EP4379742A1 - Decontamination of pipe sections - Google Patents

Abstract

The method presented here for chemical decontamination of a pipe section (1) is based on the fact that the entire cross-section of the pipe section (1) is not flowed through by a decontaminant. Instead, a blocking body (5) is introduced into the pipe section (1) so that decontaminant only flows in a circumferential gap (10). This allows the necessary volume of decontaminant to be significantly reduced. At the same time, the volume flow required to achieve a certain Reynolds number is significantly reduced so that the decontamination process can be carried out more efficiently overall.

Description

The present invention relates to a method for decontaminating contaminated pipeline sections, for example from a primary circuit of a nuclear power plant.

Contamination can be caused, for example, by the adhesion of radionuclides or chemical compounds. Contamination with radionuclides occurs particularly in nuclear facilities such as nuclear power plants, for example in a nuclear power plant's primary circuit. When components are replaced or when the nuclear facility is dismantled, decontamination is necessary in order to reduce the amount of radioactive material to be deposited. For example, it is known to mechanically remove radioactively contaminated surfaces of a component until the contamination is removed. This means that the entire component does not have to be deposited, only the removed material. It is also known to chemically remove contamination by bringing a decontaminant, for example comprising hydrochloric acid, into contact with the surface to be decontaminated, so that the contamination is dissolved by chemical reactions and the reaction products remain in the decontaminant. The decontaminant must then either be completely decontaminated or concentrated, for example by evaporation or similar. This is particularly complex when pipelines with a large diameter of 400 mm [millimeters] and more are to be chemically decontaminated, since the amount of decontaminant required is considerable due to the large pipe diameters.

Building on this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art in the chemical decontamination of pipelines. The object is achieved with the features of the independent claim. The dependent claims are directed to advantageous developments.

As a precaution, it should be noted that the numerals used here ("first", "second", ...) are primarily (only) used to distinguish between several similar objects, sizes or processes, and in particular do not necessarily prescribe any dependency and/or sequence of these objects, sizes or processes in relation to one another. If a dependency and/or sequence is required, this is explicitly stated here or it is obvious to the expert when studying the specifically described design.

The method according to the invention for decontaminating a pipe section having a starting region and an end region by bringing an inner surface of the pipe section into contact with a decontamination agent is characterized in that a blocking body is introduced into the pipe section, which extends at least over the length of the pipe section and blocks the interior of the pipe section except for a gap located between an outer surface of the blocking body and the inner surface of the pipe section, wherein the blocking body has spacers which extend from the outer surface of the blocking body in the direction of the inner surface of the pipe section and which define the gap, wherein the decontamination agent flows through the gap from the starting region to the end region.

The present method is a method for chemical decontamination. The pipe section is preferably cylindrical and is preferably a piece of pipe which has been separated from a primary circuit of a nuclear facility, for example. The contamination on the inner surface of the pipe section and any coatings applied there are dissolved by chemical reactions with the decontaminant, and the corresponding reaction products are washed away with the decontaminant. Pipe sections are usually only contaminated on the inside, since, even in the primary circuit of a nuclear facility, only the inside of the pipe section comes into contact with a contaminated liquid. The method presented here can significantly reduce the volume of decontaminant required to carry out chemical decontamination, since the inside of the pipe section is no longer completely flooded with decontaminant, but only the gap. The gap preferably has a height of between 15 and 20 mm [millimeters]. By forming a By using a small gap, a minimum flow velocity required for rapid decontamination, which causes a non-laminar flow on the inner surface of the pipe section, can be achieved more easily than if the pipe section were completely filled with chemical decontamination agent. In particular, the conveying capacity or the required volume flow can be significantly reduced compared to full flow with the same achievable Reynolds number.

Preferably, the blocking body has a geometry that corresponds to the geometry of the pipe section, at least in the area that lies inside the pipe section. By means of corresponding geometries, it is possible to define a gap of essentially constant height in a simple manner.

The blocking body preferably comprises a cylinder section which lies inside the pipe section. In particular, in the case of a cylindrical pipe section, a gap of essentially constant height can be defined in a simple manner. With a gap of essentially constant height, predominantly constant flow conditions and, as a result, predominantly constant reaction conditions can be achieved.

