JPS62190496A - Purifier for coolant of nuclear 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 [Field of Industrial Application] The present invention relates to a coolant purification device for a nuclear power plant reactor.

[Conventional technology]

Figure 6 is a system diagram of a conventional pressurized water reactor (hereinafter referred to as PWR) residual heat removal equipment and chemical volume control equipment, and Figure 7 is a conventional boiling water reactor (hereinafter referred to as BWR) residual heat removal equipment and It is a system diagram of a reactor coolant purification facility.

Purification of the coolant, which is the reactor water in a nuclear power plant, is mainly carried out during normal output operation.In the case of PWR, the reactor water is extracted from the sub-cooling system 1a, in the case of BWR, the reactor system 1b, and in the case of PWR, it is extracted from the reactor system 1b. In the case of the volume control equipment 12 and BWlt, the purification equipment of the reactor coolant purification equipment 413 is used, and after cooling with the non-regenerative cooler 4, water is passed through the purification equipment 5 of these purification equipment 12.13. This is done by filling the furnace again.

The purification device 5 of the purification equipment 12, 13 uses an ion exchange resin tower or a filtration salt tower, and can remove radioactive corrosion products, nuclear fission products, etc. in the coolant.

The capacity of the purification equipment 12 and 13 is mainly for the purpose of maintaining the water quality of the coolant.In general, in the case of PWR, the reactor water is separated from the secondary system, and impurities from outside the reactor do not mix in the closed cycle. Taking this into consideration, "C approx. 20m/hr ~ approx. 30m/hr"
rn' /hr (for electrical output approximately 1100MW)
In the case of BWR, the water inside the reactor is supplied from the condenser to generate 10 steam in the reactor, so contamination with impurities from the water supply system outside the reactor, such as seawater contamination due to condenser tube leakage, and concentration of impurities are avoided. Approximately 120m/hr (fa air output approximately 1100
MW).

14a and 14b are heat removal equipment, which remove decay heat and other residual heat of the reactor, and reduce the quality of the primary coolant to 60°C or less within about 20 hours after the reactor is shut down. shall be.

To explain the system of the purification equipment 12 and 13, in the case of PWR, as shown in FIG. The water is passed to the purification device 5 via the non-regenerative cooler 4,
The water is pumped up from the volume control tank 6 by the pump 7 and filled into the primary cooling system 1a via the pipe side of the regenerative heat exchanger 8, thereby purifying the water in the furnace. In the case of BVl+l'R, as shown in FIG. The system has a system configuration in which water passes through the shell side, passes through the non-regenerative cooler 4, enters the purification device 5, and returns to the reactor system 1b via the pipe side of the regenerative heat exchanger 8. used for licking.

@PWI't residual heat removal equipment 14a and No. 7 shown in Figure 6
Not shown in the figure, the heat removal equipment such as the residual heat removal film (+114 b) of BW['t is configured in the same system, and the heat removal equipment 14
As shown in Figs. 6 and 7, a and 14b are composed of two independent systems consisting of a pump 2, a cooler 3, and related piping and valves (in Figs. 6 and 7, simplified Therefore, it is expressed in one system). Pump 2 suction side piping is primary cooling system 1a
Alternatively, it is connected to the coolant pipe a of the reactor system 1b, and the valve 10 is closed during normal operation. The outlet side of the pump 2 is connected via a cooler 3 to a coolant pipe C of the primary cooling system 1a or the reactor system 1b. The cooler 3 is provided with a bypass line f, and this bypass line f
By controlling the flow rate of the primary coolant with the valve 9, the cooling rate of the primary coolant is adjusted to be below the limit value.

When the plant is shut down, valve 10 is opened to remove residual heat from the reactor, and a circulation flow path is established to take water from coolant pipe a and return it to coolant pipe C.

In the case of PWR, the pressure of the secondary cooling system 1a is low (approximately 28 kg/car or less) at the time when the residual heat removal equipment 14a is added to the primary cooling system 1a.

