JPH0336199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a technology for reprocessing radioactively contaminated liquids generated during the work processes of nuclear power plants and radiochemical laboratories. More particularly, the present invention relates to a method for continuous decontamination of radioactively contaminated liquids by distillation and an apparatus for carrying out the method.

The invention can be utilized in the nuclear industry for decontaminating radioactively contaminated liquids and obtaining high quality cleaning vapor during the decontamination of said liquids.

One important aspect of ensuring reliable and safe operation of a nuclear power plant is the reprocessing of radioactively contaminated liquids resulting from that operation. During distillation, the liquid is evaporated, thereby increasing the concentration of radioactive material in the liquid considerably. As a result of evaporation, the volume of the radioactively contaminated liquid can thus be greatly reduced and subsequent decontamination can be simplified.

The use of distillation processes involves two problems, namely the systematic provision of bioprotection to ensure the safety of workers and the obtaining of high quality steam for reuse within nuclear power plants.

Bioprotection is usually provided around the evaporator for the reprocessing of radioactively contaminated liquids, typically in the form of concrete walls or cladding, while the high quality of the steam is This is achieved by using an evaporator. In this case, the higher the concentration of radioactive substances in the liquid, the higher the radioactivity level on the surface of the evaporator, and the lower the quality of the vapor obtained. As a result, biological defenses must become increasingly thick and steam cleaning devices must become increasingly complex.

As a method for continuous decontamination of radioactively contaminated liquids,
A method is known in which the radioactively contaminated liquid is passed through an evaporation zone, the liquid containing highly concentrated radioactive material is discharged, and the vapors generated during the treatment are washed away (L.S. Sterman, E.S.). .A. Tefrin and A.T. Siyarukov, Steam and Nuclear Plants (Russian), Energoizdat Publishers, 1982, 166.
(see page, figure 9.30) (LS Sterman, SATevlin
and ATSharkov “Teplovye i atomnye
However, this method has the disadvantage of requiring a biological barrier covering the entire evaporation zone of the decontamination process, resulting in a very large amount of protection equipment.

Alternatively, the concentration of radioactive substances in the liquid increases sequentially and is fed continuously through two evaporation zones separated from the outside by a layer or body of liquid to prevent radioactive radiation. passing through the radioactively contaminated liquid, discharging the concentrated radioactive material-containing liquid from the second evaporation zone, and cleaning the vapor generated in each of the two evaporation zones to remove the radioactive material in the vapor. A method for discharging this cleaning vapor is known (see L.S. Sturman et al., cited above, p. 167, p. 167).
(see figure 9.31b).

Compared to the prior art methods mentioned above, the second method is advantageous in that the highest concentration of radioactive material is obtained in the second evaporation zone rather than the total volume or flow rate of the liquid to be decontaminated. Based on this fact, the biological shielding of the first evaporation zone, where the concentration of radioactive material and the resulting radiation level is lower than that of the second evaporation zone, does not have to be extensive.

However, due to the high concentration of radioactive material in the liquid being treated, the amount of radiation escaping from the second evaporation zone to the outside increases, and furthermore, without a reliable bioprotection device, the amount of radioactive material in the liquid will increase. A more thorough and reliable biodefense is required that prevents concentration and affects the efficiency of equipment for continuous decontamination of radioactively contaminated liquids.

Stills are known that include a housing with pipes for supplying and discharging a heating medium, a single pipe for discharging the vapor generated in the evaporator, and a pipe for introducing and discharging decontaminated liquid. ing. This housing contains a cylindrical heating chamber and vapor purification means (L.S. Starman, "The Evaporator" (Russian), Samasgitz Publishers (Moscow), 1956, pp. 16 and 17, vol. (See Figure 14) (LS Sterman “Ispariteli”).

The described evaporator is installed horizontally and the quality of the steam obtained is therefore sufficiently high that it is not possible to employ effective means for steam cleaning, which requires considerable space inside the evaporator housing. It's not something. Furthermore, horizontal installation of the evaporator requires a large area.

These disadvantages can be partially avoided by a continuous decontamination system for radioactively contaminated liquids that includes two interconnected vertical evaporators (L.S. Sterman, “The Evaporators”, supra). pp. 22-24, No. 10
(see figure).

In this system, high concentration of radioactive material takes place exclusively in the second evaporation zone or evaporator, so strong biological protection for the two evaporation zones is not required.

However, the biodefense of the second evaporator must be reliable enough to guarantee the safety of the working conditions of the workers when the concentration of radioactive substances in the liquid to be decontaminated is high.

