 to change the degree of opening of the holes 16 or 21 in a stationary flaps 15 or 20 manually.

Literature

1. Dollezhal N. A., Emelianov, I. J. Duct nuclear power reactor. - M.: Atomizdat, 1980, pp. 95-97.

2. Emelianov, I. J., Meehan C. I., Solonin Century. And. and other Construction of nuclear reactors. - M.: Energoizdat, 1982, pp. 309-317.

3. Amethyst E. C., Grigoriev C. A., Emtsev B. T. and other Heat and mass transfer. Thermal engineering experiment: a Handbook. - M.: Energoizdat, 1982, pages 106-111, 178-188.

Claims

1. A fuel Assembly channel water-cooled nuclear reactor containing the fuel cartridge elements and their suspension with protection from gamma radiation tube with helical grooves, characterized in that the added elements forming the channel occupancy unmanaged and/or controlled reactor coolant water, and unmanaged choke is made with the possibility of providing at the output of the channel steam content close to the optimum, maximum energy release in the cartridge in the channel, and managed - in the same position named valve when changing the energy deposited in the cassettes in the range from the maximum to the minimum allowed, corresponding to a maximum burnup of fissile nuclei.

2. A fuel Assembly under item 1, characterized in that the elements unmanaged throttle made in the form of reduced cross-section of the spiral grooves in a protective tube or throttling of washers mounted on the plot above tapes.

3. A fuel Assembly under item 1, characterized in that the control means controlled throttle mounted on the plot above tapes, made in the form of bellows, a movable part which directly or through a gearbox connected to the movable part of the throttling elements, and the internal cavity through the Central sleeve in suspension with the fluid at the site below cassettes.

4. A fuel Assembly under item 1, characterized in that the control means controlled throttle mounted on the plot below cassettes made in the form of bellows, a movable part which directly or through a gearbox connected to the movable part of the throttling elements, and the internal cavity through the Central sleeve in suspension with the coolant on the site which I mounted on the plot above or below the tapes, made in the form of bellows, a movable part which is connected to the movable part of the throttling element and a mechanism to move them manually, located in the cavities of the bellows and the Central liner suspension with access from the upper end of the Assembly.

 

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