Lance unit, nuclide activation and nuclear monitoring system as well as method of producing radionuclides

Abstract

A lance unit (32) for usage in a nuclear reactor core (15) includes a nuclide activation system (22), a nuclear monitoring system (14), a tube system (28) and a yoke (34) holding the tube system (28). The nuclear monitoring system (14) has at least one nuclear monitoring tube (16) for accommodating monitoring members (18) that monitor the nuclear reactor core (15). The nuclide activation system (22) has a nuclide activation tube (24) for accommodating at least one irradiation target (26) to be exposed to neutron flux in the nuclear reactor (12) to form a radionuclide. The at least one nuclear monitoring tube (16) and the nuclide activation tube (24) are part of the tube system (28). The nuclide activation tube (24) has an internal stop (40) configured to stop the at least one irradiation target (26). The internal stop (40) of the nuclide activation tube (24) is located at a different height with regard to the lower end of the nuclear monitoring tube (16).

Claims

1-12. (canceled)

13. A lance unit for usage in a nuclear reactor core comprising: a nuclide activation system; a nuclear monitoring system; a tube system; and a yoke holding the tube system, the nuclear monitoring system having at least one nuclear monitoring tube for accommodating monitoring members for monitoring the nuclear reactor core, the nuclide activation system having a nuclide activation tube for accommodating at least one irradiation target to be exposed to neutron flux in the nuclear reactor to form a radionuclide, the at least one nuclear monitoring tube and the nuclide activation tube being part of the tube system, the nuclide activation tube having an internal stop configured to stop the at least one irradiation target, the internal stop of the nuclide activation tube being located at a different height with regard to the lower end of the nuclear monitoring tube.

14. The lance unit of claim 13, wherein the internal stop is a mechanical stop and/or a fixed stop.

15. The lance unit of claim 13, wherein the nuclide activation system is configured to permit insertion and removal of the at least one irradiation target into the nuclide activation tube during operation of the nuclear reactor core.

16. The lance unit of claim 13, wherein the at least one nuclear monitoring tube includes three nuclear monitoring tubes.

17. The lance unit of claim 13, wherein the nuclide activation tube is coated with or made of a neutron doubling material.

18. The lance unit of claim 17, wherein the neutron doubling material is beryllium.

19. The lance unit of claim 13, wherein the internal stop is provided by an axial end of the nuclide activation tube.

20. The lance unit of claim 13, wherein the internal stop is a mechanical stop that is inserted in the nuclide activation tube.

21. A nuclide activation and nuclear monitoring system for usage in a nuclear reactor core, comprising: at least one of the lance unit according to claim 13.

22. The nuclide activation and nuclear monitoring system of claim 21, wherein an irradiation target drive system is provided that is connected with the nuclide activation tube, wherein the irradiation target drive system is configured to insert the at least one irradiation target into the nuclide activation tube and to remove the at least one irradiation target from the nuclide activation tube.

23. The nuclide activation and nuclear monitoring system of claim 22, wherein the irradiation target drive system comprises a gas source.

24. The nuclide activation and nuclear monitoring system of claim 23, wherein the gas source is a nuclide activation gas source that is assigned to the irradiation target drive system solely or wherein the gas source is a common gas source assigned to a valve battery.

25. The nuclide activation and nuclear monitoring system of claim 21, wherein at least one control unit is provided that is configured to control the nuclide activation system and/or the nuclear monitoring system.

26. The nuclide activation and nuclear monitoring system of claim 25, wherein the at least one control unit is configured to control the nuclide activation system and the nuclear monitoring system separately.

27. A method of producing radionuclides from irradiation targets in a nuclear reactor, comprising the steps of: providing at least one tube system including a nuclear monitoring tube passing through a core of the nuclear reactor and a nuclide activation tube with an internal stop that is located at a different height with regard to the lower end of the nuclear monitoring tube; inserting at least one irradiation target into the nuclide activation tube and activating the irradiation target by exposing the irradiation target to neutron flux in the nuclear reactor core to form a radionuclide; and retrieving the irradiation target from the nuclide activation tube, the irradiation target being held by the internal stop at a predetermined axial position in the reactor core, the axial position corresponding to a pre-calculated neutron flux density sufficient for converting the irradiation target to the radionuclide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The foregoing aspects and many of the attendant advantages of the subject matter of the present disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0064] FIG. 1 shows a schematic sketch of a nuclear reactor with a nuclide activation and nuclear monitoring system according to the present disclosure

