JP2549155B2 - Radioactive waste liquid treatment equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radioactive liquid waste treatment apparatus for treating a radioactive liquid waste generated in a radionuclide handling facility.

(Prior art) A radioactive waste liquid is generated from a radionuclide handling facility such as a nuclear power plant, a nuclear fuel reprocessing plant, or a radioisotope handling facility. The composition of these radioactive liquid wastes varies greatly even in the same facility. Only the representative nuclides generated in each facility are listed below.

(1) Nuclear power plants: Most of the nuclides such as ⁵¹ Cr, ⁵⁴ Mn, ⁵⁸ Co, ⁵⁹ Fe, and ⁶⁰ Co, but ¹³¹ Cs and ¹³⁷ Cs may be included.

(2) Nuclear fuel reprocessing plant ... As the nuclides contained in the waste liquid, there are many ¹³¹ Cs, ¹³⁷ Cs, ⁹⁰ Sr, etc., and various other nuclides are contained.

(3) Radioisotope handling facility: It is completely different depending on the facility because what is handled is not decided.

A conventional radioactive waste liquid treatment device will be described by taking a nuclear power plant as an example. In this facility, the treatment device is different depending on the level of electric conductivity of the waste liquid. That is, as shown in FIG. 12, the low-conductivity waste liquid is treated by the treatment device in which the filter 1 and the desalting device 2 filled with the ion exchange resin are connected.

Here, the filter 1 is a device for removing the suspended matter in the waste liquid, the desalting device 2 is a device for removing the ionic components that have passed through the filter 1, and the removed deionized water is reused. ,
Or it is released.

On the other hand, the high-conductivity waste liquid is treated by the treatment device connected to the evaporative concentrator 3 and the desalting device 2 as shown in FIG. The latest equipment is a filter 1 shown in Fig. 12 that uses a hollow fiber membrane filter.

In this way, the desalting device 2 filled with the granular ion-exchange resin or the like is provided at the subsequent stage of the filter 1 or the evaporative concentrator 3, and the filter 1 removes ⁵⁴ Mn, ⁶⁰ Co and the like at the same time as removing the suspension. Then, the desalting device 2 removes the ionic components. When treated with the evaporative concentrator 3, ⁵⁴ Mn, ⁶⁰ Co remains in the concentrate.

(Problems to be solved by the invention) Although not limited to Cs and Sr, the radionuclide contained in the waste liquid is highly diluted from the chemical point of view even if the radionuclide concentration is high. is there. Considering the removal of such low-concentration ions with an ion exchange resin,
High-concentration components other than the radionuclide contained together are removed, and the effluent increases in purity and approaches pure water, but low-concentration ionic components (radionuclides) do not decrease in the same way, that is, at the same rate. Is normal.

Therefore, it is considered that the ionic nuclide is also detected through the desalting device 2. It is considered that Cs is a monovalent cation and has a large ionic radius, so that it is difficult to be captured by the ion exchange resin (has a small affinity with the ion exchange group).

In any case, the conventional radioactive liquid waste treatment device has a drawback that it is not effective in removing Cs, Sr and the like among ionic radionuclides.

The present invention has been made to solve the above drawbacks,
Radionuclides associated with suspended solids (corrosion products) ( ⁶⁰
It is to provide a radioactive waste liquid treatment device capable of rational treatment, which combines efficient separation and collection of Co, ⁵⁴ Mn, etc.).

