JPS62106395A - Boiling water type reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a pool liquid in addition to the primary coolant in the reactor pressure vessel, and in the event of an abnormality, the pool liquid flows into the reactor core and the reactor shutdown function is activated. This invention relates to a boiling water reactor that has a high degree of safety by being able to exhibit the following characteristics.

[Conventional technology]

In the reactor disclosed in Japanese Patent Application Laid-Open No. 57-175293, pool liquid and cooling water are kept at a predetermined level K in the reactor pressure vessel.
A configuration is described in which pool liquid flows into the reactor core due to a pressure difference caused by a change in fluid density when the fM cooling water temperature rises.

In this conventional example, the cooling water and pool liquid passing through the reactor core are pressurized by a pressurizer, and the reactor type is a pressurized water reactor.

[Problem that the invention seeks to solve]

Since the above-mentioned conventional technology is based on a pressurized water reactor, it has the following problems.

(1) Since it is necessary to install a pressurization device inside the reactor pressure vessel, the reactor equipment is complicated and the equipment is 9 times taller, and it is necessary to assume a depressurization accident event due to loss of pressurization pressure. I don't get it.

(2) As it is a pressurized water reactor, reactor power control must depend on the concentration control of the neutron absorbing material (hereinafter referred to as boron) in the primary coolant. Control responsiveness is poorer than in the control case. It also requires a boron concentration control device.

(3) Since it is a pressurized water reactor, the reactor pressure has to be higher than that of a boiling water reactor, so the reactor pressure vessel is a high pressure vessel, resulting in high equipment costs.

An object of the present invention is to reduce the potential for primary coolant to flow out in a boiling water nuclear reactor, and to ensure that pool liquid flows into the reactor core in the event of an abnormality.

[Means for solving problems]

In order to solve the problems associated with the above-described pressurized water reactor concept, the present invention provides a primary coolant circulation circuit and a pool liquid storage section in the reactor pressure vessel, and provides a primary coolant circulation circuit that passes through the reactor core. It applies the principle of a water reactor.

That is, a feature of the present invention is that a primary coolant circulation flow path passing through the reactor core, a pool liquid holding section, and a vapor phase section formed above the pool liquid holding section are provided in the reactor pressure vessel. A communicating passageway is installed in the upper part of the reactor core and the lower part of the reactor core, and a heat exchanger is provided in the primary coolant circulation flow path for exchanging heat with each part of the system.

[Effect]

By boiling the primary coolant in the reactor core, the generated steam pressure can simultaneously pressurize and control both the primary coolant and the pool liquid to a predetermined pressure, making it possible to eliminate the need for a dedicated pressurizing device.

Since the reactor output can be controlled by controlling the core flow rate and the amount of void generation, the above-mentioned boron concentration control device is not required, and control responsiveness can be greatly improved.

Furthermore, since the boiling water reactor principle is used, the reactor operating pressure can be reduced to about half that of a pressurized water reactor.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Inside the reactor pressure vessel 1, the downcomer 2° circulation pump 4
, riser 3 constitutes a primary coolant circulation circuit. A pool liquid containing boron, which is a neutron absorbing material, is stored outside this circulation circuit.

The primary coolant that is forcibly circulated by the circulation pump 4 is heated in the reactor core 5, reaches a boiling state, and ascends the riser 3 in the form of a gas-liquid two-phase flow. Of the two-phase flow that exits the riser 3, steam is condensed and cooled in the upper heat exchanger 8 in the vapor phase section 12. Further, the saturated water is cooled in the lower heat exchanger 9 to obtain subcooled water. As described above, the primary coolant circulation circuit constitutes a closed cycle inside the reactor pressure vessel 1, and care is taken to prevent the primary coolant from flowing out of the system.

A lower passage 6 and an upper passage 7 are installed in the lower and upper parts of the reactor core 5 to connect the primary coolant side and the pool liquid side in a driftwood manner. In the upper passage 7, the primary coolant side steam section pressure is transmitted to the pool liquid side. In the lower passage 6, care is taken to balance the pressure on the primary coolant side and the pressure on the pool C night side, as shown in the formula below, so that no flow occurs between the two fluids.

(Primary coolant side pressure) P2 = P1 + ΔP (G) + ρtg
H...-■ (Pool liquid side) P2=Pl+ρ2
gH・・・■Pa・ΔP (G) = (ρ2−ρl)
gH...■Where, ΔP(G) Flow pressure loss on the secondary coolant side ρ, Secondary coolant density ρ2: Pool night density H2 Position head difference between the upper and lower passages g: Gravitational acceleration, that is, the above ■ As shown in the equation, the pressure loss ΔP (G) due to the movement of the primary coolant passing through the reactor core, the density difference between the primary coolant and the pool liquid (ρl-ρ2), and the positional head difference H between the upper and lower passages. Care has been taken to balance the product of

Now, if we assume an event where the secondary heat removal source of the upper heat exchanger 8 or the lower heat exchanger 9 is lost, the temperature of the primary coolant will rise and the density will decrease, so the pressure shown in equation The balance is lost and the pool liquid is in the primary coolant circulation circuit.
In other words, it will flow into the reactor core.

