JPH0339682A - Sampling device for high-level radioactive material - Google Patents

Abstract

PURPOSE:To improve purging effect and to enable high-accuracy sampling by providing a nozzle part with by-pass piping and increasing the flow velocity in piping for collection at the time of the purging operation. CONSTITUTION:The by-pass piping 15 which has a by-pass valve 16 is connected to the branch part between piping 2 for circulation and piping 4 for collection. Sample gas which flows fast in the piping 2 at the time of the sampling is sucked in the piping 4 at the same speed at the part of a nozzle 14 and the duct spreads behind the nozzle 14, so that the gas is reduced in speed. At this time, a valve 1 is closed, but the valve 16 is opened at the time of purging and the gas in the piping 2 is able to flow in the piping 4 without passing through the nozzle 14, so the nozzle 14 causes no pressure drop and the purging air can flows fast even in the piping 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is used in nuclear power plants, etc., to collect dust and iodine at high concentrations in order to monitor radioactivity in exhaust gas released in the event of an accident. This relates to a radioactive material sample collection device.

[Prior Art] Fig. 2 and Fig. 3 show a conventional high-concentration radioactive material sampling device. ) and circulation piping (2
A collection pipe (4) branched at 46 parts is installed from Aa, and a collection pipe (4) is connected to the circulation pipe (2) and the collection pipe (4).
) are connected to pumps (5), <6), respectively.

A sample collector (7) for collecting dust and iodine in the gas passing therethrough and a sampling gas flow rate control valve (8) are inserted into the collection pipe (4). The circulation piping (2) and the purge piping (3) are each equipped with an inlet shutoff valve (9).
> and (10) are provided.

(11) is a purge gas cleaning filter. Flanges (12) and (13) for connection with external piping are provided on the intake side and the exhaust side of the circulation piping (2), respectively, with dimensions f. Note that the arrows in the figure indicate the flow direction of the sample gas, with arrow B indicating the flow direction during sampling, and arrow C indicating the flow direction during purging.

Figure 3 shows details of parts ^a and ^b in Figure 2,
The tip of the collection pipe (4>) is a nozzle (14).

Next, the operation will be explained. During sampling, the sample gas is sucked into the circulation pipe (2) connected to the external pipe by the flange (12>) by the circulation pump (5>), passes through the opened valve (9>), and then flows into the main body <1>. After circulating within the sample gas, it is exhausted to the external piping connected by the flange (13).This circulation piping (2) is used to detect dust and iodine in the external sample gas due to the effects of condensation and precipitation. A high flow rate is required to allow sampling into the sampler (7) without change.

On the other hand, a part of the sample gas is sucked into the collection pipe (4>) branched from the Aa section of the circulation pipe (2> by operating the collection pump (6>), and is sucked into the collection pipe (4>) branched from the Aa section of the circulation pipe (2> ) to obtain the required amount of sample gas from the sampler (7).
The sample collector (
Collect in 7). Thereafter, the repaired gas returns to the circulation path at the Ab section. This repair piping (4) allows only the amount necessary for sampling to flow, so especially for highly concentrated radioactive gases, it is necessary to flow a small flow rate in order to suppress the radiation dose in the sampling device to a manageable amount.

However, in order to branch the gas so as not to change the state inside the sample gas, the branching parts of parts ^a and ^b are connected to circulation piping (2> collection piping <4> at the same high speed as the internal gas). Therefore, the collection pipe (4
The tip of the nozzle <14> has a small opening area.

Further, after sampling, dust and iodine in the gas remaining in the pipes will cause measurement errors during the next sampling, so it is necessary to purge the pipes.

This purge is performed by closing the valve (9), opening the valve (10>, and operating the pumps (5) and (8) to circulate and capture indoor air that has been purified by the purge air filter (11). This is done by flowing it into the collection pipes (2) and (4).

[Problem to be solved by the invention] Since the conventional high-concentration radioactive material sampling device is configured as described above, the opening area of the nozzle part must be made very small, so the flow rate is low during purging. There was a problem that the purging effect in the collection pipe (4) was low.

This invention was made to solve the above-mentioned problems. During sampling, a nozzle enables uniform suction, while during purging, high-concentration radioactive material samples can be collected by increasing the flow rate. The purpose is to obtain equipment.

[Means for Solving the Problems] A highly concentrated radioactive material sample collection device according to the present invention is provided with a bypass pipe in the nozzle portion.

[Function] In the present invention, when sampling the bypass piping, the valve installed in the piping is closed and sampling is performed through the nozzle part, but when purging, the valve is opened to increase the flow rate in the collection piping. This makes it possible to more effectively blow away radioactive substances left inside the collection pipe.

[Example] Figure 1 shows an example of the present invention, in which circulation piping (2)
A bypass valve (16) is installed at the branch of the collection pipe (4).
> is connected to the bypass pipe (15).

The configuration of the pond is similar to that shown in Figure 2.

With the above configuration, during sampling, the circulation piping (2)
The sample gas flowing at high speed inside the nozzle (14) is sucked into the collection pipe (4) at the same speed;
After passing through the section, the pipe widens and the speed becomes low. (In this case, the bypass valve (16) is closed.) On the other hand, when purging, the bypass valve (16) is opened and the gas in the circulation piping (2) does not pass through the nozzle (14). Since the 2s can flow into the collection pipe (4), the nozzle (14)
Collection piping (4)
Purge air can also flow inside at high speed.

In addition, in the above embodiment, the case of collecting a highly concentrated radioactive material sample was explained, but even if the concentration is low, sampling is performed by dividing into two routes such as circulation and collection, and if the flow rates are different, , has the same effect.

[Effects of the Invention] As described above, according to the present invention, since the bypass piping is provided in the nozzle portion, the inside of the collection piping can be purged more effectively, so that highly accurate sampling can be performed.

[Brief explanation of drawings]

FIG. 1 is a piping diagram of a main part of an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional highly concentrated radioactive material sample collection device, and FIG. 3 is a piping diagram of a part of FIG. 2. (2)...Circulation piping, (4>...Collection piping, (7)
... Sample collector, (14) ... Nozzle, (15) ... Bypass piping, <16> ... Bypass valve. In each figure, the same reference numerals indicate the same or corresponding parts. Agent Zeng Ga Dao Class 15
．． 1 is high E'IF

Claims (1)

[Claims] A circulation pipe that circulates sample gas by a pump, a purge pipe that branches from this circulation pipe and is open to the atmosphere via a valve, and a sample collector that branches and joins from the circulation pipe via a nozzle. and a collection pipe in which a collection pipe is inserted, and a bypass pipe is provided at a branch part between the circulation pipe and the collection pipe to increase the purge flow rate of the collection pipe. Radioactive material sampling device.