JPH04299299A - Intermediate heat exchanger for fast breeder reactor - Google Patents

Abstract

PURPOSE:To make uniform the flow speed distribution of a tube bundle inlet part, prevent the production of a stagnation part and contrive cost-down of primary coolant and the improvement of heat exchange efficiency and soundness. CONSTITUTION:In order that the flow distribution of coolant of a downcomer to a tube bundle inlet part 27 may be made uniform in regard to the intermediate heat exchanger of a tank fast breeder reactor, a guide plate 40 or a porous resistant plate 42 is provided in an inlet tube 17 near to the tube bundle inlet part 27.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Industrial Application Field] The present invention is an intermediate heat exchanger for a fast reactor, which has an improved structure of the inlet part of a heat transfer tube bundle of secondary coolant in an intermediate heat exchanger for a tank-type fast breeder reactor (hereinafter referred to as a fast reactor). Concerning vessels.

0003

[Prior Art] In general, fast reactors use liquid metal sodium (hereinafter referred to as coolant) as the primary and secondary coolant, and the primary coolant heated in the reactor core is installed inside the reactor vessel. The cooled primary coolant is guided to an intermediate heat exchanger where it exchanges heat with the secondary coolant, and then the cooled primary coolant is sent back into the core.

FIG. 9 shows a conventional fast reactor equipped with an intermediate heat exchanger 11 of the tube primary coolant type. A core part 8 consisting of a core fuel assembly 5, a blanket fuel assembly 6, and a reflector plate 7 is installed in the center of the partition wall 2.

A core upper mechanism 10 and an intermediate heat exchanger 11 are mounted on the roof slab 9 that closes the upper end opening of the reactor vessel 1, and a circulation pump 12 that circulates the primary coolant is mounted on the roof slab 9. is driven by a motor 13 of
The primary coolant in the lower plenum 4 is fed by a high-pressure plenum 15 through an inlet pipe 14 arranged on the discharge side.

As shown in an enlarged view in FIG. 10, the intermediate heat exchanger 11 includes a shroud 16, a secondary coolant inlet pipe 17 disposed in the center of the shroud 16, and this inlet pipe 17.
a secondary coolant outlet pipe 18 disposed outside the shroud 16; a large number of heat transfer tubes 19 disposed within a heat exchanger chamber formed between the secondary coolant inlet pipe 17 and the shroud 16; Upper tube sheet 20 and lower tube sheet 2 supporting each heat exchanger tube 19
1. The shroud 16 is provided with an inflow hole 22 at a position above the partition wall 2 for sucking in the primary coolant, and an outflow hole 23 at a position below the partition wall 2 for sending out the primary coolant to the lower plenum 4. It is provided. Furthermore, heat exchanger tube support mechanisms 24 and 25 are alternately arranged between the shroud 16 and the secondary coolant inlet pipe 17 so that the heat exchanger tubes 19 penetrate therethrough.

In the conventional fast reactor having the above configuration, the primary coolant in the upper plenum 3 flows into the intermediate heat exchanger plenum 26 of the intermediate heat exchanger 11 through the inlet hole 22, and flows into the intermediate heat exchanger plenum 26 of the intermediate heat exchanger 11. It flows inside toward the lower tube plate 21 side, and further flows into the lower plenum 4 through the outflow hole 23.

The primary coolant flowing into the lower plenum 4 is sent to the inlet piping 14 by the circulation pump 12 driven by the drive motor 13, and is then sent to the high pressure plenum 1.
5 and is heated while rising inside the core fuel assembly 6. The heated primary coolant collides with the lower end of the upper core mechanism 10, changes the flow to the reflection direction, and enters the intermediate heat exchanger 11 through the inflow hole 22 again.

On the other hand, as shown in an enlarged view in FIG.
At step 7, the direction of the flow is changed to the outer diameter side and flows into the tube bundle portion, and further flows upward with an oblique flow component between the heat exchanger tube support mechanisms 24 and 25 that support the heat exchanger tubes 19, and flows into the annulus at the tube bundle outlet portion 28. The heat of the primary coolant that has been removed through the secondary coolant outlet pipe 18 having a flow path is taken out to the outside via a secondary system piping (not shown).

FIG. 11 is an enlarged mechanical view of the flow of the coolant outside the tube bundle. As is clear from FIG. 11, the tube bundle inlet section 27 and the tube bundle outlet section 28
Since the flow direction has a horizontal component, heat transfer tube 1
It is conceivable to apply vibration force to 9. Therefore, conventionally, vibration prevention plates 29 are installed at the tube bundle inlet portion 27 and the tube bundle outlet portion 28 to prevent the vibrations.

[0011] Here, as an example, considering the flow outside the heat transfer tubes 9 of which about 7,000 to 8,000 are installed in one intermediate heat exchanger 11, the vibration prevention plate 29 has the lowest vibration resistance, for example. It is composed of an egg crate type (plates arranged in a grid pattern), and the heat exchanger tube support mechanism 24
, 25 consists of an egg crate type flow path closed with a tab. Moreover, the heat exchanger tube support mechanism 31 between the B and C spans shown in FIG. The sides are designed to flow easily. Since both heat exchanger tube support mechanisms 24 and 25 are arranged alternately, the secondary coolant flowing through the tube bundle portion flows through the tube bundle portion with an oblique flow component, thereby improving heat exchange performance. It will be done.

