Explosives create mass casualties and property destruction.

Explosives create mass casualties and property destruction.


Weapons of Mass Effect— Radiation Hank T. Christen Paul M. Maniscalco Harold W. Neil III

• Describe the differences between a radiation incident and a traditional hazardous materials incident.

• Define the three types of radiation.

• Differentiate between the terms dose and exposure.

• Describe the distinction between acute and delayed effects of radiation exposure.

• Explain the difference between radiation exposure and contamination.

• Outline the first responder considerations in a radiological terrorism incident.



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Radiation is effective as a weapon of mass effect be- cause of its long-term consequences and psychological effect on victims and the community. The word radiation immediately generates mental images of hideous and doomed casualties. This chapter provides an explana- tion of radiation and the types and hazards of radiation exposure. First responders need to understand the basics of radiation physics and protective measures to operate safely and effectively at a radiation attack or accident. Additional topics include the use of radiation as a terror- ism weapon, the medical effects of radiation, and tactical considerations and critical factors related to an effective response to a radiation incident.

Radiation incidents are a special type of hazardous materials incident because of several common factors, including internal exposure pathways, contamination concerns, decontamination techniques, and personal pro- tective equipment (PPE) requirements. These factors share commonality with chemical and biological threats.

Basic Radiation Physics Radiation travels in the form of particles or waves in bun- dles of energy called photons. Some everyday examples are microwaves used to cook food, radio waves for radio and television, light, and X-rays used in medicine.

Radioactivity is a natural and spontaneous process by which the unstable atoms of an element emit or ra- diate excess energy in the form of particles or waves. These emissions are collectively called ionizing radiation. Depending on how the nucleus loses this excess energy, a lower energy atom of the same form results, or a com- pletely different nucleus and atom are formed.

Ionization is a particular characteristic of the radia- tion produced when radioactive elements decay. These radiations are of such high energy that they interact with materials and electrons from the atoms in the material. This effect explains why ionizing radiation is hazardous to health and provides the means for detecting radiation.

An atom is composed of protons and neutrons contained in its nucleus. The only exception is the natu- rally occurring hydrogen atom, which contains no neu- trons. Protons and neutrons are virtually the same size. Electrons, which are much smaller than protons and neutrons, orbit the nucleus of the atom. The chemical behavior of an atom depends on the number of protons, which are positively charged, and the number of elec- trons, which are negatively charged. Neutrons, which have no electric charge, do not play a role in the chemical behavior of the atom.

Special placards are required when transporting certain quantities or types of radioactive materials. In

facilities that use radioactive materials, the standard radioactive symbol is used to label the materials for identification (CP FIGURE 10-1). Placard information is useful when responding to an accident involving ra- dioactive materials. However, in a terrorist attack, there are no labels or placards to identify the hazards involved.

Alpha, beta, and gamma energy are forms of radiation (FIGURE 10-1). Because alpha particles contain two protons, they have a positive charge of two. Further, alpha particles are very heavy and very energetic compared to other com- mon types of radiation. These characteristics allow alpha particles to interact readily with materials they encounter, including air, causing much ionization in a very short dis- tance. Typical alpha particles travel only a few centimeters in air and are stopped by a sheet of paper.

Beta particles have a single negative charge and weigh only a small fraction of a neutron or proton. As a result, beta particles interact less readily with material than alpha particles. Beta particles travel up to several meters in air, depending on the energy, and are stopped by thin layers of metal or plastic.

Like all forms of electromagnetic radiation, the gamma ray has no mass and no charge. Gamma rays interact with material by colliding with the electrons in the shells of atoms. They lose their energy slowly in material and travel significant distances before stopping. Depending on their initial energy, gamma rays can travel from one to hundreds of meters in air and easily go through people. It is important to note that most alpha and beta emitters also emit gamma rays as part of their decay processes.

Radiation is measured in one of three units as noted. A roentgen is a measure of gamma radiation. A radiation-absorbed dose (RAD) is a measurement of absorbed radiation energy over a period of time. Radiation dose is a calculated measurement of the amount of energy deposited in the body by the radiation to which a person is exposed. The unit of dose is the roentgen equivalent man (REM). The REM is derived by taking into account the type of radiation producing the exposure. The REM is approximately equivalent to the RAD for exposure to external sources of radiation. Detecting and measuring external radiation levels are critical at the scene of a radiation incident.

Radiation Measurements

It is equally important to develop an understanding of the dangers associated with different levels of exposure. Response agencies should develop policies regarding PPE and acceptable doses for emergency responders.

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These policies should be consistent with agency risk assessments and PPE standard operating procedures.

Radiation levels are measured with survey instru- ments designed for that purpose (FIGURE 10-2). Survey instruments usually indicate units of R/hr where R stands for either RAD or REM. The unit R/hr is an exposure (or dose) rate. An instrument reading of 50 R/hr means re- sponders exposed for 1 hour will receive a 50-RAD dose. Dividing the unit determines the exposure for shorter or longer periods of time (e.g., a 30-minute exposure results in a 25-RAD dose). An exposure (or dose) rate can be compared to a speedometer. A speed of 80 miles per hour means traveling 1 hour to go 80 miles. Traveling for half an hour at that rate covers a distance of 40 miles.

Some instruments measure radiation dose over a period of time. These instruments are comparable to an odometer, which measures total miles traveled regardless of the speed. Handheld survey instruments may have this capability, but they are more useful in an emergency situation for measuring the exposure rate. Radiation do- simeters are useful for measuring the exposure received over time (FIGURE 10-3).

Responders must wear dosimeters during opera- tions in any radiation hot zone or suspected radiation environment. Dosimeters should be checked frequently to determine the exposure received by on-scene first responders. Medical personnel should conduct final

dosimeter checks during postdecontamination medical evaluation.

