Citation

Highw. Res. News 1970; (41): 38-40.

Copyright

(Copyright © 1970, National Research Council, Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Since 2 September 1969 a Phoenix freeway has been equipped with a directional sign powered by krypton 85, a radioisotope, that excites a modular light source (phosophor). This isotope has a half life of 10.6 years, and it is expected that the sign will have a service life at least this long. The sign will require no power maintenance. Lead shielding reduces gamma radiation to the level of solar exposure and completely retains beta rays. Installation of the sign is a research project conducted with the atomic energy commission and american atomics corp. To gather data on krypton 85 effects on the emission spectra of various phosphors used in light sources, on source brightness with increasing age, and on emission spectra and brightness under different ambient temperatures. As krypton 85 is expected to become a plentiful isotope in the near future, its price will make it adaptable for highway uses.

Language: en