阅读说明：本技术 产生放射性同位素的气动靶辐照系统 (Pneumatic target irradiation system for producing radioactive isotope ) 是由 T.G.昂德沃特 M.A.阿尔博伊诺 B.D.费希尔 A.朗 于 2019-08-26 设计创作，主要内容包括：一种用于对裂变反应堆的容器贯穿结构中的放射性同位素靶进行辐照的靶辐照系统,该靶辐照系统包括靶升降机组件,该靶升降机组件包括限定中心孔和开口底端的主体部分、设置在主体部分的中心孔内的中心管、可滑动地容纳在中心管内的靶篮、以及通过电缆连接至靶篮的绞盘,其中,所述靶篮配置为在其中接收放射性同位素靶,并在对放射性同位素靶进行辐照时被降到反应堆的容器贯穿结构中。(A target irradiation system for irradiating a radioisotope target in a vessel penetration structure of a fission reactor, the target irradiation system comprising a target elevator assembly including a body portion defining a central bore and an open bottom end, a central tube disposed within the central bore of the body portion, a target basket slidably received within the central tube, and a winch connected to the target basket by a cable, wherein the target basket is configured to receive the radioisotope target therein and to be lowered into the vessel penetration structure of the reactor upon irradiation of the radioisotope target.)

1. A target irradiation system for irradiating a radioisotope target in a vessel penetration structure of a fission reactor, comprising:

a target lift assembly comprising a body portion defining a central bore and an open bottom end, a central tube disposed within the central bore of the body portion, a target basket slidably received within the central tube, and a winch connected to the target basket by a cable, the target lift assembly being attached to a vessel penetration structure of a reactor; and

a target passageway in fluid communication with the target lift assembly,

wherein the target basket is configured to receive a radioisotope target therein via a target passage and upon irradiation of the radioisotope target, the target basket is lowered into a vessel penetration structure of the reactor, the target lift assembly forming a portion of a pressure boundary of the reactor when in fluid communication with the reactor.

2. The target irradiation system of claim 1, wherein the fission reactor is a heavy water moderating fission reactor and the vessel penetration structure is a regulator assembly port.

3. The target irradiation system of claim 2, wherein the radioisotope target is comprised of native molybdenum.

4. The target irradiation system of claim 1, wherein the target lift assembly is attached to the vessel penetration structure such that a portion of the body portion of the target lift assembly extends down into the vessel penetration structure.

5. The target irradiation system of claim 1, wherein the target basket further comprises a cylindrical sidewall including a plurality of apertures such that a moderator fluid of the fission reactor can enter the target basket when the target basket is in the fission reactor.

6. The target irradiation system of claim 5, wherein the target basket further comprises a bottom flange that forms a seal with the bottom of the central tube when the target basket is in the retracted position.

Technical Field

The presently disclosed invention relates generally to a system for irradiating radioisotope targets in nuclear reactors, and more particularly, to a system for irradiating radioisotope targets in heavy water moderated fission nuclear reactors.

Background

Technetium-99 m (Tc-99m) is the most commonly used radioisotope in nuclear medicine (e.g., medical diagnostic imaging). Tc-99m (m is metastable) is typically injected into a patient and used to image the internal organs of the patient when used with certain devices. However, the half-life of Tc-99m is only six (6) hours. Thus, readily available sources of Tc-99m are of particular interest and/or need, at least in the field of nuclear medicine.

Given the short half-life of Tc-99m, Tc-99m is typically obtained by a Mo-99/Tc-99m generator at the desired location and/or time (e.g., in a pharmacy, hospital, etc.). The Mo-99/Tc-99m generator is a device for extracting a metastable isotope of technetium (i.e., Tc-99m) from a decaying molybdenum-99 (Mo-99) source by flowing brine through the molybdenum-99 material. Mo-99 is unstable and decays to Tc-99m over a 66 hour half-life. Mo-99 is typically produced in high throughput nuclear reactors by irradiation with highly concentrated uranium targets (93% uranium-235) and, after subsequent processing steps, is transported to Mo-99/Tc-99m generator manufacturing plants to reduce Mo-99 to a usable form, such as titanium molybdate-99 (Ti-Mo 99). Mo-99/Tc-99m generators are then distributed from these centralized locations to hospitals and drug stores across the country. Because Mo-99 has a short half-life and the number of existing production sites is limited, it is desirable to minimize the time required to reduce the irradiated Mo-99 material to a usable form and to increase the number of sites where the irradiation process can occur.

