JPS58213275A - Automatic pretreatment of radioactive iodine in cooling water of nuclear reactor - Google Patents

Abstract

PURPOSE:To decrease the operation amount and the radiation exposure amount of an operator, by putting a sample liquid from a nuclear reactor cooling water into a tank and providing processes, etc. for adding an aqueous iodine carrier solution and sodium hypochlorite to the sample and for jetting a gas into the liquid for agitation. CONSTITUTION:The sample water is transferred to the first stirring tank 12 from a sample water tank 4, then the aqueous iodine carrier solution and NaClO are poured therein and stirred together with the sample water. Here, the transfer and injection of the aqueous iodine carrier solution and NaClO are performed by opening a solenoid valve V attached at these tanks 5, 6 by a signal from a microcomputer and simultaneously by compressing and transferring the liquid in the tank to the tank 12 by supplying the compressed gas into each tank from a gas supplying unit 13. Since a pretreatment using solvent extraction is performed automatically by this invention, the labor of operator and the radiation exposure amount of the operator can be decreased.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides an improved automated sample preparation method suitable for measuring extremely low 14 degree radioactive iodine contained in reactor cold N1 water and shipping water. Regarding a pretreatment method.

[Technical background of the invention and its problems] In a nuclear reactor, its cooling water (including shipping water)
It is extremely important to know the presence of radioactive iodine contained in the water and to measure its content for the following reasons. In other words, among the many fuel rods installed in the core of a nuclear reactor, healthy fuel rods are
When there are missing fuel rods, such as pinholes or other breaks in the fuel cladding, radioactive gas leaks from the burning fuel. In particular, the presence of radioactive iodine among radioactive gases is considered to be a source of information on fuel rod damage, and the amount of radioactive iodine can be used as an indicator of the extent of damage.

Therefore, measurements of radioactive iodine in reactor cooling water are regularly carried out as part of maintenance management work at nuclear power plants where nuclear reactors are installed.

To prepare a measurement sample containing tiIi cleavable iodine, it is first necessary to perform pretreatment, but this pretreatment method allows the lower limit of radioactive iodine quantification (mci/IIIβ) to be determined by gamma ray spectrometry using a GO detector. Now, the collected cold u1
Approximately 10-5 when measuring water as it is, approximately 10-5 to 10 when separating and measuring iodine by passing the collected cooling water through an ion exchange vapor or ion exchange column.
-6, when iodine is separated and measured by solvent extraction method, it is approximately 10-7 to 10-8.

As mentioned above, in order to know if fuel rods are damaged and to what extent, extremely low levels of water contained in the reactor cooling water that cooled the fuel rods must be detected. 1
Since the amount of radioactive iodine must be measured, it is necessary to use a solvent extraction method as a pretreatment method.

Conventionally, this solvent extraction work was carried out manually in the laboratory by a person working on the collected sample, but this method took time to measure and also increased the radiation exposure of the workers involved in the measurement. was there.

In order to solve these problems, the present applicant has developed an automated pretreatment method for radioactive iodine and has previously filed a patent application (Japanese Patent Application No. 5/1-115711).

However, in the method of this invention, stirring is performed using a magnetic stirrer or air bubbles passing through the pores of a cylindrical separation membrane to promote contact between the sample and various reagents added to it, so the stirring effect is sufficient. There was a drawback that it was not.

In other words, when a stirring tank and a separation tank are provided separately, mechanical stirring is performed using a magnetic stirrer in the stirring tank, and when stirring and separation are performed in one tank, air is sent through a cylindrical separation membrane. Stirring is performed by air passing through pores, but the former method has little stirring effect, and the latter method damages the separation membrane with the air pressure required to obtain a sufficient stirring effect. A sufficient stirring effect could not be obtained in either method.

Therefore, the contact between the aqueous phase and the organic carbon tetrachloride phase is not sufficient, and the extraction transfer of radioactive iodine to the carbon tetrachloride phase and the re-extraction from the carbon tetrachloride phase to the aqueous phase are not complete. The drawback is that it doesn't work.

