JPS6142819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an apparatus for measuring the concentration of impurities contained in a liquid.

For example, in a fast breeder nuclear reactor, a liquid metal such as liquid sodium is used as a medium for extracting heat generated in the reactor core to the outside. When the concentration of impurities contained in liquid metal used for such purposes increases, its function as a heat transfer material is impaired, making it difficult to use.

Therefore, when using liquid metals for the above purposes, it is necessary to constantly or periodically measure the concentration of impurities by some means, and to take prompt countermeasures based on the results.

By the way, various devices for measuring the concentration of impurities in liquid metal have been known in the past, and a device generally called a Plagging meter is used in nuclear power facilities and the like. This device measures the concentration by utilizing the phenomenon that the solubility of impurities depends on temperature, and is specifically constructed as shown in FIG. Note that this figure shows what is said to be an automatic oscillation type of bragging meter.

In the figure, reference numeral 1 denotes a pipe, and a liquid metal, which is a sample, is passed through the pipe 1 via a pump (not shown). A constriction mechanism 2 that locally reduces the flow cross-sectional area of the conduit 1 is provided in the conduit 1, and on the upstream side of the constriction mechanism 2, a liquid metal flowing through the conduit 1 is provided. A heating and cooling device 3 for selectively heating and cooling is provided. The heating and cooling device 3 includes, for example, an electric heater 4 disposed around the pipe line 1.
and a blower 5 that air-cools the pipe line 1. Note that if the sample is high-temperature liquid sodium, the heating source may be omitted. However,
A temperature detector 6 is provided between the throttle mechanism 2 and the heating/cooling device 3 to detect the temperature of the flowing liquid metal, and further downstream of the throttle mechanism 2 is a flow rate detector represented by an electromagnetic flowmeter. 7 is provided. and,
The output of the flow rate detector 7 is introduced into a flow rate comparator 8 and a decoder 9 via a filter (not shown). Further, the output of the temperature detector 6 is also introduced into the decoder 9. The flow rate comparator 8 compares the flow rate Q ₀ preset by the flow rate setting device 10 and the flow rate Q ₁ obtained from the flow rate detector 7, and outputs an output when Q ₁ changes in a direction exceeding Q ₀ . It is configured to send out a signal P ₁ and send out an output signal P ₂ when Q ₁ changes below Q ₀ . And the above output signal
P ₁ and P ₂ are introduced into the switching controller 11. The switching controller 11 is configured to energize only the blower 5 when the signal P ₁ is introduced, and to energize only the electric heater 4 when the signal P ₂ is introduced.

Therefore, this device measures the impurity concentration in the following manner. In other words, several hundred degrees Celsius
With the liquid metal flowing through the pipe 1,
First, the blower 5 is activated. When the blower 5 operates, the liquid metal passing through the throttle mechanism 2 is gradually cooled. Now, assuming that the liquid metal contains impurities, when the liquid metal is cooled to a temperature lower than the saturation solubility of the impurities, the supersaturated portion is precipitated on the inner surface of the throttle mechanism 2, and as a result, the flow rate decreases. begins to decrease. Then, the flow rate Q ₁ is the flow rate setting device 10
When the value Q set by decreases to a value below ₀ ,
The flow rate comparator 8 sends out an output signal P ₂ . Therefore, the switching controller 11 is activated, stops energizing the blower 5, and energizes only the electric heater 4 this time. In this case, the temperature of the liquid metal passing through the throttle mechanism 2 gradually rises, and when the temperature exceeds a certain level, the impurities deposited on the inner surface of the throttle mechanism 2 dissolve. Therefore, the flow rate increases, and this flow rate becomes the set flow rate.
When attempting to exceed Q ₀ , the flow rate comparator 8 is activated,
Send out an output signal P ₁ . As a result, switching controller 1
1 is activated and switches to energize only the blower 5. As a result, the flow rate begins to decrease again. Thereafter, the above-described operations are repeated. Therefore, the decoder 9 has a flow rate curve as shown in FIG.
A temperature curve will be recorded.

Here, the temperature at which the flow rate starts to decrease due to the precipitation of impurities and the temperature at which the flow rate starts to increase due to the dissolution of the impurities are:
The same temperature difference above and below the impurity saturation dissolution temperature T _P1 can be regarded as temperature. Therefore, assuming that the cooling characteristics and heating characteristics are symmetrical, the temperature change of the liquid metal passing through the throttle mechanism 2 will pulsate vertically symmetrically around the impurity saturation dissolution temperature T _P1 . Become. Therefore,
If the midpoint between the maximum and minimum values in the temperature curve is calculated from the recording paper, this temperature will be the saturated melting temperature at that time, so by comparing this temperature with the predetermined correction curve, Therefore, the concentration of impurities can be determined. Conventional devices perform measurements in this manner.

