CN117079853A

CN117079853A - Method for producing radioisotope using heavy water nuclear power station

Info

Publication number: CN117079853A
Application number: CN202310644462.6A
Authority: CN
Inventors: 威廉·亨利·库珀
Original assignee: Framatome Canada Ltd
Current assignee: Framatome Canada Ltd
Priority date: 2015-06-22
Filing date: 2016-06-16
Publication date: 2023-11-17
Also published as: WO2016207054A1; RO132736B1; CA2895622A1; CN107710333A; CA2986976A1; CA2986976C; RO132736A2; AR105081A1

Abstract

A method of producing a radioisotope source using a heavy water reactor, comprising: inserting a target into a heavy water moderator of the heavy water reactor through a guide tube in a moderator port of the heavy water reactor, irradiating the target with neutron flux generated by the heavy water reactor in operation, thereby converting the target into a radioisotope; and withdrawing the radioisotope from the heavy water reactor through the moderator port, wherein the moderator port is a port located within a reactive mechanism deck of the heavy water reactor or a facility port of the heavy water reactor.

Description

Method for producing radioisotope using heavy water nuclear power station

The application relates to a divisional application of patent application No. 201680033989.3, of which the application date is 2016, 6 and 16, and the name is 'a method for producing radioactive isotopes by using a heavy water type nuclear power station'.

Technical Field

The present disclosure relates generally to a radioisotope, and more particularly, to a method of producing a radioisotope source using a heavy water nuclear power plant.

Background

Radioisotopes are used in a variety of fields such as industry, research, agriculture, and medicine. Typically, artificial radioisotopes are produced by exposing a suitable target material to a neutron flux for a suitable time in a cyclotron or nuclear reactor for research. Irradiation sites for nuclear reactors for research are very expensive and will become more scarce in the future as the reactor shuts down due to aging. Molybdenum-99 (Mo-99) is particularly useful in the medical field, and it is desirable to provide alternative production sites for Mo-99 and other radioisotopes.

EP 20947373 A2 shows a radionuclide generation system in which short-term radioisotopes with medical applications are generated by nuclear fission in commercial light water nuclear reactors. Existing instrumentation tubes within the pressure boundary of the reactor vessel and within the main coolant loop, typically used to house neutron detectors, are used to generate radionuclides during normal operation of the reactor. The spherical targets are pushed linearly into the instrumentation tube and removed linearly from the instrumentation tube. When the axial neutron flux distribution of the core of the reactor is considered known or computable, the optimal location of the target in the core of the reactor and the amount of exposure time are determined based at least on the parameter. A drive gear system, actuator or pneumatic drive may be used to move and hold the target. An automatic flow control system maintains synchronicity between all subsystems of the ball measurement system.

Similar systems are also known from US 8842798 B2 and US 2013/0170927 A1, which, for example, specifically describe several drive system embodiments (channels and delivery mechanisms of targets) based on existing TIP (movable in-core detector (traversing incore probe)) systems within the pressure boundary of the light water reactor vessel. Components such as shut-off valves or gate valves may be used in combination when dispensing targets in a particular manner at a particular time. US 2013/0315361 A1 proposes a valve for sealing the base of an instrumentation tube. An alternate path is provided within the pressure boundary of the reactor vessel to maintain access to an existing TIP tube indexer (indexer) or to provide an alternate route to a desired destination. In US 2013/0177126 A1, a holding assembly is shown comprising a limiting structure, such as a fork, for selectively blocking the movement of irradiation targets through the channel and/or into/out of the instrumentation tube.

The neutron flux density within the core of some commercial nuclear reactors is measured, inter alia, by introducing solid state spherical probes ("pneumatic pellets") of a pellet measurement system into instrumentation tubes passing through the core of the reactor using pressurized gas to drive the pneumatic pellets. Such a ball measurement system is disclosed, for example, in US patent No. 3263081.

