FIELD OF THE INVENTION

The present invention is directed to a lubricating device for introducing a lubricant into a pipeline, an instrumentation tube system of a nuclear power reactor and a method for lubricating the instrumentation tube system of said nuclear power reactor.

TECHNICAL BACKGROUND OF THE INVENTION

The neutron flux density in a core of a commercial nuclear reactor is measured, inter alia, by introducing irradiation targets in the form of solid spherical probes, also known as aeroballs, into pipelines of an instrumentation tube system passing through the reactor core. Pressurized gas can be used for driving the aeroballs in the instrumentation tube system comprising the pipelines.

The instrumentation tube system of commercial nuclear reactors can also be used for producing radionuclides by introducing irradiation targets into the instrumentation tube system. In this case, the irradiation targets comprise suitable precursor materials, which are converted into desired radionuclides by the irradiation experienced in the core of the nuclear reactor.

WO 2016/128177 describes a movable irradiation target processing system for inserting and retrieving irradiation targets into and from an instrumentation tube in a nuclear reactor core comprising a target retrieving system, a target insertion system and a transport gas supply system.

Conventional irradiation targets for use in an irradiation target processing system are driven into and out from pipelines of the instrumentation tube system using pressurized gas. Therefore, the irradiation targets designed for use in the instrumentation tube system must be able to withstand high mechanical loads. To avoid damages due to friction between the pipelines of the system and the irradiation targets, a lubricant is used. This lubricant needs to be applied unto the irradiation targets or directly into the pipelines.

Conventionally, this is done manually in an operating room of the nuclear facility. However, manual handling leads to exposure of personnel to radioactive radiation, e.g. due to the radiation from the irradiation targets or the aeroballs after they are removed from the nuclear core. Furthermore, manual application of the lubricant is not optimal in terms of reproducibility of the amount of lubricant applied.

EP 2 898 514 B1 shows a ball measurement system comprising a pipeline and a device for applying a lubricant into said pipeline. The device comprises a supply line for a transport gas, which is connected to the pipeline. The device further comprises a transverse line with a lubricant plunger, which can be moved within the transverse line by means of pressure applied by the transport gas via a branch line. The plunger has a depression, which in the rest position of the plunger is in contact with a lubricant reservoir. Upon applying pressure via the branch line, the plunger moves into a delivery position, in which the lubricant can be transferred from the depression into the pipeline by a gas stream. While this device offers the possibility for automated application of a lubricant, complex architecture of pipelines is needed. The device is therefore rather expensive to implement and cannot be installed in every existing reactor structures.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a simple and cheap possibility to introduce a lubricant in a pipeline, e.g. a pipeline of an instrumentation tube system of a nuclear reactor.

It is a further object of the invention to provide a system for lubricating a pipeline, e.g. a pipeline of an instrumentation tube of a nuclear reactor, which does not need manual operation.

The above objects are solved by a lubricating device according to claim 1 , an instrumentation tube system according to claim 8 and a method for lubricating at least one pipeline of an instrumentation tube system of a nuclear power reactor according to claim 12. According to a first aspect, the invention provides a lubricating device for introducing a lubricant into a pipeline by means of a gaseous transport medium. The lubricating device comprises a feed pipe, which can be connected to the pipeline and on which a pressure can be applied by means of the gaseous transport medium. The lubricating device further comprises a check valve, arranged in the feed pipe, and a filling device for the lubricant, which is in fluid connection with the feed pipe. The check valve is mounted downstream of the filling device towards the pipeline, and the filling device is set up to introduce a predetermined amount of lubricant into the feed pipe, which can be introduced from the feed pipe through the check valve into the pipeline by means of said gaseous transport medium.

The lubricating device allows lubricating the pipeline without manual dosing of the lubricant. Rather, the filling device can be operated such that the pipeline can automatically be lubricated if necessary. Thus, exposure of operating personnel to radiation is reduced.

Additionally, the lubricating device can be implemented within the nuclear reactor containment of a nuclear power plant if necessary, as no manual operation will be needed.

This also allows lubricating the pipeline independent of the current reactor state, so that sufficient lubrication of the pipeline can be achieved at every point in time.

The check valve decouples the lubricating device from the pipeline and prevents gas from flowing from the pipeline into the device.

The predetermined amount of lubricant introduced into the feed pipe by the filling device can be set depending on the conditions in the pipeline, especially depending on the degree of friction to be expected within the pipeline.

