JPS6031094A - Treating facility for radioactive waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to pretreatment equipment for radioactive waste pulverization and assimilation equipment, and particularly to a pretreatment equipment for waste liquid supplied to a centrifugal thin film dryer.

[Background of the invention]

Figure 1 shows a typical equipment configuration of radioactive waste powdering and solidification equipment using a conventional centrifugal thin film dryer. The following (1) and (2) are typical examples of radioactive liquid waste generated from nuclear power generation facilities.

(1) A reactor coolant purification system installed to prevent the accumulation of fission products generated by the nuclear reaction of fuel within the reactor 1 and the reactor system and the contamination of the coolant by corrosion products. There is a waste liquid generated from the filter 8. This is a reactor material in which powdered resin or the like is pre-coated on the filtration element of the reactor coolant purification system filter 80. Although the coolant is continuously purified, the amount of fission products and corrosion products trapped in the filter 8 increases with the passage of operating time, and the difference between the entrance and exit of the filter 8 increases. As the pressure increases, the purity of the water at the outlet of the filter 8 exceeds the specified value. At this point, the filter 8 is regenerated, and the fission products and corrosion products captured in the filter 8 as well as materials such as powdered resin pre-coated on the filter element of the filter 8 are removed from the filter 8. In the backwashing process, the waste sludge is discharged to a waste sludge receiving tank 11 provided on the downstream side. Thereafter, the filtration element of the filter 8 is precoated with new, unused powdered resin, etc., and the above steps are repeated.

(2) In a system in which the steam generated in the reactor 1 drives the turbine 2, the steam is converted to condensate in the turbine condenser 3, and the condensate is recovered to the reactor 1 by the condensate transfer pump 4, the turbine Waste liquid generated from the condensate filter 5 and condensate demineralizer 6 that are installed in the condensate recovery line from the condenser 3 to the reactor 1 for the purpose of preventing a decrease in operating efficiency and purifying the inside of the reactor 1. There is. The condensate filter 5 adopts the same filtration method as the reactor coolant purification system filter 8, and the filtration element is pre-coated with powdered resin, etc., and after use, the captured fission products, crud, etc. Powdered resin etc. silicated on the filtration element together with the corrosion products of the waste sludge receiving tank 11
will be collected. In operation, the waste liquid generated from the reactor coolant purification system filter 8 and the condensate filter 5 may be collected in separate receiving tanks.

The condensate demineralizer 6 is composed of a cation exchange resin and an anion exchange resin in which a polymer base and an ion exchange group are bonded.
", Mg", etc.) and H11m ions (C1-, PO:
When water is passed through a cation exchange resin and an anion exchange resin, the cations and anions in the waste liquid are captured by ion exchange with the ion exchange groups bonded to the polymer base. Here, the cation exchange resin generally contains a carboxyl group (-COOH), a sulfonic acid group (S O
a H), and includes strongly acidic cation exchange resins (R5OsH), weakly acidic cation exchange resins (R-C0OH), etc. - As an example, the ion exchange reaction between a strongly acidic cation exchange resin (R80s H) and Na+ in waste liquid is shown in equation 0.

R5OsH+Na”→R80aNa+H”・・・・・・
・・・・・・■ In addition, anion exchange resins, like cation exchange resins, have amino groups (-NHs
), imino group (>NH), and strongly basic anion exchange resin (R, -NHsOH).
) 9 weakly basic anion exchange resins (R-NH), etc. - For example, strongly basic anion exchange resins (RNHs)
The ion exchange reaction between OH) and Ct- in the waste liquid is shown in equation (2).

RNHsOH+C1-→R, -NH3CL +OH-・
・・・・・・・・・・・・・・・■ Due to the above ion exchange reaction, the impurities in the condensate flowing to the condensate demineralizer 6 are captured by the condensate transfer pump 4. Ru. However, since the amount of ion exchange resin filled in the condensate demineralizer 6 is limited, the condensate demineralizer 6 does not lose its ability to capture impurities after capturing a certain amount of impurities in the condensate. Since impurities exceeding the specified value will flow out at the outlet of the salter 6, the ability to capture impurities in the waste liquid must be restored by regenerating the ion exchange resin before the impurities exceeding the specified value flow out.

In general, cation exchange resins in nuclear power generation facilities are regenerated using sulfuric acid (HgSO4), anion exchange resins are regenerated using caustic sorter (NaOH), and the ion exchange resins after regeneration are reused.