Disclosure of Invention

A method for producing radioisotopes using a heavy water reactor or a heavy water nuclear power plant is provided. The application is based on the following findings: the main purpose of this is/will be that existing or future nuclear power plants producing electricity can be used for the production of radioisotopes. The preferred embodiment uses a pressurized heavy water reactor of uranium deuteride canadian (CANDU: CANada Deuterium Uranium).

The method includes inserting a target into a heavy water moderator of the heavy water reactor through a guide tube in a port within a reactive mechanism deck of the heavy water reactor. The heavy water reactor operates to irradiate the target to convert the target to a radioisotope. The method further includes withdrawing the radioisotope via the reactive mechanism deck.

A heavy water nuclear reactor is also provided. The heavy water nuclear reactor includes reactor core cladding; a plurality of pressure tubes including fuel bundles in a core cladding of the reactor through which a heavy water primary coolant flows from outside the core cladding of the reactor, the core cladding of the reactor including a heavy water moderator separate from the plurality of pressure tubes; and a reactive mechanism deck located above the core cladding of the reactor, the reactive mechanism deck including a port extending therethrough, the port housing a guide tube including a target, the guide tube configured to convert the target to a radioisotope when exposed to radiation emitted by the fuel bundle. The heavy water nuclear reactor may include a pressure tube reactor that is a pressure boundary of a primary coolant loop having a plurality of pressure tubes (also referred to as fuel channels) including fuel bundles in the core. Heavy water main coolant flows from the heat transfer manifold through the pressure tube. The reactor calandria contains heavy water moderator and is located outside the pressure boundary of the main coolant loop. The nuclear power plant also includes a reactive mechanism deck located above the core cladding of the pressure tube reactor. The reactive mechanism deck includes a port extending therethrough. The port houses a new guide tube including a target configured to convert the target to a radioisotope when exposed to radiation emitted by the fuel bundle. The new pilot tube forms a pressure boundary with the moderator system at lower temperatures and pressures, rather than with the main coolant loop containing the fuel bundles at higher pressures and temperatures.

Drawings

The application is described below with reference to the accompanying drawings, in which:

figure 1 shows a typical CANDU6 reactor assembly that will irradiate a target according to an embodiment of the present application.

Fig. 2 shows a partial sectional side view of a reactor calandria (calandria) of the heavy water reactor shown in fig. 1.

Fig. 3 shows a top view of a typical CANDU6 of the heavy water reactor shown in fig. 1, showing the position of the peepholes and schematically showing the position of the reactivity control device in the reactive mechanism deck (reactivity mechanisms deck) above the reactor calandria.

Fig. 4 shows an end view of a typical CANDU6 of the heavy water reactor shown in fig. 1, showing the position of the peephole.

Fig. 5 shows a reactive mechanism deck of a typical CANDU6 of the heavy water reactor shown in fig. 1, showing the position of the peephole.

Fig. 6 shows an end view of a typical CANDU6 of the heavy water reactor shown in fig. 1, showing the location of a peephole in which a new radioisotope production guide-tube is properly positioned according to an embodiment of the present application.

Fig. 7 shows an enlarged view of the new radioisotope guide tube assembly of fig. 6 and a portion thereof.

Fig. 8 shows a cross-section of a detail of the dispenser, bulb and pressure boundary tube of the new radioisotope guide tube assembly of fig. 7.

Fig. 9 shows a cross-sectional view of the lower portion of the new radioisotope production guide tube assembly of fig. 7.

FIG. 10 shows a typical neutron flux density of a CANDU core.

FIG. 11 shows a neutron capture cross section in Mo-98, which shows the formants.

Detailed Description

Heavy water nuclear power plants (especially CANDU pressurized heavy water reactors) have very high thermal neutron flux and high levels of epithermal neutron flux in a wide range of resonances that can activate non-uranium based targets that can capture neutrons. This neutron capture significantly reduces the waste generated to obtain the radioisotope while also having the ability to produce large amounts of radioisotope such as Mo-99 instead of using retired aged research reactors.

