Device for securing pressurized-water reactor core

FIELD: pressurized-water reactor equipment.

SUBSTANCE: proposed device for securing pressurized-water reactor core with coolant flowing over it has supporting cylinder and flexible member. Supporting cylinder is mounted on pressurized tank flange. Flexible member has a number of adjacent circular segments disposed between and engageable with supporting cylinder flange and pressurized tank cover flange. Each circular segment of flexible member has segmental supporting plate. The latter mounts hold-down devices secured thereon by means of locking devices. Each hold-down device has supporting sleeve accommodating working element of precompressed thermally expanded graphite which is locked therein by means of locking device, as well as hold-down bushing. The latter is in contact with working element or with locking device.

EFFECT: reduced vibration of reactor core when changed over to fuel load incorporating zirconium-can fuel assemblies.

7 cl, 10 dwg

 

The technical field

The invention relates to a device for fastening internal equipment of a nuclear reactor, namely, devices for securing active zones in the reactor with pressurized water and washed by the cooling fluid.

The level of technology

Know the device /1/ (Drawing 1135.01.04.000. Mine with the screen. Izhora plant. 1972). to secure the active zone containing the reference cylinder, mounted on the flange on the pressure vessel of a nuclear reactor, the elastic element comprising a number of adjacent ring segments disposed between the flange of the support cylinder and the flange of the lid of the pressure vessel. The ring segments of the elastic element is made of pipes. The compression of the elastic element is a cover of the pressure vessel when the seal main connector of the pressure vessel. This creates a clamping force on the flange of the support cylinder, which, along with the force from the spring units of fuel assemblies, biasing pressure cylinder, and the force from the weight of the support cylinder with fuel loading presses the supporting cylinder to the flange of the pressure vessel and keeps it from surfacing and vibration when exposed to a differential pressure of the coolant circulating in the reactor.

A disadvantage of the known device is that during the transition to the recalls the reactor fuel assemblies with a frame made of zirconium alloy instead of fuel assemblies with stainless steel frame there is a significant reduction efforts the generated pressure cylinder during the compression springs in the heads of fuel assemblies, since the output at the operating temperature of the heat carrier Zirconia framework of the fuel Assembly is extended to 12-15 mm less than the corresponding channel, formed by the reactor internals are made of stainless steel 08KH18N10T (elongation taken for VVER-1000 reactor with a length of fuel 3.5 m).

When the reduction of the pressing force from the spring units of fuel assemblies decrease the contact force of the reference cylinder to the flange of the pressure vessel and the contact force of the pressure cylinder to the cover of the pressure vessel, so there is a need to compensate for the reduction efforts of the pressing of the support cylinder to the flange of the pressure vessel due to the increase of the pressing force from the elastic element. Otherwise, the internals will break away from the supports, which will lead to vibration as their own, and fuel assemblies, and regulators, have significantly reduced the reliability and safety of the reactor.

The weakening of the pressure vessel internals to the supports can also occur due to stress relaxation in the spring heads fuel assemblies and known elastic element under the action of high temperature and radiation.

In the conditions of limited space, exhaust in a nuclear reactor for placement of the elastic element, the increase of the pressing force (load bearing capacity) can be achieved, for example, by increasing the wall thickness of the toroidal ring segment. In this case, simultaneously with the increase of linear load on the pipe reduces its elastic deformation (both relative and absolute), and also decreases the relaxation resistance of such pipes.