In addition, since the liquid being processed by the reagent is transferred using a pump, etc., the liquid tends to remain inside the pump, which not only tends to reduce yield and cause contamination, but also requires maintenance and repair of many pumps. The problem was that it took a lot of time.

Furthermore, as shown in FIG. 1, in the latter method in which stirring is performed using a cylinder-type Il membrane 1, carbon tetrachloride phase a and the like remain at the bottom of the stirring tank 2, that is, near the separation membrane support part 3. This had the disadvantage of causing a decrease in yield and contamination.

[Objective of the invention] The present invention eliminates these drawbacks and reduces the yield loss and M 1l
) The aim is to provide an improved automatic pretreatment method free of contamination by ionic iodine.

[Summary of the Invention] 1J In other words, the present invention involves placing a sample placed above reactor cooling water into a tank, adding an iodine carrier aqueous solution and prium hypochlorite to the tank, and blowing out gas into the liquid. a step of stirring by adding carbon tetrachloride, hydroxylamine hydrochloride, and nitric acid to the stirred liquid in the tank and stirring by blowing out gas again; and a step of separating the stirred liquid by using a filter. passing through a membrane to avoid separating the carbon tetrachloride phase, transferring the separated carbon tetrachloride phase to another tank, adding J-t-lium sulfite or sodium hydrogen sulfite and water and stirring], and This is an automatic pretreatment method for radioactive iodine in reactor cooling water, which is characterized by the step of passing the liquid through a filter-like separation membrane to separate the aqueous phase.

[Embodiments of the Invention] Examples of the present invention will be described in detail below based on the drawings.

FIG. 2 is a block diagram illustrating the preprocessing method of the present invention.

In the method of the present invention, 11 pretreatments are performed through the steps described below. , 41, these stages are automatically controlled by the V-Ike 11-P1-Y, and the operational status of the Libe C tank and equipment is displayed on the cathode ray tube.

(1) First, l-11 collected from reactor cold 7JI water
2. Tank 4 of sample water containing various ion-dominant forms of used bamboo iodine of IO"-1103-1IO4-
Like J, IO body aqueous solution tank 5, hypochlorite II
)゛)-Riu lz (Na CJ20) Tank 6
, carbon tetrachloride (CCl2) tank 7, hydroxylamine hydrochloride (N+-120Ll/l-1cI tank 8.6
HNO3 tank9. ! lN! A zatorium hydrogen sulfate (NallSO3) tank 1-0 and a pure water tank 11 are prepared.

(2) After transferring the test r1 water from the test fit water tank 4 to the first stirring tank 12, add the iodine carrier aqueous solution and NaC
Stir J20 with 1 ship trial Y + 1 water.

Here, transfer injection of iodine 1!1 aqueous solution and Na C10 is done! At the same time, the solenoid valves V attached to these tanks 5 and 6 are opened in response to a signal from the Croni 1 pump coater, and at the same time pressurized gas is sent into each tank from the gas supply device 13. 1 stirring tank 12 under pressure.

The subsequent transfer and injection of reagents is also carried out in this manner.

Next, in the first stirring tank 12, a carbon tetrachloride tank 7,
Nt1201-1・I-I CA tank 8 and (-I
Carbon tetrachloride from NO3 tank 9, N I-120I-I
- Inject HCβ and HN Ox under pressure and stir thoroughly to extract radioactive iodine (12) into the carbon tetrachloride phase.

In order to cover a large amount of the contact area between the aqueous phase and the carbon tetrachloride phase during this stirring, pressurized gas from the gas supply device 13 is injected into the liquid through a glass filter. Alternatively, this can be carried out by blowing out gas using a single jet pump (AJP). In addition, the above Na
The stirring after the CJ20 is heated and the stirring in the subsequent steps are all performed by jetting gas into the liquid as described above.