Several studies have been conducted focusing on modifying CANDU fuel bundles contained in a main coolant loop main pressure tube to include irradiation targets that allow isotope production. This involves the use of an on-line fuel handling machine to insert and retrieve modified fuel bundles, which presents operational risks to the reactor, as the handling fuel function limits the operating unit and may increase the risk of an emergency shutdown due to an unexpected event. The use of modified Fuel bundles also requires significant changes in the design of the nuclear power plant to process the modified Fuel bundles and remove the Fuel bundles from a Spent Fuel library (Spent Fuel Bay) to extract isotopes.

The present disclosure provides a method of inserting and retrieving targets into heavy water nuclear power plants that can be accomplished during operation of the plant without significant impact on operational risk. A guide tube is disposed within the moderator, with the region of the moderator being located outside of the main pressure tube of the main coolant circuit, separate from the fuel bundles.

Figure 1 illustrates an exemplary CANDU6 reactor assembly according to an embodiment of the present application. In this embodiment it is for a CANDU pressurized heavy water reactor, but in other embodiments it may be another type of heavy water reactor. Typical CANDU6 reactor assemblies have individual pressure boundaries that are categorized as a primary cooling circuit containing fuel, a moderator that is a separate system isolated from the primary cooling circuit that slows neutrons, and an end shield that provides radiation shielding and supports the primary cooling circuit fuel channels. The main cooling circuit components shown in fig. 1 consist of a fuel channel end fitting 10 and a heat transfer manifold (feeder pipe) 11. The moderator system components shown in fig. 1 are a reactor calandria 1, a reactor calandria shell 2, a reactor calandria tube 3, an inlet-outlet filter 8, a moderator outlet 12, a moderator inlet tube 13, a conduit 18 leading to a moderator top expansion tank, a moderator discharge tube 20, a burst disk 21, a reactivity control device nozzle 22, and a reactor calandria side tube sheet 29. The end shield comprises an end shield pre-buried ring 4, a loader side tube plate 5, an end shield grid tube 6, an end shield cooling tube 7 and a steel ball shield 9. Ports (ports) penetrating the moderator system include ports for horizontal flux detection means and liquid injection means 14, ionization chamber 15, peephole 23, shutdown rod means 24, tuning rod means 25, control absorption rod means 26, liquid zone control means 27, and vertical flux detection means 28. The assembly is housed in a concrete reactor chamber wall 17 with a barrier shield 19 and the entire assembly is protected from seismic events by a seismic limiter 16.

The reactor core cladding of the reactor shown in fig. 1 has the form of a reactor calandria 1 delimited by a horizontal cylindrical shell 2. A plurality of reactor calandria tubes 3 are housed inside the reactor calandria shell 2. Heavy water moderator flows into and out of the volume within the reactor calandria 1 via conduits 12,13 defined between the inner surface of the reactor calandria shell 2, the outer surface of the reactor calandria tubes 3 and the reactor calandria side tube sheet 29. The primary coolant loop containing the fuel bundles is physically separate and flows from the heat transfer manifold 11 through the fuel channel end fitting 10, down the pressure tube (also referred to as the fuel channel containing the fuel bundles), out of the opposite fuel channel end fitting 10 and into the opposite heat transfer manifold 11. As schematically shown in the partial cross-sectional view of fig. 2, the heavy water moderator is contained inside the volume defined between the inner surface of the reactor calandria shell 2, the outer surface of the reactor calandria tubes 3 and the reactor calandria side tube plate 29. Each reactor calandria tube 3 encloses a pressure tube (also referred to as a fuel channel) 44 within which a plurality of fuel bundles 51 are contained. The reactor calandria tube 3, together with the gas filled annulus 48 held by the hoop spring retainer ring 46, provides a buffer between the pressure tube 44 and the moderator heavy water whereby the heated heavy water main coolant in the pressure tube 44 does not boil the heavy water moderator. The primary coolant flows into the pressure tube 44 from the cold leg of the primary coolant loop from the heat transfer manifold 11 to the end fitting 10 and flows to receive heat from the fuel bundles 51, then flows out of the pressure tube 44 at the opposite end fitting 10, and flows out of the heat transfer manifold 11 to the hot leg of the primary coolant loop to flow through a steam generator located downstream of the hot leg. A closure plug 52 is located on each end fitting 10 to allow on-line loading and unloading of fuel.