Thus, there remains at least a need for a system and process for timely production of titanium-99 molybdate material suitable for use in Tc-99m generators.

Disclosure of Invention

One embodiment of the present disclosure provides a target irradiation system for irradiating a radioisotope target in a vessel penetration structure of a fission reactor, the target irradiation system comprising: a target lift assembly comprising a body portion defining a central bore and an open bottom end, a central tube disposed within the central bore of the body portion, a target basket slidably received within the central tube, and a winch connected to the target basket by a cable, the target lift assembly being secured to a vessel penetration structure of a reactor; and a target passageway in fluid communication with a target elevator assembly, wherein the target basket is configured to receive a radioisotope target therein via the target passageway and upon irradiation of the radioisotope target, the target basket is lowered into a vessel penetration structure of the reactor, the target elevator assembly forming a portion of a pressure boundary of the reactor when in fluid communication with the reactor.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and together with the description, serve to explain the principles of the invention.

Drawings

The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

FIG. 1 is a perspective view of a target irradiation system installed on a CANDU (deuterium-uranium canada) reactor of one embodiment of the present disclosure;

FIGS. 2A and 2B are perspective and cross-sectional views, respectively, of a target capsule of the target irradiation system shown in FIG. 1;

FIGS. 3A through 3D are partial cross-sectional views of a target diverter of the target irradiation system shown in FIG. 1;

FIGS. 4A and 4B through 4I are perspective and partial cross-sectional views, respectively, of a target lift assembly of the target irradiation system shown in FIG. 1;

FIGS. 5A to 5J are schematic diagrams of the target irradiation system shown in FIG. 1; and

fig. 6A and 6B through 6H are perspective and partial cross-sectional views, respectively, of a shielded container loader assembly of the target irradiation system shown in fig. 1.

Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the disclosure.

Detailed Description

The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

The target irradiation system 100 of the present invention includes elements to be exposed to a reactor neutron flux within the core of a reactor, preferably a CANDU (deuterouranium canada) reactor, and elements to be attached to a CANDU reactor civil structure outside the reactor core. The system also includes a target capsule 190 (fig. 2A and 2B) designed to interface with other system components. The various components cooperate to form a system, and fig. 1 shows the system installed on a CANDU reactor.

As shown in fig. 1 and 6A, the target irradiation system 100 within the core preferably includes a new target loader 110, a path diverter assembly 112 (fig. 3A-3D), an air lock 150, a target lift diverter assembly 180, a pneumatic target transport system including a target transport conduit 390, one or more target lift assemblies 200 (fig. 4A-4I), and a shielded container loader assembly 300 (fig. 5A-5H), each of which will be described in greater detail below.

As best shown in fig. 1 and 4A, the target irradiation system 100 of the present invention preferably includes four target lift assemblies 200, the target lift assemblies 200 including a body portion 202 constructed of stainless steel and a target basket 250 constructed of zirconium alloy (i.e., Zircalloy-4), the target lift assemblies 200 being inserted vertically into an existing pass-through structure on the reactor's reactive mechanism platform 104. The predetermined pass-through configuration preferred for installation of the target lift assembly 200 is to deactivate the regulator assembly port 108, however, in alternative embodiments, the target lift assembly 200 may be installed in other reactor pass-through configurations that meet installation specifications.

As shown in fig. 2A and 2B, the target bay 190 is a carrier for a radioisotope target that, when in a reactor core, isolates the material from the ambient medium in an inert environment designed to eliminate corrosion-related degradation. The target capsule 190 includes a body portion 198 and an end cap 192, the end cap 192 preferably being constructed of a commercial grade zirconium alloy, with other materials such as titanium-aluminum-vanadium (Ti-6Al-4V) being an option. End caps 192 are welded to both ends of the body portion 198 to provide a leak-proof interior compartment. The target capsule 190 is shaped to maximize flow through the pneumatic transport tube 390. Fig. 2A and 2B show a target capsule design in which native molybdenum 194 is used as the preferred target material, although enriched molybdenum may also be used. To ensure that the target capsule 190 is safe prior to use in a reactor, and to maintain its integrity, a comprehensive leak test and verification process is employed during manufacture. The closed design of end cap 192 preferably includes features (e.g., annular protrusion 196) for absorbing end forces that target capsule 190 may experience, thereby helping to ensure that the weld joint does not degrade or fail due to impact forces during delivery. It should be noted, however, that in alternative embodiments of the target capsule 190, the annular projection 196 may not be used. The weld joint, end cap 192 and body portion 198 are preferably designed so that they do not become stretched or jammed due to the stresses experienced during operation of the system.

