A radioactivity well logging tool including a gamma radiation detector is field calibrated with the help of a flexible sheet having a radioactive substance dispersed therein, which is wrapped about the tool so as to completely surround the detector. The sheet is made of an elastomer such as polyurethane, and the radioactive substance is carnotite. This sheet is placed within a nylon sheath which has straps for holding the calibrator wrapped around the tool.

There is disclosed a method for sealing or closing the cutting surfaces of radioactive foils covered at both sides with protective- or support layers formed of a noble metal, which comprises the steps of heating the foil for at least ten minutes to at least 60 percent of the absolute temperature of the melting point of the lowest melting protective- or support metal layer.

Californium, as metal or oxide, is uniformly dispersed throughout a noble metal matrix, provided in compact, rod or wire form. A solution of californium values is added to palladium metal powder, dried, blended and pressed into a compact having a uniform distribution of californium. The californium values are decomposed to californium oxide or metal by heating in an inert or reducing atmosphere. Sintering the compact to a high density closes the matrix around the dispersed californium. The sintered compact is then mechanically shaped into an elongated rod or wire form.

A solution containing radioisotope and palladium values is atomized into an air flow entering a cryogenically cooled chamber where the solution is deposited on the chamber walls as a thin layer of frozen material. The solvent portion of the frozen material is sublimated into a cold trap by elevating the temperature within the chamber while withdrawing solvent vapors. The residual crystals are heated to provide a uniformly mixed powder of palladium metal and a refractory radioisotope compound. The powder is thereafter consolidated into a pellet and further shaped into rod, wire or sheet form for easy apportionment into individual radiation sources.

A flexible source wire is provided containing a radioactive source that is capable of maneuvering through a tortuous narrow passage to a treatment site within the body. This source wire includes a thin flexible housing tube, housing therein a flexible backbone wire, wherein both the tube and the wire are constructed from a material exhibiting little or no memory retention when bent. A radioactive core is provided in the proximal end (i.e., the treatment end) of the thin flexible housing tube and abuts the proximal end of the backbone wire. Both ends of the source wire are sealed and the proximal end of the source wire is rounded to allow ease of movement as it travels through the bends and turns in the body.