JPH03277994A - Tank-shaped fast breeder - Google Patents

Abstract

PURPOSE:To suppress the disturbance of the surface of sodium in a vessel and to prevent the involution of the cover gas from the surface by providing a flow path deflecting part prescribing the flow in the vicinity of the surface of a cooling material between a circulation pump and a heat exchanger. CONSTITUTION:A cooling material is sent in the core 8 of a reactor vessel 1 by the circulation pump 4 provided so as to pierce the roof slab 3 closing the opening part of the reactor vessel 1 to be circulated. A heat exchanger 6 performs the heat exchange with the cooling material to the take out heat to the outside of the vessel 1. Flow path deflecting plates 15 are inserted between the pump 4, the heat exchanger 6 and a core upper mechanism 10 through the slab 3 and immersed in the lower part of liquid sodium 2 being the cooling material from the surface 13 thereof. The flow of sodium 2 passing through the gap between the pump 4 and the heat exchanger 6 in the vicinity of the surface 13 of sodium 12 to go toward the mechanism 10 is bent in a definite direction by the deflecting plates 15. Therefore, a stable swirl is generated around the mechanism 10 and the generation of a vortex in the surface 13 is suppressed and the involution of cover gas is prevented.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention deals with fluctuations in the coolant liquid level within the reactor vessel.

This invention relates to a tank-type fast breeder reactor that suppresses ripples, prevents gas entrainment, and reduces imaging and thermal stress applied to the reactor vessel and internal equipment.

(Prior art) In general, in a fast breeder reactor, the upper opening of the reactor vessel is roughly closed with a roof slab, and the reactor, in which a large number of fuel assemblies are installed, is supported by a core support mechanism in the lower part of the reactor vessel. At the same time, a core upper mechanism is installed in the upper part of the core, penetrating the roof slab, and a plurality of circulation pumps and intermediate heat exchangers are arranged around the outer periphery of the core upper mechanism, hanging from the roof slab. ing. In addition, liquid metallic sodium is used as a coolant in fast breeder reactors, and the reactor core is cooled with low-temperature sodium pumped in by circulation pumps. The sodium, which has cooled to a high temperature after cooling the reactor core, is cooled by exchanging heat with the secondary coolant in a heat exchanger, and then pumped into the reactor core again by a circulation pump.

FIGS. 6 and 7 show longitudinal sections of tank-type fast breeder reactors showing conventional examples. Note that FIG. 7 shows a cross section taken in the direction of the arrows ■-■ in FIG. 6.

In FIGS. 6 and 7, liquid sodium 2, which is a coolant, is stored in a reactor vessel 1, and the upper opening of the reactor vessel 1 is closed by a roof slab 3. The roof slab 3 is provided with a circulation pump 4 passing through the roof slab 3, and a secondary sodium inlet 5a and outlet 5 at the top.
A heat exchanger 6 with a heat exchanger 6 is inserted, the lower part of each of which is supported by a partition wall 7.

Further, in the center of the reactor vessel 1, a reactor core 8 in which a large number of fuel assemblies are installed is arranged by a core support mechanism 9. A core upper mechanism IO is disposed in the upper part of the core 8, passing through the roof slab 3.

The flow of coolant with this configuration cools the core 8 by the low-temperature sodium 2b sent into the core 8 by the ring pump 4. The high-temperature sodium 2a, which has become hot by cooling the core 8, flows radially upward obliquely as shown by the arrow along the lower end of the upper core mechanism 1O, and a part of the sodium flows from the inlet window 11 of the heat exchanger 6 to the heat exchanger. 6 into the heat exchanger 6
It exchanges heat with the secondary sodium through a large number of heat exchanger tubes (not shown) built into the heat exchanger 6, and the temperature becomes low.
It flows out from the outlet 12 of. The low temperature sodium 2b flowing out from the outlet 12 is guided by the circulation pump 4 and sent into the reactor core 8 again.

In this way, the heat of the core 8 is transferred to the secondary sodium by the heat exchanger 6, but the flow of the high-temperature sodium 2a is quite complicated. That is, as described above, the sodium 2a that has passed through the core 8 flows diagonally upward radially as shown by the arrows along the upper core mechanism 1O, with one direction flowing toward the inlet window 11 of the heat exchanger 6, and the other flowing toward the inlet window 11 of the heat exchanger 6. The main flow hits the wall of the reactor vessel l and the wall of the circulation pump 4, and becomes an upward flow. This mainstream is sodium liquid level 1
In the vicinity of 3, the surface flow becomes complicated as shown in FIGS. 6 and 7. Note that the flow hitting the wall of the circulation pump 4 becomes an upward flow toward the sodium liquid level 13 along the wall.