Another continuous decontamination device (evaporator) for radioactively contaminated liquids that is closest to the present invention is known. The device includes a pipe for supplying radioactively contaminated liquid;
It includes a vertical housing with pipes for supplying and discharging the heating medium and one pipe for discharging the steam generated in the evaporator. The apparatus includes an evaporation chamber including a cylindrical heating chamber and some of the tubes of the cylindrical heating chamber, an upper area of the evaporation chamber being open to form an escape path for vapor into the interior of the housing; It comprises means for supplying the liquid to be decontaminated into it and pipes for discharging the liquid to the outside of the housing, and further comprises steam cleaning means above the heating chamber and the evaporation chamber (UK Patent No. 1347354). ,
(See IPCB01D1/12, 1/26, published in 1974).

The evaporation chamber is defined by a radially extending partition separating an area within the housing that includes some of the tubes of the heating chamber and a volume occupied by the liquid to be decontaminated. The upper rib of the septum is arranged to be at the same level as the liquid to be decontaminated. In this way two evaporation zones are provided within one evaporator.

The liquid to be decontaminated is supplied to the housing, where it is partially evaporated, and then supplied through holes in the liquid partition to the evaporation chamber for further evaporation.

Unlike the previously mentioned prior art devices, highly concentrated contaminants are collected within the evaporation chamber rather than throughout the interior of the device.

According to the device described above, radiation leakage to the outside through the housing of the device occurs only in the area where the evaporation chamber is provided.

Since no substantial increase in radioactive material occurs throughout the evaporator, the average concentration of these contaminants in the liquid occupying the interior of the evaporator is comparable to that described in the prior art devices mentioned above. It will be quite low. A high quality vapor is obtained with this device in view of the fact that the radioactivity of the vapor is determined by the concentration of radioactive material in the droplets carried by the vapor from the liquid being decontaminated. However, due to the increased concentration of radioactive substances where the evaporation chamber is set up, even more formidable biological protection is required, which further increases the construction cost of the device. In addition to this, another disadvantage is that the vapor is still of insufficient quality because it transports small droplets of liquid containing concentrated radioactive material from the evaporation chamber to the interior of the housing. be.

The present invention provides a method for continuous decontamination of radioactively contaminated liquids by distillation and the use of improved bioprotectants to increase the efficiency of the method and improve the quality of the vapor produced. The purpose is to provide a device.

This involves continuously passing radioactively contaminated liquid through two evaporation zones that are isolated from the outside by the liquid to prevent radiation from leaking to the outside as the concentration of radioactive substances in the liquid gradually increases. ,
Continuation of the radioactively contaminated liquid by discharging the liquid containing the concentrated radioactive material from the second evaporation zone and washing the vapor generated in each evaporation zone to remove the radioactive material present therein. The second evaporation zone has a radioactive material concentration that is higher than that of the first evaporation zone as the concentration of radioactive material in the liquid increases sequentially compared to the first evaporation zone. The liquid to be decontaminated contained in the active part of one evaporation zone and supplied to the first evaporation zone is used as a liquid layer that prevents radioactivity from leaking to the outside from the second or internal evaporation zone. This was achieved by a method characterized by:

It also includes a vertical housing having pipes for supplying radioactively contaminated liquid, discharging a heating medium, and discharging steam, the vertical housing incorporating a cylindrical heating chamber and an evaporation chamber, the evaporation chamber includes some of the tubes of said heating chamber, the upper part of which is open for discharging internally generated steam into the interior of the housing and providing means for introducing the liquid to be decontaminated from the interior of the housing. further comprising a pipe for discharging the liquid to the outside of the housing, and means for vapor treatment are provided above the cylindrical heating chamber and the evaporation chamber to continuously remove the radioactively contaminated liquid by distillation. In this apparatus, an evaporation chamber is provided substantially coaxially with the cylindrical heating chamber, and includes two shells of the same diameter fixed to the upper and lower end surfaces of the evaporation chamber, and a tube of the heating chamber. This was achieved by means of a device characterized in that the end of the tube is located inside a shell and the lower shell has a bottom.

Preferably, the means for supplying the liquid to be decontaminated from the housing to the evaporation chamber are configured as at least one inlet in the lower shell, while the interior of this shell is substantially coaxial therewith. A cowl is housed in the shell and a flow guide plate is provided above each inlet on the shell.

It is also desirable for the device to include additional means for steam cleaning mounted on the upper shell of the evaporation chamber.