Survey instruments and dosimeters have limitations because some instruments measure only beta and gamma radiation, not alpha radiation. The capability to measure alpha radiation is a requirement. It is important to de- velop a maintenance and inspection program that ensures instruments and dosimeters are properly functioning. Survey instruments, like all electronic devices, require inspection and recalibration by certified technicians at specified intervals. Survey instrument batteries must also

FIGURE 10-1 Alpha, beta, and gamma radiation.




FIGURE 10-2 A radiation detection device.

FIGURE 10-3 Dosimeters stay on the responder throughout an incident.

It is critical that responders detect and measure radia- tion levels and exposure at an attack or accident.

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154 Homeland Security: Principles and Practice of Terrorism Response

be checked and replaced when necessary. Dosimeters must be zeroed and checked on a regular basis.

Internal Radiation Exposure

For internal radiation exposure, the terms RAD and REM are not synonymous. It is important for first responders to know whether an internal exposure hazard exists and how to protect themselves by using PPE, including respirators. However, first responders should not be concerned with measuring internal radiation because internal exposure assessment is complicated due to the large number of factors involved. Some of these factors are the chemical form of the material, the type of radiation emitted, how the material entered the body, and the physical charac- teristics of the exposed person. Months of assessment may be required to determine an internal dose. Common methods for assessing internal exposure are sampling of blood, urine, feces, sweat, and mucus for the presence of radioactive material. Special radiation detectors measure the radiation emitted by radioactive materials deposited within the body. By considering the results of these mea- surements along with the characteristics of the material and the body’s physiology, a measurement of radiation dose from internal sources is made.

Characteristics of Radiation

Despite the similarities to hazardous materials incidents, radiation incidents have a unique characteristic that first responders must understand. Namely, radiation expo- sure may occur without coming in direct contact with the source of radiation, which is a primary difference between chemical and biological incidents. A chemical or biological agent exposure occurs when a material or agent is inhaled, ingested, injected, absorbed through the skin, deposited on unprotected skin, or introduced into the body by some means.

Radioactive materials are naturally occurring or manufactured and emit particle radiation and/or elec- tromagnetic waves. Contrary to popular science fiction, radioactive materials do not glow and do not have spe- cial characteristics making them readily distinguishable from nonradioactive materials. This means responders cannot detect or identify radioactive materials using the five human senses.

Radiation emitters may be liquid, solid, or gas. For example, radioactive cobalt, or cobalt-60, has the same chemical properties and appearance as nonradioactive cobalt. Radioactive water, known as tritium, cannot be readily distinguished from nonradioactive water. The difference lies in the atomic structure of the mate- rial, which is responsible for the characteristics of the material.

To understand the mechanism for radiation ex- posure, an explanation of radiation is necessary. Radiation is often incorrectly perceived as a mysterious chemical substance. Radiation is simply energy in the form of invisible electromagnetic waves or extremely small energetic particles. Waveforms of radiation are X-rays and gamma rays. Radiation is emitted by X-ray machines and similar equipment commonly found in medical and industrial facilities (FIGURE 10-4). Alpha, beta, and gamma are different types of radiation that have different penetrating abilities and present differ- ent hazards.

FIGURE 10-4 Radiation is emitted by medical equipment such as com- puted tomography scans.

Responders must wear personal dosimeters when op- erating in or near any radiation hot zone.

Radiation exposure can occur without direct contact with a radioactive source.

Radiation cannot be detected by human senses.

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Medical Effects of Radiation

Radiation energy can be deposited in the body during the exposure process regardless of the form or source. The amount of energy deposited in the body by a radiation source varies widely. It depends largely on the energy of the radiation, its penetrating ability, and whether the source of radiation is located outside or inside the body. Radiation exposure from a source outside the body is known as external exposure. Radiation exposure from a source within the body is known as internal exposure.

Consider the example of the radioactive cobalt, or cobalt-60, source discussed earlier. A person located within a few meters (the distance depends on the strength of the source) of the cobalt-60 source is exposed to the gamma radiation emitted from the source without di- rectly touching the source. This is an external exposure. If the source becomes damaged, the cobalt-60 could leak from the container. In order to cause an internal expo- sure, the cobalt-60 has to enter the body via inhalation, ingestion, or some other means.

Another important concept involving radioactive materials is demonstrated with the cobalt-60 source. Radioactive contamination is the presence of radioactive material in a location where it is not desired. Radioactive contamination results from the spillage, leakage, or other dispersal of unsealed radioactive material. The presence of radioactive contamination presents an internal expo- sure hazard because of the relative ease of radiation en- tering the body. There may also be an external exposure hazard depending on the radioactive material involved. Any location where radioactive material is deposited becomes contaminated. The contamination spreads by methods including air currents, water runoff, and per- sons touching the source and cross-contaminating other objects and areas by touch or walking.

The effects of radiation exposure on responders vary depending on the amount of radiation received and the route of entry. Radiation can be introduced into the body by all routes of entry and through the body by irradia- tion. Victims can inhale radioactive dust from nuclear fallout or a dirty bomb, or they can absorb radioactive liquid through the skin. In the body, radiation sources

irradiate the person internally rather than externally. Some common signs of acute radiation sickness are listed in TABLE 10-1. Additional injuries such as thermal and blast trauma, trauma from flying objects, and eye injuries occur from a radiological dispersal device (dirty bomb) detonation or a nuclear blast.

First responders should be aware of radiation’s health effects and risks because a radiation incident presents both internal and external exposure hazards that may be significant. The fundamental question is how much radiation is too much? A substantial number of scientists and academics argue that any exposure is dangerous and extraordinary precautions are necessary to minimize exposure. At the other end of the spectrum, many scientists and academics argue that

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