The cylinder section preferably has a cylinder length that is greater than or equal to a length of the pipe section. Preferably, the entire pipe section is thus filled with the cylinder section, so that the entire inner surface lies at a gap of essentially constant height. In this way, essentially uniform reaction conditions can be achieved over the entire length of the pipe section. Preferably, two conical sections that protrude above the pipe section are connected to the end of the cylinder section.

Preferably, the cylinder section has a cylinder diameter and the pipe section has an inner diameter and the difference between the inner diameter and the pipe section is 30 to 40 mm [millimeters]. The height of the gap then corresponds to half the difference. The height of the gap is therefore preferably 15 to 20 mm. Alternatively or additionally, the cylinder section preferably has a cylinder diameter and the pipe section has an inner diameter and the quotient of cylinder diameter and inner diameter is between 0.8 and 0.97. By forming a small gap between the inner surface of the pipe section and the blocking body, a high flow velocity and thus a high Reynolds number can be achieved at a low volume flow. The at least quasi-turbulent flow thus enables efficient contact of the decontaminant with the inner surface of the pipe section and thus efficient chemical decontamination at a low volume flow of the decontaminant.

Preferably, the blocking body has a maximum diameter due to the spacers and the pipe section has an inner diameter, and the difference between the inner diameter and the maximum diameter is in the range from 10 to 15 mm. Alternatively or additionally, it is preferred that the blocking body has a maximum diameter due to the spacers and the pipe section has an inner diameter, and the quotient of maximum diameter and inner diameter is in the range from 0.85 to 0.98. The maximum diameter is determined by the spacers. For example, if there is a cylindrical blocking body or a blocking body with a cylinder section with a cylinder diameter, the maximum diameter is larger than the cylinder diameter but smaller than the inner diameter. The maximum diameter is determined by the maximum distance perpendicular to the longitudinal axis of opposing spacers. For example, an inner diameter is 400 mm and the cylinder diameter is 360 mm. If the spacers extend 10 mm in the radial direction relative to the longitudinal axis of the pipe section, the maximum diameter is 380 mm. The design of the spacers so that the maximum diameter is smaller than the inner diameter enables the blocking body to be easily inserted into the pipe section and easily pulled out of the pipe section without it becoming jammed. This makes handling the blocking body much easier. In addition, the spacers do not constantly rest on the inner surface of the pipe section due to the flow, so that decontamination takes place over the entire surface. and thus also the areas of the inner surface of the pipe section where the spacers temporarily rest are decontaminated.

The blocking body, or at least the blocking body in the region of the outer surface, is preferably made of a material that is inert to the chemically active components of the decontamination agent. The following could be identified as an example: The blocking body, at least in the region of the outer surface, is preferably made of at least one plastic that is inert to the chemically active components of the decontamination agent. In particular, the blocking body, at least in the region of the outer surface, is made of a plastic selected from the following plastics: polyethylene (PE) and polytetrafluoroethylene (PTFE). These plastics are particularly inert with respect to hydrochloric acid, i.e. they do not react with hydrochloric acid. Hydrochloric acid is fundamentally a preferred active component of a decontamination agent, which can comprise other components, in particular water. Polyethylene and/or polytetrafluoroethylene enable the formation of a blocking body that can be used in many different ways without being attacked by the decontamination agent. It is also preferred that the blocking body be made, at least in the area of its outer surface, from at least one of the following plastics: polyethylene (PE), polytetrafluoroethylene (PTFE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS plastic). For these plastics and mixtures of at least two of these plastics, it is preferred to select a decontamination agent whose chemically active components do not attack the plastic(s).

Fig. 1

schematisch einen Rohrleitungsabschnitt, der dekontaminiert wird;

Fig. 2

schematisch einen Blockierkörper wie in Fig. 1 eingesetzt; und

Fig. 3

ein Beispiel einer Anlage zur Dekontamination eines Rohrleistungsabschnitts, in der das Verfahren zur Dekontamination eines Rohrleitungsabschnitts wie hier beschrieben eingesetzt wird.

The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description and/or figures. In particular, it should be noted that the figures and in particular the size relationships shown are only schematic. The same reference numerals denote the same objects, so that explanations from other figures can be used as a supplement if necessary. They show:

Fig.1

schematically a section of pipeline being decontaminated;

Fig.2

schematically a blocking body as in Fig.1 used; and

Fig.3

an example of a system for decontamination of a pipeline section in which the method for decontamination of a pipeline section as described here is used.