Furthermore, even if we consider an event where the circulation pump 4 stops, the pressure balance of equation (2) will collapse and the pool liquid will flow into the reactor core.

As mentioned above, boron, which is a neutron absorbing material, is added to the pool liquid, so the inflow of the pool liquid achieves the reactor shutdown function.

The circulation pump 4 is a variable speed pump, and by controlling the rotation speed of this pump, it changes the 'FI' in the core,
Furnace output can be controlled.

Core/i! By changing the amount, the dynamic pressure loss ΔP (G) shown in equation (2) changes, but the fluctuation outside of this change is absorbed as the water level fluctuation at the interface between the primary coolant and the pool liquid in the lower passage 6. Ru.

As described above, according to this embodiment, reactor shutdown can be safely achieved using passive principles based on the laws of physics in response to possible accidental events such as loss of heat removal source in the secondary system and stoppage of the circulation pump. It is possible to provide a nuclear reactor with high safety.

FIG. 2 shows another embodiment of the invention. The difference from FIG. 1 is that there is no primary coolant circulation pump and it is a natural circulation boiling water reactor, and that a valve 11 is installed in the lower passage 6.

Since it is a natural circulation type, ΔP (G) in formula ■
becomes very small, and considering the physical shape, the range in which the pressure balance shown in equation (2) is established is limited to a very narrow range and becomes unrealistic. Therefore, in this embodiment, a valve 11 is installed to mechanically separate the primary coolant side and the pool liquid side. When a disturbance occurs and it is necessary to shut down the reactor, opening the valve 11 causes the pool liquid to flow into the reactor core and shutting down the reactor. However, in this embodiment, the valve 11 is actively opened. It is essential to be open and
Compared to the embodiment shown in FIG. 1, this embodiment is inferior in terms of safety.

In the configuration shown in FIGS. 1 and 2, an upper heat exchanger 8 is provided inside the reactor pressure vessel 1 for transferring heat to the secondary system. A lower heat exchanger 9 is installed so that the primary coolant circulation circuit forms a closed cycle inside the reactor pressure vessel, and care is taken to prevent primary coolant from leaking out of the system.

〔Effect of the invention〕

According to the present invention, the effect of .mu.do is great.

(1) Since the primary coolant circulation circuit is implemented as a closed cycle inside the reactor pressure vessel, the potential for primary coolant leakage can be reduced, improving safety.

(2) A pool liquid containing neutron absorbing material is kept inside the reactor pressure vessel, and in the event of an abnormality, the pool liquid flows into the reactor core based on the passive principle, so the reactor shutdown function can be reliably achieved. , high safety can be ensured.

(3) By using the principle of a boiling water reactor, economic efficiency can be improved by simplifying equipment, improving reactor output controllability, and lowering the design pressure of the reactor pressure vessel.

[Brief explanation of drawings]

1 is a schematic cross-sectional view of the furnace structure.

Claims (1)

[Scope of Claims] 1. A primary coolant circulation flow path passing through the reactor core, a pool liquid holding section, and a vapor phase section formed above the pool liquid holding section are provided in the reactor pressure vessel; A boiling water nuclear reactor characterized in that passages communicating with each other are installed in the upper part of the reactor core and the lower part of the reactor core, and a heat exchanger is provided in the primary coolant circulation flow path for exchanging heat with other parts of the system. 2. A boiling water nuclear reactor according to claim 1, characterized in that the primary coolant and pool liquid are pressurized by the boiling steam pressure of the primary coolant in the vapor phase. 3. A boiling water nuclear reactor according to claim 2, characterized in that a vapor phase section is installed so that the pressures of the primary coolant and the pool liquid are balanced. 4. A boiling water nuclear reactor according to claim 1, characterized in that the primary coolant circulation circuit forms natural circulation using heat generated by the reactor core. 5. A boiling water nuclear reactor according to claim 1, characterized in that a primary coolant circulation pump is installed in the primary coolant circulation circuit to provide forced circulation. 6. A boiling water nuclear reactor according to claim 5, characterized in that the circulation flow rate is controlled by controlling the rotation speed of a circulation pump. 7. A boiling water nuclear reactor according to claim 4, characterized in that a valve for shutting off a flow path is installed in a passage provided in the lower part of the reactor core.