Referring to FIG. 5A, the target irradiation sequence will now be discussed. As shown in FIG. 5A, at the beginning of a target irradiation sequence, all isolation valves within target irradiation system 100 are in a closed position. To begin the sequence, the operator first loads a number of target bays 190 (eight in this example) into a new target loader 110 and ensures that the path diverter assembly 112 is configured to receive a new target bay 190 from the new target loader 110. Referring additionally to fig. 3A-3D, the diverter assembly 112 includes a body portion 114 defining an interior cavity 116, the interior cavity 116 configured to rotatably receive a cylindrical roller 118. The cylindrical drum 118 defines a curved channel 120 therethrough, the curved channel 120 configured to align a first inlet tube 140 or a second inlet tube 142 with the outlet tube 138, wherein the first inlet tube 140 connects the new target loader 110 to the diverter assembly 112 and the second inlet tube 142 connects the shielded container loader 300 to the diverter assembly 112. A motor 122 is coupled to the cylindrical drum 118 by a shaft and is configured to rotate the cylindrical drum 118 between two positions. As shown in fig. 3A, a locking paddle 124 extends radially outward from the shaft and indicates which of the first and second inlet tubes 140 and 142 is aligned with the outlet tube 138.

A pair of first and second locking plungers 126 and 128 are provided for securing the locking paddle 124 and channel 120 in a first position aligned with the first inlet tube 140 or a second position aligned with the second inlet tube 142, respectively. A pair of first and second locking switches 130 and 132 provide an indication as to whether the first locking plunger 126 is fully extended, thereby securely holding the roller 118 and channel 120 in alignment with the first inlet tube 140; or whether the first locking plunger 126 is fully retracted so that the motor 122 can be used to rotate the roller 118 and channel 120 to their second position in alignment with the second inlet tube 142. Referring specifically to fig. 3B and 3C, the position of the locking paddle 124 now indicates that the roller 118 has been rotated to the second position, such that the channel 120 now aligns the second inlet tube 142 with the outlet tube 138. When closing the switch 131 provides an indication that the locking paddle 124 has rotated to the second position, the second locking plunger 128 is fully extended, thereby engaging the locking paddle 124 and reliably properly aligning the channel 120 with the second inlet tube 142. Like the first locking plunger 126, a pair of first and second locking switches 134 and 136 are provided to indicate the position of the second locking plunger 128.

Referring now to fig. 5B, after verifying that the diverter assembly 112 is aligned with a new target loader 110, a series of eight target capsules 190 are pneumatically advanced to the airlock 150. The damper 150 is defined in part by a transfer conduit 390 disposed between the first and second outboard isolation valves 152 and 154 and the pair of first and second inboard isolation valves 156 and 158, respectively. As shown in fig. 5B, during the transfer of the target capsule 190 to the airlock 150, the first and second outboard isolation valves 152 and 154 are opened while the first and second inboard isolation valves 156 and 158 remain closed. A motive gas flow is applied to the series of target capsules 190 at the new target loader 110 and a blocking gas flow is provided via the gas inlet pipe 168 by opening the air isolation valve 170. The provision of a blocking airflow at the same time as the series of target capsules 190 enters the airlock 150 is to slow the velocity of the series of target capsules 190, thereby helping to prevent any potential damage due to impact. When the boost flow and the block flow begin to flow, the exhaust isolation valve 166 is placed in an open position so that the combined flow may exit the damper 150 through the exhaust pipe 164.