(Problem to be Solved by the Invention) However, due to the complicated surface flow, the sodium liquid level 13 is disturbed and fluctuated, causing ripples.

In particular, when the circulation pump 4 and heat exchanger 6 are arranged symmetrically as shown in FIGS. The flow toward the upper core mechanism IO also becomes a symmetrical flow.

That is, as shown in FIGS. 6 and 7, the flow of high-temperature sodium 2a passing through the gap between the circulation pump 4 and the heat exchanger 6 hits the core upper mechanism 10 and becomes a flow that tends to split into left and right sides. Therefore, this flow is transferred to the adjacent circulation pump 4.
The liquid collides with the flow that has passed through the heat exchanger 6, and large liquid level fluctuations and swirling vortices occur in this area.

The large turbulence of the sodium liquid level 13 and the generation of swirling vortices may cause the cover gas 14 to be drawn into the flow from the sodium liquid level 13 in the form of fine bubbles.

If the cover gas 14 is entrained in the flow, the cover gas 14 is guided to the circulation pump 4 and sent into the reactor core 8 via the heat exchanger 6.

The cover gas 14 sent into the reactor core 8 is heated by the reactor core 8 and expands in volume, thereby partially preventing contact between the reactor core 8 and the sodium 2 .

Therefore, cover gas 14. For example, when argon is a gas, the heat transfer coefficient is very poor, less than 1/1000 compared to sodium, so the core 8 becomes overheated in the area where the cover gas 14 passes, causing the core 8 to melt and cause a serious accident. there is a possibility.

Further, the sodium liquid surface 13 is covered with a cover gas 14 having a temperature of about 180°C. Even under normal conditions, the sodium liquid level 13 is exposed to the walls of in-furnace equipment such as the upper furnace mechanism, circulation pump 4, heat exchanger 6, and furnace vessel 1 due to the temperature difference between the high-temperature (500°C or higher) sodium 2a and the cover gas 14. A temperature gradient occurs and thermal stress occurs. As described above, the sodium liquid level 13 fluctuates due to the flow of the high-temperature sodium 2a, which poses a problem of impairing the integrity of the structural material due to thermal fatigue.

As described above, there is a problem in that the sodium liquid level 13 is disturbed in the upper plenum, the cover gas 14 is drawn into the mainstream, and the integrity of the core 8 is impaired. Further, there is also the problem that the soundness of the structural material is impaired due to thermal fatigue due to repeated thermal stress caused by fluctuations in the liquid level 13.

The present invention has been made to solve the above problems, and it prevents core melting accidents by suppressing liquid level fluctuations and ripples and swirling vortices in the upper brenum, and preventing entrainment of cover gas. It is also an object of the present invention to provide a highly reliable tank-type fast breeder reactor that prevents repeated thermal stress from occurring in reactor equipment that comes into contact with the sodium liquid level and ensures the integrity of the reactor core and structural materials.

[Structure of the invention]

(Means for Solving the Problems) A first invention provides a roof slab disposed to close an upper opening of a reactor vessel which houses a liquid metal coolant and has a liquid surface, and a roof slab provided inside the reactor vessel. A circulation pump is installed through the roof slab to feed coolant into the reactor core installed in the reactor vessel and circulate the coolant inside the reactor vessel, and a circulation pump is installed through the roof slab to circulate the coolant inside the reactor vessel, and a circulation pump that exchanges heat with the coolant to circulate the coolant outside the reactor vessel. In a tank-type fast breeder reactor equipped with a heat exchanger for extracting heat from
A flow path deflection plate is provided between the circulation pump and the heat exchanger, inserted from the upper part of the roof slab, reaching the lower part of the coolant liquid level, and regulating the flow near the liquid level. shall be.

The second invention includes a roof slab disposed to close an upper opening of a reactor vessel that houses a liquid metal coolant and has a liquid level, and a roof slab that is arranged to close an upper opening of a reactor vessel that houses a liquid metal coolant and that supplies a coolant to a core provided in the reactor vessel. a circulation pump provided through the roof slab for circulating coolant inside the reactor vessel; and a heat exchanger for exchanging heat with the coolant and extracting heat to the outside of the reactor vessel. In a tank-type fast breeder reactor equipped with
The circulation pump is characterized in that a flow path deflecting plate is provided on the outer circumferential portion of the circulation pump to deflect the flow path of the coolant flowing out from the core and suppress the flow velocity.

(Function) In the first invention, the flow of sodium near the liquid surface passes through the gap between the circulation pump and the heat exchanger, is bent in a certain direction by the flow path deflection plate, and a flow is formed along the upper core mechanism. , a constantly stable swirling flow is formed around the upper core mechanism. Therefore, opposing flows and colliding flows are eliminated, and the generation of fluctuating undulations and swirling vortices in the sodium liquid level can be suppressed, and entrainment of the cover gas can be prevented. moreover,
The sodium liquid level is also stable, reducing repeated thermal stress on structural materials due to liquid level fluctuations and ripples.

