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Rad Resilient City Initiative

The RRC Approach

Tenets Underpinning this Approach to Fallout Preparedness

Much of what the public knows or imagines about nuclear detonations has been shaped in the context of Cold War science, military strategy, and movies such as The Day After. Many such notions, however, do not apply to nuclear terrorism involving a low-yield explosion in a modern urban setting. Ideas about what constitutes the best protective actions may similarly be based on false premises. This section, therefore, provides a common baseline of understanding in advance of a community integrating fallout preparedness into its larger disaster agenda. It reviews relevant scientific details, operational considerations, and planning assertions that underpin the proposed checklist for fallout protection.

Tenet 1: In contrast to Cold War images of widespread destruction, terrorist-sponsored nuclear threats pose a more contained range of damage and a higher degree of survivability.

  • These guidelines are based on a 10-kiloton ground-level detonation, with no advance warning, as outlined in National Planning Scenario #1.14  Ten kilotons is considered the “approximate yield of a fully successful entry-level fission bomb made by a competent terrorist organization.”15 It is also the scale of the attack outlined in the first of 15 national planning scenarios developed by the Department of Homeland Security (DHS) to support national and local preparedness and to help identify what resources and abilities are needed to respond to a range of terrorist attacks and natural disasters. Many unknowns about an actual weapon, however, have implications for fallout preparedness and response. These include the nuclear yield of the weapon, the device’s location, its altitude above ground, weather conditions, and the time of detonation (ie, during the workday or at night). Such factors determine the potential impact and the populations at risk. The actions in the Fallout Preparedness Checklist, however, are sound and apply to the full range of nuclear detonation scenarios, not just the 10-kiloton context. Alternative scenarios, such as the situation in which a terrorist organization claims to have placed a nuclear device in a city, present additional challenges such as interdiction and are outside the scope of this document.

  • In terms of scale, an act of nuclear terrorism bears no resemblance to a Cold War nuclear attack on the United States. A nuclear war scenario modeled in 1985 assumed 6,559 megatons (6,559,000-kilotons) of nuclear explosives aimed at targets throughout the U.S., and it projected only 93 million survivors, of whom approximately one-third would be injured.16 By comparison, a 10-kiloton groundburst would create an explosion 5,000 times greater than the Oklahoma City bomb.6,17In other words, 10 kilotons is about two-thirds the estimated yield of the atomic bomb (approximately 14 kilotons)18 dropped on Hiroshima—a city that has recovered and is thriving once again.

  • A 10-kiloton nuclear detonation will cause severe damage at ground zero; the damage will then decrease over a distance of a few miles. The initial explosion will produce a blast wave and an intense thermal pulse that will dissipate over a few miles resulting in severe damage within a radius of approximately one-half mile or 10 average city blocks (Damage and Fallout Zones Modeled for a 10-Kiloton Groundburst). Within this severe damage zone, nearly all buildings and structures will be reduced to rubble; few people will survive unless protected by robust buildings or stable underground structures. From 0.5 to 1 mile beyond the blast area, the moderate damage zone will include blown-out building interiors and destroyed lighter buildings.5 In this zone, many people will survive, although many will have significant injuries. A greater number of survivors are expected in the light damage zone, which may extend from 1 mile to beyond 3 miles from the blast area and will be characterized by broken glass and damaged roofs due to shock waves.

  • Most destruction in the damage zones will happen in seconds, leaving people little time to take protective actions. The nuclear detonation will also produce a flash of radiation, with intense light and heat. The immediate (or prompt) radiation generated during the detonation (which is distinguished from delayed outdoor radiation or fallout) could injure people who are outdoors up to a mile away. Fires and serious burns will affect buildings and people up to a mile from the explosion. “Flash blindness” (usually temporary blindness, lasting from several seconds to minutes) may also affect those people who observe the flash of intense light energy—perhaps as much as 10 miles from the explosion.5

Tenet 2: Not all casualties due to a nuclear detonation are destined to happen; those that result from exposure to radioactive fallout can be prevented.

  • Fallout is made of highly radioactive particles mixed with dust and debris, and it can be spread quickly and widely by upper and lower air patterns. The highly radioactive particles that make up fallout are generated when vaporized and irradiated earth and debris are drawn upward by the fireball’s heat and combine with the radioactive fission products created by the detonation. This cloud rapidly rises to an altitude of 2-5 miles for a 10-kiloton detonation, where, under some weather conditions, it assumes a mushroom shape.19 As the cloud cools, highly radioactive particles coalesce and fall to earth, with the heaviest and most dangerous falling first. Fallout will likely be visible as ash, rain, or particles the size of sand, but it may be present even if it is not visible. The distribution of fallout is determined primarily by upper level and surface wind patterns, which often travel in different directions from each other. Because wind patterns are so variable, fallout deposition cannot be predicted ahead of time. Even in real time, fallout patterns are difficult to predict because of microclimates, urban canyon effects, and other complications. Hence, actual measurements on the ground should augment plume models.

