Healthcare facilities employ radioactive materials in both diagnostic and treatment procedures. If a hospital has a nuclear medicine section, that is usually where most of the radiation therapy takes place. Radioactive waste can come in many forms: medical equipment contaminated with trace amounts of certain isotopes, clothing, the actual radiation source (e.g. a cobalt block). When radioactive materials are inserted inside patient bodies - for instance iodine to treat a diseased thyroid gland or iridium pellets to destroy prostate tumors - body parts and fluids can become radioactive. The patient’s urine and feces can end up being radioactive pathological waste. Radioimmunoassay is a widely employed technique for finding levels of substances inside the body by injecting radioactive antigens into the bloodstream, Packaging material, washing fluids, and paper wipes may be radioactive wastes.
The good news is that many radioactive materials used inside the body have very short half lives. Doctors choose fast-decaying isotopes partly to avoid side effects - so residual radiation will not harm healthy tissue. This means waste containing those tends to lose its radioactivity quickly, reducing storage and disposal risks. However, every case and application of radioactive materials must be evaluated to determine the best storage and disposal solution. Brachytherapy pellets, for instance, are made of materials with relatively long half-lifes.
Medical waste managers distinguish between unsealed (or open) sources or sealed radiation sources. Radioactive materials in sealed containers usually comes to the hospital that way from the manufacturer, and the purchase contract may allow the hospital ro return the unit to the seller when finished. Applying this policy removes this bit of radioactive waste from the hospital’s waste stream.
Healthcare facilities send their radioactive medical waste offsite for treatment and disposal. Storage on site is a concern for the waste manager and can pose risks and cause regulatory headaches. Try to keep the radioactive waste away from other waste (to avoid cross-contamination) and away from areas where people and animals frequent. Good ventilation and ease of access are always good attributes when considering where to put waste. Rad waste produced at healthcare facilities is alomost always classified as low-level radioactive waste (LLRW) - radioactive waste that is not high level radioactive waste or spent nuclear fuel.
The new radiation symbol was adopted by the United Nations in 2007, but the older symbol is still widely recognized and expected to remain in common use for many years.
In contrast to hazardous waste and bio waste, which you normally want to get quickly out of your facility and to a treatment/disposal outfit, medical facilities that produce radioactive waste usually want to keep it on site until the radiation level declines. This is a common practice for radioisotopes with half-lives under 90 days; radioactive materials used in treatment and diagnosis are usually in the class of short-lived materials. One method is to store the waste for a minimum of 10 half-lives. That will reduce the quantity of the isotope to less than 0.1 percent of its starting quantity.
Doing it this way requires batch-wise storage. Once a quantity of radioactive waste is designated as a waste for disposal, no new waste is added to it. Any newly generated waste goes into a new batch. That allows the clock to start on the original batch. If you add new waste, you need to start the clock again.
If the radioactive waste has an infectious material, disinfect it before starting the count-down.
You can’t practically make something radioactive into something not radioactive. That is the reality that waste management engineers stuck with radioactive waste must live with, Radioactive materials decay - the actual atoms decay - so they lose their radiation level over time. The time-scale for decay is characterized by the “half life” of each isotope. These isotopes are often referred to as radionuclides or radioisotopes. Half lives can range from fractions of a second to thousands of years. In some cases the radioactive isotope decays to an isotope that is also radioactive, prolonging the period of radiation.
The best the waste manager can do it to ensure the radioactive material stays away from people and animals and plants, which is why immobilization has become the go-to disposal method for radioactive waste. (The correct term is radioactive waste, not nuclear waste.) Treatment is focused on reducing volume, solidifying fluids to reduce chances of it running off, and immobilizing radioactive constituents
Radioisotopes used in hospitals include technetium-99m (Tc-99m)
Iodine-131, 125, and 123 (I-131, I-125, and I-123)
Sodium iodide (Na 131-I) is used in over 700,000 thyroid scans in the United States every year. Each procedure utilizes about 0.01-0.1 millicuries of I-131
The cost of disposing of radioactive waste is on the order of ten times that of disposing of municipal solid waste. The design of radioactive waste disposal systems is guided by the philosophy of "confine and contain". Waste is treated to the point that, when placed in final disposal, it will not leak, leach, or fragment. Most radioactive waste from health care facilities ends up specially designated and permitted low-level radioactive waste landfills,
The other philosophy, which is less responsible, is called "dilute and disperse". It results in release of radioactive material into the environment distributed over a large geographic area so that the final concentration of radionuclides is low. If you employ this method be ready to answer questions to regulators and to the public.