(Means for Solving the Problems) The present invention relates to a collection tank for collecting radioactive waste liquid,
Connected to this collection tank, a pre-stage hollow fiber membrane filter for removing suspended radionuclides contained in the radioactive waste liquid, and treated water treated by the pre-stage hollow fiber membrane filter for further treatment. A reaction tank for performing, a scavenger tank for storing the scavenger to be charged into the reaction tank, and a stirring device for mixing the treated water and the scavenger received in the reaction tank, A post-stage hollow fiber membrane filter for removing ionic radionuclides from the scavenger-containing solution after the reaction in the reaction tank, and a treated water treated by the post-stage hollow fiber membrane filter A water tank, a sludge receiving tank for receiving suspended solids discharged during backwashing of each of the hollow fiber membrane filters and a used scavenger, and a treated material treated by the preceding hollow fiber membrane filter. Radiation of water A first radiation detector for measuring the concentration in-line, and a second radiation detector for measuring the radiation concentration of the treated water treated with the hollow fiber membrane filter at the latter stage in-line, A control device for inputting a signal from the second radiation detector and the first radiation detector is provided, and the control device determines whether the radioactivity concentration is high or low based on the signal from the first radiation detector. When the concentration is sufficiently low, it is determined that the radioactivity should be transferred to the treated water tank without being transferred to the reaction tank, and whether the radioactivity concentration is high or low is determined by the signal from the second radiation detector. ,
If the concentration is not sufficiently reduced, it is for making a decision to return the treated water to the reaction tank and instructing backwashing of the scavenger adhering to the hollow fiber membrane filter at the latter stage. Is characterized by.

(Operation) If most of the radioactive nuclides contained in the radioactive waste liquid are associated with the suspension, the treated liquid is collected only by the hollow fiber membrane filter treatment in the preceding stage. When an ionic radionuclide is also contained, an inorganic ion exchanger is added to the filtering solution, the radionuclide is collected by this ion exchanger, and the ion exchanger is attached to the ion exchanger by the hollow fiber membrane filter in the latter stage. Captured ionic radionuclides. Since the inorganic ion exchanger can capture a very dilute ionic component and has selectivity for the target ion to be captured, it can also capture a low concentration of ionic radionuclide that cannot be captured by an ion exchange resin.

Also, a first radiation detector for in-line measuring the radioactivity concentration of the treated water treated by the hollow fiber membrane filter in the preceding stage, and the radiation of the treated water treated by the hollow fiber membrane filter in the latter stage. A second radiation detector for measuring the active concentration in-line is provided, and the second radiation detector and the first radiation detector are connected to the control device.

This controller determines whether the radioactivity concentration is high or low based on the signal from the first radiation detector, and if the radioactivity concentration is sufficiently low, it is determined not to transfer to the reaction tank but to the treated water tank. Also, the level of the radioactivity concentration is judged based on the signal from the second radiation detector, and if the concentration is not sufficiently reduced, it is judged that the treated water should be returned to the reaction tank and the latter stage Command backwashing of the scavenger adhering to the hollow fiber membrane filter.

(Example) The Example of the radioactive waste liquid processing apparatus which concerns on this invention is described with reference to drawings.

FIG. 1 is a system diagram showing the configuration of an embodiment of the present invention. As shown in FIG. 1, the radioactive liquid waste treatment apparatus of this embodiment is roughly divided into two zones, A and B. Zone A is the suspension radionuclide removal zone, B
The zone is an ionic radionuclide removal zone. The main equipment in the A zone is the radioactive waste liquid collection tank (T ₁ ) and the hollow fiber membrane filter (F ₁ ) in the previous stage, and the main equipment in the B zone is the reaction tank (T ₂ ) and scavenger tank (T ₄ ). The hollow fiber membrane filter (F ₂ ) in the latter stage. In addition, sludge (suspended solids) discharged during the backwash filter of the treated water tank (T ₃ ) that receives the final treated water and the hollow fiber membrane filters (F ₁ and F ₂ ) at the front and rear stages. Of the concentration of sludge in the sludge receiving tank (T ₅ ) that receives the concentrate and spent scavenger) and the outlet water (treated water) of the front and rear hollow fiber membrane filters (F ₁ , F ₂ ) The first and second radiation detectors (D ₁ , D ₂ ) to be measured, the first and second radiation detectors (D _1
1 , a control device (N) for making a judgment on the transfer of the treated water by a signal from D ₂ ) is provided. Incidentally, the reference numeral P1 P4 in the pump, V ₉ from V ₁ was shows the valve.

Next, a method for treating radioactive waste liquid in the radioactive waste liquid treatment apparatus of the above embodiment will be described with reference to FIGS. 2 to 7. Further, FIGS. 8 to 11 show changes in radioactivity concentration due to each treatment step.

(1) The treatment method when most of the radionuclides are associated with the suspended solids is as follows.