In the second invention, the sodium flowing out from the core flows obliquely upward along the lower edge of the upper core mechanism, one flow toward the inlet window of the heat exchanger, and the other flow toward the outer wall of the circulation pump. flows along. and,
The flow toward the sodium liquid surface is deflected and dispersed by a flow path deflection plate provided in the circumferential direction of the outer wall of the circulation pump. This suppresses the flow velocity toward the sodium liquid level, suppresses fluctuations and ripples in the sodium liquid level, and prevents entrainment of the cover gas. In addition, the sodium liquid level is stable, reducing repeated thermal stress on structural materials due to liquid level fluctuations and ripples.

(Example) A first example of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1 showing a tank-type fast breeder reactor according to the present invention, inside a reactor vessel 1, there is liquid sodium 2, which is a coolant.
is housed, and the upper opening of the reactor vessel l is the roof slab 3.
is blocked by. A circulation pump 4 and a heat exchanger 6 having an inlet 5a and an outlet 5b for secondary sodium at the upper part are inserted through the roof slab 3, and the lower part of each is supported by a partition wall 7. .

A reactor core 8 in which a large number of fuel assemblies are installed is disposed in the center of the reactor vessel 1 by a core support mechanism 9. A core upper mechanism IO is disposed in the upper part of the core 8, passing through the roof slab 3.

The flow of coolant with this configuration cools the core 8 by the low-temperature sodium 2b sent into the core 8 by the circulation pump 4. The high-temperature sodium 2a, which has become hot by cooling the core 8, flows radially upward obliquely as shown by the arrow along the lower end of the upper core mechanism IO, and flows into the heat exchanger 6 from the inlet window 11 of the heat exchanger 6. It passes through a large number of heat exchanger tubes (not shown) incorporated in the heat exchanger 6, exchanges heat with the secondary sodium, becomes low in humidity, and flows out from the outlet 12 of the heat exchanger 6. The low temperature sodium 2b flowing out from the outlet 12 is guided by the circulation pump 4 and sent into the reactor core 8 again.

A flow path deflection plate 15 is provided between the circulation pump 4, the heat exchanger 6, and the upper core mechanism 10, which is inserted from the top of the roof slab 3 and immersed below the sodium liquid level 13 of the coolant.

Therefore, the flow of sodium from the side of the reactor vessel 1 near the sodium liquid level 13 toward the upper core mechanism IO through the gap between the circulation pump 4 and the heat exchanger 6 is caused by the circulation pump 4 and the heat exchanger 6. The flow path deflecting plate 15 provided between the upper core mechanism 10 bends the flow path in a certain direction as shown in FIG.

Therefore, a stable swirling flow is always generated around the upper core mechanism 1O, and unstable flows due to collisions of flows and opposing flows are eliminated, and fluctuations in the sodium liquid level 13 and generation of rippled swirling vortices are prevented. This can prevent the cover gas 14 from being involved. Furthermore, these effects can prevent repeated thermal stress from being applied to the structural material.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3, 4, and 5.

In FIG. 3, which shows a tank-type fast breeder reactor according to the present invention, liquid sodium 2 as a coolant is housed in the reactor vessel, and the upper opening of the reactor vessel 1 is closed by a roof slab 3. A circulation pump 4 and a heat exchanger 6 having an inlet 5a and an outlet 5b for secondary sodium in the upper part are inserted into the roof slab 3 through the roof slab 3,
The lower part of each is supported by a partition wall 7.

Further, in the center of the reactor vessel 1, a reactor core 8 in which a large number of fuel assemblies are installed is arranged by a core support mechanism 9. A core upper mechanism 10 is disposed above the core 8.

The flow of coolant with this configuration cools the core 8 by the low temperature sodium 2b sent into the core 8 by the circulation pump 4. The high-temperature sodium 2a, which has reached a high temperature by cooling the reactor core 8, flows diagonally upward radially along the lower end of the core upper mechanism 10 as shown by the arrow, and a portion of the sodium 2a flows into the heat exchanger 6 through the heat exchanger artificial window 11. It passes through a large number of heat exchanger tubes (not shown) incorporated in the heat exchanger 6, exchanges heat with the secondary sodium, becomes low temperature, and flows out from the outlet 12 of the heat exchanger 6. The low-temperature sodium 2b flowing out from the outlet 12 is guided to the circulation pump 4 and sent into the reactor core 8 again. @ Sodium liquid level 13 on the outer wall of the ring pump 4
A flow path deflecting plate 17 is provided to suppress the upward flow of sodium toward the flow path and change the flow path.