Fig.1 shows a schematic view of a pipe section 1 that is being decontaminated. The contamination can be radioactive, biological and/or chemical. The pipe section 1 is preferably a pipe section 1 that has been removed from a nuclear facility and in particular from a primary circuit of a nuclear facility. The pipe section 1 has a start region 2 and an end region 3. An inner surface 4, i.e. the inner surface of the pipe section 1, is decontaminated because it was contaminated with radionuclides, for example, in a primary circuit of a nuclear facility. For decontamination, the inner surface 4 is brought into contact with a decontamination agent, for example comprising hydrochloric acid (HCl), in particular hydrochloric acid dissociated in water. Chemical reactions dissolve the contamination on the inner surface 4 and any coatings present there, and the resulting reaction products are absorbed in the contaminant. By flushing the interior of the pipe section 1 with the decontamination agent, the inner surface 4 of the pipe section 1 is brought into contact with the decontamination agent and at the same time the reaction products are flushed out of the pipe section 1. The blocking body 5 is in Fig.2 shown in detail. The following description refers, unless explicitly stated otherwise, to both Fig.1 as well as on Fig.2 .

To carry out the decontamination, a blocking body 5 is introduced into the pipe section 1. The blocking body 5 is made of a material that does not react with the decontamination agent, in particular it is made of polyethylene (PE) and/or polytetrafluoroethylene (PTFE) or with a surface made of Polyethylene and/or polytetrafluoroethylene, especially when hydrochloric acid is used as a decontamination agent.

The blocking body 5 has a cylinder section 6 and conical sections 7 adjoining the cylinder section 6. The cylinder section 6 has a cylinder length 8 and a cylinder diameter 27 (cf. Fig.2 ), the cylinder length 8 corresponding to a length 9 of the pipe section 1 or lying slightly above or below the length 9, so that the cone sections 7 protrude beyond the pipe section 1. The blocking body 5 and in particular the cylinder section 6 of the blocking body 5 block the interior of the pipe section 1 except for a gap 10 which lies outside between an outer surface 11 of the cylinder section 6 and the inner surface 4 of the pipe section 1. In order to define the gap 10, the blocking body 5 has spacers 12 located on its outer surface 11, which prevent the inner surface 4 of the pipe section 1 from coming into contact with the outer surface 11 of the blocking body 5 and thus keep the gap 10 open.

The blocking body 5 has in its cylinder section 6 at several specific points in the longitudinal direction of the cylinder section 6 several spacers 12, which are distributed over the circumference of the cylinder section 6, preferably evenly distributed. In a plane perpendicular to the longitudinal direction of the cylinder section 6, the spacers 12 define (cf. Fig.2 ) a maximum diameter 13 that is smaller than an inner diameter 14 of the pipe section 1 but larger than the cylinder diameter 27. This makes it easy to insert the blocking body 5 into the pipe section 1, while at the same time the gap 10 remains intact due to the spacers 12. Due to the flow, the spacers 12 do not constantly rest against the inner surface 4 of the pipe section, so that the decontamination takes place over the entire surface. Preferably, the maximum diameter 13 and the inner diameter 14 differ by at least 20 and at most 30 mm [millimeters]. Preferably, the cylinder diameter 27 and the inner diameter 14 differ by at least 30 and at most 40 mm, so that the gap has a size of preferably 15 to 20 mm

Furthermore, an inlet funnel 15 is formed at the start area 2 of the pipe section 1. At the end area 3 of the pipe section 1, an outlet funnel 16. Inlet funnel 15 and outlet funnel 16 are conical and correspond in their geometry to the cone sections 7. Inlet funnel 15 and outlet funnel 16 are formed on the inside with an elastomeric plastic. Inlet funnel 15 and outlet funnel 16 are preferably formed from a non-elastic or only slightly elastic material into which a seal made of an elastomeric material such as ethylene propylene diene rubber (EPDM) is inserted, which enables a tight connection to the start area 2 and the end area 3.