0012

In the conventional fast reactor, in the intermediate heat exchanger 11, it is important for the coolant outside the tubes to flow in a uniformly distributed manner in order to improve the heat exchange efficiency. However, if the flow has an oblique flow component,
At the tube bundle inlet 27, as shown in a partially enlarged view in FIG. 12, variations in the flow velocity distribution occur in the direction of the arrow. The causes of this include the following issues.

That is, the heat exchanger tube support mechanism 25 directly above the vibration prevention plate 29 has an inner side made of, for example, an egg crate with a flow passage blocking tab, which increases flow resistance, and an outer side made of, for example, an egg crate. structure to reduce flow resistance. Therefore, a large amount of the coolant flows on the outer shell side of the heat transfer tube support mechanism 25.

On the other hand, the vibration prevention plate 29 has low flow resistance. Furthermore, since the secondary coolant inlet pipe 17 is a descending pipe and the inertia of the downward flow velocity is strong at the tube bundle inlet portion 27, the tube bundle inlet portion 27 near the lower tube plate 21 and the vibration prevention plate 2
The flow velocity component at the tube bundle inlet portion 27 on the upper surface of the pipe 9 is large, and the variation in the flow velocity distribution becomes large as shown in the figure.

[0015] As described above, when the dispersion of the flow velocity distribution becomes large, the pressure loss becomes dominant in the parts where the flow velocity is high, and the pressure loss accompanied by the vortices increases in the parts where the flow velocity is slow. Therefore, the overall pressure loss in the secondary side system of the intermediate heat exchanger 11 increases. And when the pressure loss increases,
It is necessary to increase the system pressure on the secondary side, increasing the capacity of the secondary coolant pump and increasing the wall thickness as the strength of the piping system increases, resulting in higher costs. In addition, if stagnation occurs due to variations in flow velocity distribution, it will lead to a decrease in the heat exchange performance of the intermediate heat exchanger 11, and also cause uneven temperature distribution, which may cause the heat exchanger tubes 19 to buckle. be.

The present invention has been made to solve the above-mentioned problems, and it makes the flow velocity distribution at the tube bundle inlet 27 uniform, prevents the occurrence of stagnation, reduces the cost of the secondary coolant system, and improves the heat exchange efficiency. It is an object of the present invention to provide an intermediate heat exchanger for a fast reactor that can improve the soundness of the fast reactor. [Structure of the invention]

[0017]

[Means for Solving the Problems] The present invention divides the inside of the reactor vessel housing the reactor core and the primary coolant into an upper plenum and a lower plenum by a partition wall, circulates the primary coolant, and distributes the inside of the reactor vessel inside the reactor vessel. An intermediate heat exchanger is disposed through the partition wall, and heat exchange between the primary coolant and the secondary coolant is carried out through the heat exchanger tubes within the intermediate heat exchanger, and the heat exchange between the secondary coolant and the heat exchanger tubes is performed. In an intermediate heat exchanger for a fast reactor in which a heat transfer tube support mechanism and a vibration prevention plate are installed at the tube bundle section, the tube bundle inlet section, and the tube bundle outlet section, respectively, a guide plate or a porous resistor is installed at the secondary coolant inlet section near the tube bundle inlet section. It is characterized by having a board.

[0018]

[Function] In the present invention, for example, by providing a secondary coolant inlet pipe and a guide plate, the amount of inflow into the tube bundle inlet can be made uniform. Therefore, the flow velocity distribution at the tube bundle inlet becomes uniform, making it possible to prevent stagnation and reduce the cost of the secondary coolant system, as well as improve heat exchange efficiency and soundness. It becomes possible.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained with reference to the drawings. The present invention is characterized only by the structure of the tube bundle inlet of the intermediate heat exchanger, and other points have the same structure as the conventional tank-type fast reactor shown in FIGS. 9 to 12. Only the characteristic parts will be illustrated and explained.

FIG. 1 shows the vicinity of the tube bundle inlet of an intermediate heat exchanger for a fast reactor according to a first embodiment of the present invention, and FIG.
The same parts are given the same symbols. In FIG. 1, reference numeral 27 is a tube bundle inlet portion formed between the lower tube plate 21 and the heat exchanger tube support mechanism 25 at the lower end, and the secondary coolant inlet pipe 17 is connected to this tube bundle inlet portion 27. In addition, the secondary coolant inlet pipe 1
A plurality of guide plates 40 are provided near the tube bundle inlet portion 27 of 7. Note that the support 41 is for fixing the guide plate 40.

The inner shell side of the heat exchanger tube support mechanism 25, which is shown with mesh in FIG. As shown in FIG. 3, the outer body side shown in white in FIG. 1 has only an egg crate type support mechanism 31. Therefore, the heat exchanger tube support mechanism 25 has a structure in which the outer shell side has low flow resistance and allows the coolant to flow easily.