It is also known device /2/ (RF Patent No. 2061263) for fixing the active zone containing the reference cylinder, mounted on the flange on the pressure vessel of a nuclear reactor, the elastic element comprising a number of adjacent ring segments are placed between the flanges of the supporting and pressure cylinder and biasing the cover of the pressure vessel. The ring segments of the elastic element is made in the form of helical springs, which fits planted cylindrical rings. The compression is performed by sealing the main connector of the pressure vessel. This creates a clamping force on the flange of the support cylinder, which, along with the force from the spring units of fuel assemblies, biasing pressure cylinder, and the force from the weight of the support cylinder with fuel loading presses the supporting cylinder to the flange of the pressure vessel and holds the t ascent and vibration when exposed to a differential pressure of the fluid, circulating in the reactor. Also creates a clamping force on the flange of the pressure cylinder, which, along with the force from the spring units of fuel assemblies and the buoyancy force of the pressure cylinder of the pressure drop across it when the circulation of the coolant in the reactor presses the pressure cylinder to the cover flange of the pressure vessel.

The known device /2/ compared with the known device /1/ can provide more significant linear load and elastic deformation, since the elasticity of the device /2/ the sum of the elasticity of the cylindrical rings and the elasticity of cylindrical helical springs made from more durable compared to /1/ stainless steel. However, in the conditions of transition to the loading of the reactor fuel assemblies with a frame made of zirconium alloy instead of fuel assemblies with stainless steel frame, relaxation springs fuel assemblies and components of the elastic element, and in the limited space allowed in a nuclear reactor for placement of the elastic element, this increase of the pressing force may not be sufficient.

Similarly with /1/ device /2/ with increasing wire diameter of the spring simultaneously with the increase of the linear load on the spring is reduced to its elastic deformation (both relative and absolute), and t is the train decreases the relaxation resistance of the spring.

Both of the known device /1, 2/ at initial transverse compression (when sealing the main connector of the reactor) are deformed plastically. With increasing initial compression plastic deformation of these devices increases, and the magnitude of elastic deformation change slightly, which in combination with low values of residual elastic strain is a disadvantage of these known devices.

It should be noted that the main criterion for the health of the elastic element in the known devices, /1/ and /2/ is enough pressure on it (sufficient load-bearing capacity), providing the assured pressure support cylinder to the flange of the pressure vessel. Measured by the health criteria of the elastic element is the minimum permissible residual elastic strain corresponding to the minimum allowable residual force on it, which is measured in the cold state of the reactor. That is, the necessary conditions of health of the elastic element are sufficient residual linear load on the pipe /1/ spring /2/, and sufficient residual elastic deformation that can be measured with some precision on the reactor after cooling and removal cap pressure vessel.

It is also known device /3/ (Patent P is No. 2124237) for fixing the active zone, different from the /1/ and /2/ the fact that each of the annular segments of the elastic element is designed as a multilayer stack of plates, lay evenly on the perimeter of the segment top and bottom, and place the lower and upper bearing is displaced in a plane relative to each other by a half pitch. This device was supposed to increase the carrying capacity of the elastic element by increasing the mass of the metal elastic components, filling the cross section of the annular groove, and the resources of the elastic element by a significant decrease in relaxation when loading it in the region of elastic deformation. Studies single-span models of this device when modeling linear design pressures and temperatures showed that the region of elastic deformation models of this device is limited to 2 mm, that is, when the full deformation of more than 2 mm, the device is exposed to plastic deformation. For a reactor full of deformation of the elastic element is less than 2 mm is insufficient, due to tolerances in the axial dimensions of the elements of the VVER-1000 reactor, the maximum difference of the full deformation of the elastic element is 1 mm, the relative relaxation proven models of this device has almost the same values as compared with the tested models /1/. Analysis of the impact of the scheme n is gryzenia for a single proven device and multi-device (as declared in /3/) showed the rigidity of the multi-device four times higher than the stiffness of a single device, so if the same linear load, the elastic deformation of the multi-unit decrease in four times. That is, this device may not provide the desired project minimum allowable residual elastic deformation.

In the description of the /3/ are considered two schemes of arrangement of the elastic element in a nuclear reactor:

scheme 1 - elastic element is fixed on the flange of the support cylinder and cooperates with the flange of the support cylinder and the flange of the pressure cylinder;

scheme 2 - elastic element is fixed on the flange of the pressure cylinder and cooperates with the flange of the pressure cylinder and the flange of the lid of the pressure vessel.