  • Fallout poses its greatest health effect in the hours immediately following the detonation, during which time high levels of penetrating radiation can lead to death. The health hazard associated with fallout comes primarily from the human body’s exposure to penetrating radiation (similar to x-rays) discharged from fallout that has settled on the ground and building roofs. Exposure to high levels of radiation over a short period of time can cause acute radiation syndrome, in which people become very ill or die within minutes to months. The Fallout Preparedness Checklist focuses principally on the goal of saving the most lives in the immediate aftermath of a detonation by reducing the chances that people will develop acute radiation syndrome. This can be achieved if people take prompt protective actions against fallout exposure (Tenet 3 and Tenet 4). Outside the scope of the Fallout Preparedness Checklist is the delayed health effect that comes from exposure to lower doses of radiation over time, namely, an increased chance of developing cancer later in life. This delayed health effect is of secondary concern in the nuclear detonation context. In contrast, planning around nuclear accidents—usually slowly evolving events—focuses primarily on the goal of cancer avoidance by limiting individuals’ level of exposure to radiation to “as low as reasonably achievable.”

  • The strength of radiation drops sharply over time and distance from the nuclear detonation. Radiation levels from fallout particles drop off rapidly with the passage of time, with more than half (55%) of the potential exposure occurring in the first hour and 80% occurring within the first day. The most dangerous figure 1 thumbnailconcentrations of fallout particles (ie, potentially fatal to those outdoors) could extend 10 to 20 miles downwind from ground zero.This area is called the dangerous fallout zone (DFZ), which is illustrated in Figure 1: Damage and Fallout Zones Modeled for a 10-Kiloton Groundburst (click to enlarge figure 1). Larger radioactive particles will settle out within 1-2 hours of the nuclear detonation, leaving behind the DFZ footprint.5 Most people in the DFZ will experience some level of exposure to fallout,7 but a series of decisions regarding shelter and evacuation may vastly reduce their chances of becoming sick or dying from high radiation levels. figure 2 thumbnailOutside the DFZ, fallout with lower levels of radiation will be spread up to hundreds of miles away. Radiation levels in this area, known as the radiation caution zone, are not high enough to cause immediate health problems. Nonetheless, protective actions such as sheltering/evacuation, controls on food consumption, and water advisories are warranted to prevent accumulated exposure to radiation that could result in a greater chance of cancer over a lifetime.  How the radiation zones shrink dramatically over time is illustrated in Figure 2: Time Sequenced Size of Dangerous Fallout Zone and Radiation Caution Zone (0.01 R/h) for the 10 KT Groundburst Scenario (click to enlarge figure 2)

Tenet 3:  Quickly going and staying inside the closest, most protective building—not fleeing the area—saves lives by minimizing exposure to fallout.

  • Sheltering in common urban structures such as large office buildings or underground garages significantly reduces radiation exposure.6,20,21 A building’s “protective factor” (PF)—that is, the level of protection from radiation—is a measure of the structural materials and the distance between people and radioactive fallout.The greater the protective factor, the better the shelter. See Figure 3: Sample Protection Factors for a Variety of Building Types and Locations (click to enlarge figure 3). Dense materials such as brick, cement, and figure 3 thumbnailearth provide better protection than wood, drywall, and thin sheet metal. Areas within a building, such as restrooms and stairwell cores, which are distant from deposited radioactive fallout, provide better protection than those close to roofs, windows, and exterior walls. Multistory brick or concrete structures, cores of large office buildings, multistory shopping malls, and basements, tunnels, subways, and other underground areas are examples of good shelters. Many good shelters will also have ventilation systems that should be shut down or segmented to prevent the introduction of radioactive fallout in the building. Examples of poor shelters include outdoor areas, cars and other vehicles, mobile homes, single-story wood-frame houses, strip malls, and other single-story light structures.22 For more detail on protective factors, see How to Use Buildings as Shelters Against Fallout.
  • Fallout takes time to travel downwind and sink to the ground; this provides a short period of time for most people to go into buildings that will protect them. Computer modeling of a 10-kiloton detonation in Washington, DC, using actual weather conditions from May 23, 2005, illustrates the timeframe for potential fallout.6 In this scenario, the detonation occurs 1.6 miles upwind from the Capitol. In the simulation, it takes roughly 6 minutes for fallout to arrive at the Capitol, with most of it arriving in approximately 10 minutes. Fallout arrives at the beltway (which is 10 miles out) at 34 minutes. Survivors should seek the very best possible shelter before fallout arrives. As modeled above, fallout may arrive in several miles of the detonation within 10 minutes, and the window of time for finding a good shelter increases in distance from ground zero.6 This time lag may permit people on the street and in cars or other poor shelters to find a nearby shelter with adequate or better protection. However, people may be unable to judge exactly when and where fallout will arrive; those in the most hazardous areas may be caught unawares. Therefore, everyone should seek the best shelter available immediately following a detonation. Moreover, people should not assume that they can outrun fallout. Safely evacuating out 10 to 20 miles from ground zero—the anticipated outer perimeter of the DFZ—before fallout arrives may not be feasible.

