A historical overview of orphan sources and radioactivity in scrap metals

Orphan sources and radioactivity in scrap metals have emerged as significant radiation protection issues. Even so, both problems have antecedents dating to the early part of the 20th century when radium and radon sources began to come into common use. In the United States, use of radium initially grew slowly until the 1940s when its use sharply increased peaking at the end of the decade when about 5,000 to 6,000 persons used radium. Losses of radium sources were first reported in the 1911-1920 period. In 1964, the U.S. Public Health Service tabulated 396 reports of radium incidents up to that year. Some incidents resulted in radiation exposures and extensive contamination of property. Improperly stored or discarded radium sources sometimes found their way into the public domain. Most US users of radium were not subject to effective regulatory oversight for radiation safety until the 1960s when it was recognized that regulation was needed to assure the safe use and storage and proper disposal of radium. As regulatory oversight increased, many radium users discontinued their use of such sources creating an inventory of unwanted radium sources and a need to provide for their safe storage and disposal. Although the term was not used then, the lost, stolen and unwanted radium sources were an early manifestation of the orphan source' problem. Radioactivity in scrap metals also manifested itself. A radioactive decay product of radium, radon, contained in gold seeds came into use for therapy. Unused seeds were sometimes sold as scrap gold. Jewelry made from such gold became contaminated by radon decay products that were in the seeds causing radiation injuries to persons who wore the jewelry for extended time. Such jewelry was made as early as 1910. The nuclear energy era has seen a vast increase in the variety and number of radioactive materials that can be incorporated into sources. In the US, the numbered of licensed uses of radioactive materials is about 157,000, about 30 times greater than the peak number of radium users. Further, each year, there are about 200 reports of lost, stolen or abandoned radioactive sources. In some cases, serious radiation exposures and property contamination resulted. Lost, stolen or abandoned sources have been found in the public domain, creating a need for programs to recover, store and dispose of such sources. Radioactive sources have also become accidentally mixed with scrap metals destined for recycling. When melted in metal making furnaces, the radioactive material can cause contamination of the metal product, byproducts, and the facility making the metal. The first reported incident of this type in the nuclear energy era occurred in the US in 1983. By 1999, thirty incidents of this type had occurred in the US. The US experience with radium, in retrospect, provided some early insights into the problems associated with use of radioactive sources, particularly the importance of assuring adequate controls and accountability of sources, assuring that they do not become inadvertently mixed with metal scrap intended for recycling, and the need to provide for the safe recovery, secure storage and proper disposal of orphan sources. (author)