(:IN!lγ After completion of r, the liquid in the first stirring tank 12 is transferred to the first separation tank 1/I, and a certain carbon tetrachloride phase is removed through the filter-like separation membrane. Minute #1
Ru. #1 membrane and C are commercially available solvent extraction valve #1 membranes, such as Polydetranol J [known under the trade name P Palta X].
: ], 1 membrane made of 1-1-lene is used and covered. subsequent minutes 11
111 'I culm odor (1 lllll membrane is used for hazubeni).

The carbon tetrachloride phase that has passed through the (/I) minute Q is the second ffi
The mixture is eluted after stirring. The aqueous phase remaining in the tank 1/l before the first minute is transferred to the aqueous phase waste liquid tank 16 using a capillary tube.

(5)) Second stirring tank 15 t' is minutes till L,
Wash the carbon tetrachloride phase. 1, the aforementioned N
ti 2011・IICJ2 Tank 8 and HN 03
NlI2011・It Cn and II from tank 9
After adding and transferring N O3 to the second stirring tank 1F) and stirring with a Avoid separating the carbon chloride phase, and elute the carbon tetrachloride phase into the third stirring tank 18.Inside the second separation tank 17, the remaining aqueous phase is the same as in step 4 above. Then, the C aqueous phase PfP is transferred to the liquid tank 16 using a capillary tube.

J Me, this washing [culm is sample water! J, -)
'C can be omitted.

(6) Transported 8r of carbon tetrachloride phase! 3 stirring tank 1
Add Nall5O:+ pure water from NaH8O3 tank 10 and pure water tank 11 to 8 and stir it.

(7) The liquid in the 33rd stirring tank 1B is transferred under pressure to the 3rd separation tank 19 of Rebe C, and -C is separated through a filter-like separation membrane.The carbon tetrachloride phase is transferred to the organic phase waste liquid tank (
Transfer to a storage facility (not shown in the figure) and dispose of it.

(8) Transfer the mizuhiki remaining in the first separation tank 1/I to the sample container 20 through a capillary tube to obtain a measurement sample.

(9) A certain amount of the sample for measurement is collected into the recovery rate measuring device 21, and the temperature of the iodine carrier is measured by the colorimetric method or the iodine electrode method, and the temperature of the iodine carrier is determined.

<'i ni , J, tsu17. i'A nffi
When using +41θ, [Test file size”?: < 2
(At 1%, use CI as L and 2 measuring instruments 21
B) Kotoka C monkey.

('I O) Finally, the entire Cisno 18 mentioned above is a? 7!
Add a prefecture 1U body aqueous solution to the sample water to make it! Zuni,
The 43 works of (2) - (8) above (J now. At this time 1
The tested sample zl is discarded without being transferred to the sample t'l container 20.

Next, the shape and structure of the split tank used in the present invention C will be explained in more detail with reference to the drawings.

FIGS. 3 and 4 are cross-sectional views for explaining the structure of the storage tank indicated by 22 in the figures. In FIG. 33, a glass-noir tank 23 is installed in one part of the stirring tank 22, and one gas tank is installed.
The gas that was pressurized from ~24 to the glass noilter't
2:1 passing through the 1st hole and heading towards F1 (-spout,
The liquid collected at the bottom of the stirring tank 22 can also be efficiently stirred and
It has a structure where J is 0.

'', tJ, 11 ends 25 between the double gas tubes 24 are hemispherical or cylindrical, and have a structure that prevents liquid from remaining in the upper part of the gas pipes 24.

Further stir 1゛I' to f? -II L/1. : In this case, this part will become a sword reservoir and the liquid will flow out.
Use 4' to prevent intrusion.

In Fig. 4, C indicates that a ΔJ r' 26 is provided at the tip of the gas tube 24 inserted into the upper part of the stirring tank 22, and the gas is sucked by the ΔJ I) 26 and ejected into the liquid. It is configured to stir & l J, and the agitation is stopped (in this case, △J r) 26
There is a part that acts as a gas reservoir and prevents liquid from entering the gas tube 24.

