JPH07111470B2 - Reactor cooling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor cooling system, and more particularly to a reactor cooling system suitable for a reactor coolant purification system.

[Background of the Invention]

In a conventional general reactor cooling system, as shown in FIG. 1, a coolant is taken out from a reactor pressure vessel 1 through a pipe 2, sent to a heat exchanger 4 by a pump 3, and then the heat exchanger 4 is used. After cooling, the loop is returned to the reactor pressure vessel 1 via the pipe 5 to cool the reactor. Cooling of the heat exchanger 4 uses a cooling system of an auxiliary machine or seawater as a cooling source, and heat is exchanged through a pipe 6.

In this configuration, Co-60 and Co- produced in the reactor
Corrosion product nuclides such as 58 adhere to the coolant wetted parts of the pipes and equipment while circulating in the piping system and equipment together with the coolant. Therefore, there is a problem that the worker is exposed to γ-rays emitted from the attached nuclide. On the contrary,
Measures are being taken to reduce the nuclides in the coolant, but this is not complete. Regarding the nuclides that have adhered, measures are being taken to reduce the intensity of γ-rays by installing radiation shields such as lead, but rotating equipment such as pumps should be regularly checked for wear of parts. Since the disassembling work is required, the shielding method has a drawback that it is difficult to apply.

FIG. 1a is a diagram showing a conventional low pressure reactor cleaning system. Since this system has the filter 40 and the mixed bed type demineralizer 41, the reactor pressure is reduced to about 10 kg / cm ² g by the valve 44, and then the filter 40 and the demineralizer 41 are passed. Pump 3 was operating in order to drain water and return it to the reactor with a reactor pressure of 70 kg / cm ² g. Also, when the reactor pressure drops below 10 kg / cm ² g, the pressure loss in the piping and equipment upstream of the pump 3 is 10
Since the NPSH (suction side pressure necessary to prevent cavitation of the pump) of the pump 3 is insufficient and cavitation occurs due to insufficient kg / cm ² g, and the steady flow rate cannot be secured, start the auxiliary pump 45. Measures were taken to secure the NPSH of Pump 3.

As described above, in this method, the pump 45, the valve 43, and the like are in contact with the high-temperature reactor water, and there is a tendency that the radiation dose of the worker especially when inspecting the pump 45 and the like increases.

[Object of the Invention]

The object of the present invention is to effectively reduce the radioactivity adhesion to the pump that is regularly inspected for overhaul, and to reduce the NP of the pump.
It is to provide a reactor cooling device that can reliably secure SH.

[Outline of Invention]

In order to achieve the above object, the present invention provides a first pipe for taking out a first coolant, which is a coolant for a nuclear reactor, and the first pipe.
A cooler for cooling the coolant, a filter desalination device disposed downstream of the cooler for filtering and desalting the first coolant, a pump for boosting the pressure of the first coolant, and In a nuclear reactor cooling device including a second pipe for returning a first coolant to the reactor, the cooler may convert the first coolant in the first pipe into a second pipe in the second pipe. A first cooler that cools by exchanging heat with the first coolant, and a second coolant that is arranged downstream of the first cooler and that is supplied from an accessory cooling system. And a second cooler for cooling the first coolant according to the above, wherein the filter desalting apparatus is a powder precoat type filter, the differential pressure of the filter is maintained at 1.75 kg / cm ² or less, and the pump is , Located at a position sufficiently lower than the water level of the reactor, on the downstream side of the filter desalination apparatus. Further, temperature measuring means for measuring the temperature of the first coolant between the second cooler and the filter demineralizer, and the temperature measured by the temperature measuring means is 200 ° C. or less, The flow rate of the first coolant or the second flow rate
And a control means for controlling the flow rate of the coolant.

According to the invention, the control means are arranged so that the first means in the position of the pump
Since the temperature of the coolant can always be controlled to 200 ° C. or less, where the amount of radioactivity adhering to the pump is very small, the radioactivity adhering to the pump can be effectively reduced. Further, by arranging the pump on the downstream side of the filter desalting apparatus, the radioactivity in the first coolant is removed by the filter desalting apparatus. It greatly contributes to the reduction of radioactivity adhesion.

Further, according to the present invention, by always maintaining the filter differential pressure of the filter desalting apparatus to 1.75 kg / cm ² or less, it is possible to sufficiently suppress the pressure loss by the filter desalting apparatus,
By arranging the pump at a position sufficiently lower than the water level of the reactor, it is possible to secure a sufficient height difference between the reactor water and the pump, so that the suction side pressure of the pump should always be maintained within the allowable range. NPSH can be secured reliably.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. Third
The figure is an example in which the present invention is applied to a reactor coolant cleaning system.

The coolant taken out of the reactor pressure vessel 1 is guided to the regenerative heat exchanger 14 by the pipe 2 and further cooled to 200 ° C. or less by the non-regenerative heat exchanger 4. The outlet temperature of the non-regenerative heat exchanger 4 is measured and monitored by the thermometer 8. The heat exchanger 4 can be cooled by exchanging heat from an auxiliary cooling system 7 that supplies cooling water from a cooling source such as seawater or a river via a pipe 6, or by using a heat source of a nuclear reactor to generate steam. Alternatively, a heat source such as hot water for heating may be used.

