JPH0623699B2 - Liquid metal purity monitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plugging meter type purity monitoring device capable of monitoring the purity of liquid sodium or the like online, and more specifically, it is provided in a liquid metal channel. The present invention relates to a liquid metal purity monitoring apparatus in which a plurality of orifices and a liquid metal inflow portion are connected by extension pipes, and each extension pipe is equipped with an electric heater for flushing that can operate independently.

[Prior Art] A plugging meter has been put into practical use as an apparatus for monitoring the purity of liquid sodium online. This utilizes the property that impurities in liquid sodium precipitate under temperature conditions below the saturation temperature.By cooling sodium, impurities are precipitated at the orifice, and the saturation temperature is measured from the change in the flow rate at this time. However, the concentration of impurities in sodium is indirectly measured from the relationship between the solubility of impurities and the temperature of sodium prepared in advance.

FIG. 3 shows an example of a conventional plugging meter. It has a structure in which a plurality of orifice portions 12 are provided in the flow path of liquid sodium (see FIG. 4) and a cooling portion 14 is provided outside thereof.

The liquid sodium that has entered the sodium inflow section 10 is
It is designed to be cooled by the cooling gas flowing from the cooling gas inlet pipe 16 to the cooling gas outlet pipe 18, whereby impurities are deposited on the orifice portion 12 and the flow rate of sodium changes. Normally, several to several tens of orifice portions 12 are formed.

The outline of the measurement by the plugging meter is shown in FIG. At the start of measurement A, the temperature of the orifice begins to drop. Eventually, when the temperature becomes lower than the saturation temperature, the precipitation of impurities on the orifice portion starts (at the time of starting the flow rate decrease B). When the flow rate falls to a preset specified value (generally about 90 to 80%), a control signal for raising the temperature is issued (at the time of reversal C from temperature drop to rise). However, the flow rate continues to decrease until the temperature recovers to the saturation temperature.
When the saturation temperature is reached, the flow rate starts to increase (at the start of flow rate increase D). The temperature rises further because the flow rate is below the specified value.

Here, the temperatures at B and D are read and set as plugging temperatures.
However, in reality, there is a difference between the saturation temperature at the start B of the flow rate decrease (start of precipitation) and the saturation temperature at the start of the flow rate increase (dissolution start), and the average value of both is often called the plugging temperature.

[Problems to be Solved by the Invention] The saturation temperature and deposition rate of impurities and the rate at which once deposited materials are dissolved again depend on the type of impurities. Regarding the oxygen and hydrogen impurities, which are important in controlling the purity of sodium as a fast reactor coolant, the precipitation and dissolution rates have been clarified, and oxygen is about 20 minutes and hydrogen is about 20 seconds.

However, when the operation of the nuclear reactor is started and the temperature of the coolant sodium rises, impurities other than oxygen and hydrogen (which are said to be the third impurities because the type has not been identified) elute into the sodium. The third impurity has a high saturation temperature (it is considered to be about 200 ° C. when the saturation temperature of oxygen or hydrogen is about 150 ° C.) and the deposition / dissolution rate is slow (about 25 hours).

For this reason, the third impurity slowly deposits in the orifice of the plugging meter, cannot be controlled by the control system for oxygen and hydrogen, and the indication becomes unstable, resulting in a decrease in measurement accuracy.

Therefore, in order to remove the third impurities deposited on the orifice portion, it is necessary to perform a manual flushing operation as appropriate, which not only complicates the operation but also has a drawback that the measurement is interrupted due to the flushing.

An object of the present invention is to solve the above-mentioned drawbacks of the conventional technology, to eliminate the need for a manual flushing operation for removing the deposited third impurities, and to save labor.
It is an object of the present invention to provide a purity monitoring device that does not need to interrupt the measurement of the plugging temperature and that does not make the indication unstable even if the temperature of the liquid metal rises and can improve the measurement accuracy.