As shown in Fig. 2, the waste liquid collected in the collection tank (T ₁ ) is transferred to the previous hollow fiber membrane filter (F ₁ ) by the pump (P ₁ ) and most of the suspended solids are removed. . Since radionuclides are removed by the hollow fiber membrane filter (F ₁ ),
The signal from the radiation detector (D ₁ ) is input to the control device (N) and it is judged that there is no need for further processing by the control device (N), and the reaction tank (T ₂ ) is bypassed and processed. Transferred to the water tank (T ₃ ).

The change in radioactivity concentration in this treatment step is shown in FIG.

In the figure, the vertical axis represents the radioactivity concentration, and the horizontal axis represents the collection tank T ₁ , the outlet of the front hollow fiber membrane filter F ₁ (reaction tank T ₂ ) and the outlet of the rear hollow fiber membrane filter F ₂ (treated water tank T ₃ ) shows the position. The dotted line (a) shows the case where a fixed amount of ionic radionuclide is contained and the amount of radionuclide associated with the suspended solid content is different. That is, it is clear that even if the amount of radionuclide associated with the suspended solids increases, it is almost captured by the hollow fiber membrane filter (F ₁ ) in the preceding stage. The solid line b shows the concentration in each device.

(2) The treatment method when the radionuclide and the ionic radionuclide associated with the suspended solid content coexist is as follows.

As shown in Fig. 3, the waste liquid collected in the seed collection tank (T ₁ ) is transferred to the previous hollow fiber membrane filter (F ₁ ) by the pump (P ₁ ) and most of the suspended solids are removed. To be done. However, since the ionic radionuclide is contained, the signal from the _first radioactive detector (D ₁ ) is input to the control device (N), and in this control device (N), the reaction tank (
Transfer to ₂ ) is judged.

The scavenger is put into the waste liquid transferred to the reaction tank (T ₂ ) from the scavenger tank (T ₄ ) and sufficiently stirred by the stirring device (M). After the ionic radionuclide is captured by the scavenger, the waste liquid (containing scavenger) is transferred by the pump (P ₂ ) to the hollow fiber membrane filter (F ₂ ) in the subsequent stage, and the ionic radionuclide is captured. The collecting agent is removed, and the treatment liquid is transferred to the treated water tank (T ₃ ). The change in radioactivity concentration at this time is shown in FIG.

However, when it is determined by the radiation detector (D ₂ ) and the control device (N) that the activity concentration of the outlet water (treatment liquid) of the hollow fiber membrane filter (F ₂ ) in the subsequent stage is not sufficiently reduced, The change in radioactivity concentration at this time is shown in FIG. 10, and as shown in FIG. 4, the treatment liquid is returned to the reaction tank (T ₂ ) and a new scavenger is again charged to treat it. The radioactivity concentration at this time is shown in FIG.

(3) The method of treating when backwashing due to an increase in the differential pressure of the hollow fiber membrane filter (F ₁ ) is as follows.

With the treatment of the waste liquid, the differential pressure (difference between the inlet pressure and the outlet pressure of the filter) of the preceding hollow fiber membrane filter (F ₁ ) rises,
It will be backwashed. The state at this time is as shown in FIG. Sludge (concentrate) discharged from the hollow fiber membrane filter (F ₁ ) in the previous stage is transferred to the sludge receiving tank (T ₅ ).

(4) The normal batch treatment and the treatment method when the differential pressure of the hollow fiber membrane filter is increased (when the ion trapping ability of the trapping agent remains) are as follows.

When the scavenger is added to the treatment liquid transferred from the hollow fiber membrane filter (F ₁ ) in the previous stage in the reaction tank (T ₂ ), but the scavenger still has the ability to trap ions (this is It is used again (as many times as possible) for the hollow fiber membrane filter (F ₂ ) at the latter stage, which is judged from the radioactivity concentration of the water. The state in this case is as shown in FIG. 6, in which the backwashing liquid (collector) of the hollow fiber membrane filter (F2) at the latter stage is returned to the reaction tank (T ₂ ) and mixed with the waste liquid flowing in next. It is processed. Despite the ion-capturing ability, this state also occurs when the differential pressure of the hollow fiber membrane filter (F ₂ ) in the latter stage increases.

