JPH0454914B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a nuclear reactor coolant supply facility, and more particularly to a nuclear reactor coolant supply facility including a merging piping section where a main circulation system coolant and a purification system coolant are merged. [Background of the Invention] Heat generated in a nuclear reactor is extracted to the outside by a coolant that is circulated as a heat medium and used for power generation or the like. Normally, a part of the coolant that is circulated at this time is continuously extracted and purified in a purification system, and then is allowed to join the main circulation system again. A conventional example of such reactor coolant supply equipment is described in Part 1 for a boiling water reactor.
This will be explained using the system configuration diagram shown in the figure. In FIG. 1, a main circulation system coolant is supplied to a boiling water type nuclear reactor 1 from a main circulation system coolant supply device (not shown) via a main coolant supply pipe line 2. In FIG. The coolant in the reactor 1 is forced to convect by a recirculation pump 3. A predetermined amount of this recirculated coolant is extracted by a purification system circulation pump 4 and guided to the coolant purification system. The coolant purification system is composed of a regenerative heat exchanger 5, a non-regenerative heat exchanger 6, a super desalination device 7, and the like. The coolant flowing into the purification system is cooled to a predetermined temperature by the regenerative heat exchanger 5 and the non-regenerative heat exchanger 6, and then flows into the super-demineralizer 7. The thus purified coolant is pressurized by the purification system circulation pump 4, heated by the regenerative heat exchanger 5, and then transferred to the confluence pipe section 8 provided in the main coolant supply pipe line 2. is flowing into the country. In conventional reactor coolant supply equipment configured in this way, the temperature of the return coolant from the coolant purification system and the temperature of the main circulation system coolant during normal operation are almost the same. It is now controlled and merged. However, during reactor start-up, shutdown, or high-temperature standby (continuation of operation without reactor output), the temperature balance of these combined coolants is disrupted, and the main circulation system coolant supply pipe line is affected. While the temperature may be below 40°C, the temperature of the coolant from the purification system may be above 220°C. When two fluids with a temperature difference of 180°C or more are merged in this way, a region with a very large temperature difference locally occurs in the merging piping section 8, resulting in a very large thermal stress. will come into play. The thermal stress acting on any one point on the pipe wall (the side in contact with the coolant) of the confluence piping section 8 becomes a repetitive stress that changes significantly depending on the flow behavior of the confluence fluid. Moreover, since this stress acts repeatedly every time the reactor is started and stopped, the merging piping section 8
Damage such as cracks may occur due to high cycle thermal fatigue. Conventionally, attempts have been made to provide the confluence piping section 8 with a thermal sleeve structure to alleviate thermal stress in the main section, reduce thermal fatigue, and prevent damage such as cracks. . However, it is difficult to absorb high-cycle thermal fatigue due to extremely large temperature differences such as those that occur during startup or shutdown using only the thermal sleeve structure, and there is a drawback that the above-mentioned damage cannot be sufficiently prevented. Ta. FIG. 2 shows a conventional example of reactor coolant supply equipment designed to compensate for this drawback. The reactor coolant supply equipment shown in Figure 2 is designed to operate in the same operating mode as the reactor coolant supply equipment shown in Figure 1, which is likely to cause damage such as cracks due to high-cycle thermal fatigue, i.e., reactor startup, shutdown, or high-temperature operation. During standby, the purified coolant is not heated by the regenerative heat exchanger 5, and the bypass line 1 is
1 and the main circulation system coolant supply main pipe line 2.
The system has a system configuration in which the coolant flows into the confluence piping section 8 provided in the confluence piping section 8, thereby maintaining the temperature balance of the respective coolants that are merged in the confluence piping section 8 and preventing the generation of excessive thermal stress. . However, since the reactor coolant supply equipment shown in FIG. 2 does not heat the purification system return coolant using the regenerative heat exchanger 5, the reactor coolant supply equipment shown in FIG. From piping section 8 to reactor 1
At the same time, the risk of high-cycle thermal fatigue due to the temperature difference between the reactor nozzle 12 and the reactor water increases. Since the refrigerant is not cooled by the regenerative heat exchanger 5 and is led to the refrigerant purification device, it is necessary to increase the capacity of the non-regenerative heat exchanger 6 in order to cool it to a predetermined temperature and then flow it into the over-desalination device 7. The problem was that it needed to be increased. [Object of the Invention] The object of the present invention is to solve the problem without the above-mentioned problems.
An object of the present invention is to provide reactor coolant supply equipment that can significantly reduce thermal fatigue of a merging piping section that joins purification system coolant with main circulation system coolant, and can prevent damage to the merging piping section due to high-cycle thermal fatigue. . [Summary of the Invention] The present invention provides a main circulation system coolant supply main pipe line;
A purification system having a regenerative heat exchanger, a non-regenerative heat exchanger, and a super-demineralizer, and a main circulation of the purification system return coolant that passes through the super-demineralizer of this purification system and passes through the return side in the regenerative heat exchanger. In the reactor coolant supply equipment, which consists of a merging section that joins the system coolant supply main pipe line, it branches from the main circulation system coolant supply main pipe line to the return side in the regenerative heat exchanger and upstream of the super desalination device. A bypass line that bypasses the purification system flow path between the side and the normally closed valve provided in the bypass line, and a valve located downstream of the bypass line branch point in the main circulation system coolant supply main pipe line. When the flow rate and temperature of the coolant in the main circulation system coolant supply pipe line drop below predetermined values, the former valve is opened and the latter valve is closed. The invention is characterized in that it is equipped with an automatic control device that performs the following functions. [Embodiment of the Invention] An embodiment of the present invention will be described with reference to FIG. In the figure, parts having the same configuration and function as those of the conventional example shown in FIG. In FIG. 3, unlike the conventional example shown in FIG. 1, a line 14 bypasses the return coolant from the purification system to the purification system return line 13 at the confluence piping section 22 before passing through the regenerative heat exchanger 5. is branched from the main coolant supply line 2, and automatic valves 15 and 16 are provided on this bypass line 14 and the main coolant supply line 2 downstream from the branch, respectively. A valve 23 is provided. Further, the main coolant supply pipe line 2 is provided with a flow rate detector 17 and a temperature detector 18 for detecting the coolant supply amount and temperature of the main circulation system, respectively, and the flow rate signals output from these detectors 17 and 18 are provided. F and temperature signal T are each output from comparator 1
9 and 20. The other input terminals of the comparators 19 and 20 are connected to a preset reference flow rate signal.
F ₀ and reference temperature signal T ₀ are input. Comparators 19 and 20 operate when the input signal F becomes less than F ₀ and when the input signal T becomes less than T ₀ , respectively.
It is configured to output a logic signal that opens the automatic valve 15 and closes the automatic valve 16. This comparator 19,2
The output signal of 0 is sent to automatic valve 1 via AND circuit 21.
5 and 16. The operation of the embodiment of the present invention configured in this manner will be described below. During normal operation, the coolant supplied from the coolant supply main pipe line 2 of the main circulation system is heated to about 210°C. Meanwhile, the temperature of the return coolant from the purification system is also raised to approximately 225°C. These coolants are combined in a confluence piping section 8 and supplied into the reactor 1. That is, at this time, automatic valve 15 is closed and automatic valve 16 is open. However, when the reactor 1 is started, stopped, or is in high-temperature standby, the flow rate of the coolant supplied from the main circulation system is as shown in Table 1.
The temperature is reduced to about 2% of the rated operating temperature, and furthermore, the temperature is reduced to about 38°C. Meanwhile, the temperature of the purification system return coolant remains maintained at the above-mentioned approximately 225°C. When two coolants with such a large temperature difference flow into the confluence piping section 8, there is a great risk of damage occurring due to high-cycle thermal fatigue, as described above.