Referring back to fig. 1, it further comprises a moderator inlet pipe 13 for supplying cooling water from the moderator main circuit, a moderator outlet pipe 12 for supplying heated moderator water back to the moderator main circuit for cooling, and a pressure relief pipe 20 for relieving the pressure inside the reactor calandria shell 2. A plurality of horizontally extending neutron flux detection devices 14 extend horizontally through the reactor calandria 1 to monitor neutron flux within the reactor calandria 1 during reactor operation. Extending vertically through the core are a plurality of reactivity control devices therein.

Fig. 3 is a top view schematically showing the position of the reactivity control device in the deck 45 of the reactivity mechanism located above the reactor calandria 1. The reactive mechanism deck holds all the reactivity control devices extending below the reactive mechanism deck and penetrating the reactor calandria 1 from above. As can be seen in fig. 1, the reactivity control means comprises vertically extending neutron flux detection means 28, liquid zone control means 27, tuning rod means 25, control absorption rod means 26 and reactor shutdown rod means 24, all of which need to be available and capable of operation during operation. In addition to the reactivity control means, the reactivity mechanism deck 45 also includes two peepholes 23 extending therethrough. The first peephole 49 (i.e., high-flux inspection port) is aligned with a high-flux region of the reactor core and the second peephole 50 (i.e., low-flux inspection port) is aligned with a low-flux region of the reactor core. Peepholes 49,50 are used during periodic inspection to monitor corrosion and wear at two areas of the reactor exposed to different levels of neutron flux.

Fig. 4 is a sectional side view showing the positioning of the reactive mechanism deck 45 above the reactor calandria 1 and the position of the peepholes 23. Existing thimble 53 is located in the proper position of the peephole to allow the introduction of a guide tube to monitor neutron flux during initial start-up of the reactor when new fuel is provided in the reactor. Aluminum guide tubes are typically provided with barium fluoride detectors having a very high sensitivity to neutron flux. Once the reactor is started and neutron flux is detected by the barium fluoride detector, the aluminum guide tube is removed. Leaving the aluminium guide tube during normal operation can lead to permanent damage. After initial priming, a radioisotope production guide-tube may be inserted using the peephole.

Fig. 5 shows the position of the reactive mechanism deck 45 and the peephole 23 and its relative positions with the shutdown rod device 24, the adjustment rod device 25, the control absorption rod device 26, the liquid zone control device 27 and the vertical flux detection device 28.

Fig. 6 is a cross-sectional side view showing the positioning of the reactive mechanism deck above the reactor calandria and the position of the peepholes 23. The existing cannula 53 is positioned in the proper location of the peephole to allow insertion of the guide tube and a new radioisotope production guide tube 30 is shown inserted.

Fig. 7 shows the entire radioisotope production guide tube 30 assembly including the distributor 36, the baffle (bulkhead) 31 and the upper flange 32. At the top is a solid hollow tube 33 with a centrally located bearing sleeve 34. In this embodiment, the bottom is perforated with a plurality of radially extending holes 35 to allow moderator water to flow into and out of the guide tube 30 (fig. 8 and 9) along the pressure boundary tube 39, but the bottom may be a solid pressure boundary tube and/or may form a pressure boundary tube if alternative delivery systems are used. The bottom has a pilot tip 40 to allow positioning within the reactor calandria. The guide tube 30 is approximately 46 feet (14 meters) in length and 3.5 inches (9 cm) in diameter.

