Method and System for Removing Radioactive Nuclides from Water

Abstract

The present invention concerns a method for the removal of radionuclides from water, wherein at least one absorption additive that has an absorptive effect on the nuclides and at least one filter device that is impermeable to the adsorption additive and the nuclides absorbed thereon are used. An improved removal rate is achieved with reduced equipment expenditure when an adsorption layer is formed from the adsorption additive on an inflow-side surface of the respective filter device.

Claims

1. Method for the removal of radionuclides from water, wherein at least one absorption additive that has an absorptive effect on the nuclides is used, and wherein at least one filter device that is impermeable to the respective adsorption additive is used, characterized in that an adsorption layer is produced from the adsorption additive on an inflow-side surface of the respective filter device.

2. Method as claimed in claim 1, characterized in that the adsorption layer is produced from an adsorption additive that is essentially free of nuclides.

3. Method as claimed in claim 1, characterized in that the adsorption layer is produced from an adsorption additive that is at least 50% free of nuclides.

4. Method as claimed in claim 1, characterized in that adsorption of the nuclides takes place during a filtration phase of a filtration process largely or essentially in the adsorption layer.

5. Method as claimed in claim 1, characterized in that at least 50% of adsorption of the nuclides takes place during a filtration phase of a filtration process in the adsorption layer.

6. Method as claimed in claim 1, characterized in that production of the adsorption layer takes place during a start phase of a filtration process by means of addition of the adsorption additive to a water flow flowing through the respective filter device.

7. Method as claimed in claim 6, characterized in that the adsorption additive is added to the water flow largely or essentially only during the start phase.

8. Method as claimed in claim 1, characterized in that at least 50% of the total adsorption additive used during a filtration process is contained in the adsorption layer.

9. Method as claimed in claim 1, characterized in that, in order to produce the adsorption layer, the adsorption additive is added to a water flow flowing through one of the respective filter devices at a concentration of at least 50 ppm.

10. Method as claimed in claim 1, characterized in that at least one ceramic filter membrane is used in the respective filter device.

11. Method as claimed in claim 1, characterized in that the adsorption additive is a particulate solid.

12. System for removal of radionuclides from water, having at least one filtering station that contains at least one filter device in a filter tank, through which a water flow can flow, and having at least one dosing device for addition of an adsorption additive to the water flow, characterized in that the respective dosing device is arranged and/or configured in such a way that it can add the adsorption additive to the water flow inside the respective filter tank or immediately upstream thereof.

13. System as claimed in claim 12, characterized in that at least two filtering stations are provided, specifically at least one main flow filtering station and at least one secondary flow filtering station, and the dosing device for addition of the adsorption additive to the water flow inside the respective filter tank of the at least two filtering stations is configured in such a way that a filtration rate is produced in the respective main flow filtering station that is different from that in the respective secondary flow filtering station.

14. System as claimed in claim 12, characterized by having a control device for operating the system that is connected to the respective dosing device and is configured and/or programmed so that during operation of the system, it carries out a method for the removal of radionuclides from water, wherein the absorption additive has an absorptive effect on the nuclides, and wherein the filter device is impermeable to the adsorption additive, characterized in that an adsorption layer is produced from the adsorption additive on an inflow-side surface of the filter device.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0043] The figures are schematic representations of the following:

[0044] FIG. 1 shows a highly simplified, circuit diagram-like schematic representation of a system for removal of radionuclides from water, and

[0045] FIG. 2 shows a highly simplified sectional view of a filter device in the area of an adsorption layer.

DETAILED DESCRIPTION OF THE INVENTION

[0046] As shown in FIG. 1, a system 1 by means of which radionuclides such as radium isotopes can be removed from water, for example in order to produce drinking water or process water, comprises at least one filtering station 2, 3 and at least one dosing device 4. In the example of FIG. 1, two such filtering stations 2, 3 having a common dosing device 4 are shown purely by way of example. Another system 1 can also function with only a single filtering station 2, 3 or have more than two filtering stations 2, 3. Several dosing devices 4 may also be provided.

[0047] Each of the respective filtering stations 2, 3 has a filter tank 5 or 6 in each of which at least one filter device 7 or 8 is configured. In this case, a water flow 9 or 10 indicated by an arrow can flow through each of the respective filter devices 7, 8. The water flows 9, 10 are supplied via a common supply line 11 that branches at 12 in order to feed contaminated water, i.e. water containing radionuclides, to the filter tanks 5, 6 in parallel. Separate lines 13, 14 leading away are used to discharge the purified water, i.e. the decontaminated water or product water, from the filter devices 7, 8.