In the case of a BWR, the residual heat removal equipment 14b cools the reactor water temperature to approximately 60°C in approximately 20 hours by using the turbine main condenser and water supply equipment in order to perform fuel exchange work after the reactor is shut down. reactor shutdown cooling mode). The shutdown cooling mode is the most normal operation mode for removing decay heat after reactor shutdown, in which reactor water is taken from the coolant pipe a of the reactor system 1b, pressurized by the bongo 2, and cooled by the cooler 3. After cooling, it is returned to the reactor system 1b via the coolant pipe C of the reactor system 1b.

A portion of the cooled reactor water can also be sprayed from a head spray nozzle at the top of the reactor pressure vessel to cool the reactor pressure vessel/RAD section. The 1611 device 3 has a bypass line f, and by adjusting the bypass flow rate with the buff 1 buff 9, it is possible to adjust the amount of heat exchange.

During normal operation, the residual heat removal equipment 14b and Platt are used as one system of the emergency core cooling equipment (low-pressure water injection system) and are in a state of waiting to be filled with water from the pressure suppression chamber pool, so the system is cleaned prior to operation in shutdown cooling mode. and warm-up operation is required.

When the reactor pressure reaches 10kg/cnf, the function as an emergency core cooling facility is no longer required, so system cleaning can begin, and the reactor pressure drops to about 8kg/cI.
You can enter the main driving mode from lr.

[Problem that the invention seeks to solve]

During power operation, impurities such as radioactive cobalt, nickel, and iron in the coolant adhere to piping and other equipment through which the coolant flows, increasing the source strength and damaging the reactor vessel after the plant is shut down. During the opening of the lid and subsequent periodic inspections, workers are exposed to increased radiation doses due to working around these contaminated equipment. Generally, coolant purification equipment is operated continuously during normal output operation, but impurities such as radioactive cobalt, nickel, iron, etc. that adhere to piping and other equipment through which this coolant flows are removed during normal output operation. , in the coolant,
Since these impurities are only slightly eluted, there is a limit to how effectively these impurities can be removed.

Figure 5 shows changes over time in Pratt's coolant temperature t, coolant pressure P, boron B in the coolant, and PH from normal power operation to reactor shutdown, and the corresponding radioactive cobal I-G degree CO in the coolant. Changes are shown by broken lines, but during normal output operation (
, no concentration, after blunt disassembly T1, the coolant temperature t changes from the temperature ta during normal output operation (300°C in the case of PWR) to the cool-down time T2 when residual heat removal equipment performs temperature tb (approx. 170℃ for PWR)
and 1 degree tc to open the reactor vessel lid (approximately 60℃)
Until then, the concentration of released Q=j cobalt during normal output operation Lj increased by about 10 to 10 times C1o, and radioactive cobal L- and Ninkel gradually adhered to piping and other equipment during normal output operation. It was found that a large amount of impurities such as iron were released into the coolant at once due to transient changes in water quality such as a sharp drop in pH due to an increase in the coolant temperature, an increase in boron B in the coolant, and a decrease in lithium. Ta. During this period from T1 to T3 and beyond, if the impurities eluted into the coolant are removed, the impurities attached to equipment such as piping will be removed, and the intensity of these sources will increase to a large extent. This makes it possible to reduce the radiation exposure of workers during periodic inspections after plant shutdowns.

However, as shown in Figure 5, in conventional plants, the radioactive L concentration in the coolant when the reactor is shut down is
The sudden rise of ΔC from no to Csh indicates that the current purification equipment has a small capacity to remove such impurities from the coolant.

In order to significantly increase the capacity of the conventional chemical volume control equipment 12 or reactor coolant purification equipment 13, it is necessary to significantly increase the pump 7, valves, and piping of this equipment. This will result in a significant increase in costs. In addition, increasing the overall capacity of this equipment only for purification operation when the reactor is shut down takes into account that such large-capacity equipment is not required during normal output operation (there is no problem with conventional equipment). However, it is not an economical design.

Also, from cooldown T2 to T2 when the reactor vessel lid is opened.
It is conceivable that the period up to Plan 1-4 would be longer than in conventional plants (approximately 3 days) and the purification operation for removing eluted radioactive materials would be carried out for a long time, but in the conventional purification equipment of Plan 1-,
It is necessary to make this period (T2 to Ta) considerably long, which makes it impossible to shorten the periodic plant inspection.