A filter desalting device 9 having an ion exchange resin or the like is provided downstream of the non-regeneration heat exchanger 4, and a pump 3 is arranged downstream of the filter desalting device 9 to cool the coolant purified by the filter desalting device 9. It is returned to the reactor pressure vessel 1 through the pipe 5 through the regenerative heat exchanger 14. In the present embodiment, in order to minimize the pressure loss on the suction side of the pump 3, only the minimum equipment is arranged, the piping is designed to be the shortest from the reactor pressure vessel 1, and it is more than the reactor water level. Pump 3 to a lower level
Is installed to secure the NPSH for pump 3.

The primary cooling water system is always in continuous operation, but when the purifying device such as the filter desalting device 9 is stopped, the purifying device can be bypassed by the pipe 12 and the valve 13. Further, when the coolant is discharged to the outside of the system, the valve 11 of the pipe 10 can be opened to discharge the coolant to the radioactive waste treatment system or the like for treatment.

In these operations, although not shown in detail in FIG. 3, the flow rate of the pump 3 or the flow rate of the cooling water pipe 6 is adjusted so that the thermometer 8 does not exceed 200 ° C. According to the present embodiment, the temperature at the position of the pump 3 is about 50 ° C., and the surface dose rate of the pump 3 can be suppressed to a very low level from the characteristics shown in FIG. That is, in this embodiment, the temperature measured by the thermometer 8 is controlled so as to be approximately 50 ° C to 200 ° C.

Incidentally, in the conventional reactor coolant purification system, since the pump 3 was provided on the line of the pipe 2 upstream of the regenerative heat exchanger 14, the temperature at this position was as high as about 280 ° C. Therefore, the difference in the surface dose rate of the pump 3 due to the difference in temperature is 5 in this embodiment from 220 in the conventional example due to the characteristics in FIG. 2, and the surface dose rate is approximately 40 by the temperature difference alone.
The effect that it can be reduced to one-half is obtained.

What needs special attention in this embodiment is the differential pressure of the filter desalination apparatus 9. For example, when a powder precoat type filter is used as the filter desalting device 9, the filter pressure difference is 1.75.
If it becomes larger than kg / cm ² , pump 3 can be removed by performing a new filter precoat.
NPSH can be secured. Generally, a new powder precoat filter has a differential pressure of about 0.1 kg / cm ² , so the effective control range of the differential pressure is about 0.1 kg / cm ^{2 to} 1.7 kg.
It will be 5 kg / cm ² .

According to this embodiment, the radioactivity in the coolant is filtered by the desalination unit 9
Since it is removed by, the adhesion of radioactivity to the pump 3 is further reduced.

Since the removal rate of radioactivity of the filter desalting apparatus 9 is usually about 1/100, the present embodiment considering both the radioactivity reducing effect of the filter desalting apparatus 9 and the radioactivity adhesion reducing effect due to the temperature difference described above. The surface dose rate of pump 3 in the example is 5/100 = 0.0
As compared with the conventional example, the adhesion of radioactivity can be reduced to about 0.05 / 220 = 1/4400.

〔The invention's effect〕

As described above, according to the present invention, in addition to the effect of removing the radioactivity by the filter desalting device, the temperature of the coolant at the position of the pump has a very small amount of radioactivity attached to the pump.
Since the temperature can be constantly controlled to 0 ° C. or lower, it is possible to effectively reduce the radioactivity adhesion to the pump.

Further, according to the present invention, it is possible to sufficiently suppress the pressure loss due to the filter desalination apparatus, and it is possible to sufficiently secure the height difference between the reactor water and the pump, so that the suction side pressure of the pump is always within the allowable range. The NHSH of the pump can be reliably secured by maintaining at.

[Brief description of drawings]

FIG. 1 is a conventional reactor cooling system diagram, FIG. 1a is a conventional low pressure reactor cleaning system diagram, FIG. 2 is a characteristic diagram showing the relationship between coolant temperature and surface dose rate, and FIG. 3 is the present invention. It is a figure which shows the Example which applied to the reactor coolant purification system. 1 ... Reactor pressure vessel, 2,5,6 ... Piping, 3 ... Pump, 4 ... Heat exchanger, 7 ... Auxiliary cooling system, 8 ... Thermometer, 9 ... Filtration desalination device .

Claims (1)

[Claims] 1. A first pipe for taking out a first coolant, which is a coolant for a nuclear reactor, a cooler for cooling the first coolant, and the first pipe arranged downstream of the cooler. Reactor cooling device comprising: a filter desalting device for performing filter desalination of the coolant of claim 1, a pump for increasing the pressure of the first coolant, and a second pipe for returning the first coolant to the reactor. In the first cooling device, the first cooling device cools the first cooling material in the first pipe by exchanging heat with the first cooling material in the second piping; And a second cooler which is arranged on the downstream side of the cooler and cools the first coolant by exchanging heat with the second coolant supplied from the auxiliary equipment cooling system. salts apparatus in powder precoat type filter, the differential pressure of the filter is maintained at below 1.75 kg / cm ^2, the pump A temperature of the first coolant between the second cooler and the filter demineralizer, which is arranged at a position sufficiently lower than the water level of the reactor downstream of the filter demineralizer. And a control means for controlling the flow rate of the first coolant or the flow rate of the second coolant so that the temperature measured by the temperature measurement means becomes 200 ° C. or less. A reactor cooling device characterized by being provided.