  • Any sheltering, even in a poor shelter, can save a majority of lives among people caught in the DFZ. State-of-the-art modeling using the city of Los Angeles demonstrates the importance of promptly seeking shelter after a nuclear detonation.7 For people in the dangerous fallout zone, being outside for the first 24 hours would expose approximately 280,000 individuals to enough radiation to sicken or kill them. If everyone in the DFZ were to go inside a poor shelter (ie, one with a PF=3 such as a car or small house), then 160,000 would avoid significant radiation exposure. If all went into a just adequate shelter (ie, one with a PF=10 such as a shallow basement), then 240,000 would escape significant exposure and 40,000 would avoid death but would be very sick. If everyone sheltered in the core of an office building or an underground basement (PF=50 or greater), then no one would be exposed to significant or deadly levels of radiation.

Tenet 4:  Evacuation may further reduce radiation exposure (after initial sheltering), but it only makes sense when sufficient information and logistical capacity exist. 

  • Just how long a person in the dangerous fallout zone should stay sheltered before evacuating cannot be predicted in advance.6 The best time for an individual to leave the safety of a shelter will depend on several factors: the quality of the shelter, the levels of radiation around that shelter, and the feasibility of moving to greater safety quickly.6 Precise knowledge of radiation levels and speedy routes to safety, however, will not be available in the early, chaotic hours following a nuclear detonation. Communities implementing a fallout preparedness program nonetheless need a framework with which to educate people in advance about the best course of action to minimize fallout exposure and to save lives. Recognizing that a complicated algorithm does not serve a majority of people in the DFZ, the Expert Advisory Group proposes the following rule of thumb for the sequence of recommended protective actions:

1 Minute ⇒ Shelter: Immediately after a detonation—by minute one, for ease of planning and public communication, the best course of action is to take shelter quickly in a solid structure with the highest protective factor as possible. In some instances, this may have to be a poor shelter. The most extreme radiation levels are present in the first hour following a detonation; being inside a protective shelter at this time is essential to saving one’s life.

1 Hour ⇒ Upgrade: At hour one postdetonation, people who were forced to locate in a poor shelter should relocate quickly to a building with a higher protective factor and resume sheltering.23 Exposure during the brief time spent outdoors seeking a better shelter is an investment in a lower radiation dose overall. For those in an adequate shelter, however, staying put is more important.

1 Day ⇒ Prepare to evacuate: By day one postdetonation (24 hours), potential exposure to radiation will have dropped off by 80%. Those sheltering should be prepared to evacuate according to guidance from authorities who will have mapped the DFZ to determine the safest routes for evacuation. Until information on safe evacuation routes is available, people should stay sheltered. In some instances, this may be 2-3 days or more.

  • Choices about when and who to evacuate will be very complex and context dependent. Decisions about who to evacuate, and in what order, should be driven by the hazards faced by survivors and logistical considerations.5 The anticipated impact of a nuclear detonation is immense—in terms of geographic area and potential evacuees—and it could exceed available infrastructure and resources (eg, transportation, hospitals). It may be necessary to relocate in phases according to available assets and accommodations, both in the area being evacuated and in the receiving locations.24 High-priority candidates for early evacuation are people who are located in poor quality shelters in the highest dose regions of the DFZ; who require critical medical attention or who are threatened by building collapse or fire; or who face special circumstances or vulnerabilities, such as children and the elderly.5 Uninjured people in adequate shelters are not priorities for early evacuation, nor are individuals in minimally protective shelters outside the DFZ (unless other threats to survival exist).5 People located in good shelters (ie, large buildings or underground) should be considered candidates for late-phase evacuation (days after a detonation).22 A phased evacuation is a complex undertaking, with the strong possibility for disorganization. Nonetheless, survivors and their families will expect that response professionals and evacuation planners employ a rational approach.