The present invention was made in view of the above-mentioned circumstances, and includes residual heat removal equipment (in the case of RWR, the same equipment is used) that has the function of circulating a large volume of coolant in the furnace to cool it when the reactor is shut down, that is, after cool-down. We will provide a coolant purification device that has the function of installing a purification device in the circulation loop of a residual heat removal facility (referred to as residual heat removal equipment) and performing purification operation using the piping, valves, pumps, and coolers of this circulation loop. It is something to do.

[Means for solving problems]

Therefore, the nuclear reactor coolant purification device of the present invention has the following advantages:
Install a purification device corresponding to the capacity of the heat removal equipment described above and a bypass line in parallel with it.

[For production]

The circulation loop of the heat removal equipment can circulate the water in the reactor using a large-capacity pump, and if a purification equipment with a low differential pressure is installed, this circulation flow rate (approximately 700 m' /
hr (approximately 1,700 m'/hr in the case of BWR), making it possible to perform purification operations several tens of times the capacity of conventional purification equipment. Almost all impurities such as metal and iron can be effectively removed.

FIG. 5 shows the change in cobalt concentration in the coolant when the conventional purification equipment is operated as a COl curve (broken line), and the COl curve (solid line) shows the change in the cobalt concentration in the coolant when the purification equipment of the present invention is operated. Indicated by As shown in FIG. 5, the purification equipment of the present invention is capable of one-way purification, making it possible to remove almost all of the cobalt eluted when the reactor is shut down.

Compared to the conventional residual CO concentration CR1, the residual CO concentration CRλ of the present invention is greatly reduced, and radiation exposure during regular inspections can also be reduced.

In addition, the total cost of the residual heat removal equipment pump and cooler was approximately 700 yen.
rn' / hr (approximately 1700rn for BM/IN
Since a part of the water ('/hr) can be bypassed and used for purification, it is also possible to provide economical purification equipment.

〔Example〕

Embodiments of the present invention will be described in detail below based on the accompanying drawings.

Fig. 1 is a system diagram of a coolant purification equipment using a PWR residual heat removal equipment circulation loop showing an embodiment of the present invention, and Fig. 2 is a system diagram of a coolant purification equipment using a BWR residual heat removal equipment circulation loop showing the same embodiment. Fig. 3 is a system diagram of a coolant purification equipment using a PWR residual heat removal equipment circulation loop showing another embodiment of the present invention, and Fig. 4 is a system diagram of a BWR showing another embodiment of the present invention. It is a system diagram of a coolant purification equipment using a residual heat removal equipment circulation loop.

When one embodiment of the present invention is applied to a PWR, a purification device 11a is provided downstream of the cooler 3, as shown in FIG. The purifier 11a has a valve 15. 16
A and I 6 b provide a bypass line so that the purification flow rate can be adjusted.

The reactor coolant is taken from the coolant pipe a of the secondary cooling system 1a, and the water is taken from the pop 2. Jfr quencher 3, purification device 11 a
A circulating purification operation in which the coolant is returned to the coolant pipe C via 1e becomes possible.

On the other hand, when one embodiment of the present invention is applied to BWR, the second
As shown in the figure, the system configuration is basically the same as that of PWR, in which reactor water is taken from the coolant pipe a of the reactor system 1b, brought to pressure by the pump 2, cooled by the cooler 3, Water is passed through the purification device 11a, and after purification, it is passed through the coolant pipe C to the reactor system 1.
A circulation purification operation returns to b.

When another embodiment of the present invention is applied to PWR, as shown in FIG.
(Fig. 6) is scaled up to form a purification device 11b,
Even from the circulation loop of the residual heat removal equipment 14a, the purification device 11
Pipes B, B and valve 16 a so that water can flow to b.
, 16 b, 17, . 17b is provided so that the purification device 11b can be used from either the chemical volume control equipment 12 system loop or the residual heat removal equipment 14a system loop. In this case, a conventional purification device can be used for 1) F, making it an economical facility.