Fig. 8 shows a cross section of one of the pressure boundary tube 39 assemblies in conjunction with the dispenser 36 shown in fig. 7. The distributor 36 comprises a bulb 38 forming its innermost radial surface and a pressure boundary tube 39 forming its outermost radial surface. The dispenser 36 provides the ability to input and output the target 37 into and from the bulb 38 via pneumatic actuation 41,42 from the delivery system. The left side view shows the top of the pressure boundary tube 39 and the distributor 36, and the right side view shows the bottom of the pressure boundary tube 39. The target 37 is transported by the dispenser 36 via a transport system as proposed in US patent No.3,263,081. By pushing the pneumatic pressure 41 of the target 37 downward, the target 37 descends into the port 55 and bulb 38 on the dispenser 36 until they hit the ball stop 54 stopping at the bottom of the bulb 38. The ball stopper 54 has a clearance to allow the pneumatic pressure to easily pass through the ball stopper 54 in the up-down direction. After the irradiation period, the pneumatic pressure is reversed by applying the pneumatic pressure 42 down the pressure boundary tube 39 at another port 56 on the dispenser 36, which is then returned from the bottom up to the bulb 38, past the ball stop 54 and pushes the target 37 through the bulb 38 to push the target upward and out of the dispenser 36. A separate pressure boundary tube 39 seals the moderator system pressure boundary and accommodates bulb 38 and ball retainer 54 therein. In this embodiment, as shown in fig. 7, there may be a number of pressure border tubes 39 within one guide tube 30, depending on the desired yield of radioisotope desired. The diameter of the target is nominally 2mm, but can rise to a few centimeters based on the radioisotope in question. The outer diameter of the target 37 defines the inner diameter of the bulb 38 with a small gap to allow the target 37 to move easily. The outer diameter of the bulb 38 in turn defines the inner diameter of the pressure boundary tube 39, with a radial gap between the bulb 38 and the pressure boundary tube 39 to allow air to flow downwardly in the axial direction between the bulb 38 and the pressure boundary tube 39. Thus, the diameter of the target 37 ultimately limits the maximum amount of the pressure boundary tube 39 per guide tube 30 (see fig. 7), or the guide tube 30 itself forms the pressure boundary tube 39.

Fig. 9 is a cross-sectional view of the lower portion of radioisotope production guide tube 30, showing a plurality (five in this example) of pressure border tubes 39, each including a bulb 38 therein, the bulb 38 having an outer diameter substantially spaced from the inner diameter of the corresponding surrounding pressure border tube 39. Two of the pressure boundary tubes 39 are shown from the outside and two of the pressure boundary tubes are shown in full cross section. The fifth pressure boundary tube 39 is shown in partial section, showing the interior section of the corresponding bulb 38, with the spherical stop 54 supporting the target 37. Also shown are spacer plates 43 for the shock resistant design, which are suitably spaced along the length of the guide tube 30. A pilot tip 40 is also shown.

FIG. 10 shows a typical neutron flux density of a CANDU core. It has a very high thermal neutron flux and a high constant epithermal neutron flux in a wide range of resonances that are capable of activating non-uranium based targets that can capture neutrons.

FIG. 11 shows a neutron capture cross section in Mo-98, which shows formants entirely within the broad range of neutron flux for a CANDU pressurized heavy water reactor.

The present disclosure may be used to produce a radioisotope source (in a preferred embodiment, mo-99 for use in the medical field) by inserting a target, which in a preferred embodiment is formed of Mo-98, into the reactor calandria 1 using the high throughput peephole 49. At any time after the initial start-up operation, when the power station is running and the radioisotope production guide tube 30 is in the proper position as shown in fig. 6 and 7, the target 37 may be transported into the guide tube 30 and removed from the guide tube 30 via the transport system. In a preferred embodiment, the guide tube 30 is formed of a zirconium alloy. In another embodiment, the guide tube 30 may be formed of stainless steel.

