,mote Opening of Metal Containers with a laser Beam Donald L. Horrocks and Martin H. Studier, Argonne National Laboratory, Argonne, Ill. HERE are many experiments which Tinvolve the opening of a sealed sample by remote handling. In many cases the containers are metal. Often i t is necessary to trap gases from sealed containers for further memurements or to prevent the escape of gases to the atmospherei.e., radioactive fission product gases. In these cases opening of the metal containers has t,o be accomplished remotely and in a closed system. Now that new high flux reactors are available it is necessary to irradiate samples in metal containers. The remote opening becomes more important since the metal containers themselves constitute a radiation hazard. (Even ultrapure aluminum containers exposed to high fluxes for long times will build up considerable amounts of radioactivity as the result of (n,a) and (n,2n) types of reactions.) In this laboratory we have found a laser to be a useful tool for remotely opening metal containers, even those in closed systems. In the past the opening of metal containers in closed systems was accomplished with some difficulty. Intricate sawing and cutting devices have been constructed (S),high electrical currents have been used to melt holes in the metal containers (4, and sometimes the metal containers (or a part of them) have been dissolved (1). This new technique involves focusing the beam of light from a laser through a
Figure 1 .
Experimental orrongement:
laser, lens, ond gloss trap contoining
metal sample container 1782
ANALYTICAL CHEMISTRY
lens onto the metal container which can be inside a closed system-Le., a glass vacuum line (Figure 1) or behind a protective wall-i.e., in a cave area. I n this work a laser (Maser Optics, Inc., Model 3020) with a 65/8 X J/rinch 0.05’% chromium doped ruby rod cooled to liquid nitrogen temperature was employed. At liquid nitrogen temperature this laser has a rated maximum output energy of 30 to 35 joules. For the approximate 10-3-second pulse duration, the laser would have an output of 30 to 35 kw. By focusing this amount of power upon a small area with a lens, a hole can he melted in a metal tube with a wall as thick as 0.015 inch. By carefully successively locating the beam position or the metal tube position, slits can he obtained (Figure 2). Single holes as large as I/,. inch in diameter have been obtained. It was demonstrated that the laser beam could be directed around corners by the use of mirrors or prisms. The mirrors have to be of high quality; otherwise considerable amounts of the light beam may be lost by absorption and/or scattering. This technique is useful for remote opening operations when there is no direct viewing of the metal container through a window transparent to the light from the laser. This technique proved useful €or opening metal containers inside a closed system to trap gaseous products (2). The sample and metal container are placed inside a glass trap, which is part of a vacuum line (Figure I), and thelaser beam is focused upon the metal container. The glass trap is transparent to the red light emitted hy the ruby laser. There is no attenuation of the energy of the light beam. This technique would be useful for the study of chemical reactions using fluorine-many fluorine or hydrogen fluoride-containing reactions are performed in nickel containers because of their reactivity with glass. Some of the advantages of this new technique are: Anywhere from one to many holes can he put into the metal container. The laser is outside the closed system and can be moved, repaired, or altered without disturbing the closed system. It is applicable to any type of remote operation provided the light beam from the laser can be focused, directly or indirectly, by mirrors and/or prisms, onto the metal containers (for different depths of penetration, lenses with different focal length are used).
A
8
C
Figure 2. Metal tubes with slits and holes produced by laser beam (A) Cu-Ni alloy: ‘/*-inch 0.d. with 0.010inch wall thickness (6) Staiden steel: a/8-imh a d . with 0.010Inch wall thickness (Cl Monel: 7 / d n c h ad. wilh 0.01 0-inch woll thickness
Finally, small holes are produced which decrease the chances of vaporizing large amounts of the metal container or possibly the sample itself. Some problems associated with this technique, if solved, would make it more useful-only small holes are produced which means many firings of the laser are necessary to sever a metal tube, and only about five firings per minute are possible, for instance, with the laser used in this work. (The continuous gas lasers unfortunately have much lower energy outputs, in the milliwatt range, insufficient for melting holes in the metal containers.) LITERATURE C m O
(1) . . Blanco. R. E.. “SvmDosium on the
Reproc&ing of Irradiated Fuels,” TID-7534, Brussels, May 1957. (2) Homcks, D. L., “Transactions of the 1965 Annual Meetinr.” ~. ANS., D.. 12.. June 1965. (3) Mohr, W. C., “Proceedings of the 12th Conference on Remote Systems Technology,” ANS, p. 373, November ~ . . lY64. (4) Sloth, E. N., Horrocks, D. L., Boyce, E. J., Studier, M. H., J. Inmg. Nuel. Chem. 24, 337 (1962).
BASEDon work performed under the auspice4 of the U. S. Atomic Energy Commission. Presented at Thirteenth