[0065] FIG. 2 shows a schematic top view on a nuclear reactor core having a nuclide activation and nuclear monitoring system according to the present disclosure,

[0066] FIG. 3 shows a sectional view of the nuclear reactor core of FIG. 2,

[0067] FIG. 4 shows a schematic view of a lance unit according to a first embodiment of the present disclosure that is used by the nuclide activation and nuclear monitoring system shown in FIGS. 2 and 3,

[0068] FIG. 5a shows a schematic view of a lance unit according to a second embodiment of the present disclosure that is used by the nuclide activation and nuclear monitoring system shown in FIGS. 2 and 3,

[0069] FIG. 5b shows a schematic sectional view of a nuclide activation tube of the lance unit shown in FIG. 5a, and

[0070] FIGS. 6a to 6b show top views on different embodiments of lance units according to the present disclosure.

DETAILED DESCRIPTION

[0071] In FIG. 1, a basic setup of a nuclide activation and nuclear monitoring system 10 within a commercial nuclear reactor 12 is shown, in particular a power plant with an EPR™ nuclear reactor.

[0072] As opposed to a research reactor, the purpose of a commercial nuclear reactor 12 is the production of electrical power. Commercial nuclear reactors typically have a power rating of 300+ Megawatt electric.

[0073] The basis of the nuclide activation and nuclear monitoring system 10 described in the example embodiments is derived from a nuclear monitoring system 14, for instance an aeroball measuring system (AMS) or a Traversing Incore Probe (TIP) System, the main purpose of which is to measure the neutron flux density in the core 15 of the nuclear reactor 12.

[0074] For this purpose, the nuclear monitoring system 14 comprises at least one nuclear monitoring tube 16 that passes through the core 15 of the nuclear reactor 12. The nuclear monitoring tube 16 may accommodate a plurality of monitoring members 18, for instance aeroballs, arranged in a linear order thereby forming a monitoring members column.

[0075] The nuclear monitoring system 14 further includes a pneumatically operated drive system 20 configured to insert the monitoring members 18 into the nuclear monitoring tubes 16 extending into and passing the nuclear reactor core 15 through its entire axial length, and to remove the monitoring members 18 from the nuclear monitoring tubes 16 after activation for monitoring purposes. The monitoring members 18 are evaluated in a known manner

[0076] In the following, the major components of the nuclide activation and nuclear monitoring system 10, which are provided in addition to those of the nuclear monitoring system 14, will be further described.

[0077] FIG. 1 also schematically shows that the nuclide activation and nuclear monitoring system 10 also comprises a nuclide activation system 22 that comprises at least one nuclide activation tube 24 which is formed in addition to the at least one nuclear monitoring tube 16 of the nuclear monitoring system 14.

[0078] The nuclide activation tube 24 is configured to permit insertion and removal of irradiation targets 26 that will be activated by the neutron flux within the core 15 as will be described later.

[0079] The irradiation targets 26 and/or the monitoring members 18 used by both systems 14, 22 may have a round or spherical shape and having a diameter corresponding to the clearance of the respective tubes 16, 24. For instance, the diameter of the irradiation targets 26 and/or the monitoring members 18 is in the range of between 1 to 3 mm, preferably about 1.7 mm.

[0080] The at least one nuclide activation tube 24 as well as the at least one monitoring tube 16 correspond to a tube system 28 that is assigned to the core 15 wherein the tube system 28 is also assigned to a tubing of the nuclear reactor 12 that penetrates a reactor confinement 30 and the pressure vessel cover of the nuclear reactor 12 as shown in FIG. 1.

[0081] In fact, the tube system 28 is assigned to a lance unit 32 being part of the nuclide activation and nuclear monitoring system 10. Different embodiments of the lance unit 32 are shown in FIGS. 3 to 6 in more detail.

[0082] In general, the lance unit 32 comprises a yoke 34 that interconnects a lance head 36 and the respective tubes 16, 24, namely the at least one nuclear monitoring tube 16 and the at least one nuclide activation tube 24 forming the tube system 28. Thus, the tube system 28 is held by the yoke 34 in a mechanical manner.

[0083] The lance head 36 is assigned to a top end 38 of the lance unit 32 that is accessible from the outside when the lance unit 32 is installed in the core 15 as shown in FIG. 3. In contrast thereto, the respective tubes 16, 24 each have a closed end that face the bottom of the core 15 when the lance unit 32 is installed in the core 15. This becomes also obvious from FIG. 3.