The target delivery system may also be removably added to the reactive mechanism deck area to insert a target, such as Mo-98. In one embodiment, the target delivery system is a pneumatic pellet delivery system as disclosed in US patent No.3,263,081. The pneumatic pellet transport system delivers the target 37 into the guide tube 30 via the distributor 36 using aerodynamic force, and extracts the irradiated target 37 upward from the guide tube 30 after irradiation and conversion to Mo-99. In alternative embodiments, the target may be lowered into the guide tube 30 by gravity and removed upwardly from the guide tube 30 by a mechanical drive system. The mechanical delivery system is characterized in that the mechanical drive system comprises a shutter device for expelling the irradiation targets into the collection container after irradiation. In another alternative embodiment, the delivery system may be portable and may be connected to the dispenser 36 as desired by manually feeding the target 37 into the port 55 of the bulb 38 of the dispenser 36 with a commercially available funnel. Next, a standard commercially available pneumatic canister with a commercially available fitting may be connected to port 55 of bulb 38 of dispenser 36 and used to supply a delivery gas into bulb 38 to ensure that target 37 is fully inserted. After the irradiation time, a standard commercial transport bottle may be connected to port 55 of bulb 38 of dispenser 36 and a standard commercial pneumatic canister with a commercial fitment may be connected to port 56 of pressure boundary tube 39 of dispenser 36. The commercially available pneumatic canister may then be operated to eject the target 37 from the bulb 38, out of the dispenser 36 and into a standard commercially available transport bottle.

Advantageously, providing target 37 in the form of Mo-98 into reactor calandria 1 of a CANDU pressurized heavy water reactor using high flux peephole 49 allows exposing target 37 to sufficient radiation to convert to Mo-99 in about 6-12 days. In alternative embodiments, other forms of targets 37 may be provided to other moderator ports by alternative delivery systems and other radioisotopes, such as L-177 (Lu-177), may be produced for other periods of time. In a preferred embodiment, the moderator port for target 37 is a back-up port, particularly peephole 23,49. In other embodiments, other spare ports may be used, such as unused flux detector ports or other ports that do not include devices (e.g., any of the ports shown in fig. 1), provided that for some reason these ports do not accommodate the corresponding liquid injection devices 14, ionization chambers 15, peepholes 23, shutdown rod devices 24, conditioning rod devices 25, control absorption rod devices 26, liquid zone control devices 27, or vertical flux detection devices 28. As a further advantage, the use of an existing peephole 23 or other spare port to provide the target 37 does not require removal of any equipment that is frequently used during operation of the plant, thereby eliminating the need for significant modification of the reactor to produce the radioisotope.

In the foregoing specification, the application has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope of the application as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. A method of producing a radioisotope source using a heavy water reactor, comprising:

inserting a target into a heavy water moderator of the heavy water reactor through a guide tube in a moderator port of the heavy water reactor,

irradiating the target with a neutron flux generated by the heavy water reactor in operation, thereby converting the target into a radioisotope; and

the radioisotope is removed from the heavy water reactor through the moderator port,

wherein the moderator port is a port located within the reactive mechanism deck of the heavy water reactor or a device port of the heavy water reactor.

2. The method of claim 1, wherein the moderator port is a dedicated equipment port for a reactor liquid injection device, an ionization chamber, a peephole, a shutdown rod device, a tuning rod device, a control absorption rod device, a liquid zone control device, or a vertical flux detection device.

3. The method of any one of claims 1-2, further comprising modifying the port to include a delivery system.

4. A method according to claim 3, wherein the delivery system is a pneumatic delivery system.

5. The method of claim 4, wherein removing the radioisotope from the heavy water reactor comprises using the pneumatic transport system to force the radioisotope out of the guide tube.

6. The method of claim 4, wherein inserting the target into the heavy water moderator comprises inserting the target into the guide tube using the pneumatic conveying system.