Referring additionally to fig. 5C, first, second and third stop pistons 172, 174 and 176, respectively, selectively extend into and retract from the air lock 150 to properly position the series of target compartments 190. As shown in fig. 5C, when a new series of target capsules 190 is inserted into the airlock 150, only the third stop piston 176 extends into the airlock 150 so that the series of target capsules 190 is properly positioned within the airlock 150. As shown in FIG. 5D, once the series of target capsules 190 is positioned within the airlock 150, the first and second outside isolation valves 152 and 154 are moved to a closed position such that the airlock 150 is isolated from the environment outside of the target irradiation system 100. Prior to the step of transporting the series of target capsules 190 to the respective target lift assemblies 200, the airlock 150 and the series of target capsules 190 are purged with helium gas through the helium inlet 160 by placing the helium isolation valve 162 in an open position. Similar to the drive gas flow and the block gas flow, the purge helium gas exits the damper 150 through the exhaust tube 164. Once the helium purge is complete, the exhaust isolation valve 166 is placed in the closed position.

Referring now to fig. 5E, prior to transporting the series of target capsules 190 out of the airlock 150, the operator ensures that the target lift diverter 180 is configured to be in fluid communication with the desired target lift assembly 200. In the preferred embodiment shown, three target lift diverters 180 are used, as this embodiment includes four target lift assemblies 200. If an alternative embodiment uses only two target lift assemblies 200, only one target lift diverter 180 is required. The function of the target lift diverter is the same as the path diverter assembly 112 previously discussed and therefore will not be described in detail.

Referring now to fig. 5F, when the target lift diverter 180 is aligned with the correct target lift assembly 200, a flow of purge gas for the series of target capsules 190 is generated by activating the first pneumatic pump 360 and placing the inboard isolation valve 364 of the outlet duct 362 in an open position. Like the airlock 150, the blocking airflow for the series of target capsules 190 is provided by activating the second pneumatic pump 370 and opening the outlet isolation valve 374 of the outlet tube 372. While propelling the air flow and preventing the air flow from beginning to flow, an exhaust line is provided for both air flows by opening the inlet isolation valve 378 of the inlet pipe 376 of the second pneumatic pump 370 so that the air flow is recirculated back to the inlets of the first and second pneumatic pumps 360 and 370 through the inlet pipe 376. As the propulsion, blocking, and exhaust flows develop, the third stop piston 176 retracts from within the airlock 150 and the series of target capsules 190 are propelled through the delivery conduit 390 to the respective target lift assemblies 200. As best shown in fig. 5F, the blocking airflow is configured to flow upward through the target lift assembly 200 such that the series of target pods 190 slows as they begin to enter the target lift assembly 200. The series of target capsules 190 may be selected to prevent airflow sufficiently strong to levitate the series of target capsules 190 as they enter target lift assembly 200. By slightly reducing the level of impeded airflow, the series of target pods 190 may be lowered significantly to the bottom of the target basket 250. Additional outlet and inlet pipes and corresponding isolation valves are provided so that the outlet and inlet pipes 372 and 376 of the second pneumatic pump 370 can be aligned with each target lift assembly 200.

It should be noted that alternative embodiments of the present system may include first and second hydraulic pumps, rather than first and second pneumatic pumps 360 and 370, so that the liquid may be used as both a propellant flow and a blocker flow to transport the string of target capsules 190 to the target lift assembly 200. When using liquid as both a propellant flow and a deterrent flow, isolation valves are used on the outlet tube 372 and the portion of the transfer tube 380 closest to the target elevator assembly 200 to minimize the amount of fluid released into the calandria vessel as the target basket 250 descends within the calandria vessel. Preferably, the liquid used in such an embodiment is reactor grade water, in particular heavy water when the reactor used is a CANDU reactor. In addition, when using liquid for the transport of the target compartment 190, a vent for moving liquid from the air lock 150 to the air environment is provided.

Referring now to fig. 4A and 4B, each target lift assembly 200 of the target irradiation system 100 is mounted to a corresponding regulator assembly port 108 or sleeve that is accessible from above the reactivity mechanism platform 104 and extends down into the calandria reactor vessel 106 of the CANDU reactor. As can best be seen in fig. 4B, the target lift assembly 200 includes an elongated body portion 202 defining a central aperture 204 and includes a mounting flange 206 that attaches the target lift assembly 200 to the top of the regulator assembly port 108. A curved target passageway 208 is formed in the upper end of the body portion 202, and the target passageway 208 extends from the delivery conduit 390 to the central bore 204. Similarly, the upper end of the body portion 202 defines the pneumatic channel 210 in fluid communication with both the outlet tube 372 and the central bore 204 of the second pneumatic pump 370. As can best be seen in fig. 4E and 4H, the bottom of the central bore 204 includes a frustoconical inlet surface 214, the inlet surface 214 configured to slidably receive a corresponding target basket 250.

