The nuclei of atoms work toward becoming stable by getting of excess energy. Unstable nuclei may emit a quantity of energy (gamma- or x-ray), or they may emit a particle (alpha, beta, or neutron). This emitted atomic energy or particle is call radiation. There are two basic kinds of radiation:
Ionizing/non-ionizing - Ionization is the process of removing electrons from atoms, leaving two electrically charged particles (ions) behind. Some forms of radiation, like visible light, microwaves or radio waves, do not have sufficient energy to remove electrons from atoms and, hence, are called non-ionizing radiation. The negatively charged electrons and positively charged nuclei may cause changes and damage in living tissue.
Radioactive decay - Large unstable atoms can become more stable by emitting radiation. This process is called radioactive decay. This radiation can be emitted in the form of a positively charged alpha particle, a negatively charged beta particle, or gamma rays.
Fission or nuclear fission - Some elements can split as a result of absorbing an additional neutron. This is called fission or nuclear fission. Such isotopes are called fissile isotopes. One particular fissile isotope is Uranium-235. This is the isotope used in commercial nuclear reactors. When a nucleus fissions, three important events occur that result in the release of energy: release of radiation, release of neutrons (usually two or three), and formation of two new nuclei (fission products).
Four types of radiation are of concern following a nuclear explosion or a radiological dispersion device: alpha and beta particles, gamma-rays, and neutrons.
For gamma radiation, equivalent shielding is accomplished by 0.7 of lead, 1.3 of iron, and 4.7 of concrete.
By far, the most significant source of man-made radiation exposure to the public is from medical procedures, such as diagnostic X-rays, nuclear medicine, and radiation therapy. Some of the major isotopes are 131I, 99mTc, 60Co, 192Ir, 137Cs.
Additional exposure comes from consumer products, such as tobacco (polonium-210), building materials, combustible fuels (gas, coal), ophthalmic glass, TVs, luminous watches and dials (tritium), airport X-ray systems, smoke detectors (americium) and lantern mantles (thorium). Of lesser magnitude is radiation from the nuclear fuel cycle, and residual fallout from nuclear weapons testing and accidents.
| Background Radiation Sources (total ~365 millirem/yr) | |
|---|---|
| Inhaled radon and progeny - 200 | External terrestrial - 30 |
| Medical procedures - 55 | External cosmic - 30 |
| Radionuclides in the body - 40 | Consumer products - 10 |
Think of biological effects of radiation in terms of their effect on living cells. The body has defense mechanisms against many types of damage induced by radiation. Consequently, biological effects of radiation on living cells may result in three outcomes: (1) injured or damaged cells repair themselves, resulting in no residual damage; (2) cells die, much like millions of body cells do every day, being replaced through normal biological processes; or (3) cells incorrectly repair themselves resulting in a biophysical change.
The associations between radiation exposure and the development of cancer are mostly based on populations exposed to relatively high levels of ionizing radiation (e.g., Japanese atomic bomb survivors and recipients of selected diagnostic or therapeutic medical procedures). Cancers associated with high dose exposure include leukemia, breast, bladder, colon, liver, lung, esophagus, ovarian, multiple myeloma and stomach cancers.
Cancers that may develop as a result of radiation exposure are indistinguishable from those that occur naturally or as a result of exposure to other carcinogens. Other chemical and physical hazards and lifestyle factors (e.g., smoking, alcohol consumption and diet) may contribute to many of these same diseases.
Although radiation may cause cancer at high doses and high dose rates, public health data do not unequivocally establish the occurrence of cancer following exposure to low doses and dose rates. Even so, the radiation protection community conservatively assumes that any amount of radiation may pose some risk for causing cancer and hereditary effect, and that the risk is higher for higher radiation exposures.
High radiation doses tend to kill cells, while low doses tend to damage or alter the genetic code (DNA) of irradiated cells. High doses can kill so many cells that tissues and organs are damaged immediately. This in turn may cause a rapid whole body response often called acute radiation syndrome. The higher the radiation dose, the sooner the effects of radiation will appear, and the higher the probability of death.