Introducing the lubricant into the pipeline by a gaseous transport medium allows a good control for transferring the lubricant. Furthermore, less mechanical and moving elements are needed within the lubricating device, whereby mechanical wear of the components of the lubricating device is reduced. The lubricant can be a powdered dry lubricant. A powdered dry lubricant has the advantage that it can be poured easily, which facilitates handling. Furthermore, a powdered dry lubricant can easily be transported by the gaseous transport medium. Preferably, the lubricant is molybdenum disulfide.

In one embodiment, the gaseous transport medium comprises nitrogen as main component, or preferably is highly purified nitrogen. The term highly purified nitrogen corresponds to nitrogen class 5 and consists of 99,999 mol-% or more of nitrogen.

As it is chemically inert and readily available, nitrogen is especially suited as gaseous transport medium.

In one embodiment, the filling device comprises a dosing pen and an activator element, preferably a motor, for actuating the dosing pen. The filling device is capable of dosing lubricant into the feed pipe when the dosing pen is actuated by the activator element.

The amount of lubricant introduced into the feed pipe is therefore easily controllable by the activator element. Additionally, the lubricant can be dosed into the feed pipe discontinuously, as the dosing pen prevents the lubricant from entering the feed pipe if the dosing pen is not actuated by the activator element.

A lubricant storage container can be connected to the filling device by a supply line, so that the lubricant is introduced into the filling device through the supply line.

This allows to simplify the design of the filling device, as the storage container and the supply line can be spatially separated from the filling device itself.

Furthermore, a dosing pressure line can be connected to the lubricant storage container and pressure is applied through the dosing pressure line, preferably with an overpressure of 0.1 bar or less, for introducing the lubricant into the filling device. This allows for controlled transport of the lubricant from the lubricant storage container into the filling device. Additionally, the slight overpressure can be used to supplement the transport of the lubricant from the supply line through the filling device into the feed pipe.

In a second embodiment, the filling device comprises a control device, preferably a stepping motor, and a volumetrically controlled feed line, in which the lubricant is stored and wherein the lubricant is dosed from the feed line into the feed pipe as long as the control device gets activated.

In this embodiment, control of the amount of lubricant transferred into the feed line is possible by the duration for which the control device is activated. By using a stepping motor as control device, a cheap and reliable operation is possible.

According to a second aspect, the invention provides an instrumentation tube system of a nuclear power reactor comprising at least one pipeline containing an amount of irradiation targets and a lubricating device as presented above for introducing a lubricant into the pipeline. The instrumentation tube system is part of the core instrumentation of the nuclear power reactor, as it is shown, for example, in WO 2016/128177. The at least one pipeline of the instrumentation tube system includes an instrumentation tube section passing through the reactor core.

Irradiation targets are inserted into the instrumentation tube system and transported through the at least one pipeline into and from the nuclear reactor core, preferably by means of pressurized gas.

The irradiation targets can be solid spherical probes or transport cartridges, which can be used for the generation of radioisotopes.

The irradiation targets can also be aeroballs of an aeroball measurement system (AMS), which is used for monitoring the neutron flux within the core of the nuclear power reactor.

The gaseous transport medium of the lubricating device can also be used for the transport of irradiation targets within the at least one pipeline.

Therefore, the existing infrastructure for gaseous transport media of the nuclear facility can be used both for the lubricating device and for the instrumentation tube system. This reduces the cost for implementing the lubricating device into existing nuclear reactor structures and during operation of the nuclear facility.

Furthermore, the simple design of the lubricating device can easily be implemented in existing nuclear reactor structures. Lubrication is especially important in the case of an instrumentation tube system, as the irradiation targets are pneumatically operated to flow into and out of the nuclear reactor core. This results in high amounts of frictional stress, both on the irradiation targets and on the pipelines of the instrumentation tube system. The inventive instrumentation tube system offers a simple and automated possibility for lubricating the pipelines to reduce frictional stress, mitigating the wear of the components of the instrumentation tube system.

The check valve is especially advantageous in such an instrumentation tube system, as it prevents that the gas flow used for moving the irradiation targets within the instrumentation tube system from streaming further into the lubricating device.

In a third aspect, the invention provides a method for lubricating at least one pipeline of an instrumentation tube system of a nuclear power reactor comprising the following steps: - Coupling the at least one pipeline to a lubricating device as presented above;

Introducing a predetermined amount of the lubricant from the filling device into the feed pipe of the lubricating device; and

Transferring the lubricant from the feed pipe into the pipeline by means of the gaseous transport medium.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the invention will become more apparent from the following description of preferred embodiments and from the accompanying drawings wherein like elements are represented by like numerals. The preferred embodiments are given by way of illustration only and are not intended to limit the scope of the invention, which is apparent from the attached claims.