However, the device configured as described above has the following problems. That is,
As can be seen from the above explanation, in the case of a certain impurity concentration, the temperature at which a decrease in flow rate is observed is, for example, about 10° C. lower than the saturation dissolution temperature at that time. For this reason, depending on the sample liquid, it may not be possible to measure a low impurity concentration region. For example, taking liquid sodium as an example, the solidification temperature of sodium is 97.9°C. Now, if the saturated dissolution temperature of impurities in the sample liquid sodium is 105℃,
If it is cooled to measure this, the sodium will solidify before the flow rate starts to decrease due to the precipitation of impurities, making it impossible to measure it. Note that some plugging meters are manual types, and in these manual types, the temperature is decreased linearly and the concentration is measured from the temperature at the point when the flow rate begins to decrease. However, even with this method, for the reasons mentioned above, it is not possible to measure the concentration of impurities whose saturation dissolution temperature is close to the solidification temperature. As described above, the conventional device has a drawback that it cannot be used in a low impurity concentration region.

The present invention was made in view of these circumstances, and its purpose is to provide an easy-to-use impurity concentration measuring device that can accurately measure the concentration of sample liquid even when the concentration has a saturation dissolution temperature near the freezing point. Our goal is to provide the following.

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 3 shows a schematic configuration of an apparatus according to an embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. Therefore, the explanation of the overlapping parts will be omitted.

The difference between the device of the present invention according to this embodiment and the conventional device is that the signal sent from the temperature detector 6 is directly used to automatically calculate the saturated melting temperature, and that the temperature is lowered to a predetermined temperature during cooling. The reason is that I tried not to do that.

That is, a calculation device 21 is provided, and a signal at the time when the switching controller 11 performs switching control, for example, a signal at the time when the blower 5 starts operating, is introduced into the calculation device 21, and the signal is inputted between the times when this signal is introduced. The time difference, that is, the control period, is calculated, and the output signal of the temperature detector 6 is introduced and integrated over the period, and the integrated value is divided by the period to calculate the average temperature, which is displayed on the display. I am trying to display it on 22. Further, the output signal of the temperature detector 6 is introduced into one input terminal of the comparison circuit 23, and the lower limit set temperature signal _T0 is introduced into the other input terminal of the comparison circuit 23, and the difference between the two is calculated. For example, the rotation speed of the blower 5 is controlled using this difference signal. In addition, comparison circuit 2
3 is designed to operate only when the switching controller 11 is switched to the side that energizes the blower 5. Further, numeral 24 in the figure indicates a filter for cutting off high frequency signals.

With such a configuration, not only can the saturated dissolution temperature of impurities be measured more accurately and automatically, but also the measurable range can be expanded to a low impurity concentration region. The reason for this will be explained below.

Now, suppose that when this measurement system is operated, the temperature of the liquid metal passing through the throttle mechanism 2 changes as shown in FIG. 4, for example, and the actual saturated melting temperature at this time is T _PI .

Therefore, the amount ΔM of precipitation and dissolution of impurities per time Δt is generally expressed as in equation (1).

ΔM/Δt=KS (C _(T) − C _PI ) ...(1) However, K is the mass transfer coefficient, S is the area where impurities are precipitated or dissolved, and C _(T) is the temperature of the drawing mechanism 2. The impurity saturation concentration, C _PI is the impurity concentration.

The amount of impurity precipitation M _P in the region where the temperature of the liquid passing through the throttling mechanism 2, that is, the temperature of the throttling mechanism 2, is below the saturation melting temperature T _PI is calculated by the integral amount from time t ₂ to time t ₃ shown in FIG. Therefore, M _P is calculated from equation (1) as follows: M _P =KS∫ ^t3 _t2 (C _(T) − _{C PI} )dt =KS{∫ ^t3 _t2 C _(T) dt−C _PI (t ₃ −t ₂ )} ...(2) becomes.

In addition, when precipitation and dissolution are repeated stably as shown in Figure 4, all of the impurities precipitated from time _t3 to time _t5 shown in Figure 4 are dissolved. Therefore, this amount of solubility Md
Similarly to equation (2), M _d = KS∫ ^t5 _t3 (-C _(T) dt+C _PI dt = KS{-∫ ^t5 _t3 C _(T) dt+C _PI (t ₅ -t ₃ )}...( 3).Then, since the precipitation amount M _P and the dissolution amount Md are equal, M _P = Md = KS {∫ ^t3 _t2 C _(T) dt−C _PI (t ₃ − t ₂ )} = KS {− ∫ ^t5 _t3 C _(T) dt+C _PI (t ₅ - t ₃ )}, so, becomes.