This regeneration reaction is carried out using a used strongly acidic cation exchange resin (R80s Na) after capturing Na+ ions and a used strongly basic anion exchange resin (R-NHs) after capturing Ct- ions.
The case of Ct) is shown in formulas (■) and (2).

In the used cation exchange resin, 2(R5OsNa)+H2SO4→2(R5OsH)+
Naz80i・・・・・・・・・・・・・・・■ In the used anion exchange resin, RNHaC4+NaOH−+RNHsOH+NaC1・
・・・・・・・・・・・・■ The ion exchange resin regenerated by the above regeneration operation is refilled into the condensate demineralizer 6 and reused, and the waste liquid generated during the regeneration operation is transferred to the switching valve 1o. through the floor drain system waste liquid receiving tank 12
After being collected, the waste liquid is concentrated by the waste liquid concentrator 16 and then stored in the concentrated waste liquid storage link 17 .

Here, the ion exchange resin is used repeatedly to capture impurities in condensate through ion exchange reactions and to perform regeneration operations after capture, but the ability of this ion exchange resin to capture impurities in condensate increases as the number of regenerations increases. Therefore, the recycled ion exchange resin is recycled to some extent and then discharged as a used ion exchange resin to the waste resin receiving tank 13 via the switching valve 9, and then to the condensate demineralizer. is filled with new ion exchange resin.

In this discharge operation, the trapping capacity of the ion exchange resin is 1
Not only those that have been lost are also discharged, but some that have the ability to capture them are also discharged.

The radioactive liquid waste generated in the above process is temporarily stored in the waste sludge receiving tank 11, concentrated waste liquid storage tank 17, and waste resin receiving tank 13, respectively, but these wastes are not used in the operation of the nuclear power generation equipment. After being temporarily stored in a tank, it is transferred to the dryer supply tank 19 by the waste sludge receiving tank 14, waste resin receiving pump 15, and concentrated waste liquid transfer pump 18, and then processed. Ru.

The radioactive liquid waste transferred to the dryer supply tank 19 is adjusted as necessary for the properties of the waste liquid, such as the solid content concentration, and then a certain amount of waste liquid is supplied to the dryer 21 by the dryer supply pump 20. . Here, the water in the radioactive liquid waste is evaporated by the dryer 21 and separated into powder and evaporated water. The powder thus produced is supplied to an assimilation facility provided downstream of the dryer 21 and mixed with a solidification material to produce a stable assimilate. The evaporated moisture is treated by a vent treatment system connected to the dryer 21. That is, the evaporated moisture passes through a mist separator 22 installed in the vent treatment system, is condensed in a dryer condenser 23, is collected as drain in a receiving tank (not shown), and is then appropriately treated. Furthermore, since the dryer 21 is operated at a weak negative pressure, gas may leak, and the waste liquid supplied to the dryer 21 contains non-condensable radioactive gas. A vent treatment filter 24 is installed downstream of the water dispenser 23 to safely treat these gases. This vent processing filter 24 is used as a vent gas processing filter for equipment that handles radioactive gaseous waste, and is also used as a vent gas processing filter for towers and tanks that generate or handle gases such as radioactive iodine. After being processed, it is released into the atmosphere from the exhaust stack 26. In addition, as a typical gas processing device, a rare gas hold-up device 2 that processes gas leaking into the turbine condenser 3, etc.
There are 5. The treated gas is also discharged into the atmosphere from the exhaust stack 26.

In such conventional equipment, the waste to be treated by the dryer 21 is used ion exchange resin.

(9) Since there are used powdered resins and concentrated waste liquids, there are the following disadvantages in handling them.

(1) Because the specific radioactivity of the waste to be treated is high and the concentration of volatile radioactive substances such as radioactive iodine dissolved in the waste is high, it is difficult to treat the vent gas generated from each equipment and monitor its treatment performance. It becomes necessary.

(21 When pulverizing used powder resin and used ion exchange resin individually, there is a possibility of dust explosion due to the generated powder, so countermeasures are required.

(3) Since concentrated waste liquid containing a large amount of corrosive substances such as Ct- is handled, it is necessary to select and operate equipment specifications (especially materials) that fully consider corrosion resistance.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a radioactive waste treatment facility that is safe and easy to manage.