As can best be seen in fig. 4B and 4C, a cylindrical center tube 216 is mounted within the central bore 204 of the target lifter assembly 200 by a flange 225, the flange 225 extending radially outwardly from an uppermost end of an upper body portion 224 of the tube. As shown in fig. 4B, the center tube 216 includes an annular ring 220 attached to its uppermost portion, the annular ring 220 being secured to an upper body portion 224 by a bellows 218 or an optional spring pack. As discussed in more detail below, the bellows 218 allows for limited sliding of the center tube 216 relative to the body portion 202 of the target lift assembly 200. As can best be seen in fig. 4H, the bottom end 222 of the center tube 216 includes a bottom bushing 228, an outer surface of the bottom bushing 228 forming a seal with an inner surface of the elevator assembly central bore 204; and a frustoconical inner surface 232, the frustoconical inner surface 232 configured to form a seal with a corresponding frustoconical surface of the bottom flange 267 of the target basket 250. At the bottom end 222 of the base pipe 216, a plurality of flow holes 226 are provided adjacent to a bottom liner 228. When the target basket 250 is fully seated within the target lift assembly 200 (fig. 4B), the flow bore 226 provides fluid communication between the interior of the center tube 216 and the flow ring 234 defined between the outer surface of the center tube 216 and the inner surface of the central bore 204.

Referring again to fig. 4B and 4C, the target lift assembly 200 includes a target basket 250 slidably received within the center tube 216. The target basket 250 includes a cylindrical sidewall 252 defining a plurality of flow apertures 254, and a target aperture 253 at an upper end thereof. When the target basket 250 is fully seated within the target elevator assembly 200, the target aperture 253 is aligned with the target channel 208 of the body portion 202. The target hole 253, together with the target hole 227 of the center tube 216 and the target channel 208 of the body portion 202, form a continuous curved guide path so that the series of target capsules 109 can slide freely into the target basket 250. As best seen in fig. 4C, target basket 250 includes a nose 256 extending upwardly therefrom, the nose 256 being defined by two curved cam surfaces 258 that meet at an apex 260 at an upper end thereof. An alignment slot 262 is provided between the lower ends of the cam surfaces 258, and the alignment slot 262 is configured to slidably receive an alignment pin 264 (fig. 4F and 4G), the alignment pin 264 extending radially inward into the recess 212 at the top of the central bore 202, the recess 212 configured to receive the nose 256 of the target basket 250. The upper portion of the target basket 250 also defines an alignment plane 266 and a locking recess 268 configured to receive the roller 242 disposed at the innermost end of the piston 244 of the locking pin assembly 240, as discussed in more detail below.

As best seen in fig. 4A and 4D, a mechanical cable drive assembly 270 is mounted at the uppermost end of the body portion 202 of the target lift assembly 200 and is configured to lower and raise the target basket 250. The cable drive assembly 270 includes a roller 272 rotatably received on a drive screw 274 and a drive motor 278 disposed within a housing 280. The feed line 276 is rotatably received around the drum 272 and is secured at its bottom end to the upper end of the target basket 250. The drum 272 is configured to advance along its mounting axis as the feed line 276 winds and unwinds such that the feed line 276 remains centered in the target basket 250. Preferably the roller 272 is received on a cantilevered mounting shaft that includes a force sensor at the end to enable determination of when an entire cluster of targets is received within the target basket 250 based on the sensed weight. Likewise, the cantilevered rollers 272 are able to determine when the target basket 250 and the corresponding series of target capsules 190 are located within or above the moderator within the calandria 106 of the reactor based on the weight supported. In addition, the force sensor detects the phenomenon that the feed line 276 is caught and tension is lost, thus causing the motor 278 to be entangled, to avoid damage.

Referring now to fig. 5F, 4B and 4I, as previously described, the second pneumatic pump 370 provides a blocking gas flow as the series of targets 190 enter the target elevator assembly 200. The airflow is prevented from entering the target lift assembly 200 through the pneumatic channel 210 and flowing downward through the flow ring 234 until it reaches the flow aperture 226 formed in the bottom end 222 of the center tube 216. As shown in fig. 4H, the bottom bushing 228 of the center tube 216 forms an air tight seal with the central bore 204 of the body portion 202 and the bottom flange 267 of the target basket 250, thereby preventing further downward flow. At this point, the airflow is prevented from entering the interior of the center tube 216 through the flow aperture 226 and flowing upward, where it encounters the target compartment 190 until it exits the delivery tube 390 through the exhaust line 376.