At U.S. nuclear power plants, there are many lines of defense typically between potential terrorists and spent fuel pools. To cause possible off-site release of radioactivity from these pools, someone would have to drain the pools of water; this would be difficult. Then he/she would have to ignite the spent fuel, also difficult.
Development of a nuclear bomb by terrorists is improbably for several reasons: obtaining highly enriched uranium fuel, shielding the radioactivity, and designing the bomb design. The prevalence of commercial radioactive materials and the relative ease of construction of a dirty bomb, make this a more likely scenario.
A dirty bomb is not a nuclear bomb even though it uses radioactive material. While a nuclear bomb is surely a weapon of mass destruction, a dirty bomb is at best a weapon of mass disruption. Few people, if any, would die shortly after exposure to the ionizing radiation from a dirty bomb. Perhaps many (at most hundreds) would die from the conventional bomb blast associated with a dirty bomb. In contrast, many thousands to tens of thousands of people would likely die from the explosion of a nuclear bomb (assuming one roughly as powerful as the Hiroshima bomb, which was modest compared to modern weapons).
There are over 2,000,000 radioactive sources possessed by 157,000 licensed users in the United States. Approximately 400 sources are lost or stolen annually. Sources used by hospitals, universities, and industry have been considered a low-level health hazard, and typically provided less physical protection.
Attachment of a radioactive substance to an explosive device (such as pipe- or car-bomb) and detonation near a stadium, subway or building is a likely scenario. For an effective result, several fundamental challenges must be overcome:
Injury and death from the conventional explosion will likely be greater than that due to radiological contamination. Panic and disruption may spread contaminated dust as the public flees, and as responders enter and leave. A large radiological dirty bomb, composed of radioactive waste or spent fuel, could contaminate entire business districts for a long period of time, and has the potential to injure or kill quickly.
If a dirty bomb that combines a conventional explosive, such as dynamite, with a radioactive material, causes an explosion, one should take the following steps:
If radioactive material was released, local news broadcasts will advise people where to report for radiation monitoring and blood and other tests to determine whether they were in fact exposed and what steps to take to protect their health
Radioactive iodine is a health hazard for children, because they are still growing and their thyroid glands are very active. Radioactive iodine absorbed in the body tends to accumulate in the thyroid. This accumulation could lead to development of thyroid cancer. If it is suspected that radioactive iodine has been released from a nuclear power plant accident or a dirty bomb, people in the surrounding area are advised to take potassium iodide (KI) in order to flood their thyroids with non-radioactive iodine to block the absorption of radioactive iodine. To be most effective, KI should be taken before exposure to radioactive iodine. However, it is unlikely that radioactive iodine would be used in a dirty bomb, since other radioisotopes are more likely candidates for terrorist use.
What radioactive material or sources pose the greatest threat for use in a radiological dispersion device, based on the inherent radiological risk and on their relative availability?
Seven radioisotopes pose inherent radiological security risks (if present in large enough amounts in a radioactive source):
Except for certain restrictions on plutonium, americium, and californium, essentially unlimited amounts of the other isotopes can be exported to almost all countries (except those under embargo, such as North Korea, Iran, and Iraq).
Can authorities distinguish between a dirty bomb that has released beta radiation and one that has released gamma radiation?
Radiation detectors can distinguish different types of radiation. Each radioisotope emits radiation with definite energy characteristics - a fingerprint in essence. Certain radiation detectors can precisely analyze the energy of the radiation. This information can then point to what type of radioisotope was used in the dirty bomb and whether it is an alpha, beta or gamma-emitter.
Your instructions may include directions for evacuating your location or for remaining in place (called sheltering) to reduce any possible exposure to radiation.
If outside, cover your nose and mouth with a cloth. If inside, close all windows and doors, and tightly seal with plastic sheeting and duct tape for protection against radioactive dust. Stay in the basement until the radioactive cloud passes.