The first scheme of fixing the elastic element was also seen in /2/ and its advantage is the possibility of measurement of residual elastic deformation of the elastic element in a cold state without unloading fuel assemblies from the support cylinder.

The peculiarity of the second circuit fixing the elastic element is that the force from spring units of fuel assemblies, biasing pressure cylinder, presses the pressure cylinder to the lid of the pressure receptacle and does not affect the pressure of the reference cylinder to the flange of the pressure vessel.

Advantage is the your second scheme is more convenient access to the elastic element during installation and dismantling. However, much more difficult measurement of residual elastic deformation of the elastic element without unloading fuel assemblies, as the residual stress on their spring blocks can raise the pressure cylinder together with the elastic element relative to the flange of the main connector of the pressure vessel.

In addition, in both of these schemes /3/ temperature deformation of the elastic element is 1.5 times more than in the scheme of fixing the elastic element /1/, that is, after thermal loading of the elastic element residual linear load and the residual elastic deformation to decrease in these schemes to a greater extent, because the stiffness of the elastic element when the elastic unloading is significantly higher than in elastic-plastic loading.

In /1/ elastic element is fixed on the flange of the support cylinder and cooperates with the flange of the support cylinder and the flange of the lid of the pressure vessel. In this embodiment, the fixing elastic element presses not push the cylinder to the cover flange of a pressure vessel (pressure of the pressure cylinder to the cover flange of the pressure vessel is only due to the efforts from the spring units of fuel assemblies), which is a disadvantage of this scheme fastening.

The closest technical solution is known /3/.

Disclosure of inventions

A the Yu of the invention is to improve the reliability and security of a nuclear reactor.

The objective of the invention to increase the bearing capacity, the area of elastic deformation and damping properties of the elastic element.

The technical result - the reduction of vibration internals and the active zone of the nuclear reactor during the transition to fuel load, including fuel assemblies with Zirconia framework.

The proposed device for fixing the active zone of the nuclear reactor with pressurized water includes a support cylinder mounted on the flange on the pressure vessel, the elastic element comprising a number of adjacent ring segments disposed between the flange of the support cylinder and the flange of the lid of the pressure vessel and interacting with them.

What's new is that each of the annular segments of the elastic element contains the segmented support plate, on which is placed and fixed by means of clamping devices clamping devices, each of which includes a support glass placed in him and locked with the locking devices of a work item from a pre-pressed thermally expanded graphite, and the gland in contact with the working element or locking device.

The locking device designed to prevent the ingress of thermally expanded graphite in the cylindrical gap between naru is Noah surface of the pressure sleeve and the inner surface of the base glass, can be done in the following ways:

option 1 - Locking device made in the form of a ring having on the perimeter of the thin-walled cylindrical collar in contact on the outer diameter with the inner cylindrical surface of the base Cup and the inner diameter with a working element of thermally expanded graphite, while the locking device is located between the pressure sleeve and a work item from a thermally expanded graphite;

option 2 - Locking device contains two identical locking split ring in contact with each other on the end surfaces and the contacting outer diameters of the inner cylindrical surface of the support glass at the top of the locking ring is in contact with the push sleeve and the sections of the rings are in different vertical planes;

option 3 - the Locking device comprises three locking rings: two rings for option 2 and the third split ring of a smaller diameter that the outside diameter is in contact with two rings for option 2 on its upper side with a packing sleeve, the height of the third ring is greater than height rings for option 2, and sections of all three rings are in different vertical planes.

The locking device is designed for fastening and fixing the clamping device is a TV segment on the plate. Each locking device includes two clamps mounted on the segmental plate having cylindrical protrusions extending in a response step bayonet grooves made on the outer side surface of the glass clamping device.

Data holding devices can reduce the time of Assembly-disassembly clamping devices on the segment plate and, consequently, to reduce exposure doses of personnel in the conduct of these operations.