As shown in fig. 4I, the series of target pods 190 are inserted into the target basket 250 only when the target basket 250 is fully within the target lift assembly 200 and locked into place by the locking pin assembly 240. When the nose 256 of the target basket 250 is fully received in the recess 212 of the target lift assembly 200, the roller 242 of the piston 244 can only engage the locking recess 268 of the target basket 250. The engagement of the locking pin assembly 240 with the locking recess 268 ensures that the target holes 253 of the target basket 250 are properly aligned with the target channel 208 in both the vertical and rotational directions, and also helps reduce stress on the connection between the feed line 276 and the target basket 250 because the locking pin assembly 240 provides support when the series of target compartments 190 strike the bottom of the target basket 250. When the series of target capsules 190 has been received within the target basket 250, as shown in fig. 5G, the thrust and gas flow is stopped by deactivating the first and second pneumatic pumps 360 and 370, respectively, and closing the respective inboard isolation valves 364 and 374 and the isolation valve 378 of the vent line, respectively, as shown in fig. 5G. Referring now to fig. 4C and 4D, after the series of target capsules 190 are received within the target basket 250, the piston 244 is retracted such that the roller 242 is no longer engaged with the locking recess 268. The motor 278 is used to lower the target basket 250 and thereby the series of target compartments 190 into the heavy water moderator within the calandria 106 of the reactor. While within the moderator, the string of target capsules 190 is exposed to the neutron flux of the reactor.

After the series of target pods 190 has been irradiated for the desired amount of time, the motor 278 of the cable drive assembly 270 is again activated to lift the target basket 250 out of the moderator. Preferably, the target basket 250 is suspended in the gas space above the moderator to allow the moderator to be expelled from the target basket 250 and to allow the short half-life radioisotope to decay to an acceptable level before retrieval of the string of target compartments 109 from the target lift assembly 200. As shown in fig. 4E, the frustoconical inlet surface 214 at the bottom of the target lifter assembly 200 is configured to guide the nose 256 of the target basket 250 into the center tube 216. The cable drive assembly 270 continues to raise the target basket 250 until the bottom flange 267 of the target basket 250 contacts the frustoconical inner surface 232 of the bottom bushing 228, as shown in FIG. 4H. In this position, the target basket 250 may not be properly aligned within the center tube 216, making it difficult to remove the string of target capsules 190. For example, as shown in FIG. 4F, the target basket 250 is offset approximately 180. In most cases, by slightly lifting target basket 250, alignment pin 264 will contact one of the two cam surfaces 258 of basket nose 256, causing target basket 250 to rotate until alignment pin 264 is slidably received in alignment slot 262. When alignment pins 264 are received within alignment slots 262, target basket 250 is properly positioned for retrieval of the series of target capsules 190. An alignment flat 266 is provided only if the apex 260 of the nose 256 of the target basket is directly aligned with the alignment pin 264, as shown in fig. 4F. In this case, piston 244 of locking pin assembly 240 extends radially inward until roller 242 engages alignment flat 266, causing target basket 250 to rotate slightly, which results in the desired misalignment of apex 260 with alignment pin 264. Note that during further upward movement of target basket 250, bellows 218 (fig. 4B) of center tube 216 is compressed. Bellows 218 helps to ensure that a hard stop 223 (fig. 4C) engaged with the top of target basket 250 can simultaneously contact sealing surfaces 232 and 267 (fig. 4H), thereby achieving vertical alignment and sealing despite manufacturing tolerances and possible age-related elongation between the bodies of target basket 250.