[0048] The dosing device 4 is configured in such a way that it can add an absorption additive 15 indicated in FIG. 2 to the water flows 9, 10 upstream from the filter devices 7, 8. The dosing device 4 can add the adsorption additive 15 to the respective water flow 9, 10 inside the respective filter tank 5, 6. A corresponding dosing line 16 of the dosing device 4 is directly attached to the respective filter tank 5, 6. The respective filter device 7, 8 is adjusted with respect to its filtration effect or particle size in such a way that it is permeable to water and essentially impermeable to the adsorption additive 15 and the nuclides accumulated thereon.

[0049] Provided that, as shown in FIG. 1, at least two filtering stations 2, 3 are configured, the one filtering station 2 can serve as the main flow filtering station 2, while the other filtering station 3 serves as a secondary flow filtering station 3. The dosing device 4 can separately add the required amount of adsorption additive 15 to the separate filtering stations 2, 3 or supply it to the respective filter tank 5, 6. It is advantageous to carry out dosing of the adsorption additive 15 to the two filter tanks 5, 6 individually in such a way that different filtration rates can be set at the two filtering stations 2, 3.

[0050] For operation, the system 1 should preferably be equipped with a control device 17 that is attached for example via a control line 18 to the dosing device 4. The control device 17 should preferably be configured or programmed in such a way that it can carry out the method for the removal of radionuclides from water explained in detail above and summarized below while the system 1 is in operation.

[0051] In order to remove the nuclides from the contaminated water, for example in order to produce product water that can be used as drinking or process water or is to be processed into drinking or process water, the adsorption additive 15 is configured in the filter tanks 5, 6 in such a way that an absorption layer 20 is formed from the adsorption additive 15 as shown in FIG. 2 on an inflow-side surface 19 of the respective filter device 7, 8. The adsorption layer 20 is produced from the adsorption additive 15, which is essentially still free of nuclides, so that absorption of the nuclides essentially takes place during a filtration phase of a filtration process only when it reaches the adsorption layer 20, and preferably exclusively in said layer.

[0052] For example, this kind of adsorption layer 20 can be produced by adding the adsorption additive 15 during a start phase of the filtration process to the respective water flow 9,10 flowing through the respective filter device 7, 8. During the start phase, the respective water flow 9, 10 cannot be composed of uncontaminated or already purified water. However, it is generally possible to use contaminated raw water during the start phase in order to apply the adsorption layer. By addition of the adsorption additive 15 to the water flow 9, 10 flowing through the respective filter device 7, 8, the adsorption layer 20 automatically forms as a filter cake on the inflow-side surface 19 of the respective filter device 7, 8. Addition of the adsorption additive 15 to the respective water flow 9, 10 or the respective filter tank 5, 6 should preferably be carried out in such a way that to the extent possible, the entire inflow-side surface 19 of the respective filter device 7, 8 is loaded as uniformly as possible with the adsorption additive 15. The start phase can last a few minutes. In any case, the start phase is much shorter than the subsequent filtration phase, in which the nuclides can be removed from the contaminated water by the adsorption layer 20.

[0053] Addition of the adsorption additive to the water flow 9, 10 should preferably be carried out exclusively during the aforementioned start phase so that no addition of the adsorption additive 15 takes place during the much longer filtration phase in particular. The addition of the respective adsorption additive 15 during the start phase or during a dosing period within the start phase is carried out at a relatively high concentration, which for example can be at least 50 ppm or at least 100 ppm, preferably at least 500 ppm, and particularly preferably at least 1000 ppm. Here, the absolute amount of the adsorption additive depends on the contamination of the raw water, the volume flow of the raw water, and the absolute amount of the raw water to be purified during the filtration process. At the end of the filtration process, the adsorption layer 20 should ideally be almost saturated with the adsorbed nuclides. For a new filtration process, the respective filter device 7, 8 may be regenerated, for example by means of backflushing, in which the exhausted or used adsorption layer 20 is rinsed off the inflow-side surface of the filter device 7, 8. After this, a new, unused adsorption layer 20 can be applied in a new start phase.

[0054] In a particularly advantageous embodiment, the filter device 7, 8 is equipped with at least one ceramic filter membrane 21 that has at least a part of the inflow-side surface 19 of the respective filter device 7, 8. According to FIG. 2, the filter membrane 21 has at least one internal channel 22 through which the purified water flow 9, 10 enters and from which the purified water flow 9, 10 can be discharged from the respective filter device 7, 8. The filter membrane 21 should preferably have a particle size in the single- or double-digit nm range.

[0055] As an absorption additive 15, a solid is preferably used that is granular or floccular, i.e. is used in the form of particles. The solid used may be solid or porous. This provides the adsorption layer 20 with a porous structure. The porosity of the absorption layer 20 is preferably within the single- or double-digit pm range. The porosity of the adsorption layer 20 can generally also be less than that of the filter membrane 21.

[0056] Purification or decontamination of the water is conducted by means of adsorption of the nuclides to the adsorption additive 15 that takes place while the water flows through the adsorption layer 20 in such an efficient manner that an adsorption rate of at least 90% to 95% can be achieved.

[0057] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0058] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0059] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.