Storage of Radioactive Minerals
Because mineral specimens containing radioactive elements are naturally occurring substances and are collected in small quantities, there are no official licensing requirements for their possession and storage. However, the Environmental Protection Agency (EPA) does provide recommendations on acceptable radon levels. In addition to the normal concerns of collection storage, it is necessary to minimize the risk to people presented by the nature of the specimens.
When considering plans to store radioactive minerals, there are three categories of potential radiation hazard that have to be addressed:
- External exposure to alpha, beta and gamma radiation;
- Contamination from radioactive particulate material; and
- Radon gas emanation which is the major concern in a storage environment.
Ellen Warren Faller
Peabody Mus. of Natural History
New Haven, CT 06511 USA
Tel (203) 432-3141
Fax (203) 432-9816
Kenneth W. Price
Radiation Safety Department
Univ. of Connecticut Health Ctr.
Farmington, CT 06032 USA
Tel (203) 679-2250
Fax (203) 679-3826
Alpha particles, beta particles and gamma rays are emitted in the course of the release of excess energy from atomic nuclei of the elements uranium and thorium. This nuclear disintegration process is known as radioactive decay.
Radon is a radioactive gas which is in the decay chain of natural uranium. Radon itself decays and forms other short-lived radioactive decay products. These “radon daughters” become attached to dust particles in the air and may be inhaled and deposited in the lungs where their released alpha particles may damage the lung tissue.
The objective of radiological protection is to keep all exposures to radiation As Low As Reasonably Achievable (ALARA). Fortunately, these exposures in small collections can be controlled easily and inexpensively by using distance, containment and time instead of money. More elaborate storage is possible for collections with substantial numbers of radioactive specimens, but controls require greater financial resources.
Specimens should be stored as far away from areas of human activity as possible in order to maximize the distance from the radiation source and to minimize the duration of exposure.
Materials Tools Supplies
- Adhesive-backed labels indicating caution radioactive material, magenta on yellow (technically for licensed material, but the intent is to warn, not mislead)
- Polyethylene bags with zippered closure
- Radiation measurement and Radon monitoring equipment
- Clearly label all radioactive specimens and their storage locations in order to keep museum staff aware and to alert any visitors.
- To minimize inhalation and ingestion of dust, wear washable or disposable plastic gloves, keep areas free of dust by using a damp wipe, and wash hands thoroughly after working with or near mineral specimens.
- Cut and grind specimens outdoors or in a properly ventilated area with restricted-use equipment. Wear an appropriate particulate filter mask, eye protection, gloves and an apron. use small or portable fans with caution as they may tend to stir up dust and may serve only to recirculate air.
- Store specimens in plastic bags with zippered closure, tightly closing plastic boxes, metal cans with plastic lids (e.g., coffee can), or any similar, appropriately cushioned container that allows a specimen to be seen, reduces handling, and controls dust and radon escape.
- Open containers in a well-ventilated area to allow the radon daughters to be diluted to a very low concentration. Display cases in which radioactive minerals are housed should be treated as containers.
Carefully seal and open display cases only under controlled circumstances, or the cases should be ventilated in such a way that the radon is directed away from human activity and diluted with large volumes of air.
- Specimens should be stored as far away from areas of human activity as possible, such as against an outside wall, or at the back of a drawer or case. Be aware of the human activity and use of the space on the other side of the wall or case.
- Monitor regularly, at least yearly, in areas where radioactive specimens are stored or exhibited. The results will determine if a problem exists. Your local, state, or regional EPA, or university radiation safety office or physics department should be able to advise you on radiation measurement and radon testing.
The use of lead shielding is not recommended for most collections, especially those with fewer than 100 radioactive specimens. It should be remembered that lead has its own well-documented health hazards.
For medium-sized collections (50 to a few hundred specimens of average radioactivity), it is not advisable to store all the radioactive material in one case.
For collections with highly radioactive specimens, and/or with hundreds of radioactive specimens, it may be necessary to build a separate, limited access storage room in order to control the potential radiation hazards and the ventilation of radon.