Stirring tank 2 shown in Figure 33 and Figure 4
2. There is a capillary-like reagent injection chamber 27 in a part of the body, and there is a structure that allows fine adjustment of human fluid flow. The tip of the entry tube 27 is formed in the shape of a tapered circle ε1 in order to minimize adhesion of the reagent to the tube wall.

As described above, the 11-meter tank shown in Fig. 6'A3 and Fig. 4 uses an internal stirring method that does not use an external drive shaft where leakage from the seal 8 (-) is a problem. 'r It is impossible for the liquid to remain inside the drying tank, so that the cumulative extraction yield is low (/1).

FIG. 5 is a cross-sectional view C of 28 (I, : DA) which explains the structure of the eastern part of the divided tank which is to be reduced in size.

5) In the figure! 3C is the l in the leaky divided tank 28.
・A Noirter-like membrane 29 is attached to the crotch GJ, and its edge is pressed down with a 7-inch punch 30 with a cross section of -1.
Therefore, the entire wetted surface of 11i1929 acts effectively as separation N9, but the separation membrane 29
Part 1. -1 liquid may remain. In addition, the action of the rose 1-30 having a U-shaped cross section fi11 prevents the liquid from leaking in the horizontal direction of the front 29, allowing the aqueous phase to be contained in a well-contained manner. It's going to take 1ill a minute or C.

Furthermore, in this separation tank 28, I3 U G, L, min.
11 A drainage capillary 31 is provided in a part of the membrane 291 with the L1 end kept away from the membrane surface, and the aqueous phase separated by water pressure and surface tension and remaining in the separation membrane -1- is sucked up and transferred. Type 11 has been adopted. Therefore, it is necessary to use a transport device such as the transport bomb 1 (4T), and it is possible to improve the yield and avoid contamination.

1. In addition, an automatically open/close valve (t!f on the same vehicle) is installed on the 47F water line that connects the +JI Mizukawa service pipe 31←, so that only the separated water phase flows to the IJ + water line. It is composed of (is).

In addition, 5) In the figure, 32μ liquid H inlet tube, 3C3 is the air vent tube, and 34 is the divided transfer tube shown on the right.

[Effect of Defense 1 As explained above/: J. Sea urchin According to the present invention, J. Pretreatment for solvent extraction to obtain a sample for measurement of Q4t'l iodine contained in cold 7JI water. automatically f-7
Not only is it possible to reduce the number of damaged wires caused by workers, but it is also possible to significantly reduce the variation in recovery rate compared to the variation due to individual differences among workers. .

In the present invention, almost no liquid remains in the equipment used for each culm, making it possible to carry out pretreatment with extremely high yields.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the structure of a conventional separation tank, Figure 2 is a 71'J diagram of I-Kome explaining the embodiment of Akira Honkita, Figures 3, V3 and 4 are 1. A cross-sectional view for explaining the structure of a stirring tank used in the embodiments of the invention; Cross-sectional view (・Yes.

Claims (1)

[Claims] (1) Put the sample placed in the reactor cooling water into the tank,
There is a step of adding an aqueous iodine carrier solution and sodium hypochlorite and stirring by blowing gas into the solution, and adding carbon tetrachloride, hydroxylamine hydrochloride, and nitric acid to the stirred solution in the tank, and then adding it again. Similar to the previous step, there is a step of stirring by blowing out gas, a step of passing the stirred liquid through a filter-like separation membrane to separate the carbon tetrachloride phase, and a step of transferring the separated carbon tetrachloride phase to another tank. It is characterized by comprising a step of adding sodium sulfite or sodium hydrogen sulfite and water to the mixture and stirring by blowing out gas, and a step of passing the stirred liquid through a filter-like separation membrane to separate the aqueous phase. Automatic pretreatment method for M-sulfur iodine in nuclear reactor cooling water.