To prevent slippage of the glass of the clamping device relative to the segmental plate on the bottom end of the support body is made of cylindrical protrusion, which comes in response to axial hole made in the segmental plate. This prevents breakage (forming) clamps. Slippage of the glass of the clamping device relative to the segmental plate at the implementation of the first scheme of fixing the elastic element would be possible due to the different coefficients of linear expansion of the materials of the support cylinder, which is fixed to the segmental plate, and the cover of the pressure vessel, and during the implementation of the second circuit fixing the elastic element due to the different coefficients of linear expansion of the materials of the pressure cylinder, the flange of which is secured a segmental plate, and cap the pressure vessel.

To prevent any possible escape of the pressure sleeve of the base glass of the clamping device when the mounting-Dismounting device on the segment plate or by lifting the lid of the pressure vessel, pressure on the sleeve of the clamping device is made of at least one of the flats, and at the upper end of the support Cup fixed at least one response striker.

A brief description of the drawings.

1 shows a diagram of a nuclear reactor, a longitudinal section.

Figure 2 shows the site And figure 1 - scheme of fixing the elastic element on the flange of the pressure cylinder, in which the elastic element is in contact with the flange of the pressure cylinder and the flange of the pressure vessel.

Figure 3 shows the node a figure 1 - scheme of fixing the elastic element on the flange of the support cylinder, in which the elastic element is in contact with the flanges of the supporting and pressure cylinders.

Figure 4 shows cross-section B-B in figure 2.

Figure 5 shows the node In figure 2 in an enlarged scale.

Figure 6 shows the form G figure 5.

7 shows the section d-D figure 5.

On Fig shows E figure 5.

Figure 9 shows the node W figure 5 - options 1-3 locking devices.

Figure 10 shows a perspective view of the scheme of fixing the clamping device.

The reactor device for securing the support cylinder with the active area is Soboh the vessel 1 under pressure, the sealing cover 2. In the vessel 1 on the flange 3 has a base 4 cylinder with an active area containing the fuel assemblies 5. According to figure 2 (scheme 2) between the end cap 2 and the flange 6 of the pressure cylinder cooperating with the flange 3 of the reference cylinder, has an elastic element that contains the number of segments 7 (Fig 4)fixed to the flange 6. According to figure 3 (scheme 1) between the flange 3 of the reference cylinder and the flange 6 of the pressure cylinder communicating with the end cover 2, has elastic element containing the number of segments 7, secured to the flange 3 of the reference cylinder. Each of the segments 7 includes a support segment plate 8, on which is placed and fixed clamping devices, each of which (figure 5) includes a support Cup 9, which is placed and locked with the locking device 10 work item 11 of the pre-compressed thermally expanded graphite, and the gland 12 in contact with the working element or locking device. Fixing device for fusing and fixing of the clamping device on the segment plate contains two clamps 13 (7), mounted on the segmental plate 8 having a cylindrical protrusions 14 extending in the response speed bayonet slots 15, are made on the outer side surface of the support Cup 9 paginagialleithu (6, 7). On the lower end of the support body is made cylindrical projection 16 (Fig. 5, 7), which comes in response to axial hole 17 made in the segmental plate. To push the sleeve 12 of the clamping device (7, 8) made of at least one of the flats 18, and at the upper end of the support Cup fixed at least one response striker 19.

The vessel 1 (Fig. 1) is provided with a suction inlet 20 and the outlet pipe 21 and forms with the wall of the support cylinder 4 and lowering the channel 22 of the brine circuit in the reactor.

The implementation of the invention

The device operates as follows.