On the other hand, when another embodiment of the present invention is applied to BWR, the fourth
As shown in the figure, the conventional purification device 5 (FIG. 7) of the reactor cooling purification equipment 13 is scaled up to provide a purification device 11.
b, and the distribution trC; Bp so that water can flow to the purification device 11b even from the circulation loop of the residual heat removal membrane
B and valves 16a, 16b.

+7a and 17b are installed, and reactor coolant purification equipment 14
The purifier J11b can be used even from the a-system loop. In this case, conventional purification equipment can be used in combination, making it an economical facility.

The purification devices 11a and llb are for removing radioactive cobalt, nickel, and iron, and the residual heat removal equipment 14
It has a capability equivalent to that of old-fashioned heat removal equipment such as the residual heat removal installation 14a or the residual heat removal installation 14b, and is capable of passing a large amount of cooling water. Types include ■Cation demineralization tower ■Mixed bed demineralization tower ■Filtration demineralization tower (Paude, Sox resin) ■High temperature adsorption filter, etc.In particular, the cation demineralization tower has water flowing through f-÷,・. It can be used at a temperature of about 100° C. or less, and the temperature of the three coolers immediately drops to about 100° C. or less after leaving the furnace, so water can be passed through quickly. Furthermore, since the high temperature adsorption filter cannot be used even under high temperature conditions, it can be used from the stage when water starts flowing through the residual heat removal membranes @ 14a, 14b.

The above purification device can also be used in conjunction with a spent fuel pit water purification device (not shown).

〔Effect of the invention〕

According to the present invention described above, the following effects are produced.

■ By installing a purification device in the circulation loop of the heat removal equipment, it is possible to effectively remove large amounts of impurities such as radioactive cobalt, nickel, and iron that are eluted into the coolant when the reactor is shut down. The exposure dose rate can be reduced to 11%.

■ When increasing the capacity of conventional coolant purification equipment to make it 7-layer during reactor shutdown, it is necessary to increase the capacity of only the purification equipment, the entire piping of the reactor coolant purification equipment, valves, and other equipment. In that case, unnecessary equipment will be added during normal output operation, which is not economical.

By using the circulation loop of the conventional heat removal equipment for purification, there is almost no need for capacity amplifiers for equipment such as piping valves in the entire heat removal equipment, resulting in a more economical design than the one described above.

■ Compared to conventional plants, the coolant purification operation from cool-down to opening of the reactor vessel lid is shorter, and the period for periodic inspections can be shortened accordingly.

[Brief explanation of drawings]

Figure 1 is a system diagram of a coolant purification equipment using a residual heat removal equipment circulation loop of a PWR showing an embodiment of the present invention, and Figure 2 is a system diagram of a coolant purification equipment using a residual heat removal equipment circulation loop of a BWR showing an embodiment of the present invention. Fig. 3 is a system diagram of a coolant purification equipment using the residual heat removal equipment circulation loop of Pwl (PWL) showing another embodiment of the present invention, and Fig. 4 is a system diagram of a BWR showing the same embodiment. A system diagram of the coolant purification equipment using the residual heat removal equipment circulation loop, Figure 5 is a graph showing the temperature, pressure, coolant water quality conditions, and radioactive cobalt degree changes during cooling +4 after the reactor was shut down. , FIG. 6 is a system diagram of residual heat removal equipment and chemical volume control equipment of a conventional PWR, and FIG. 7 is a system diagram of a conventional BWR residual heat removal equipment and reactor coolant purification equipment. ]a - secondary cooling system, 1b reactor system, 2.7 pop, 3 cooler, 4 non-regenerative cooler, 5. lla, llb purification device, 6 volume control tank, 8 regenerative heat exchanger, 9,
+0.15.16a, 16b, 17a, 17b
valve, 12 - chemical volume control equipment, 13 reactor coolant purification equipment, 14a residual heat removal equipment, 14b residual heat removal equipment,

Claims (1)

[Claims] In heat removal equipment such as residual heat removal equipment and residual heat removal equipment, a purification device equivalent to the capacity of the heat removal equipment or less is installed downstream of the circulation loop pump or cooler, and a bypass line is installed in parallel with this. Features of nuclear reactor coolant purification equipment.