The inlet funnel 15 and outlet funnel 16 are tightly connected to the pipe section 1 via connecting areas 17, which are formed by the seal in the case of an inserted seal, so that a gap 18 is formed between the inlet funnel 15 and the cone section 7 and the outlet funnel 16 and the corresponding cone section 7, which gap is fluidically connected to the gap 10. During operation, decontamination agent flows through a supply line 19 into the gap 18 of the inlet funnel 15, the gap 10 between the blocking body 5 and the inner surface 4 of the pipe section 1, the gap 18 of the outlet funnel 16 and a discharge line 20. The inner surface 4 is decontaminated by bringing it into contact with and the flow onto the inner surface 4 of the pipe section 1.

The decontaminant flows through the gap 10 past the inner surface 4 to be decontaminated. Compared to a situation in which the decontaminant flows through the entire pipe section 1, the volume of decontaminant required is significantly reduced. This also significantly reduces the amount of decontaminant that needs to be processed later. At the same time, the flow cross-section is significantly reduced compared to the inner diameter 14 of the pipe section 1, meaning that the minimum flow velocity required for efficient decontamination can be achieved in a more energy-efficient manner.

The blocking body 5 further comprises fixing pins 21, which engage frictionally in corresponding recesses 22 of the inlet funnel 15 and thus fix the blocking body 5 to the inlet funnel 15. In the present example, three fixing pins 21 are evenly distributed in the circumferential direction with respect to the longitudinal axis of the cylinder section 6, so that two fixing pins 21 adjacent in the circumferential direction with respect to the longitudinal axis of the cylinder section 6 each have the same angle to one another.

The pipe section 1 is preferably held in a receiving frame 23. This comprises two rollers 24 that are adjustable in the vertical direction to enable the discharge funnel 16 to be centered in relation to the receiving frame 23. The discharge funnel 16 is accommodated in a recess 25 in the receiving frame 23. A drain line 26 is also formed, which enables the decontaminant to be drained. Due to the vertical adjustability of the rollers 24, pipe sections 1 of different diameters can be accommodated in the receiving frame 23.

Fig.3 shows schematically a system 28 for decontamination of a pipeline section 1, which is placed in a receptacle 29. The receptacle 29 comprises the Fig.1 shown and thus allows the pipe section 1 to be placed on the receiving frame 23. The central longitudinal axis of the pipe section 1 is then set vertically on the central axis of the outlet funnel 16, which is preferably firmly connected to the receiving frame 23. The blocking body 5 connected to the inlet funnel 15 via the fixing pins 21 is introduced into the pipe section 1 and the inlet funnel 15 is moved against the pipe section 1 such that the pipe section 1 initially moves horizontally in the direction of the outlet funnel 16. Starting from the inlet funnel 15, pressure is applied to the pipe section 1 so that the starting area 2 clings to the inlet funnel 15 and the end area 3 clings to the outlet funnel 16, thus creating a liquid-tight connection between the inlet funnel 15, the pipe section 1 and the outlet funnel 16.

The spacers 12 attached to the cylinder section 6 of the blocking body 5 enable the cylinder section 6 to be supported on the inner surface 4 of the pipe section 1, whereby the design of the spacers 12 ensures that the blocking body 5 can move to an extent defined by the difference between the maximum diameter 13 and the inner diameter 14 of the pipe section 1, so that when flowing through the gap 10 with Decontamination agent causes a slight movement of the blocking body 5, which causes a full-surface decontamination of the inner surface 4 of the pipeline section 1.

The receptacle 29 also has heating means (not shown) via which the pipe section 1 can preferably be heated to a decontamination temperature of, for example, 70°C or more. After connecting the pipe section 1 to the receptacle 29 as described here and, if necessary, after heating the pipe section 1, the decontamination takes place as described below by way of example.

The decontaminant with chemically active components, for example hydrochloric acid, is stored in a reservoir 30. The reservoir 30 preferably has a heatable region 31. The heatable region 31 is formed in particular in the lower part of the reservoir 30, but can also comprise the entire reservoir 30. Here, the decontaminant is heated to a temperature that corresponds at least to the decontamination temperature. A suction system 32 is formed above the reservoir 30, which sucks off any vapors that may form above the reservoir 30. Decontaminant and other substances, for example hydrochloric acid (HCl) and copper(II) chloride (CuCl ₂ ), can be introduced into the reservoir 30 via a feed line 33.