The continuous decontamination method for radioactively contaminated liquid proposed here reduces the amount of biological defenses by using the radioactively contaminated liquid as a shield surrounding the evaporation zone where radioactive substances in the liquid to be decontaminated are concentrated. can be reduced. As a result, the shields conventionally used to shield the external evaporation zone can be reduced or even eliminated altogether, depending on the final concentration requirements of the radioactive material in the liquid. As a result, the amount of material used for decontamination devices and the plant area occupied thereby is substantially reduced, making these devices useful when employed in the nuclear industry.

Moreover, high quality steam is obtained because the zone of high concentration of liquid radioactive material is located within the evaporation zone of lower concentration. This is because more evaporation is produced in the outer evaporation zone where the concentration of radioactive material in the liquid droplets carried by the vapor is very low. It is also possible to obtain higher quality steam by using additional steam cleaning means that can be installed inside the internal evaporation zone, so that the cleaned steam can be used in nuclear plants without after-treatment. .

The method of continuously decontaminating a radioactively contaminated liquid by distillation is based on the method of continuously decontaminating a radioactively contaminated liquid. The method consists in passing radioactively contaminated liquid continuously through two evaporation zones. In the second evaporation zone, the concentration of radioactive substances in the liquid is higher than in the first evaporation zone, but the second evaporation zone is accommodated inside the first evaporation zone, and the latter inner zone, that is, the second evaporation zone. It is used as a protective body to prevent radiation from leaking to the outside.

The liquid containing radioactive material is discharged from the internal evaporation zone, and the vapor generated from each of the two evaporation zones is cleaned of the radioactive material contained therein and discharged for reuse.

The continuous decontamination device for radioactively contaminated liquids for carrying out the method of the invention consists of a vertical housing 1 (FIG. 1), the lower part of which contains the liquid to be decontaminated, forming an external distillation zone. It includes a cylindrical heating chamber 2.

In the upper part of the housing 1, overlapping the heating chamber 2, there is a steam cleaning means 3 which in this embodiment comprises two perforated plates 4, which are arranged horizontally one above the other. Furthermore, a separator 5 in the shape of a horizontal adjustment plate is attached above the two plates 4. The perforated plate 4 serves to clean the steam, while the separator 5 is used to dry the steam. A steam exhaust pipe 6 is provided at the top of the housing 1 above the separator 5.

The lower half of the housing 1 has two shells 8 and 9 of the same diameter arranged substantially coaxially with the cylindrical heating chamber 2.
The shells 8 and 9 are attached to the upper and lower end surfaces of the heating chamber 2, and are coaxial with one of the tubes 10 of the heating chamber 2 and attached to the end of the tube 10. part is ciel 8,9
It is installed so that it is housed inside. The lower shell 9 has a bottom 11 . The cavity surrounded by the upper and lower shells 8, 9 and the pipe 10 of the heating chamber 2 constitutes an internal evaporation zone.

The evaporation chamber 7 comprises means for circulating the liquid to be decontaminated, which means are embodied as passages 12 communicating with the cavities defined by the upper and lower shells 8,9. In the embodiment now considered, the passage 12 is constituted by a tube of the heating chamber 2, which tube has a substantially larger diameter than the other tubes 10 of the chamber 2 and is arranged coaxially therewith. It is being

An annular downcomer or space 11 is provided between the heating chamber 2 and the side wall of the housing 1 to aid in the circulation of the liquid to be decontaminated.

In order to avoid circulation and irregularities of the decontaminating liquid inside the evaporation chamber 7, a pipe (not shown) is provided outside the housing 1, and a pump, a cooler, a throttle valve, etc. are provided in the outer part of the pipe. It may also be used as a means for circulating the liquid.

In its lower part, the evaporation chamber 7 communicates with the interior of the housing 1 through means, for example a short pipe 14, for supplying the liquid to be decontaminated from the interior of the housing to the evaporation chamber. The evaporation chamber 7 has a pipe 15 for discharging a liquid containing concentrated radioactive material to the outside of the housing 1.

The housing 1 comprises a pipe 16 for introducing a radioactively contaminated liquid, which in this example is supplied onto the lower perforated plate 4 for carrying out the primary steam cleaning. The housing 1 also has respective pipes 17, 1 for supplying and discharging the heating medium.
8 and also a pipe 19 for supplying liquid to the upper perforated plate 4 for repeated steam cleaning. The perforated plate 4 is adapted to communicate with the lower part of the housing 1 through a pipe 20. Sleeves 21 are provided where the pipes 20 are attached to the plate 4, the height of these sleeves determining the level of liquid supplied onto the plate 4 for steam cleaning.