In the drawings: - Figure 1 shows a schematic sketch of a nuclear facility comprising an instrumentation tube system according to the invention;

- Figure 2 shows a schematic sketch of a first embodiment of a lubricating device for introducing a lubricant into a pipeline as shown in Figure 1 ; - Figure 3 shows a second embodiment of the lubricating device of Figure 2; and

- Figure 4 is a flowchart of the method according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 illustrates the basic setup of a commercial nuclear power plant 10 with a nuclear reactor core 12 and an instrumentation tube system 14.

As opposed to a research reactor, the purpose of a commercial nuclear reactor is the production of electrical power. Commercial nuclear reactors typically have a power rating of 100+ Megawatt electric.

According to a preferred embodiment, the nuclear reactor 10 is a pressurized water reactor. More preferably, the instrumentation tube system 14 corresponds to a conventional aeroball measuring system or a radionuclide generation system of a pressurized water reactor (PWR) such as an EPR™ or Siemens™ PWR nuclear reactor.

The person skilled in the art will however recognize that the invention is not limited to use of an aeroball measuring system or a radionuclide generation system of a PWR reactor. Rather, it is also possible to use the instrumentation tube system of a Traversing Incore Probe (TIP) system of a boiling water reactor (BWR), the instrumentation of a CANDU reactor and temperature measurement and/or neutron flux channels in a heavy water reactor. Referring to Figure 1 , the instrumentation tube system 14 comprises at least one pipeline 20 including an instrumentation tube section 16 passing through the nuclear reactor core 12 of the nuclear power plant 10. In general, a multitude of pipelines 20 is used. Preferably, the at least one pipeline 20 penetrates the pressure vessel cover of the nuclear reactor core 12, with the instrumentation tube section 16 extending from the top to the bottom over substantially the entire axial length of the nuclear reactor core 12.

The instrumentation tube system 14 is configured to permit insertion and removal of irradiation targets 18 into the at least one pipeline 20 including the instrumentation tube section 16.

A plurality of irradiation targets 18 are arranged in a linear order in the instrumentation tube section 16, thereby forming a column of irradiation targets 18. The irradiation targets 18 are substantially spherical or round probes but can have other forms as long as they are capable of moving through the at least one pipeline 20 of the instrumentation tube system 14. The irradiation targets 18 can be e.g. ellipsoids or cylinders or transport cartridges.

The irradiation targets 18 have a diameter corresponding to the clearance of the at least one pipeline 20 of the instrumentation tube system 14. Preferably, the diameter of the irradiation targets 18 is in the range of between 1 to 3 mm, preferably 1 .7 mm.

A respective end of the instrumentation tube section 16 at the bottom of the nuclear reactor core 12 is closed and/or provided with a stop so that the irradiation targets 18 inserted into the instrumentation tube section 16 form a column wherein each irradiation target 18 is at a predefined axial position.

The pipeline 20 of the instrumentation tube system 14 connects the instrumentation tube section 16 with a target drive system 22. The target drive system 22 is located behind an access barrier 24. Accordingly, the pipeline 20 penetrates the access barrier 24.

The target drive system 22 is configured to insert the irradiation targets 18 into the instrumentation tube section 16 and to remove the irradiation targets 18 from the respective instrumentation tube section 16 in the nuclear reactor core 12.

Preferably, the target drive system 22 is pneumatically operated, allowing for a fast processing of the irradiation targets 18 using pressurized gas such as nitrogen or air, preferably nitrogen and more preferably highly purified nitrogen class 5 with 99.999 mol-% or more of nitrogen.

An instrumentation control unit (ICU) 26 is connected to the target drive system 22. Therefore, the ICU 26 receives information about the irradiation targets 18 from the target drive system 22.

The instrumentation tube section 16 and the at least one pipeline 20 of the instrumentation tube system 14 can be lubricated by a lubricating device 28.

The lubricating device 28 comprises a feed pipe 30, which is coupled to the instrumentation tube section 16 of the at least one pipeline 20 by a connection element 32 to establish a fluid connection. The connection element 32 is preferably a T-piece.

The lubricating device 28 could also be connected to the at least one pipeline 20 outside of the instrumentation tube section 16.

In general, coupling the lubricating device 28 to the at least one pipeline 20 to form the instrumentation tube system 14 is needed for lubricating the at least one pipeline 20 of the instrumentation tube system 14 (Step S1 in Figure 4).

Pressure can be applied on the feed pipe 30 by means of a gaseous transport medium supplied by a transport medium source 34.

The lubricating device 28 further comprises a filling device 36, which is in fluid connection with the feed pipe 30. The filling device 36 is set up to introduce a predetermined amount of lubricant into the feed pipe 30.

A check valve 38 is mounted downstream of the filling device 36 towards the pipeline 20, and arranged in the feed pipe 30.