The cold fluid enters the pipe 20, having a buried channel 22 through the holes in the bottom of the supporting cylinder 4 is adjudged to be in an active zone, takes heat from the fuel assemblies 5 and heated leaves through pipe 21 from the reactor. During the flow of coolant through the reactor pressure decreases and the pressure difference at the inlet and outlet is the force that pushes the supporting cylinder 4 up, if the weight of the support cylinder with an active area smaller than the buoyancy force. Pressure reference of the cylinder to the support is a necessary condition for retention of the support cylinder and the fuel assemblies from the vibration displacements (causing wear and damage)that may occur under the influence of flowing teplonositel is. When sealing the main connector cover 2 compresses work items 11 clamping the elastic element 7, which creates the necessary contact force of the flange of the support cylinder to the support. Because work items clamping devices made of pre-compressed and locked thermally expanded graphite having a high elastic properties and bearing capacity, multiple clamping devices capable of withstanding the desired draft load, while the residual elastic deformation will be 5-10 times higher than in the prototype /1-3/. Studies of models of clamping devices showed that, with sufficient residual elastic deformation of the clamping devices (not less than 2 mm) rated load capacity of the elastic element is achieved by their number (for VVER-1000 reactor is not more than 24 pieces). That is, for the proposed device, the elastic element health criteria (load-carrying capacity of the elastic element and its residual elastic strain) do not contradict each other (with the increase of the bearing capacity of the elastic element its residual elastic deformation is not reduced, as in /1-3/). In addition, the proposed design of the clamping device has good damping properties due to internal friction in thermal expanded graphite and a friction locking element is in the inner cylindrical surface of the supporting glass in the area of elastic deformation of the clamping device.

Thus, the proposed design of the elastic element makes it possible to increase the contact force of the reference cylinder to the required size without increasing its dimensions, to increase the elastic and damping properties, while increasing its working life, long-term thermal Cycling loading.

Sources of information

1. Drawing 1135.01.04.000. Mine with the screen. Izhora plant, 1972.

2. The patent of Russian Federation №2061263.

3. The patent of Russian Federation №2124237.

1. Device for securing active zone of the nuclear reactor with pressurized water containing the reference cylinder, mounted on the flange on the pressure vessel, the elastic element comprising a number of adjacent ring segments disposed between the flange of the support cylinder and the flange of the lid of the pressure vessel and interacting with them, characterized in that each of the annular segments of the elastic element contains the segmented support plate, on which is placed and fixed by means of clamping devices clamping devices, each of which includes a support glass placed in him and locked with the locking devices of a work item from a pre-pressed thermally expanded graphite and gland in contact with the working element or locking device.

2. the device for fixing the active zones according to claim 1, characterized in that the locking device is made in the form of a ring having a perimeter thin-walled cylindrical collar in contact on the outer diameter with the inner cylindrical surface of the base Cup and the inner diameter with a working element of thermally expanded graphite, while the locking device is located between the pressure sleeve and a work item from a thermally expanded graphite.

3. Device for securing active zones according to claim 1, characterized in that the locking device comprises two identical locking split ring in contact with each other on the end surfaces and the contacting outer diameters of the inner cylindrical surface of the support glass at the top of the locking ring is in contact with the push sleeve and the sections of the rings are in different vertical planes.

4. Device for securing active zones according to claim 1, characterized in that each locking device comprises two clamps mounted on the segmental plate having cylindrical protrusions extending in a response step bayonet grooves made on the outer side surface of the supporting glass clamping device.

5. Device for securing active zones according to claim 1, characterized in that the bottom end of the supporting glass of the implementation of the Yong cylindrical protrusion, which comes in response to axial hole made in the segmental plate.

6. Device for securing active zones according to claim 1, characterized in that the pressure on the sleeve of the clamping device is made of at least one of the flats, and at the upper end of the support Cup fixed at least one response striker.

7. Device for securing active zones according to claim 3, characterized in that the locking device comprises a third split ring of a smaller diameter that the outside diameter is in contact with the two specified in clause 3 rings on its upper side with a packing sleeve, the height of the third ring is greater than height of rings according to claim 3, and sections of all three rings are in different vertical planes.



 

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