[0084] As discussed above, the at least one nuclear monitoring tube 16 is configured to accommodate irradiation targets 26 that are exposed to an irradiation in the core 15 for producing radionuclides.

[0085] In general, the at least one nuclear monitoring tube 16 of the lance unit 32 has an internal stop 40 that stops the irradiation targets 26 to be irradiated at a certain location. In fact, the internal stop 40 is located at a different height compared to the lower end of the at least one nuclide activation tube 24 as shown in FIGS. 1, 3 to 5.

[0086] The internal stop 40 may be established by a mechanical stop 42 that is inserted in the nuclide activation tube 24 as shown in the embodiments of the lance units 32 in FIGS. 1 and 5.

[0087] The mechanical stop 42 may be formed by a disk and/or a plate that has been mechanically fixed to a certain location within the nuclide activation tube 24 (prior) to the installation of the complete lance unit 32 within the core 15.

[0088] The mechanical stop 42 ensures that the active length of the nuclide activation tube 24 is reduced, which may be called the usable length of the inner space 44 of the nuclide activation tube 24.

[0089] As shown in FIGS. 1 and 5a, the nuclide activation tube 24 itself has the same (outer) length as the nuclear monitoring tube 16. However, the active length, namely the inner length, of the nuclide activation tube 24 is shorter than the one of the nuclear monitoring tube 16 due to the internal stop 40 that has been inserted into the nuclide activation tube 24 in front of the closed end of the nuclide activation tube 24.

[0090] This ensures that the irradiation targets 26 inserted into the nuclide activation tube 24 are stopped by the internal stop 40 at a location being higher than the lower end of the nuclear monitoring tube 16 so that the first irradiation target 26, which corresponds to the overall first object inserted after the installation of the lance unit 32, is exposed by a higher neutron flux density compared to the location assigned to the lower end of the nuclear monitoring tube 16.

[0091] Therefore, the irradiation targets 26 are positioned in upper areas compared to the lower areas assigned to the nuclear monitoring tubes 16 as shown in FIG. 1 so that the irradiation targets 26 are exposed to a higher neutron flux density compared to the lowest or rather first inserted monitoring members 18 since the nuclear monitoring tube 16 typically passes through the entire core 15 of the nuclear reactor 12 so that the entire core 15 can be monitored.

[0092] Alternatively to the separately formed disk-like stop 42, the internal stop 40 may be established by the axial end 46 of the nuclide activation tube 24 itself as shown in the embodiments of the lance units 32 in FIGS. 3 and 4.

[0093] Therefore, the internal stop 40 is simultaneously formed by the external end 46 of the nuclide activation tube 24. However, the length of nuclide activation tube 24 is reduced compared to the one of the nuclear monitoring tube 16 as shown in FIGS. 3 and 4. In other words, the outer length of the nuclide activation tube 24 is shorter than the one of the nuclear monitoring tube 16 that passes through the nuclear reactor core 15.

[0094] Generally, it is ensured that the first inserted irradiation target 28 is located in an area with a higher neutron flux density compared to the first inserted monitoring member 18.

[0095] For instance, the internal stop 40 may be located 60 cm higher than the lower end of the nuclear monitoring tube 16. Thus, the separately formed stop 42 may be located at a height of 60 cm with regard to the axial end 46 of the nuclide activation tube 24 having the same length as the nuclear monitoring tube 16 or the nuclide activation tube 24 is shorten by 60 cm compared to the nuclear monitoring tube 16.

[0096] In both embodiments, the internal stop 40 is a mechanical stop and a fixed stop since the separately formed stop 42 is positioned within the nuclide activation tube 24 and fixed in the respective position. Further, the first irradiation target 26 abuts the respective internal stop 40 in a mechanical manner.

[0097] Due to the inventive concept, the length of the respective nuclide activation tube 24 can be adapted to the desired axial position within the core 15 so as to expose the irradiation targets 26 to a desired neutron flux density. In a similar manner, the separately formed stop 42 is positioned at the desired axial position.

[0098] For improving the nuclide activation, the respective nuclide activation tubes 24 may be coated with or made of a neutron doubling material, in particular beryllium. Hence, the irradiation time can be reduced so that the efficiency is increased.