There are places you can send LLW for disposal. It might not be cheap but you can pay someone to take your radioactive waste and bury it in approved landfills. The waste manager at a healthcare facility rarely gets involved in those details much.
Liquid scintillation cocktails are a common form of radioactive waste in hospitals.
Every radioactive isotope has a characteristic half-life - the time it takes for half of the atoms to decay to a different isotope. In some cases the isotope it decays to is stable (not radioactive) but sometimes the result is another radionuclide with its own half-life.
Half-lives range from fractions of seconds to thousands of years.
There are three kinds of radiation (this is a little oversimplified) - alpha, beta, and gamma. All can be dangerous to humans and animals. Alpha and beta particles are relatively easy to stop - separating the radioactive material from people with a piece of cardboard is enough. Gamma radiation is stronger and can pass through concrete. Radiation specialists have methods for determining the hazards posed by materials and for designing shielding mechanisms.
Exposure to radiation can cause headache and nausea for light exposure to more serious symptoms (anemia, skin rashes, tissue damage) for heavy exposure. Even the radioactive material used in diagnostic instruments (e.g. gallium) can cause damage. Long-term radiation exposure (if the material becomes embedded in the body) can cause birth defects in offspring.
Knowing the composition of a material can enable specialists to predict how radiation levels will change over time. Unlike conventional hazardous waste the dangers posed by radioactive waste decline over time.
Iodine 125 has a half-life of about 60 days. Iodine 131, which is used to kill thyroid cells in patients with thyroid cancer, has a half-life of 8 days. Most of its energy comes out as beta radiation which is why it is used for to treat cancer, not in imaging where other isotopes are preferred.
Waste management professionals (and often regulations) distinguish waste by amount of radiation energy coming off it: low-level (LLW), intermediate-level (ILW), or high-level (HLW).
There is also VLLW - very low level waste - a designation given to mine operations waste and similar but rarely to materials made by or significantly modified by humans.
Most radioactive waste in the world is LLW. The overwhelming majority of radioactive waste produced in medical facilities is LLW. Waste that is both radioactive and meets the criteria for RCRA hazardous waste is called mixed waste.
As with infectious waste, radioactive materials are more of a threat to human health if they enter the body. Alpha radiation does not travel through solid barriers and only a couple feet through air. If an alpha source is sitting on the table, a person has no reason to be concerned. However, if the alpha source becomes aerosolized and the person breathes in the material, it can cause cancer and other problems. Ingestion is also a possible route of entry to the body. Beta radiation travels farther than alpha, and is easy to shield, so long as the material does not enter the body. Gamma radiation is of greatest concern as it can penetrate walls. When nuclear engineers speak of “shielding” they mean shielding to protect people from gamma rays.
Aside from direct exposure to radioactive waste, people can be threatened if the external surfaces of containers get contaminated or if there is a hole in the storage container. Some radiation safety protocols specify the maximum amount of time a radiation source can remain in storage. Hospital or facility technicians, equipment operators, doctors, nurses, cleaning people, and waste management personnel are at most risk for radiation exposure.
The term mixed waste is used in the radioactive waste industry to refer to waste that meets the definitions for hazardous waste and for radioactive waste, Some landfills can take treated hazardous waste but not radioactive waste and vice versa, Only few places can accept mixed waste and it can be expensive to deal with, even when it is not particularly dangerous. This is another reason to segregate and avoid mixing waste streams, although sometimes the production of mixed waste cannot be dodged without disrupting medical operations.