Radiological weapon

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A radiological weapon or radiological dispersal device (RDD) uses a conventional explosive or other mechanical means to disperse a hazardous radioactive and thus contaminate an area. While the radioactive material might have been generated in a nuclear reactor, or even collected from a nuclear weapon test site, the radiological weapon does not, itself, use fission or fusion.

The U.S. military uses some simplified terminology to discuss the problem at the policy level. They use the generic term TIM for toxic, infectious, or radioactive compounds in solid, liquid, aerosolized, or gaseous form; it can also stand for toxic industrial material, as in the Bhopal Disaster. TIMs may be used or stored for use for industrial, commercial, medical, military or domestic purposes.^[1]

Especially if those constructing the weapon are not concerned with their own health or survival, such a weapon is quite simple to make, assuming radioactive material is available. Between 1994 and 2003, there were at least several hundred illicit transfers of radioactive material, relatively little of which was of bomb grade^[2]

RDDs are designed to disperse radiation and/or contamination. The explosive itself may cause blast injuries. Unless an unusually efficient dispersion technique were used (e.g., aerosol spray from an aircraft), the actual area of contamination of a practical "dirty bomb" will not be that great; the quantity of radioactive material is far less than was generated by a high-fallout bomb test such as CASTLE BRAVO, or a major reactor catastrophe such as Chernobyl. Nevertheless, effective dispersion remains the worst-cases scenario, and more and more resources are available to manage such events, such as the National Atmospheric Release Advisory Center.

The main purpose of a dirty bomb remains frightening people by contaminating their environment with radioactive materials and threatening large numbers of people with exposure. Well-engineered weapons may also result in area denial and costly cleanup or decontamination.

Typically, acute radiation syndrome will result if individuals are exposed, over a short period of time, to 75 rad/0.75 Gray of penetrating radiation; the threshold may be lower if neutrons rather than gamma or X-ray source.

Representative source: the Goiania Incident

Unfortunately, isotopes with appropriate medical or industrial uses may not be as well-guarded as military-grade nuclear material. On Sept 13, 1987, two scavengers looked in building, an abandoned radiotherapy center, for scrap metal that could be sold to a junkyard. Unknown to them, they 1400 Curie cesium-137 radiation source, which, under the shield, was in pellets the size of rice grains (that glowed in the dark).^[2] It found its way to a junkyard operator in Goiania, Brazil. He pried it open, and was fascinating by the glowing objects. ^[3]

Public health authorities recognized the incident on September 28. By then, approximately 250 people had been contaminated, out of 113,000 who were monitored. There were 4 deaths. 85 homes were contaminated, 41 evacuated, and 4 demolished.^[2]

Response

Response will vary with the nature of the contamination, the awareness and resources of the emergency services and public health authorities that become involved, news and rumor with their psychological effect, and the availability and political acceptability of foreign help.

In the Chernobyl disaster, it is not clear that outside help would have been useful in dealing with the massive contamination, far greater than virtually any plausible terrorist device. The time to mitigate it was in the missing safety designs of the reactor, and of a test in which multiple safety systems were disabled. A substantial number of plant, fire service, and helicopter pilots took action to contain it, and many knew that they would suffer fatal radiation exposures.

A more plausible terrorist event was simulated in TOPOFF2. This addressed public perception ^[4], command and control using the DMIS incident management software^[5], and strategic implications. ^[6]

References