Abstract: Iodine-125 is produced by neutron irradiation of .sup.124 Xe gas to form .sup.125 Xe and permitting decay of .sup.125 Xe to form .sup.125 I. Irradiation of the xenon-124 is effected in a first chamber within an enclosure and decay is effected in a second chamber within the enclosure and free from neutron flux. The apparatus is submersible in a nuclear reactor pool so as to absorb any radiation escaping the apparatus during the process. Xenon can be caused to move between the chambers remotely, underwater. The second chamber is removable from said enclosure and is transported to a suitable location to recover the .sup.125 I from its interior. Such recovery is effected by admitting an aqueous wash solution into the second chamber, whereupon it is heated, causing water from the wash solution to reflux and cleanse the interior surfaces of the second chamber, thus creating an aqueous solution of .sup.125 I, which then is caused to drain into a suitable container.

Abstract: Iodine-125 is produced by neutron irradiation of .sup.124 Xe gas to form .sup.125 Xe and permitting decay of .sup.125 Xe to form .sup.125 I. Irradiation of the xenon-124 is effected in a first chamber within an enclosure and decay is effected in a second chamber within the enclosure and free from neutron flux. The apparatus is submersible in a nuclear reactor pool so as to absorb any radiation escaping the apparatus during the process. Xenon can be caused to move between the chambers remotely, underwater. The second chamber is removable from said enclosure and is transported to a suitable location to recover the .sup.125 I from its interior. Such recovery is effected by admitting an aqueous wash solution into the second chamber, whereupon it is heated, causing water from the wash solution to reflux and cleanse the interior surfaces of the second chamber, thus creating an aqueous solution of .sup.125 I, which then is caused to drain into a suitable container.