Decontaminating agent is fed to the receptacle 29 via a line 34, which can be shut off and opened via a valve 35, and flows through gap 18 within the inlet funnel 15 into and through gap 10, where it reacts with substances on the inner surface 4 of the pipe section 1. From gap 10, the decontaminating agent flows with the reaction products through gap 18 in the outlet funnel 16 to the discharge line 36 to a filter 37, in which solids, in particular precipitated reaction products, are filtered out. The filter 37 has a shield 38, which shields radiation emanating from the filtrate. A pump 39, which is formed in the discharge line 36, conveys the flow of decontaminant to a three-way valve 40. Depending on the position of the three-way valve 40, the decontaminant flows back to the reservoir 30 via a return line 41. If the decontaminant is used up, i.e. it is no longer sufficiently chemically reactive, the decontaminant solution can be fed into a Neutralization container 42, in which chemical neutralization takes place. Via a second pump 43, the neutralized decontamination solution can be fed via a second filter 44 for further treatment or into the environment.

The method presented here for chemical decontamination of a pipe section 1 is based on the fact that the entire cross-section of the pipe section 1 is not flowed through by a decontaminant. Instead, a blocking body 5 is introduced into the pipe section 1 so that decontaminant only flows in a circumferential gap 10. In this way, the necessary volume of decontaminant can be significantly reduced. At the same time, the volume flow required to achieve a certain Reynolds number is significantly reduced so that the decontamination process can be carried out more efficiently overall.

Reference symbols

1

Pipeline section

2

Initial area

3

End area

4

Inner surface

5

Blocking body

6

Cylinder section

7

Cone section

8th

Cylinder length

9

length

10

gap

11

Exterior surface

12

Spacers

13

Maximum diameter

14

Inner diameter

15

Inlet funnel

16

Discharge funnel

17

Connection area

18

gap

19

Supply line

20

Derivation

21

Fixing pin

22

Recess

23

Support frame

24

role

25

Recess

26

Drain line

27

Cylinder diameter

28

Decontamination facility

29

Holder for pipe section

30

reservoir

31

heated area

32

Extraction

33

Supply line

34

Line

35

Valve

36

Derivation

37

filter

38

shielding

39

pump

40

Three-way valve

41

Return line

42

Neutralization tank

43

second pump

44

second filter

Claims (8)

Method for decontaminating a pipe section (1) which has a start region (2) and an end region (3) by bringing an inner surface (4) of the pipe section (1) into contact with a decontamination agent, characterized in that a blocking body (5) is introduced into the pipe section (1), which extends at least over the length (9) of the pipe section (1) and blocks the interior of the pipe section (1) except for a gap (10) lying between an outer surface (11) of the blocking body (1) and the inner surface (4) of the pipe section (1), wherein the blocking body (5) has spacers (12) which extend from the outer surface (11) of the blocking body (5) in the direction of the inner surface (4) of the pipe section (1) and which define the gap (10), wherein the decontamination agent flows through the gap (10) from the start region (2) to the end region (3) flows. Method according to claim 1, wherein the blocking body (5) comprises a cylinder section (6) which lies inside the pipeline section (1). Method according to claim 2, wherein the cylinder section (6) has a cylinder length (8) which is greater than or equal to a length (9) of the pipeline section (1). Method according to claim 2 or 3, wherein the cylinder section (6) has a cylinder diameter (27) and the pipe section (1) has an inner diameter (14) and the difference between the inner diameter (14) and the pipe section (1) is 30 to 40 mm [millimeters]. Method according to one of claims 2 to 4, wherein the cylinder section (6) has a cylinder diameter (27) and the pipe section (1) has an inner diameter (14) and the quotient of cylinder diameter (27) and inner diameter (14) is between 0.8 and 0.97. Method according to one of the preceding claims, in which the blocking body (5) has a maximum diameter (13) due to the spacers (12) and the pipe section (1) has an inner diameter (14) and the difference between inner diameter (14) and maximum diameter (13) is in the range of 20 to 30 mm. Method according to one of the preceding claims, in which the blocking body (5) has a maximum diameter (13) due to the spacers (12) and the pipe section (1) has an inner diameter (14) and the quotient of maximum diameter (13) and inner diameter (14) is in the range from 0.85 to 0.98. Method according to one of the preceding claims, in which the blocking body (5) is formed at least in the region of the outer surface (11) from at least one plastic selected from the following plastics: polyethylene (PE), polytetrafluoroethylene (PTFE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polycarbonate (PC) and acrylonitrile butadiene styrene (ABS).

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