(5) The treatment method when the outlet water quality of the subsequent hollow fiber membrane filter (F ₂ ) is poor and when the differential pressure increases (when the scavenger does not have the ability to collect ions) is as follows.

The back-stage hollow fiber membrane filter (F ₂ ) is backwashed when the radioactivity concentration of the outlet water of the post-stage hollow fiber membrane filter (F ₂ ) is high or when both the radioactivity concentration and the differential pressure are high. The scavenger that has captured the ionic radionuclide is discharged to the sludge receiving tank (T ₅ ) as shown in Fig. 7.

Therefore, in the present example, in the case where most of the radioactive nuclides contained in the radioactive liquid waste are associated with the suspension, the treatment liquid can be recovered only by the hollow fiber membrane filter in the preceding stage, and the ionic radioactive nuclide coexists. If so, an inorganic ion exchanger is introduced into the filtering solution, the radionuclide is collected by this ion exchanger, and the ionic radionuclide associated with the ion exchanger is captured by the hollow fiber membrane filter at the subsequent stage. According to this embodiment, the radioactivity concentration of the treatment liquid is reduced from 1/1000 as compared with the conventional example.
It can be reduced to 1/10.

[Effects of the Invention] According to the present invention, the radionuclide (the one associated with the suspension, the one ionic) present in the radioactive liquid waste can be efficiently removed. Further, since a control device having a function of judging transfer and processing by the signal input of the first and second radiation detectors is provided, rational processing can be performed.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a radioactive liquid waste treatment apparatus according to the present invention, and FIGS. 2 to 7 show respective operating states of a processing method for treating a liquid waste using the apparatus shown in FIG. System diagrams, FIGS. 8 to 11 are characteristic diagrams similarly showing changes in radioactivity concentration with each waste liquid treatment, and FIGS. 12 and 13 are system diagrams showing a conventional radioactive waste liquid treatment apparatus, respectively. A: Suspended radionuclide removal zone B: Ionic radionuclide removal zone T ₁ …… Collection tank T ₂ …… Reaction tank T ₃ …… Treated water tank T ₄ …… Collection agent tank T ₅ …… … Sludge receiving tank F ₁ …… _First stage hollow fiber membrane filter F ₂ …… _Second stage hollow fiber membrane filter D ₁ …… First radiation detector D ₂ …… Second radiation detector M …… Stirrer N ...... Control device P ₁ to P ₄ …… Pump V ₁ to V ₉ …… Valve

Claims (1)

(57) [Claims] 1. A collection tank for collecting radioactive waste liquid, a hollow fiber membrane filter in the preceding stage connected to the collection tank for removing suspended radionuclides contained in the radioactive waste liquid, and A reaction tank for receiving the treated water treated by the hollow fiber membrane filter and further treating it.
A scavenger tank for storing the scavenger to be charged into this reaction tank, a stirring device for mixing the treated water and the scavenger received in the reaction tank, and after the reaction in the reaction tank A hollow fiber membrane filter in the latter stage for removing the ionic radionuclide from the scavenger-containing solution, a treated water tank for receiving the treated water treated in the hollow fiber membrane filter in the latter stage, and each of the above. In-line the sludge receiving tank that receives the suspended solids discharged during backwashing of the hollow fiber membrane filter and the used scavenger, and the radioactivity concentration of the treated water treated by the preceding hollow fiber membrane filter. And a second radiation detector for measuring in-line the radioactivity concentration of the treated water treated by the hollow fiber membrane filter at the latter stage, and the second radiation detector for measuring Radiation detector and said And a control device for inputting a signal from the first radiation detector, the control device judges whether the radioactivity concentration is high or low based on the signal from the first radiation detector, and when the concentration is sufficiently low, When it is judged not to transfer to the reaction tank but to the treated water tank, and whether the radioactivity concentration is high or low based on the signal from the second radiation detector, and the concentration is not sufficiently reduced Is for returning the treated water to the reaction tank and for instructing backwashing of the collecting agent adhering to the hollow fiber membrane filter at the latter stage. .