[Summary of the invention]

(10) In actual waste liquid tests at nuclear power plants, the present invention confirmed that the pH decreases in the process of mixing concentrated waste liquid and used ion exchange resin, and at the same time confirmed that the radioactive iodine dissolved in the waste liquid was dissolved in the gas phase. It has been confirmed through experiments that the amount of radioactive iodine released into the gas increases as the pH decreases. Detects pH in tanks where resin may be mixed.
It is designed to adjust.

That is, a feature of the present invention is that in a waste liquid supply facility that supplies concentrated waste liquid generated from a nuclear power plant and used ion exchange resin to a centrifugal thin film dryer, the pH of the concentrated waste liquid before being pulverized is adjusted. The point is that the device was installed.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings. FIG. 1 is a diagram showing an outline of a conventional radioactive waste processing facility. The configuration of the equipment shown in this figure is as described above, but it is designed to handle radioactive fluid waste such as used ion exchange resin, used powder resin, and concentrated waste liquid that is not generated during the operation of a nuclear power plant (11). When processing with the dryer 21, the waste resin receiving tank 13,
After being stored in the waste sludge receiving tank 11 and the concentrated waste liquid storage tank 17, it is transferred to the dryer supply tank 19, and after confirming and adjusting the solid content concentration in the waste liquid, it is transferred to the dryer 2.
It will be supplied to dryer 21 and processed into powder.
The amount of waste generated and the treatment pattern will vary depending on the operation of nuclear power generation facilities and fluctuations in the amount of radioactive waste generated due to performance fluctuations in equipment upstream of radioactive waste treatment facilities, as well as changes in the amount of radioactive waste generated due to changes in the performance of equipment upstream of radioactive waste treatment facilities. There is a possibility of a dust explosion due to the generated powder when the equipment capacity and operation etc. vary widely, and when used powdered resin, used ion exchange resin, etc. are supplied to the dryer 21 alone. When the powder is granulated and formed into pellets, the strength of the pellets becomes lower than that in the treatment of concentrated waste liquid, so it becomes necessary to add a binder or the like after pulverization. For this reason, the dryer 2 is a unique operation when processing radioactive waste liquid (12) as a dry powder.
In some cases, the mixture is mixed with concentrated waste liquid at a predetermined ratio before being supplied to the dryer 21.
As for the properties of the artificial waste liquid, there is a possibility that the concentrated waste liquid and the used ion exchange resin are mixed or mixed together in the dryer supply tank 19 and the transfer piping.

Here, the reaction formulas shown in Equation 0 and Equation 0 above are chemical formulas at the time of regenerating the used ion exchange resin, but the reactions are reversible.

Therefore, the type, concentration, etc. of the ion exchange resin and regenerating chemicals are selected so that the reaction is virtually irreversible, and it can be said that the reverse reaction will hardly proceed under normal conditions.

However, when we conducted a test in which concentrated waste liquid generated from nuclear power plants and actual waste liquid from used ion exchange resin were mixed at a volume ratio of 7:3, it was found that the concentration of waste liquid before mixing was
pH of H=9.8±3 and used ion exchange resin=
When 4.7±1.0 was mixed and stirred in a tank,
Agitation at a depth of about 2 to 3 minutes (13) A phenomenon in which the punching pH decreased to about 2 was confirmed. This is thought to be due to the following reaction between the unused ion exchange resin contained in the used resin and Na2804 in the concentrated waste liquid due to the action of various impurities contained in the concentrated waste liquid.

2(R5OsH)+NazSO4→2(R5OsNa)
+HzSO4・・・・・・・・・・・・■ Figure 2 shows 35m of concentrated waste liquid and 15m of used ion exchange resin.
This is a titration curve obtained by titrating with 1N-NaOH. , the amount of p in solution is easily determined by NaOH.
It was confirmed that as H decreased, that is, shifted to the acid side, the amount of iodine released into the gas phase increased as shown in Figure 3.
Ta. The same applies to non-radioactive iodine. pH in waste liquid
The lower the concentration of hydrogen ions in the waste liquid, the higher the concentration of hydrogen ions in the waste liquid.Iodine ions (IN) dissolved in the waste liquid become iodine (
This is thought to be because it is oxidized to (2) and then liberated into the gas phase.

(14) 1 2H"+2I-+ 02→I z + Hz O...
■This means that when the waste liquid is mixed in the dryer supply tank 19, the pH of the waste liquid decreases, which promotes corrosion of the dryer 21, etc., and also causes radioactive iodine dissolved in the waste liquid in the dryer supply tank 19 to decrease. There is no need to increase the amount of emissions.
This is also undesirable from the viewpoint of increasing the capacity of the vent filter 24 installed in the tank vent system or reducing radiation exposure to the public.