Next, the operation of the first embodiment will be explained. When the coolant flows downward through the secondary coolant inlet pipe 17,
Since the coolant has a strong downward inertial force, the tube bundle inlet 27
A flow velocity distribution is created in which the flow rate is large at the bottom and small at the top. By providing a plurality of guide plates 40, the descending coolant flows along the guide plates 40, so that the tube bundle inlet portion 2
It can be made to flow in at 7. The flow rate distribution at the tube bundle inlet portion 27 becomes uniform, thereby preventing the occurrence of stagnation and reducing the cost of the secondary coolant system.

FIG. 4 shows a second embodiment of the present invention.
A porous resistance plate 42 is provided between the channels partitioned by the plurality of guide plates 40 of the first embodiment, and the hole processing of the porous resistance plate 42 makes the inflow amount of the coolant uniform at the tube bundle inlet 27. This is how it was done.

FIG. 5 shows a third embodiment of the present invention.
The intervals between the guide plates 40 partitioned by the plurality of guide plates 40 of the first embodiment (guide plate ring diameters φD1, D2, D in the figure)
3 and D4), the inflow amount into the tube bundle inlet portion 27 is made uniform.

FIG. 6 shows a fourth embodiment of the present invention. That is, by providing the porous resistance plate 43 at the tube bundle inlet 27, the amount of coolant flowing into the tube bundle inlet 27 is made uniform.

FIG. 7 shows a fifth embodiment of the present invention. That is, by providing the baffle plate 44 at the tube bundle inlet 27, the amount of coolant flowing in at the tube bundle inlet is made uniform.

FIG. 8 shows a sixth embodiment of the present invention. That is, a plurality of guide plates 40 are provided near the tube bundle inlet portion 27 of the secondary coolant inlet pipe 17, and a porous resistance plate 43 is further provided.

[0028] The second to sixth embodiments described above all have the same effects as the first embodiment, so the explanation thereof will be omitted.

[0029]

According to the present invention, by providing a plurality of guide plates at the secondary coolant inlet near the tube bundle inlet or by providing a porous resistance plate at the tube bundle inlet, the flow velocity distribution at the tube bundle inlet can be improved. This makes it possible to prevent stagnation and reduce the cost of the secondary coolant system.
Further, it is possible to improve heat exchange efficiency and health.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of main parts showing an intermediate heat exchanger of a tank-type fast breeder reactor according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a heat exchanger tube support mechanism.

FIG. 3 is a perspective view showing another example of a heat exchanger tube support mechanism.

FIG. 4 is a partial sectional view showing a second embodiment of the present invention.

FIG. 5 is a partial sectional view showing a third embodiment of the present invention.

FIG. 6 is a partial sectional view showing a fourth embodiment of the present invention.

FIG. 7 is a partial cross-sectional view showing a fifth embodiment of the present invention.

FIG. 8 is a partial cross-sectional view showing a sixth embodiment of the present invention.

FIG. 9 is a vertical cross-sectional view showing a conventional tank-type fast breeder reactor.

FIG. 10 is an enlarged vertical cross-sectional view of the intermediate heat exchanger of FIG. 9;

11 is a partial sectional view mechanically showing the flow outside the tube bundle in the intermediate heat exchanger of FIG. 10; FIG.

FIG. 12 is a partial cross-sectional view showing the flow velocity distribution of coolant at the inlet of a conventional tube bundle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Reactor vessel, 2... Partition wall, 3... Upper plenum, 4... Lower plenum, 5... Core fuel assembly, 6... Blanket fuel assembly, 7... Reflector, 8... Core, 9... Roof slab, 10 ...Core upper mechanism, 11...Intermediate heat exchanger, 12...Circulation pump, 13...Drive motor, 14...Inlet piping, 15...
High pressure plenum, 16... shroud, 17... secondary coolant inlet pipe, 18... secondary coolant outlet pipe, 19... heat transfer tube, 20...
Upper tube plate, 21... Lower tube plate, 22... Inflow hole, 23... Outflow hole, 24, 25... Heat exchanger tube support mechanism, 26... IHX plenum, 27... Tube bundle inlet, 28... Tube bundle outlet, 29... Vibration prevention Plate, 31...Egg crate type support mechanism, 32
...Tab, 40...Guidance board, 41...Support, 42,43...
Porous resistance plate, 44... baffle plate.

Claims (1)

[Claims] Claim 1: The inside of the reactor vessel, which houses the reactor core and the primary coolant, is divided by a partition wall into an upper plenum and a lower plenum, and the primary coolant is circulated. A heat exchanger is arranged, and in this intermediate heat exchanger, heat exchange between the primary coolant and the secondary coolant is performed via the heat transfer tubes, and a tube bundle portion and a tube bundle inlet portion of the heat transfer tubes of the secondary coolant, In an intermediate heat exchanger for a fast reactor in which a heat transfer tube support mechanism and a vibration prevention plate are respectively installed at the tube bundle outlet, a guide plate or a porous resistance plate is provided at the secondary coolant inlet near the tube bundle inlet. Features of intermediate heat exchanger for fast reactor.