Patent Number: 052981967
Section: description

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The loading process is illustrated in FIG. 3. The apparatus comprises a furnace 70, a portion of which is inside a containment 72. Furnace 70 has sides 74 and a top 76 that define an interior. Opposing top 76 is an opening 78. At least a portion of furnace 70 is inside containment 72, the portion that includes opening 78. The remainder of furnace 70 may be outside containment 72. A target bundle 90 is transferred to containment 72 on a shipping cart 92 and into containment through a first air lock. An air lock, as is well known, is a passageway with at least two doors. With an inner door closed and sealed, an outer door is opened to admit the upended bundle 90, which is moved toward the inner door. The outer door is closed and the air inside the airlock can be exchanged to avoid the escape of gas from inside containment 72 or the introduction of contaminants to containment 72. The inner door can then be opened and bundle 90 brought into the interior of containment 72. Bundle 90 is lowered into sleeve 110 and crucible 94. Beforehand, a crucible 94 is transferred into containment 72, also through an airlock. Crucible 94 has a bottom 100, sides 102 and an interior 106 sufficient in its interior volume to hold and enclose laterally the residue of a heated target bundle 90. Sides 102 have a flange 104. By "enclosing laterally", it is meant that the sides of bundle 90 are covered but not necessarily any of the top of the bundle 90. A sleeve 110, which was depending from a pulley (FIG. 4), is lowered onto crucible 94. Sleeve 110 is essentially a hollow cylinder having a flange 112 and a skirt 114 depending from flange 112. Skirt 114 is dimensioned to fit just within sides 102 of crucible 94. Flange 112 engages flange 104 to provide good contact between sleeve 110 and crucible 94. The combined, internal volume of sleeve 110 seated on crucible 94 is sufficient to hold and laterally enclose bundle 90. Bundle 90 is then transferred to a position just below furnace 70 and on a spacer 120. Spacer 120 is on a lid 122 which is in turn on a lift 124. Lift 124 lifts bundle 90 up and into furnace 70 through opening 78 until lid 122 engages a flange 126 on furnace 70. At least one gasket 130 assures an airtight seal of furnace opening 78. Furnace 70 is heated by electrical resistance heaters 132 along its upper portion 134. Its lower portion 136, below the fully seated bundle 90, is not heated. Spacer 120 assures that crucible 94 and sleeve 110 are in upper portion 134. Once lifted to the proper elevation, with lid 122 engaging flange 126, lid 122 is tightened to seal furnace 70 and checked for leaks. Heaters 132 are then activated and heat the bundle in steps to approximately at least 660.degree. C. (the melting point of aluminum). The tritium is extracted under a partial vacuum. Only the upper part of the furnace is heated in order to protect the seal of the flange-to-lid interface. At the top of furnace 70 is a gas outlet line 140. A trap 142 in gas outlet line 140 is filled with metal shavings 144, comprising preferably copper or steel. During the tritium extraction period, metal vapor, which is radioactive, generated by heating bundle 90, is captured on the shavings 144 and separated from the tritium. Trap 142 is removable and may be replaced as conditions warrant. During the final heating period when the temperature is above about 600.degree. C., furnace 70 is filled with an atmosphere of a non-reactive gas such as argon or nitrogen, to minimize the vaporization of radioactive zinc and lithium. To prevent deposition of zinc and lithium, the lower part of the furnace can be purged by a slowly flowing, inert gas stream through purge gas line 146. If deposition of these elements does occur, the deposits can be periodically removed by scraping. Most of furnace 70 is outside the controlled atmosphere of containment 72. This positioning facilitates cooling of furnace 70 and avoids heat build up inside containment 72. When furnace 70 is opened to remove or insert crucible 94, only controlled, dry gas can enter. Tritium, being a gas lighter than air tends to remain in the inverted furnace. If, however, some tritium escaped into the facility, strippers 148 are able to recover it. The unloading process, illustrated in FIG. 4, is essentially the reverse of the loading process. With lift 124 in position just below but engaging lid 122, the connections between lid 122 and flange 126 are broken and bundle 90 is lowered from furnace 70. Bundle 90 will have melted to just fill only crucible 94. After being moved by rollers to one side, sleeve 110 is lifted free of crucible 94 so that it can be used for the next bundle. Crucible 94 is immediately covered and transferred outside of containment 72, again via an air-lock where it may be stacked on top of other crucibles in a larger, single container 150 for shipment to a disposal facility. Furnace 70 and crucible 94 are preferably made of stainless steel. It will be apparent to those skilled in the art that many changes and substitutions can be made to the preferred embodiment herein described without departing from the spirit and scope of the present invention as defined by the appended claims.