In the embodiment of the apparatus for carrying out the method of the invention described above, the means 3 for steam cleaning are used for cleaning both the steam generated in the internal evaporation zone and the steam produced in the external evaporation zone. There is.

On the other hand, another embodiment is also possible, which is basically the same as the one described above, but with an internal evaporation zone superimposed on the upper shell 8 (FIG. 2) of the evaporation chamber 7. Additional means 22 for cleaning the steam carrying the concentrated radioactive material are provided to improve steam cleaning. The means 22 are embodied and function in the same way as described for the separator 5.

The liquid to be decontaminated is transferred from the housing 1 to the evaporation chamber 7 in order to aid in the circulation of the liquid to be decontaminated inside the evaporation chamber 7 and to prevent irregularities in the flow of liquid through the tubes 10 of the heating chamber 2. The feeding means must have at least one inlet in the lower shell 9. In this embodiment, this means has two inlet portions 23 located opposite each other. A cowl 24 is provided inside the shell 9 in its radial direction, while a flow guide plate 25 is provided above the inlet section 23.

This continuous decontamination device for radioactively contaminated liquid operates as follows.

The radioactively contaminated liquid is fed into the housing 1 (FIG. 1) through a pipe 16 and poured onto the lower perforated plate 4. The liquid then flows through the pipe 20 into the lower part of the housing 1, which is the external evaporation zone, and is then introduced into the evaporation chamber 7 through the pipe 14. The liquid to be decontaminated is fed into the interior of the housing 1 and finally introduced into the chamber 7 until its level reaches above the upper end face of the cylindrical heating chamber 2.
Simultaneously with the supply of the liquid to be decontaminated to the intertube space of the heating chamber 2, a heating medium is introduced into the tubes through the pipes 17. Steam is commonly used as the heating medium. During condensation, this water vapor transfers heat to the decontamination liquid, which is conveyed through the heating chamber 2. Condensate is discharged through pipe 18.

As a result of the heating, steam bubbles are formed in the tube of the cylindrical heating chamber 2, which bubbles rise towards the upper end face of the heating chamber 2 and penetrate the layer of steam cleaning liquid to the upper part of the cylindrical heating chamber 2. Go out. The vapor is thereby separated from the liquid and rises to the upper part of the housing 1.

While rising along the tube of the cylindrical heating chamber 2, the steam bubbles adsorb droplets of the liquid to be decontaminated.
After passing through the cylindrical heating chamber 2 together with the vapor, the liquid to be decontaminated moves from the external evaporation zone into the annular space 13 between the housing 1 and the shell 8 of the heating chamber 2 and flows downwards along this annular space 13. The liquid reaches the lower end surface of the heating chamber 2 and completes the natural circulation of the liquid.

In the evaporation chamber 7, the circulation of the liquid to be decontaminated takes place in a conventional manner, the channel 12 being used as a downcomer.

During the formation and removal of the vapor, the concentration of the radioactive material introduced into the interior of the housing 1 together with the liquid increases, the increase in the concentration of the radioactive material in the external evaporation zone is less pronounced, while the concentration of the radioactive material introduced into the chamber 7 increases. The increase in concentration in the liquid is extremely large since the final evaporation of the liquid occurs here. This highly concentrated radioactive liquid is then discharged via outlet pipe 15. Due to the fact that the evaporation chamber 7 is arranged inside and coaxially with the housing 1, the part of the liquid to be decontaminated surrounding the chamber 7 has a low concentration of radioactive substances. The part of the liquid containing a low concentration of radioactive material acts to seal off the chamber 7, thereby reducing the level of radiation at the surface of the housing and thus acting as a biodefense.

In addition to this, the vapor formed in the external evaporation zone is accompanied by liquid with a relatively low radioactive concentration, resulting in a high quality vapor.

Before being discharged from the housing 1 through the pipe 6, the steam passes through a steam cleaning means 3 comprising upper and lower perforated plates 4, 5 and a separator 5. A layer of liquid forms on the perforated plate 4, the level of which is determined by the height of the sleeve 21. The liquid layer on the lower perforated plate 4 is formed by the liquid to be decontaminated, while the liquid layer on the upper perforated plate 4 is formed by the liquid supplied through the pipe 19 for steam cleaning. Ru. The liquid supplied for steam cleaning is introduced into the lower part of the housing 1 via a pipe 20.