  • Mass evacuation should be delayed until fallout hazard zones and unobstructed routes are clearly known. No evacuation should be attempted until basic information is available regarding fallout distribution and radiation dose rates. In general, it is best to assume radioactive material is present and dangerous until measurements show otherwise. Basing evacuation routes on erroneous data about high dose rate regions in the dangerous fallout zone could eliminate the very benefits of evacuation.23 The principal goal is to minimize the time that evacuees spend unsheltered when leaving the DFZ. To develop timely and safe evacuation routes, planners will also need to consider infrastructure status (eg, whether roads are passable and bridges are intact). Officials should not underestimate the time it may take to conduct a mass evacuation under postdetonation conditions. In comparison, estimated times for evacuating many major urban areas in the Atlantic and Gulf Coast regions, in advance of a hurricane and with no damage to infrastructure, exceed 30 hours; in some cases, evacuation time can exceed 48 hours.25

Tenet 5:  An informed public capable of acting on its own can save more lives following a nuclear blast than can a limited number of emergency professionals.

  • Due to the scale and severity of the incident, there will likely be long delays in assistance from emergency professionals. Rather than wait for assistance or guidance from authorities, members of the public must be poised to act promptly on their own following a nuclear detonation. Specifically, they should be ready to get themselves and others into an adequate shelter, potentially staying there for a period of several days. Given both the scale of destruction by a nuclear device and the amount of resources needed, it will also take time for authorities to characterize the situation and mobilize a response. Prior to executing the response, emergency professionals will also need to seek adequate shelter for at least an hour, if not more, postdetonation, just like the public.6 As discussed below, the infrastructure for transmitting and receiving fallout warning messages may be inoperable for several days in the most vulnerable areas, requiring survivors to act independently. Sheltering for an extended period of time is the principal protective action against fallout exposure. Therefore, being personally prepared, being able to identify shelter, having a family disaster plan, and keeping essential supplies (eg, food, water, a battery/crank powered radio, flashlight, first aid kit, medications, extra clothes) matters a great deal. Having a family reunification plan will also be important once evacuations begin.

  • The closer to ground zero, the more likely officials cannot communicate quickly with survivors; thus, people will need to know how to protect themselves in advance. Following a nuclear detonation, it will be difficult or impossible to issue fallout warning messages in the areas that most need them, because communications may be severely impaired. Within the damage zones, there will be little, if any, ability to send or receive information.5 Telephone poles, utility lines, fiber-optic cables, cell towers, and other equipment will be knocked out; restoration of communication capabilities could take days. Moreover, the detonation’s electromagnetic pulse (EMP)—a transient electromagnetic field that produces a rapid high-voltage surge—may destroy or severely disrupt surviving electronics around ground zero.* Experts generally anticipate the worst EMP effects of a 10-kiloton groundburst to be confined within a 2- to 5-mile radius of the detonation site.5 However, cascading effects along transmission lines could lead to outages of electricity, phone, and internet extending up to hundreds of miles.5 Enormous demand for telephone and internet services will further complicate communication on surviving equipment. Overall, the operability of communications systems following a nuclear detonation is unpredictable: Which systems will be affected over what distances and for how long? As a general rule of thumb, planners might assume that the ability to communicate with survivors will increase the farther the distance from ground zero and the longer the time frame from the explosion.

  • Pre-incident education that uses average citizens as spokespersons may help promote greater personal preparedness and understanding of fallout protective behaviors. The potential lack of an intact infrastructure for delivering public warnings in the time and places that protective guidance is most needed following a detonation makes it necessary to convey the value of personal preparedness to the public. Social and behavioral science experts suggest that the strongest motivator of public preparedness for disasters, including terrorism, is when average people share what they have done to prepare with others who have done much less.26 Coworkers, neighbors, friends, and family who talk about and/or demonstrate what they have done to prepare may be the most powerful preparedness spokespersons of all. A second top motivator is knowledge of what preparedness actions to take, how to take them, and why these actions are beneficial26—in this case, preparation for extended sheltering can prevent illness and death due to radiation. Preparedness education that focuses on abstract science lessons and disaster consequences is less likely to motivate the desired behavior. The third key motivator to preparedness is receiving repetitive and consistent information over multiple channels (eg, social media, newspaper, flyers, TV), so that people can hear the message above everyday background noise.

*Not all equipment within the EMP-affected area will fail, however. Electronics are more likely to fail the closer they are to ground zero, the larger their effective receptor antenna, and the more sensitive they are to EMP effects.27 Cell phones and handheld radios have relatively small antennas and will probably still function if they are not plugged in at the time of the EMP. If equipment does not work initially, turning it off and then back on, removing and then replacing the battery, or rebooting may restore function. In general, protective actions used to protect equipment from lightning strikes, such as shielding, may “harden” electronics.



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