Note that this flow path deflection plate 17 can also be provided in multiple stages along the axial direction.

That is, in FIG. 3, which shows the state of flow from the core 8 to the circulation pump 4 with arrows, a plurality of flow path deflection plates 17 are provided on the outer wall surface of the circulation pump 4 and located directly below the sodium liquid level 13. ing. This flow path deflecting plate 17 has a large number of flow holes 16 as shown in FIGS. 4 and 5.
It is made of a perforated plate with

The operation of the tank-type fast breeder reactor according to the present invention configured as described above will be explained. The high-temperature sodium 2a flowing out from the core 8 flows obliquely upward along the lower end of the core upper mechanism IO, and one side flows toward the inlet window 11 of the heat exchanger 6. The other side flows toward the outer wall of the circulation pump 4 and flows along the outer wall of the circulation pump 4, and the flow toward the sodium liquid level 13 is deflected and dispersed by the flow path deflection plate 17 provided in the circumferential direction of the outer wall of the circulation pump 4, and the sodium liquid is The flow velocity toward the surface 13 is suppressed, and fluctuations and ripples in the sodium liquid level 13 can be suppressed.

Therefore, the high temperature sodium 2a flows along the circulation pump 4 as shown by the arrow in FIG.
The flow toward is suppressed by the channel deflecting plate 17, and the flow direction is deflected. Therefore, fluctuations and ripples in the sodium liquid level 13 can be suppressed, and entrainment of the cover gas 14 from the sodium liquid level 13 caused by disturbances in the sodium liquid level 13 can be prevented. In addition, the sodium liquid level 13 fluctuates due to the channel deflection plate 17.

It is possible to prevent repetitive thermal stress caused in structural materials due to ripples.

〔Effect of the invention〕

According to the present invention, by providing a flow path deflection plate, turbulence of the sodium liquid level in the reactor vessel is suppressed, and entrainment of cover gas from the sodium liquid level is prevented, thereby preventing core melting accidents. This will ensure the integrity of the reactor core. In addition, thermal fatigue due to repeated thermal stress generated in structural materials that come into contact with sodium liquid can be reduced, and the integrity of the structural materials can be ensured.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a first embodiment of a tank-type fast breeder reactor according to the present invention, and FIG. 2 is a cross-sectional view taken along the direction of the ■-■ arrow in FIG. 1. FIG. 3 is a longitudinal sectional view showing a second embodiment of the present invention, FIG. 4 is a partially enlarged plan view of the deflection plate in FIG. 3, and FIG. 5 is a longitudinal sectional view of FIG. 4. , FIG. 6 is a longitudinal cross-sectional view showing a conventional tank-type fast breeder reactor, and FIG. 7 is a cross-sectional view taken along the direction of arrows -■ in FIG. 6. 1... Reactor vessel 2... Liquid sodium 2a... High temperature sodium 2b... Low temperature sodium 3... Roof slab 4... Circulation pump 5a... Secondary sodium inlet 5b... Secondary sodium outlet 6...heat exchanger 7
... Partition wall 8 ... Core 9 ... Core support mechanism lO ... Core upper mechanism 13 ...
・Sodium liquid level 14...Cover gas 1
5.17...Flow path deflection plate 16...Flow hole rod 3

Claims (2)

[Claims] (1) A roof slab is installed to store liquid metal coolant and close the upper opening of the reactor vessel, which has a liquid level, and a roof slab is installed to close the upper opening of the reactor vessel, which houses liquid metal coolant and has a liquid surface. A circulation pump provided through the roof slab for circulating coolant in the reactor vessel, and a heat exchanger for exchanging heat with the coolant and extracting heat to the outside of the reactor vessel. In a tank-type fast breeder reactor comprising: a flow path inserted from the top of the roof slab between the circulation pump and the heat exchanger and reaching below the coolant liquid level to regulate the flow near the liquid level; A tank-type fast breeder reactor characterized by being equipped with a deflection plate. (2) A roof slab is installed to store liquid metal coolant and close the upper opening of the reactor vessel, which has a liquid level, and a roof slab is installed to block the upper opening of the reactor vessel, which contains liquid metal coolant and has a liquid surface, and a roof slab that is installed to block the upper opening of the reactor vessel, which contains liquid metal coolant, and which supplies the coolant to the reactor core installed in the reactor vessel. A circulation pump provided through the roof slab for circulating coolant in the reactor vessel, and a heat exchanger for exchanging heat with the coolant and extracting heat to the outside of the reactor vessel. A tank-type fast breeder reactor comprising: a flow path deflecting plate for deflecting the flow path of the coolant flowing out from the core and suppressing the flow velocity on the outer periphery of the circulation pump; .