JPS6016572B2 - Sodium purity monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an apparatus for monitoring the purity of a coolant (sodium) used in a fast breeder reactor or the like.

[Background of the invention]

Conventionally, for example, in a sodium-cooled fast breeder reactor, a sodium purity monitoring device as shown in FIG. 1a has been used to monitor the concentration of impurities contained in sodium.

This apparatus has a structure in which sodium 1 to be measured is taken out from a main coolant pipe 2 by an electromagnetic pump 3 and fed into an orifice 5 through a cooler 4. As the cooling of the sodium progresses, the temperature of the sodium passing through the orifice 5 (hereinafter referred to as orifice temperature) becomes lower than the saturation dissolution temperature corresponding to the amount of dissolved impurities, as shown in FIG. 1b. From this point on, the dissolved impurities begin to precipitate on the inner surface of the orifice 5, where the flow path is narrow, and the cross-sectional area of the flow path of the orifice 5 is reduced. As a result, the flow resistance of the orifice 5 increases, reducing the flow rate of sodium.
In conventional sodium purity monitoring devices, the point P. where the sodium flow rate first decreases. P. is detected by the electromagnetic flowmeter 6, the saturated dissolution temperature of impurities is determined from the orifice temperature at the same time, and the amount of dissolved impurities is estimated from this temperature. The orifice temperature is measured with a thermocouple 11. However, in such a sodium purity monitoring device, temporal changes in the sodium flow rate signal are extremely small, making it difficult to accurately detect the time at which the flow rate begins to decrease.

For this reason, there is a drawback that the time at which the orifice temperature is read is incorrect and an error occurs in determining the saturation temperature of impurities. [Object of the invention] The object of the present invention is to accurately detect minute changes in sodium flow rate during impurity precipitation,
An object of the present invention is to provide a sodium purity monitoring device that can accurately determine the baggage dissolution temperature of impurities.

[Summary of the invention]

In order to achieve the above object, the purity monitoring device of the present invention detects minute temporal changes in sodium flow rate by applying a bridge circuit often used in electric circuits.

That is, as shown in FIG. 2, the fluid resistance R,, R2,
R3 and R4 are arranged in a bridge circuit, and the electromagnetic pump 3
The amount of sodium passing through the bypass section 7 when sodium is flowing is determined by the four resistances (R, ~
It is determined by the balance of R4). In particular, R.・R4=R2・R3……'1}
When the relationship is as follows, the sodium flow rate in the bypass section is 0.
becomes.

However, if the above relationship collapses, the sodium flow rate in the bypass section suddenly changes greatly. Since the sodium flow rate flowing through the bypass section 7 is determined by the difference between the pressure between the resistors R and R3 and the pressure between the resistors R2 and R4, the measurement of the sodium flow rate flowing through the bypass section 7 is as described above. It can also be said that the pressure difference between each pressure is measured. The present invention utilizes this principle, and the fluid resistance R
,, An orifice is adopted in one or more of R2, R3, and R4, and impurities are deposited on the inner surface of the orifice, and minute changes in fluid resistance accompanying this deposition are detected from changes in flow rate in the bypass section. be. In FIG. 2, R3 is an orifice, and the resistance increases as sodium precipitates. [
Examples of the Invention] The present invention will be described in detail below with reference to Examples.

FIG. 3a shows the configuration of a sodium purity monitoring device which is a preferred embodiment of the present invention.

Two sodium sampling pipes and branch pipes 21 and 22 are attached to take out sodium from the main coolant pipe 2.
The pond ends of the branch pipes 21 and 22 are attached to a sodium return pipe 23 that is connected to the main coolant pipe 2. Fluid resistance Also, valves 8 and 9 are used for R2. These valves 8 and 9 have a constant relationship at all times and are used as fixed resistances. The valve 8 is provided in the branch pipe 211, and the valve 9 is provided in the branch pipe 22. Further, an orifice 5 in which impurities are deposited on the inner surface is used as the fluid resistance R8, and a cooler 4 (or an economizer may be included to increase the cooling rate) is provided in front of the orifice. The cooler 4 and orifice 5 are connected to a branch pipe 21 downstream of the valve 8.
It is set in. Further, a flow control valve (or electromagnetic brake) 10 having a fluid resistance R4 is attached to the branch pipe 22 downstream of the valve 9. This resistor R4 works as a variable resistor. The bypass flow path 7 includes a valve 8 and an orifice 5.
The part of the branch pipe 21 between the valve 9 and the flow control valve 10 is connected to the part of the branch pipe 22 between the valve 9 and the flow control valve 10. The electromagnetic flowmeter 6 is provided in the bypass flow path 7. Before starting the measurement,
By adjusting resistor R4, R.・R4=R2・R
Satisfy the three relationships. At this time, as shown in FIG. 3b, the flow rate of sodium flowing through the bypass channel 7 is zero. This flow rate is measured by an electromagnetic flowmeter 6 attached to the bypass channel 7. Next, when the blower 12 is operated to start cooling the sodium in the branch pipe 21, the impurities contained in the sodium are precipitated in the orifice 5 and the resistance of the orifice 5 (resistance R3) increases.
increases, and the above-mentioned resistance balance condition begins to collapse.

As a result, sodium begins to flow into the bypass channel 7, and a change appears in the output signal of the electromagnetic flowmeter 6. The reason why sodium flows into the bypass channel 7 is because there is a difference between the pressure in the branch pipe 21 near the inlet of the bypass channel 7 and the pressure in the branch pipe 22 near the outlet of the bypass channel 7. be.
The saturated dissolution temperature of impurities is determined at the point P where the output signal of the electromagnetic flowmeter 6 changes. P. determined from the orifice temperature at The orifice temperature is measured with a thermocouple 11. Further, in this embodiment, it is also possible to repeat the cooling operation of the blower 12 synchronously and continuously measure the saturated dissolution temperature of impurities.