Here, if precipitation and dissolution are repeated continuously and stably as shown in Figure 4 (this can be said in all cases if we focus on a certain short period of time), the part indicated by A in the figure is It can be considered to be the same as the part indicated by A′, so It can be corrected.

On the other hand, in the range where the temperature amplitude of the throttle mechanism 2 can be regarded as a straight line in the impurity saturation solubility curve, T
Since ∝C, equation (5) can be rewritten as follows.

As can be seen from equation (6), the impurity saturation dissolution temperature T _PI is determined by integrating the temperature of the liquid flowing through the throttling mechanism 2 during the cooling start time period t ₁ to _{t 4} , and calculating this integral value from t ₁ to t 4 .
It can be found by dividing by the time between t _{and 4} . The arithmetic unit 11 performs the above-mentioned arithmetic operations for this reason. Therefore, the saturation dissolution temperature of the impurity at that time can be known from the calculation result of the calculation device 11, and by comparing this temperature with the correction curve determined in advance, the impurity concentration at that time can be determined. can be known.

Further, a comparison circuit 23 is provided, and during cooling, the comparison circuit 23 compares the output signal of the temperature detector 6 with a preset temperature signal _T0 , and controls the blower 5 based on the difference. Therefore, the temperature of the liquid passing through the throttle mechanism 2 during cooling is the temperature signal T ₀
It is possible to prevent the liquid from being cooled below the temperature corresponding to the sample liquid, and for example, it is possible to measure even when the saturated dissolution temperature is slightly higher than the solidification temperature of the sample liquid. For example, if the sample liquid is liquid sodium, if T ₀ is set so that the lower limit temperature is, for example, 101°C, the sodium will never solidify.
FIG. 5 shows changes in flow rate and temperature when the saturated dissolution temperature of impurities contained in sodium is, for example, 103°C. In this case, the time from starting heating to starting the next heating will be longer, but the saturation melting temperature can be determined without any problems, and the measurable range can be expanded compared to conventional methods. Become.

In addition, in the above-mentioned example, the measurement is made based on the interval between the cooling start times, but it may be measured based on the time between the heating start times, or by using both at the same time and displaying them alternately. Responsiveness may be increased. Further, the means for keeping the lower limit temperature constant is not limited to controlling only the cooling system, but may also control the heating system, or may control both. Furthermore, the present invention is not limited to use only with liquid metals.

As described in detail above, the present invention not only enables highly accurate concentration measurements without the troublesome calculations required with conventional devices, but also greatly expands the measurable range and provides an easy-to-use impurity concentration measuring device. Can be provided.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of a conventional device, Fig. 2 is an explanatory diagram of the operation of the same device, Fig. 3 is an explanatory diagram of the configuration of an embodiment of the present invention, and Fig. 4 is a measurement diagram of the same embodiment. FIG. 5, which is a diagram for explaining the principle, is a diagram showing changes in flow rate and temperature when a low impurity concentration region is measured using the same embodiment. 1...Pipeline, 2...Aperture mechanism, 3 ...Heating and cooling device,
6...Temperature detector, 7...Flow rate effector, 8...Flow rate comparator, 10...Flow rate setter, 11...Switching controller, 21
... Arithmetic unit, 23... Comparison circuit.

Claims (1)

[Scope of Claims] 1. A conduit through which a sample liquid flows, a throttle mechanism provided within the conduit to locally reduce the flow cross-sectional area of the conduit, and a constriction mechanism provided upstream of the constriction mechanism. a heating/cooling device for selectively heating and cooling the sample liquid; a temperature detector for detecting the temperature of the sample liquid passing through the constriction mechanism; and a temperature detector for detecting the temperature of the sample liquid passing through the conduit; Compare the flow rate detector to be detected, the flow rate setting device, the set flow rate set in this flow rate setting device, and the actual flow rate obtained by the flow rate detector, and when the actual flow rate decreases from the above set flow rate. a flow rate comparator that outputs a signal specifying a heating device of the heating/cooling device, and outputs a signal specifying a cooler of the heating/cooling device when the actual flow rate increases from the set flow rate; and the flow rate comparator. a switching control means for switching and energizing the heating device and the cooling device of the heating/cooling device in response to a specified signal from the switching control means; and integrating the output of the temperature sensor during the switching period in synchronization with the switching of the switching control means. An impurity concentration measuring device comprising: an arithmetic device for calculating the average temperature by dividing the average temperature by a switching period; and a display device for displaying the output of the arithmetic device. 2. The switching control means compares the temperature of the sample liquid with a set lower limit temperature while operating the cooler of the heating and cooling device, and prevents the temperature of the sample liquid from becoming less than the set lower limit temperature. 2. The impurity concentration measuring device according to claim 1, further comprising a lower limit temperature comparison circuit for controlling the cooler to prevent the impurity concentration from occurring.