The vapor formed in the two evaporation zones passes through the holes in the cleaning plate 4 and bubbles through the liquid layer on the plate 4 to clean and remove the small particles of liquid that have been conveyed from the part of the liquid to be decontaminated. Release the drops.

The primary steam cleaning is performed in the lower perforated plate 4 and the upper perforated plate 4 is used to perform the final steam cleaning. The efficiency of steam cleaning depends on the level of liquid on the perforated plate 4; the higher this level, the greater the efficiency.

The level of liquid on the perforated plate 4 is determined by the height of the sleeve 21.

The cleaning vapor is passed through the separator 5, which separates the liquid droplets carried by the vapor from the perforated plate 4.

The embodiment of the apparatus for continuous treatment of decontaminated liquids shown in FIG. The steam formed in the high chamber 7 (FIG. 2) first passes through the separator 22.
After that, it is cleaned with a separator 5.

The additional cleaning of the steam generated in the evaporation chamber 7 finally makes it possible to obtain high quality steam.

The liquid to be decontaminated is transferred from housing 1 to chamber 7.
The liquid flow can be straightened into the tube 10 of the cylindrical heating chamber 2 by means of a cowl 24 in the form of an inlet section 23 with a flow guide plate 25 on its upper part for supplying up to This can provide efficient circulation of the liquid in chamber 7 and increase the evaporation rate.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a continuous decontamination apparatus for radioactively contaminated liquid according to the present invention, and FIG. 2 is a longitudinal cross-sectional view of an improved embodiment of the present invention. means for supplying liquid from the interior of the housing to the evaporation zone, the means being configured as an inlet in the lower shell of the evaporation chamber. 1... Housing, 2... Cylindrical heating chamber, 3...
Steam cleaning means, 4... Perforated plate, 5... Separator, 6... Steam outlet pipe, 7... Evaporation chamber, 8, 9... Shell, 10... Tube, 11
...bottom, 12...passage, 13...space, 1
4, 15, 16, 17, 18, 19, 20...pipe, 21...sleeve, 22...additional steam cleaning means, 23...inlet section, 24...cowl, 25
...Flow guide board.

Claims (1)

[Claims] 1 Radioactively contaminated liquid is pumped through two evaporation zones that are isolated from the outside by the liquid so that radiation does not leak to the outside as the concentration of radioactive substances in the liquid gradually increases. By distillation, the liquid containing the concentrated radioactive material is continuously passed through and discharged from the second evaporation zone, and the vapor generated in each evaporation zone is washed to remove the radioactive material present therein. A method for continuously decontaminating a radioactively contaminated liquid, wherein the second evaporation zone, which has a higher radioactive material concentration than the first evaporation zone, is housed inside the first evaporation zone. , characterized in that the liquid to be decontaminated supplied to the first evaporation zone is utilized as a liquid layer that prevents radioactivity from escaping to the outside from the second or internal evaporation zone. 2 Pipes 16, 1 for supplying radioactively contaminated liquid, supplying and discharging heat medium, and discharging steam
comprising a vertical housing 1 having 7, 18, 6;
The vertical housing 1 houses a cylindrical heating chamber 2 and an evaporation chamber 7, each having a plurality of tubes 10 and 12 through which a radioactively contaminated liquid to be heated flows and is heated by the heating medium. The evaporation chamber 7 includes some of the tubes of the heating chamber 2, the upper part of which is open to discharge the vapor generated inside into the interior of the housing 1, and the liquid to be decontaminated from the interior of the housing 1. It has a pipe 15 for discharging the liquid to the outside of the housing 1, and a means for steam treatment is provided above the cylindrical heating chamber 2 and the evaporation chamber 7. This is an apparatus for continuously decontaminating radioactively contaminated liquid by steam cleaning means, in which the evaporation chamber 7 is provided substantially coaxially with the heating chamber 2 and has the same diameter fixed to the upper and lower end surfaces thereof. and a part 10 of the tube of the heating chamber 2, characterized in that the lower shell 9 has a bottom part 11. 3. The means for supplying the liquid to be decontaminated from the housing 1 to the evaporation chamber 7 are configured as at least one inlet 23 provided in the lower shell 9, while the interior of this shell 9 is substantially 3. Device according to claim 2, characterized in that a cowl (24) is accommodated coaxially and a flow guide plate (25) is provided above each inlet (23) on the shell (9). 4. The device according to claim 2 or 3, characterized in that the device comprises additional means 22 for steam cleaning mounted on the upper shell 8 of the evaporation chamber 7. .