7. The method of claim 4, wherein the pneumatic conveying system is a pneumatic pellet conveying system.

8. The method of claim 1, wherein the guide tube is a zirconium guide tube.

9. The method of claim 1, wherein the heavy water reactor is a CANDU reactor.

10. The method of claim 9, wherein the CANDU reactor includes a plurality of pressure tubes having fuel elements therein and a heavy water primary coolant flowing through the plurality of pressure tubes, the heavy water moderator being separate from the heavy water primary coolant.

11. The method of claim 1, wherein the port is a backup port or a port not equipped with a device.

12. The method of claim 1, wherein the removing of the radioisotope from the heavy water reactor is performed during power generation of the heavy water reactor.

13. The method of claim 1, wherein the guide tube houses at least one bulb for receiving the target.

14. A method according to claim 13, wherein the or each bulb has a ball stop for supporting a target in the respective bulb, at least one of inserting the target into the heavy water moderator and withdrawing the radioisotope from the heavy water reactor comprising passing a transport gas through the or each ball stop.

15. The method of claim 13 or 14, wherein the guide tube houses or forms at least one pressure boundary tube surrounding the or each bulb, an outer surface of the pressure boundary tube contacting the heavy water moderator.

16. The method of claim 13 or 14, wherein the guide tube houses a plurality of bulbs, each of the plurality of bulbs being surrounded by a respective pressure boundary tube, the guide tube including a plurality of holes therein allowing the heavy water moderator to flow into and out of the guide tube along the plurality of pressure boundary tubes.

17. A heavy water nuclear reactor comprising:

reactor core cladding of the reactor;

a plurality of pressure tubes including fuel bundles in a core cladding of the reactor through which a heavy water primary coolant flows from outside the core cladding of the reactor, the core cladding of the reactor including a heavy water moderator separate from the plurality of pressure tubes; and

at least one moderator port housing a guide tube comprising a target, the guide tube being configured to convert the target to a radioisotope when exposed to radiation emitted by the fuel bundle,

wherein the moderator port is a port located within the reactive mechanism deck of the heavy water reactor or any equipment port of the heavy water reactor.

18. The heavy water nuclear reactor of claim 17, wherein the moderator port is a dedicated equipment port for a reactor liquid injection device, an ionization chamber, a peephole, a shutdown rod device, a tuning rod device, a control absorption rod device, a liquid zone control device, or a vertical flux detection device.

19. The heavy water nuclear reactor of claim 17, further comprising a delivery system configured for inserting the target into the guide tube and forcing the radioisotope out of the guide tube.

20. The heavy water nuclear reactor of claim 19, wherein the transport system is a pneumatic transport system.

21. The heavy water nuclear reactor of claim 20, wherein the pneumatic transport system is a pneumatic pellet loading system.

22. The heavy water nuclear reactor as recited in any one of claims 17 to 21, wherein the heavy water nuclear reactor is a CANDU-type reactor.

23. The heavy water nuclear reactor as recited in any one of claims 17 to 21, wherein the port is a backup port or a non-device equipped port.

24. The heavy water nuclear reactor as recited in any one of claims 17-21, wherein the guide tube houses at least one bulb for receiving the target.

25. The heavy water nuclear reactor of claim 24, wherein the or each bulb has a ball stop for supporting a target in the respective bulb, at least one of inserting the target into the heavy water moderator and withdrawing the radioisotope from the heavy water nuclear reactor comprising passing a transport gas through the or each ball stop.

26. The heavy water nuclear reactor of claim 24, wherein the guide tube houses or forms at least one pressure boundary tube surrounding the or each bulb, an outer surface of the pressure boundary tube contacting the heavy water moderator.

27. The heavy water nuclear reactor of claim 24, wherein the guide tube houses a plurality of bulb tubes, each of the plurality of bulb tubes surrounded by a respective pressure boundary tube, the guide tube including a plurality of holes therein allowing the heavy water moderator to flow into and out of the guide tube along the plurality of pressure boundary tubes.