That is, the output signal of the electromagnetic flowmeter 6 is input to the comparator 13 to obtain a preset value. Compare with. When the bypass flow rate signal exceeds the above set value Qo, Prower 1 2
stops, and conversely, when the value becomes smaller than the set value Qo, the processor 12 restarts. In this case, the temporal changes in the orifice temperature and bypass flow rate are as shown in Figure 3c, and the impurity saturation dissolution temperature is the orifice temperature at the time when the bypass flow rate is maximum or minimum, or the average value of both. Continuously determined from . FIG. 4 shows another embodiment of the invention.

In this embodiment, orifices 5 and 5' are used as the diagonally arranged resistors R3 and R2, and coolers 4 and 4' are installed upstream of each orifice 5 and 5'. The cooler 4' and the orifice 5' are connected to the branch pipe 22.
established in Further, a valve 8 and an electromagnetic brake 10 are used as the resistors R and R4. The former serves as a fixed resistor, and the latter is used to balance the four resistors (R, to R4). Before starting the measurement, the relationship of equation '1} is satisfied, and then the blower 12 is operated. In this case, the sodium located upstream of the orifices 5 and 5' is simultaneously cooled, and impurities are simultaneously deposited on the inner surfaces of the orifices 5 and 5'. As a result,
The change in the flow rate through the bypass channel 7 appears to be greater than in the embodiment shown in FIG. Also,
In this embodiment as well, the blower 12 can be operated periodically to continuously determine the impurity saturation dissolution temperature. Operation control of the blower 12 is executed by comparing the bypass flow rate with a set value Q in the comparator 13. FIG. 6a shows the structure of another embodiment.

In this embodiment, impurity precipitation orifices 5 and 5' are used as fluid resistances R3 and R4, and coolers 4 and 4' are installed in front of each orifice. Unlike the embodiment shown in FIG. 4, cooling operations are performed alternately. That is, when the bypass flow rate becomes larger than the set value Qo, air blowing is started to one of the coolers, but air blowing to the other cooler is stopped. Blower 12
is always in operation, and the direction of air flow is determined by the switching valve 14.
can be alternately changed by FIG. 5b shows temporal changes in orifice temperature and bypass flow rate during repeated cooling operations. The saturated dissolution temperature of impurities is continuously measured from the orifice temperature at the time when the flow rate becomes maximum or minimum, or from the average value of both. FIG. 6 shows another embodiment. In this example, a change in resistance balance is detected by a differential pressure gauge 15. Before starting the measurement, balance the resistance in advance and
, B is set to 0. Subsequently, when the blower 12 is operated, the above-mentioned resistance balance condition (formula {1}) collapses, and the signal of the differential pressure gauge 15 changes. The impurity saturation dissolution temperature is determined from the orifice temperature at the point where the differential pressure gauge signal changes sharply. It is also possible to constantly compare the differential pressure gauge signal and the set value Po, repeat the cooling operation at the same time, and continuously measure the saturated melting temperature. FIG. 7 shows another embodiment.

This example is a more compact structure of the embodiment shown in FIG. That is, sodium from the main stream enters the double pipe and is split into two parts. At the entrance of double piping,
There are two orifices 16 and 16', fluid low resistance R,
, R2 (all fixed multi-resistors). Further, there is a cooler 4 and an orifice 5 downstream of the outer pipe, which function as a flow path for precipitating impurities. The flow rate control valve 17 attached to the outlet of the inner pipe is of a resistance balanced type [1}). The starting point of precipitation is A on the double piping,
It is detected from the signal change of the differential pressure gauge 15 installed between the two points B, and the saturated melting temperature is determined from the orifice temperature at the time when the change starts to appear. [Effects of the Invention] As explained above, according to the present invention, changes in fluid resistance when impurities are deposited on the inner surface of an orifice can be accurately and clearly detected, and the saturated dissolution temperature of impurities can be measured with high precision. I can do it.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the structural principle of a subordinate sodium purity monitoring device, FIG. 2 is a diagram explaining the principle of the present invention, and FIG. 3 is a diagram explaining the first embodiment of the present invention. FIG. 4 is a diagram explaining the second embodiment, FIG. 5 is a third embodiment, FIG. 6 is a fourth embodiment, and FIG. 7 is a diagram explaining a fifth embodiment. 4... Cooler, 5... Orifice, 6...
...Electromagnetic flowmeter, 7...Bypass flow path, 8,9
...Valve, 12...Blower, 20...
... Sodium collection tube, 21, 22... Branch pipe, 2
3... Sodium return pipe. Figure 1 (Q) Figure 1 Sail Figure 2 Figure 3 (4) Figure 3 (b, Figure 3 Figure 4 Figure 5 (4) Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A sodium collection pipe connected to the main pipe through which sodium flows, a sodium return pipe connected to the main pipe, and first and second branch pipes connected to the sodium collection pipe and the sodium return pipe, respectively. , a first resistor provided in the first branch pipe with an orifice and a fixed opening area; a second resistor provided in the second branch pipe with a fixed opening area; and a second resistor with a variable opening area. 3 resistors, a means attached to the first branch pipe to cool the sodium supplied to the orifice, a thermometer provided near the orifice, and a means between the first resistor and the orifice. A sodium purity monitoring device comprising means for detecting a pressure difference between the pressure in the first branch pipe and the pressure in the second branch pipe between the second resistor and the third resistor.