When the irradiation of the series of target capsules 190 is complete and the target basket 250 is fully seated and locked in place within the target elevator assembly 200 (as shown in fig. 5G), removal of the series of target capsules 190 from the target elevator assembly 200 may begin. Referring now to fig. 5H, removal of the series of target capsules 190 from the target assembly 200 is accomplished using a motive gas flow from the second pneumatic pump 370 and a blocking gas flow provided by the first pneumatic pump 360. Prior to initiating the propulsion flow and blocking the flow, the operator places the first and second airlock inboard isolation valves 156 and 158 in their open positions so that the train of target capsules 190 can enter the airlock 150. Upon activation of the second pneumatic pump 370, the outlet isolation valve 374 is placed in an open position and a flow of motive gas is provided through the outlet tube 372. Referring additionally to fig. 4B, the motive gas stream enters the pneumatic channel 210 of the target lift assembly 200 and flows down the flow ring 234 until it enters the interior of the center tube 216 through the flow aperture 226 (fig. 4H). At this point, the propulsion gas flow engages the series of target capsules 190, pushing the series of target capsules upwardly and outwardly out of the target basket 250 and into the delivery conduit 390, as shown in fig. 4I. Simultaneously with the initiation of the flow of the propulsion gas, the prevention of the flow of the gas is initiated by activating the first pneumatic pump 360 and placing the inboard isolation valve 364 of the outlet pipe 362 in the open position. Exhaust gas flow is not required at this stage of operation because the motive gas flow and the blocking gas flow are recirculated to the inlets of the first and second pneumatic pumps 360 and 370, respectively, through the inlet pipe 366 of the first pneumatic pump 360. As shown in fig. 6H, during removal of the series of target capsules 190 from the target lift assembly 200, the first stop piston 172 extends inward into the interior of the air lock 150 to effect an overshoot stop of the series of target capsules 190 within the air lock 150.

Referring additionally to fig. 6I, when the series of target capsules 190 is properly positioned within the airlock 150, the airlock 150 is isolated from the remainder of the target irradiation system 100 by moving the first and second inboard isolation valves 156 and 158 to a closed position. Additionally, by deactivating the first and second pneumatic pumps 360 and 370, respectively, and placing the isolation valves 364, 368, and 374 in a closed position, the propulsion flow, the blocking flow, and the recirculation flow may be assured. Similar to inserting the string of target capsules 190 into the target lift assembly 200, the airlock 150 is purged while the string of target capsules 190 is isolated in the airlock 150 during removal of the string of target capsules 190 from the target lift assembly 200. Since the outwardly moving target capsule 190 is released into the air environment, an air purge may be used instead of a helium purge. By placing air isolation valve 170 in an open position and by placing exhaust isolation valve 166 in an open position, exhaust gas flow is provided through exhaust pipe 164, thereby purging air through air inlet 168. When purging is complete, air isolation valve 170 and exhaust isolation valve 166 are placed in a closed position.

Referring now to fig. 6J, prior to releasing each target bay 190 into the shielded container loader assembly 300, the operator ensures that the path diverter assembly 112 is aligned with the second inlet tube 142 leading to the shielded container loader assembly 300. Next, a propulsion flow is created by placing the air isolation valve 170 of the intake pipe 168 in an open position and placing the first and second outboard isolation valves 152 and 154 of the damper 150 in an open position. As discussed in more detail below, the exhaust gas flow is achieved by shielded container loader assembly 300. Upon establishing the propulsion flow, the second stop piston 174 extends into the airlock 150 so that it engages a second target capsule 190 in the series of target capsules, thereby securing them in place. Next, the first stop piston 172 is retracted from the airlock 150 such that the first target bay 190 in the series of target bays is now free to advance to the shielded container loader assembly 300. After releasing the first target capsule 190, the first stop piston 172 again extends into the airlock 150 and the second stop piston 174 retracts, leaving the remaining seven target capsules 190 in the series of target capsules free to advance until abutting the first stop piston 172. At this point, the second stop piston 174 extends into the airlock 150 until it engages a second target capsule 190, which is now in the remainder of the series of target capsules. At this point, the first stop piston 172 is again retracted from the airlock 150, thereby releasing another target pod for delivery to the shielded container loader assembly 300. This process is repeated until all eight target bays 190 have been individually released to the shielded container loader assembly 300. After completing the delivery of all eight target capsules 190 to the shielded container loader assembly 300, the motive gas flow is assured by placing the air isolation valve 170 in the closed position and placing the first and second outboard isolation valves 152 and 154 of the air lock 150 in the closed position, as shown in fig. 6A.