〔Effect of the invention〕

According to the present invention, purification system return coolant can be used to cool the main circulation system without reducing thermal efficiency, increasing the risk of high cycle thermal fatigue in the reactor nozzle, and increasing the capacity of the purification system non-regenerative heat exchanger. Thermal fatigue of the confluence piping section that joins the material can be significantly reduced,
Damage to the merging piping due to high-cycle thermal fatigue can be prevented, thereby improving the reliability and availability of the nuclear reactor plant.

[Brief explanation of the drawing]

1 and 2 are system configuration diagrams of conventional nuclear reactor coolant supply equipment, and FIGS. 3 and 4 are system configuration diagrams showing different embodiments of the present invention, respectively. 1... Nuclear reactor, 2... Coolant supply main line, 5...
Regenerative heat exchanger, 6... Non-regenerative heat exchanger, 7... Super desalination device, 8... Merging piping section, 12... Reactor nozzle,
13...Purification system return line, 14...Bypass line, 15, 16...Automatic valve, 17...Flow rate detector, 1
8... Temperature detector, 19, 20... Comparator, 21...
AND circuit, 22... Bypass line inflow section, 23
...Check valve, 24...Line to the purification system.

Claims (1)

[Claims] 1 Main circulation system coolant supply main line that supplies coolant into the reactor; regenerative heat exchanger, non-regenerative heat exchanger, and over-desalination through which some of the coolant extracted from the reactor flows in order. A purification system including a demineralizer, in which the coolant that has passed through the over-desalination device flows through the return side of the regenerative heat exchanger, and a purification system that allows the coolant that has passed through the return side of the regenerative heat exchanger of the purification system to flow through the return side of the regenerative heat exchanger. In the reactor coolant supply equipment, the reactor coolant supply equipment consists of: a confluence section that joins the main circulation system coolant main pipe line; A bypass line that bypasses the purification system flow path between the upstream side of On the side, there is a valve that is installed in the main circulation system coolant supply main line and is normally open, and a valve that is installed in the main circulation system coolant supply main line when the flow rate and temperature of the coolant in the main circulation system coolant supply main line fall below predetermined values. A nuclear reactor coolant supply facility characterized by comprising: an automatic control device that opens one valve and closes the other valve.