Therefore, in the present invention, the pH of the waste liquid is adjusted to 1-1 before being supplied to the dryer 21.

FIGS. 4 and 5 are diagrams showing an outline of an embodiment of the present invention.

In FIG. 4, the waste liquid transferred to the dryer supply tank 19 is circulated and stirred by the dryer supply pump 20 before being supplied to the dryer 21, and then directly passed to the pH measuring device 34. The pH of the waste liquid is measured, and if the pH is on the acidic side based on the pI-1 measurement result, it is caustic (15).The caustic soda supply pump 2 connected to the soda tank 28
Caustic soda is added from 9, and on the other hand, if it is on the alkaline side, sulfuric acid is added from a sulfuric acid supply pump 31 connected to a sulfuric acid tank 30 to adjust the pH. I) H is adjusted to 8 to 10 for corrosion resistance of equipment in the system and for suppressing the amount of radioactive iodine released from the dryer supply tank 19. This also provides good results in terms of physical properties for the solidified product produced in the solidification equipment 27 installed downstream of the dryer 21.

According to the present invention, it is possible to adjust the pH even if the pH decreases in the process of mixing concentrated waste liquid and waste liquid treated as used ion exchange resin, which improves the corrosion resistance of the equipment and the amount of radioactive iodine generated from the equipment. This has the effect of suppressing the

In addition, in a plastic solidification method in which the curing reaction is advanced by adding an initiator and an accelerator after dispersing the powder produced in the dryer 21 in the plastic assimilation material, the accelerator and initiator are added. The radicals generated by the reaction act on the (16) unsaturated bonds of the plastic solidifying material to cause a polymerization reaction, and this reaction proceeds in a chain reaction to harden.
The powder supplied to 1 and produced has reducibility,
It is thought that the radicals generated by the reaction between the accelerator and the initiator will react and inhibit the polymerization reaction of the solidifying agent, so that a stable assimilate will not be produced. To adjust to ~10,
It also gives good results in producing stable assimilates.

FIG. 5 shows another embodiment of the present invention, and the difference from FIG. 4 is that a radiation monitor 32 is installed in the middle of the vent pipe connecting the dryer supply tank 19 and the vent filter 24 to measure the radioactive iodine concentration. and depending on the measured iodine concentration υ
A computing unit 33 for calculating the amount of caustic soda or sulfuric acid added is provided, and this computing unit 33, the caustic soda supply pump 29, and the sulfuric acid supply pump 31 are linked. This embodiment also has the effect of reliably reducing the amount of radioactive gas released from the dryer supply tank 19 and making it possible to reliably adjust the pH (17).

[Brief explanation of drawings]

Figure 1 is a system diagram showing an overview of conventional radioactive waste treatment equipment, Figure 2 is a diagram showing the neutralization titration curve of a waste liquid mixed with concentrated waste liquid and used ion exchange resin, and Figure 3 is a diagram showing the neutralization titration curve of waste liquid. 4 and 5 are system diagrams showing the outline of the radioactive waste treatment equipment used in the embodiments of the present invention. 13... Waste resin receiving tank, 17... Concentrated waste liquid storage tank, 19... Dryer supply tank, 21... Dryer, 27... Solidification equipment, 24... Vent filter, 3
2... Radiation monitor, 33... Arithmetic unit, 28...
Caustic soda tank, 29... Caustic soda supply pump,
30... Sulfuric acid tank, 31... Sulfuric acid supply pump, 3
4...pH measuring device. Agent Patent Attorney Akio Takahashi (18) Hana 2 Figure [Sou/! ]

Claims (1)

[Claims] 1. In a waste liquid supply facility that supplies concentrated waste liquid generated from a nuclear power plant and used ion exchange resin to a centrifugal thin film dryer, the pH of the concentrated waste liquid before being pulverized is adjusted. A radioactive waste processing facility characterized by being equipped with a device. 2. Radioactive waste according to claim 1, wherein the means for adjusting the pH is to detect the concentration of radioactive iodine released from the waste liquid supply equipment, and adjust the pH based on the detected concentration. Material processing equipment. 3. In claim 1, the pH is 8 to 1.
Radioactive waste processing equipment characterized by adjusting between 0 and 0.