[0099] As already discussed, the nuclide activation and nuclear monitoring system 10 comprises a pneumatically operated drive system 20 for driving the monitoring members 18. However, this drive system 20 can also be used for driving the irradiation targets 26 into the nuclide activation tube(s) 24 in a predetermined linear order and to drive the irradiation targets 26 out of the nuclide activation tube(s) 24.

[0100] Therefore, the respective drive system 20 may be called (irradiation) target drive system.

[0101] Alternatively, two drive systems 20, 48 are provided. The first drive system 20 is configured to insert and/or remove the monitoring members 18 whereas the second drive system 48 is configured to insert and/or remove the irradiation targets 26. Hereinafter, a single drive system 20 will be described that is called irradiation target drive system 20 even though it is enabled to drive the monitoring members 18.

[0102] Preferably, the target drive system 20 is pneumatically operated allowing for a fast processing of the irradiation targets 26 and/or the monitoring members 14 using a pressurized gas such as nitrogen or air.

[0103] Accordingly, the target drive system 20 comprises a (pressurized) gas source 50, for instance a (pressurized) nitrogen source or a (pressurized) air source.

[0104] Since both systems, namely the nuclide activation system 22 and the nuclear monitoring system 14, are independent from each other with regard to their tubes 16, 24, two gas sources 50 may be provided (dashed lines) instead of a common gas source. Hence, one nuclide activation gas source 50 as well as one nuclear monitoring gas source 50 are provided which each solely interact with the respective drive system 20, 48.

[0105] Alternatively, a single common gas source 50 is provided that may be connected to a valve battery 52 (dashed lines) wherein the valve battery 52 is used as an additional pneumatic system for separate control of the two different drive systems 20, 48 if provided.

[0106] The valve battery 52 may be implemented as a further subsystem, for instance in addition to valve batteries of the nuclear monitoring system 14, or a separate drive system is installed.

[0107] The target drive system 20, 48 preferably comprises a target-filling device (not shown) for inserting the irradiation targets 26 into the nuclide activation tube(s) 24.

[0108] A (instrumentation and) control unit (ICU) 54 is linked to the target drive(s) 20, 48 as well as an online core monitoring system 56 for controlling activation of the irradiation targets 26, and a fault monitoring system 58.

[0109] The control unit 54 and/or the online core monitoring system 56 are configured to calculate an optimum irradiation time for the irradiation targets 26 based on the actual state of the nuclear reactor 12 as provided by the online core monitoring system 56.

[0110] The control unit 54 is connected via an interface with the adapted online core monitoring system 56 software. The control unit 54 is further connected to the mechanical components of the nuclide activation and nuclear monitoring system 10, including sensors.

[0111] With regard to the nuclide activation and nuclear monitoring system 10, in particular the nuclear monitoring system 14, several humidity sensors may be provided to detect any ingress of primary coolant (or any other liquid) into the nuclide activation and nuclear monitoring system 10. It is understood that the lance units 32, in particular their tubes 16, 24, are in direct contact with the primary cooling water surrounding the core 15 of the nuclear reactor 12. The humidity sensors may be based on spark plugs that are modified for measuring electrical resistance.

[0112] Further sensors are preferably provided for monitoring the presence and runtime of the irradiation targets 26 passing through the tube system 28, in particular the nuclide activation tubes 24. These sensors are preferably arranged at the tubes 24 penetrating the reactor core 15. Preferably, the sensors are used to monitor that all irradiation targets 26 have left the nuclide activation tubes 24 during the removal process while the targets 26 pass the sensors. For instance, activity sensors sensing the radiation of the irradiation targets 26 may be used.

[0113] The tube system 28 may be assigned to a discharge tube 60 which is connected to the lance unit 32 and which is located outside the nuclear reactor core 15. The irradiation targets 26 are removed from the tubing through the discharge tube 60.

[0114] The discharge tube may have an outlet coupled to a storage container for receiving the irradiation targets 26 removed from the tube system 28 through the discharge tube 60.

[0115] For an efficient generation of radionuclides, optimum irradiation conditions and time for the irradiation targets 26 are determined. Practically all relevant input data for this calculation are available from the online core monitoring system 56 of the nuclear monitoring system 56. The control unit 54, which is linked to the core monitoring system 56, can calculate the optimum irradiation time, as well as further parameters, like the amount of irradiation targets 26 in a nuclide activation tube 24 defining the actual length of the respective target column and the positions of the individual irradiation targets 26.