Referring to Figure 2, a first embodiment of the lubricating device 28 is shown in more detail.

In this embodiment, the filling device 36 comprises a dosing pen 40 and an activator element 42. The dosing pen 40 can be actuated by the activator element 42, which corresponds to lifting and lowering the dosing pen 40 in the shown embodiment. Preferably, the activator element 42 is a motor or is controlled by a gas flow. A lubricant storage container 44 is connected by a supply line 46 to the filling device 36. Powdered, dry lubricant is kept within the lubricant storage container 44. The lubricant can be introduced into the filling device 36 through the supply line

46. A dosing pressure line 48 is connected with the lubricant storage container 44 through which the lubricant storage container 44 can be pressurized, preferably with a pressure of 0.1 bar.

The dosing pressure line 48 is connected to the transport medium source 34. However, the dosing pressure line 48 could also be supplied with a gaseous medium from a separate transport medium source.

When the dosing pen 40 is actuated, i.e. is lifted, by the activator element 42, the powdered dry lubricant can be dosed into the feed pipe 30. The overpressure from the lubricant storage container 44 and the supply line 46 facilitates the dosing due to the resulting pressure gradient from the lubricant storage container 44 to the feed pipe 30.

After a predetermined amount of lubricant has been dosed into the feed pipe 30 (Step S2 in Figure 4), the dosing pen 40 is actuated again, i.e. is lowered, by the activator element 42.

A typical lubricant dose comprises 10 mg of lubricant. However, the exact amount can be determined in view of the type of irradiation targets, and pipelines used in the nuclear power plant 10.

Afterwards, the lubricant can be transferred from the feed pipe 30 through the check valve 38 and the connection element 32 into the at least one pipeline 20 and the instrumentation tube section 16 by the gaseous transport medium (Step S3 in Figure 4). For this, an overpressure is applied unto the feed pipe 30 by the transport medium source 34. Preferably, an overpressure of 2 bar or less, more preferably of 1 bar or less, is used for transferring the lubricant from the feed pipe 30 into the pipeline 20.

The lubricant is preferably a powdered dry lubricant. The main component of the powdered dry lubricant is preferably molybdenum disulfide. Suitable lubricants are commercially available under the name Molykote™ Mikrofine Powder by Dow Corning.

In Figure 3, a second embodiment of the lubricating device 28 is shown.

In this embodiment, the lubricating device 28 comprises a control device 50 and a volumetrically controlled feed line 52, in which the lubricant is stored.

The lubricant is dosed from the feed line 52 into the feed pipe 30 as long as the control device 50 is activated (Step S2 in Figure 4). Therefore, the amount of lubricant transferred into the feed pipe 30 can be controlled by the duration for which the control device 50 is activated.

A typical lubricant dose comprises 10 mg of lubricant in this embodiment, too. However, the exact amount can be determined in view of the type of irradiation targets, and pipelines used in the nuclear power plant 10.

The lubricant can be transferred from the feed pipe 30 through the check valve 38 and the connection element 32 into the pipeline 20 by the gaseous transport medium (Step S3 in Figure 4). For this, an overpressure is applied unto the feed pipe 30 by the transport medium source 34. Preferably, an overpressure of 1 bar or less is used for transferring the lubricant from the feed pipe 30 into the pipeline 20.

Preferably, the control device 50 is a stepping motor.

The feed line 52 can be an auger filler or a syringe driver. The lubricant will be kept in the feed line 52 by friction and adhesive forces, so that there is no risk of an uncontrolled dosage into the feed pipe 30 without activating the control device 50.

Referring again to Figure 1 , the lubricating device 28 can be controlled by the ICU 26, too. For this, the ICU 26 can analyze the need for lubricating the instrumentation tube section 16 and the at least one pipeline 20 based on the data received from the target drive system 22. The instrumentation tube 16 and the at least one pipeline 20 can e.g. be lubricated after a predetermined time or after a predetermined amount of irradiation targets 18 have passed the instrumentation tube section 16 and/or the at least one pipeline 20. The ICU 26 will be used to control the element of the filling device 36, which determines the dosage used, i.e. in the first embodiment shown in Figure 1 the ICU 26 will control the activator element 42 and in the second embodiment shown in Figure 2 the ICU 26 will control the control device 50. The ICU 26 is connected to a transport medium control unit 54 and to the filling device 36. The transport medium control unit 54 controls the transport medium source 34. Therefore, dosing of the lubricant into the feed line 30 and transferring the lubricant from the feed line 30 into the instrumentation tube 16 can be controlled by the ICU 26. In this way, automated and reproducible dosing of lubricant into the instrumentation tube system 14 is possible.