[Means for Solving the Problems] The present invention that can achieve the above-described object is to provide a plurality of orifice portions provided in a liquid metal flow path, and a cooling portion for flowing liquid metal. In a device comprising: a liquid metal having a configuration in which each of the orifices and the liquid metal inflow portion are connected by an extension pipe, and an electric heater for flushing that can independently control the operation is attached to the extension pipe. Is a purity monitoring device.

It is desirable that each electric heater can automatically control the energization time and the energization interval by a timer or the like.

[Operation] By independently controlling the energization time and interval of each electric heater attached to the extension pipe, if a large number of orifices are sequentially flushed one by one, impurities are removed while measuring with other orifices. be able to. Therefore, it does not have to be a problem in terms of purity control, but it takes a long time to deposit and impurities with a high plugging temperature are deposited in the orifice portion.
Stable measurement is possible by eliminating the adverse effect on the measurement of oxygen and hydrogen, which require low monitoring of plugging temperature and high deposition rate.

[Embodiment] FIG. 1 is an explanatory view showing an embodiment of the sodium purity monitoring apparatus according to the present invention. A large number of orifices 12 provided in the liquid sodium flow path and the liquid sodium inflow portion 10 are connected by extension pipes 20, and an electric heater 22 is wound around each extension pipe 20 (second). See figure). Each of these electric heaters 22 is connected to a power source via a timer or the like, and can be independently operated and controlled. A cooling unit 14 is provided outside the liquid sodium inflow unit 10, and a cooling gas inlet pipe 16 and a cooling gas outlet pipe 18 are connected to each other.

The method of using this device is as follows. The basic measurement procedure is the same as before. Liquid sodium is cooled by a cooling gas at the start of measurement. When the temperature reaches the saturation temperature or lower, impurity deposition on the orifice begins. When the flow rate falls to a preset specified value, cooling is stopped and the temperature is raised. However, the flow rate continues to decrease until the temperature recovers to the saturation temperature. When the saturation temperature is reached, the flow rate starts to increase.

Here, the average value of the saturation temperatures at the start of precipitation and at the start of dissolution is taken as the plugging temperature, and the concentration of impurities in sodium is determined.

In the present invention, the energization time and the energization interval of the electric heater 22 of the extension tube 20 are controlled by a timer or the like.
As a result, a large number of orifices 12 can be sequentially flushed one by one, and the third impurities adhering to the orifices can be removed while the other orifices are being measured.

In this way, it takes a long time to precipitate / dissolve and removes the adverse effect of the third impurity having a high plugging temperature, and enables stable measurement of oxygen and hydrogen having a low plugging temperature and a high deposition rate. . Therefore, a manual flushing operation for removing impurities is unnecessary, and it is not necessary to interrupt the measurement each time.

EFFECTS OF THE INVENTION Since the present invention has a configuration in which each orifice portion and the liquid metal inflow portion are connected by an extension pipe as described above, and an independently controllable electric heater for flushing is attached to the extension pipe, the orifice portion is provided. Since it is possible to automatically perform sequential flushing, there is an effect that laborious manual flushing operation is unnecessary and labor can be saved.

Further, in the present invention, it takes a long time to precipitate and the influence of the third impurity having a high plugging temperature is removed, and stable measurement is possible, and further, the measurement may be interrupted due to flushing. It has an excellent effect such as no.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a liquid sodium purity monitoring device according to the present invention, FIG. 2 is a perspective view showing an extension pipe thereof and an electric heater attached thereto, and FIG. 3 is an example of a conventional technique. FIG. 4 is a plan view showing the arrangement of the orifices, and FIG. 5 is an explanatory view showing the outline of measurement by a plugging meter. 10 ... Liquid sodium inflow part, 12 ... Orifice part, 14 ... Cooling part, 20 ... Extension tube, 22 ... Electric heater.

Claims (1)

[Claims] 1. An apparatus comprising a plurality of orifices provided in a liquid metal flow path and a cooling unit for circulating liquid metal, wherein each of the orifices and the liquid metal inflow unit is provided between the orifice unit and the liquid metal inflow unit. A liquid metal purity monitoring apparatus, characterized in that the heaters are connected by extension pipes, and each of the extension pipes is provided with an electric heater for flushing that can be independently controlled in operation.