[0116] The online calculation of the optimum irradiation time of the irradiation targets 26 is not simply based on the assumption of an estimated constant neutron flux, but rather takes the actual state of the reactor 12 into account, especially at least one of the following parameters: neutron flux, activation values from an existing ball measuring system, burn-up, reactor power, loading, rod position(s), flow rate, inlet-temperature, pressure, and time synchronization. Not only real-time values of these parameters, but also their development over time may be considered.

[0117] In general, the nuclide activation and nuclear monitoring system 10 provides separately formed nuclear monitoring tubes 16 and nuclide activation tubes 24 relating to the nuclear monitoring system 14 and the nuclide activation system 22, respectively.

[0118] The respective tubes 16, 24 are separately formed as well as separately controlled, in particular with regard to the control unit 54 and the drive system(s) 20, 48.

[0119] In fact, the nuclear monitoring system 14 and the nuclide activation system 22 may be operated pneumatically independently from each due to the separate gas sources 50 and/or the valve battery 52.

[0120] Since the controlling may also be done separately, the control unit 54 may have two control modules 62, 64 wherein the first control module 62 is configured to control the nuclear monitoring system 14 whereas the second control module 64 is configured to control the nuclide activation system 22.

[0121] For instance, the control modules 62, 64 may be located in different rooms so that accessibility is simplified. Particularly, the second control module 64 may be located on the other side of the containment 30.

[0122] In the shown embodiments of the lance units 32, in particular FIGS. 6, it is shown that each lance unit 32 has three nuclear monitoring tubes 16 assigned to the tube system 28 of the lance unit 32 that further comprises one nuclide activation tube 24. In addition, each lance unit 32 has at least one emergency coolant injection tube 66.

[0123] Each of the tubes 16, 24 may have two pipes so that pressurized gas can be pumped in two different directions for driving the respective monitoring members 18 and/or the irradiation targets 26.

[0124] In general, the nuclide activation system 22 does not impair the nuclear monitoring system 14 since no nuclear monitoring tube 16 has to be converted into a nuclide activation tube 24. In fact, the space already provided by the lance unit 32 was only used to add the nuclide activation tube 24.

[0125] FIG. 2 schematically depicts a diagram providing information on the equipment of the reactor core 15 with lance units 32 and their distribution within the core 15 of the nuclear reactor 12, in particular the nuclide activation tubes 24, the nuclear monitoring tubes 16 as well as the emergency coolant injection tubes.

[0126] According to the example shown in FIG. 2, twelve lance units 32 are used wherein four different types of lance units 32 are shown indicated by numbers 1 to 4.

[0127] In fact, no positions are taken from a conventional nuclear monitoring system 14 as the space already available is used by the nuclide activation system 22, in particular the respective nuclide activation tubes 24.

[0128] Therefore, the nuclide activation tubes 24 forming the nuclide activation system 22 in parts can be incorporated without impairing the nuclear monitoring system 22 by converting nuclear monitoring tubes 16 into nuclide activation tubes 24. Accordingly, the number of nuclear monitoring tubes 16 is not reduced due to the nuclide activation system 22.

[0129] The radionuclides may be produced from the irradiation targets 26 within the nuclear reactor 12 as follows:

[0130] At least one tube system 28 is provided that includes a nuclear monitoring tube 16 passing through the core 15 of the nuclear reactor 12 and the nuclide activation tube 24 with the internal stop 40 that is located at a different height with regard to the lower end of the nuclear monitoring tube 16 as already described.

[0131] Then, at least one irradiation target 26 is inserted into the nuclide activation tube 24. The irradiation target 26 is held by the internal stop 40 at a predetermined axial position in the reactor core 15. The axial position corresponds to a pre-calculated neutron flux density sufficient for converting the irradiation target 26 to the radionuclide.

[0132] The irradiation target 26 is activated by exposing the irradiation target 26 to neutron flux in the nuclear reactor core 15 to form the radionuclide.

[0133] Afterwards, the irradiation target 26 is retrieved from the nuclide activation tube 24.

[0134] Generally, the irradiation targets 26 comprise a suitable parent material for generating radionuclides which are to be used for medical and/or other purposes.

[0135] More preferably, the irradiation targets 26 consist of the parent material which converts to a desired radionuclide upon activating by exposure to neutron flux present in the core 15 of an operating commercial nuclear reactor 12. Useful parent materials are Mo98 and Yb176 which are converted to Mo99 and Lu177, respectively. It is understood, however, that the present disclosure is not limited to the use of a specific parent material.