As shown in fig. 6A-6C, shielded container loader assembly 300 includes slidable drawer 302 having annular bracket 304 and outer door 306. The carrier 304 is configured to receive a shielded container box 320 therein, as shown in fig. 6C. The capsule 320 defines an interior cavity 328 (fig. 5E) configured to slidably receive a target shielded container 330, and includes a closure plug 322 secured to the body of the capsule 320 by a plurality of threaded fasteners 324. The closure plug 322 also includes a pair of lifting eyes 326 whereby a cantilever crane 392 (FIG. 1) of the reactor facility can raise and lower the cassette 320. The cassette 320 is also received in a road transport overwrap 340, the road transport overwrap 340 defining an internal cavity 344 closable with a lid 342. After the cartridge 320 is placed in the cradle 304 of the drawer 302, the threaded fasteners 324 are removed and the closure plug 322 remains in place while the drawer 302 is slid inward into the first compartment 310 of the shielded container loader assembly 300, as shown in fig. 6D. When the drawer 302 is slid inward so that the cartridge 320 is placed in the first compartment 310, the magnetized stopper puller 308 is lowered into contact with the closure plug 322 and then raised, thereby removing the closure plug 322 from the cartridge 320. Note that when the cartridge 320 is received within the first compartment 310, the door 306 of the drawer 302 seals or partially seals the interior volume of the shielded container loader assembly 300 from the outside environment. Note that some airflow may be required into shielded container loader assembly 300 while providing the exhaust airflow. Also, an exhaust tube 303 is provided to enable shielding the interior of the container loader assembly 300 from the exhaust gas flow during loading of the target bay 190.

With the closure plug 322 removed, the target shielded container 330 is now accessible and moved to the second compartment 340 of the shielded container loader assembly 300, as shown in fig. 6E and 6F. The target shield container 330 preferably includes a plurality of target cavities 332 and a central recess 334, each of which is capable of slidably receiving a pair of previously irradiated target capsules 190. The central recess 334 is configured to slidably receive a bayonet fitting 341, which bayonet fitting 341 includes a pair of opposing protrusions 346 and is disposed at the lowermost end of the vertical lift spear 342. After the central recess 334 of the target shielding container 330 is aligned below the vertical lift spear 342, the vertical lift spear 342 is lowered into the central recess 334 and rotated approximately 90 ° so that the protrusions 346 of the bayonet fitting 341 engage with corresponding recesses (not shown) defined within the central recess 334. After proper engagement with the target shield container 330, the vertical lift spear 342 is raised so that one of the shield container's target cavities 332 is aligned with the outlet of the pneumatic transport tube 350 of the shield container loader assembly 300, as shown in fig. 6G and 6H.

The stop piston 348 extends outwardly through an aperture formed therein into the pneumatic transport tube 350 prior to receiving the previously irradiated target capsule 190. Note that the use of a blocking airflow in this preferred embodiment also helps slow and/or stop the previously irradiated target capsule 190 before encountering the blocking piston 348. A receiving surface 354 is disposed at a distal end of the blocking piston 348 and is configured to receive the target capsule 190 as the target capsule 190 enters the shielded container loader assembly 300. When the target capsule 190 has been received on the shock absorbing receiving surface 354, the piston 348 is prevented from retracting from the pneumatic transport tube 350 such that the respective target capsule 190 is gently lowered into the respective target chamber 332, as shown in fig. 6H. After placing the second target capsule 190 undergoing irradiation in the corresponding target cavity 332, the lift spear 342 is indexed 90 ° to align the second empty target cavity 332 with the pneumatic transport tube 350. This process is repeated until each target capsule 180 undergoing irradiation is received in a respective target cavity 332. When the target shielded container 330 is full, the lift spear 342 is lowered until the target shielded container 330 is again received within the cassette 320 located in the cradle 304 of the drawer 302, at which point the lift spear 342 disengages from the target shielded container 330. The target shielded container 330 is again moved to the first compartment 310, at which time the stopper puller 308 lowers the closure stopper 322 into position on the cartridge 320. Drawer 302 is now slid outwardly from shielded container loader assembly 300 and closure plug 322 is again secured to cassette 320 using threaded fasteners 324, at which point it may be moved into shipping package 340 using cantilever crane 392 and secured therein with lid 342, as shown in fig. 6A. The previously irradiated target capsule 190 is now ready to be transported to the desired processing facility.

These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. Additionally, it should be understood that features of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so defined, except as set forth in the following claims. Therefore, the spirit and scope of the appended claims should not be limited to the description of the versions contained herein.