Potassium iodide (KI), if taken properly, will help reduce the dose of radiation to the thyroid gland from radioactive iodine and reduce the risk of thyroid cancer. If radioactive iodine is taken into the body after consumption of potassium iodide, it will be rapidly excreted from the body. Potassium iodide can be purchased from local pharmacies.
An Alert and Notification System is in place to notify the public. This system typically uses sirens and tone-alert radios. If you receive an alert, tune your radio or television to an Emergency Alert System station for information and emergency instructions. If you live within a radius of approximately 10 miles from a nuclear power plant, you will receive materials annually regarding the unlikely event of a plant radiological emergency.
Although exposure to ionizing radiation carries a risk, it is impossible to completely avoid exposure. We can, however, avoid undue exposure. There are simple, sensitive instruments capable of detecting minute amounts of radiation from natural and man-made sources. In addition, there are four ways to protect ourselves:
Symptoms from radiation exposure are similar to those of other sicknesses, such as nausea, vomiting, rash and dizziness. In addition:
Only very highly radioactive materials that emit penetrating radiation (e.g., gamma) would be immediately life-threatening for terrorists making dirty bombs. Terrorists may use less radioactive materials or alpha-emitting materials, which do not pose an external health threat. There are many nasty chemicals (e.g., cyanide and chlorinated organophosphates) that terrorists may be inclined to use that can kill many people. These materials may be more hazardous from the health perspective than most radioactive sources that could end up in dirty bombs.
In March 2003, U.S. Customs officials began checking all travelers arriving in the U.S. for radiation using small detectors. Customs and border security officials operating radiation detection equipment in airports, state- and national-boarder crossings and ship-cargo facilities must be properly trained. The more layers of preventive, detection and response measures erected and the more hurdles that a radiological terrorist has to pass through, and the less likely he will be able to carry out terrorist activities.
However, smugglers can try to shield radioactive materials. Alpha-emitting isotopes are one class of radioactive materials that are relatively easy to shield, and relatively difficult to detect. By combining the use of radiation detectors, with x-ray machines that can detect the presence of heavy, dense shielding, authorities may determine whether someone is trying to sneak radioactive materials past radiation sensors.
The New York State Emergency Management Office (SEMO) is responsible for coordinating all activities necessary to protect New York's communities from natural, technological and manmade disasters and other emergencies that threaten the State. In times of emergency or disaster, SEMO coordinates the response of State agencies ensuring the most appropriate resources are dispatched to the impacted area. SEMO works with local governments, volunteer organizations and the private sector across New York State to develop disaster preparedness plans and mitigation projects, and provide training and exercise activities. SEMOs headquarters is located in Albany, and it has five regional offices across the State. The Department of Health has a written response protocol, well-equipped laboratories, and participates in several practice drills annually. A compendium of analytical laboratories operating in New York, and partnerships with neighboring State health laboratories assures adequate measurement capabilities.
Much of the information provided above can be found in more detail on the following websites:
The New York State Department of Health provides Emergency Medical Services (EMS) staff and other health care providers with basic information to manage radiologically contaminated patients, or patients who received a large dose of radiation from an external radiation source. This guidance is applicable in all radiological incidents, including terrorism.
www.health.state.ny.us/nysdoh/bt/radiological_terrorism/radterr.htm
The Centers for Disease Control website provides information on many aspects of radiation occurrence, health effects, and emergency preparedness.
www.bt.cdc.gov/radiation/
The Nuclear Regulatory Commission website provides a fact sheet regarding sources and control of radioactive materials, dirty bombs, and advice should an explosion occur.
www.nrc.gov/reading-rm/doc-collections/fact-sheets/dirty-bombs.html
The Public Broadcasting Service produced a television documentary that reviewed past incidents involving unprotected radioactive materials.
www.pbs.org/wgbh/nova/dirtybomb/