Radiological Wastes in Healthcare Facilities
Radiological wastes are useful precisely
because they are lethal. Rapidly dividing cells more susceptible to
radiation damage than non-dividing cells. This property makes radiological
agents useful for cancer treatment.
Radioactivity results from reactions
involving changes in atomic nuclei. A nuclear reaction typically results
in the release of about a million times more energy per atom than a typical
chemical reaction (which involves changes in the electron distribution around
the nuclei, but leaves the nuclei themselves unchanged).
Radioactive substances are generally
prepared by bombarding stable materials with high energy particles, transforming
some of the nuclei into unstable states. To be useful as a therapeutic
agent, the unstable nuclei must persist for long enough to be administered
to a patient and to act on the target tissue. The rate at which unstable
nuclei emit radiation and decay into more stable states depends almost entirely
on the composition of the material. The rate is expressed in terms
of "half-life", the length of time needed for half of a given amount
of the material to decay. Therapeutic materials are often chosen to
have half-lives in the range of several days to several weeks. This
allows enough time for transportation and storage of the material, but also
allows the material to decay into a less hazardous form in a convenient period
Two additional properties besides half-life
are important for understanding the differences among various radioactive
Particle type. When nuclei
decay, they typically emit a low mass, fast moving particle. Most radioactive
materials encountered in hospitals emit one of three types of particle, called
(for historical reasons) alpha, beta, and gamma. The emitted particles
differ in their ability to penetrate other materials.
- Alpha particles (helium nuclei) are strongly scattered
by other nuclei, and thus have poor penetrating power. A few layers
of cloth can stop alpha particles. The greatest danger from alpha emitters
occurs when alpha-emitting material is inhaled or ingested.
- Beta particles (electrons) are intermediate.
- Gamma particles (high frequency packets of light energy,
or photons) are less strongly scattered, and thus penetrate other materials
effectively. Many feet of lead may be required to stop gamma particles.
Energy. Depending on the
isotope, the emitted particles will carry a certain quantity of energy. [add
enough background mtl to lead into risk discussion]
Need to define "isotope".
Additional benefit of using a highly
active, short-half life isotope -- a little goes a long way -- can minimize
quantity as well as storage time on site.
Measures of radiation exposure
Patients with implants (National
Cancer Institute: fact
sheet on radiation therapy for patients)
Security concerns -- how credible is "dirty bomb source
An informative and entertaining treatment of radiation hazards
is available at http://musr.physics.ubc.ca/~jess/p200/radhaz/radhaz.html (This
resource is particularly recommended for readers who may wonder how a discussion
of radiation hazards can be entertaining, but who are open to the possibility.)
from sector notebook:
from comments to sector
notebook by Dan Schultheisz (email from Seth, 1/27/05, 11:32
- common for licenses to allow storage for
- possible conditional RCRA exemption (issued
5/01) to allow storage of mixed wastes for over 90 days, available
in a few states
- radiological wastes can be mixed with RMW
as well as RCRA
list common isotopes in
use in healthcare
any risk-benefit comparisons
of isotopes available?
desirability of separating
of radiological wastes
decay on site
options for mixed
Washington State Department of Health,
Office of Radiation Protection:
These NRC resources may be helpful: