Wednesday, April 4, 2012
UrbanMan’s reply: Frank, you are doing well to think about all collapse possibilities. Perhaps protection and survival plans for a nuclear event would be the hardest to plan and prepare for without a lot of resources,…read money. I think location is a key to survival in a nuclear event. Away from high value targets,…..away from fall out patterns from predictive wind patterns,…and away from refugee routes – and, there will always be survivors.
Federal Emergency Management Agency (FEMA) recently published a study from the analysis of the specific implications of nuking the intersection of 16th and K streets NW. The key to the question, it seems, is the size of the bomb. Ten kilotons is considered “small” by nuclear weapon standards and would presumably leave survivors, according to the study. …Within a half-mile radius of the detonation, called the “severe damage zone,” buildings would be destroyed, radiation would be high and the survival rate would be low. The White House, Capitol and Mall would be destroyed. As little as three miles out, the impact would be less severe, including broken windows and minor injuries. But the real disaster would be nuclear fallout, the result of radioactive dust poisoning many in the District, Northern Virginia and Maryland.
I also found a government report on the potential of a nuclear attack on the National Capital Region. I am posting the easier to understand key points below. In any event, the first rule of survival is to understand the threat so you can develop a plan and counter measures.
Contamination vs. Exposure
Fallout contamination is salt- and sand-sized particles that contain unstable (radioactive) atoms that give off energy in the form of penetrating eadiation. Although contamination particles can be stopped by clothing and other barriers, the gamma radiation emitted by the unstable atoms penetrates through clothing, roofs, and walls and can deposit energy in living tissue. It is the exposure and absorption of this energy that is the primary concern and is measured as described below.
Roentgens, Rads, and Rems. Units of Radiation Exposure
• Roentgen (R): A unit of gamma or x-ray exposure in air. It is the primary standard of measurement used in the emergency-responder community in the US. 1,000 milliroentgen (mR) = 1 Roentgen (R).
• Roentgen per hour (R/h): A unit used to express gamma or x-ray exposure in air per unit of time (exposure rate) and the unit most commonly seen on radiation-detection equipment used by responders.
• rad: A unit expressing the absorbed dose of ionizing radiation. Absorbed dose is the energy deposited per unit mass of matter. The units of rad and gray are the units in two different systems for expressing absorbed dose. International unit conversion: 1 rad = 0.01 gray [Gy]; 1 Gy = 100 rad.)
• rem: A unit of absorbed dose that accounts for the relative biological effectiveness (RBE) of ionizing radiations in tissue (Also called equivalent dose). Not all radiation produces the same biological effect, even for the same amount of absorbed dose; rem relates the absorbed dose in human tissue to the effective biological damage of the radiation. International unit conversion: 1 rem = 0.01 Sieverts [Sv]; 1 Sv = 100 rem.)
For the purpose of this guidance, 1 R (exposure in air) = 1 rad (absorbed dose = 1 rem (whole-body dose). Whole-body doses are calculated for the middle of the body (1.5 m off the ground and 70% of the body-surface exposure), also referred to as the “midline deep dose.”
Estimated fatalities and symptoms associated with acute whole body absorbed doses:
150 initial rad dose - 5 percent chance of dying within 180 days from radiation exposure.
300 initial rad dose - 30-50 percent chance of dying within 180 days from radiation exposure.
600 initial rad dose - 95 percent chance of dying within 180 days from radiation exposure.
It will be initially difficult for those directly affected to assess the scale of devastation. On a clear day, a mushroom cloud might be visible from a distance, but the cloud is unlikely to keep a characteristic shape more than a few minutes and will be blown out of the area in one or more directions in the first few hours.
The most critical life-saving action for the public and responders is to seek adequate shelter for at least the first hour. Another urge to overcome is the desire to flee the area (or worse, run into fallout areas to reunite with family members), which can place people outdoors in the first few minutes and hours when fallout exposures are the greatest.
Those outside or in vehicles will have little protection from the penetrating radiation coming off fallout particles as they accumulate on roofs and the ground.
Sheltering is an early imperative for the public within the broken glass and blast damage area, which could extend for several miles in all directions from a blast. There is a chance that many parts of the area may not be affected by fallout; however, it will be virtually impossible to distinguish between radioactive and non-radioactive smoke, dust, and debris that will be generated by the event.
Potentially dangerous levels of fallout could begin falling within a few minutes. Those outdoors should seek shelter in the nearest solid structure. Provided the structure is not in danger of collapse or fire, those indoors should stay inside and move either below ground (e.g., into a basement or subterranean parking garage) or to the middle floors of a multi story concrete or brick building. Those individuals in structures threatened by collapse or fire, or those in light structures (e.g., single story buildings without basements) should consider moving to an adjacent solid structure or subway. Glass, displaced objects, and rubble in walkways and streets will make movement difficult.
Leaving the area should only be considered if the area becomes unsafe because of fire or other hazards, or if local officials state that it is safe to move. Fallout is driven by upper-atmospheric winds that can travel much faster than surface winds, often at more than 100 miles per hour. Outside the area of broken windows, people should have at least 10 minutes before fallout arrives for the larger multi-kiloton yields. If the detonation were to happen during daylight hours on a day without cloud cover, the fallout cloud might be visible at this distance, although accurately gauging direction could be difficult as the expanding cloud continues to climb and possibly move in more than one direction.
Providing that atmospheric conditions do not obscure visibility, dangerous levels of fallout would be easily visible as particles fall. People should proceed indoors immediately if sand, ash, or colored rain begins to fall in their area.
At 20 miles away, the observed delay between the flash of an explosion and “sonic boom” of the air blast would be more than 1.5 minutes. At this range, it is unlikely that fallout could cause radiation sickness, although outdoor exposure should still be avoided to reduce potential long-term cancer risk. The public at this distance should have some time, perhaps 20 minutes or more, to prepare.
The first priority should be to find adequate shelter. Individuals should identify the best shelter location in their present building, or if the building offers inadequate shelter, consider moving to better shelter if there is a large, solid multistory building nearby. After the shelter itself is secured, attention can be given to acquiring shelter supplies such as batteries, radio, food, water, medicine, bedding, and toiletries.
Although roads could be initially unobstructed at this range (around 20 miles), the possibility of moving the numerous people at risk before fallout arrives is highly unlikely, and those in traffic jams on the road would receive little protection from fallout. At long distances (more than 100 miles), the additional time before fallout arrival might tempt people to evacuate.
However, cloud spread and difficulties associated with predicting possible fallout locations will make avoiding the hazard difficult, even when driving. Although people at this distance will not experience life-threatening levels of fallout, using the extra time to seek the best-quality shelter in the area can help reduce exposures and the long-term risk of cancer.
Stay Indoors. People should expect to remain sheltered for at least 12 to 24 hours. During that time, the intensity of fallout radiation will decrease greatly, allowing for less hazardous egress from dangerous fallout areas. Unless a given shelter location is considered unsafe due to fire or structural damage, the length of time individuals should remain sheltered depends on instructions from regional emergency management agencies. For those in good shelters, such as a large concrete, brick, or underground structure, optimal shelter times will likely be in terms of days.
In the absence of specific guidance from authorities and adequate supplies of food and water, or for those who are in smaller 2- to 3-story structures or shallow basements, evacuation should be considered after 12 hours. Upon leaving shelter, the best course is to follow routes that take advantage of sheltered passages (subways, underground connectors, or through building lobbies) that lead away from damage and heavy fallout areas. Once clear of potential fallout areas, evacuees should seek a change of clothes (including shoes) and wipe or wash exposed skin surfaces.
Fallout consists of large particles that can be easily brushed off clothing and shoes. The radiation energy given off by fallout particles decays rapidly with time. For this reason early gross decontamination (brushing for example) is better than delayed thorough decontamination (such as a shower). An event of this magnitude will vastly overwhelm available response resources.
Get Clean. Radioactive fallout particles can spread quickly and remain on the body and clothes until removed. Those in potentially fallout contaminated areas should take off the outer layer of clothing (including shoes) and wipe or wash exposed skin and hair upon leaving a contaminated area.
• Routes make a difference for early evacuees. The exposure impact of route choice is more significant in the first few hours.
• Shelter quality determines decision time. The better the shelter, the longer the time before action is required. For poor shelters, actions should be taken in the first few hours; inadequate shelter, 4–12 hours; for adequate shelters, avoid action before 12 hours unless instructed otherwise.
• Adequate shelter, stay in place. Extended shelter-inplace inside an adequate shelter is almost always preferred over an uninformed evacuation in the first 12 hours. The gains from an informed evacuation before 12 hours are marginal, while the penalty for an uninformed evacuation can be significant.
• Poor shelter, move or evacuate. Early evacuation (at 1 hour) from lower-quality shelters in the Danger Zone can be life-saving.
– Best Strategy For Poor Shelter: Informed evacuation after approximately an hour. However, without an informed route use next strategy.
– Good Strategy for Poor Shelter: Move to a better shelter. Analysis indicates that this can result in a significant reduction of casualties even as early as 20 minutes after detonation.
– Marginal Strategy for Poor Shelter: Uninformed evacuation after approximately an hour and then leave the area, do not move toward the detonation site or directly downwind.
– Bad Strategy for Poor Shelter Extended Shelter in Place.
• In aggregate, the existing Washington , DC structures offered better than adequate protection. If all residents adopted a shelter-in-place strategy, it would reduce the number of potential acute radiation casualties by 98% (there would be an estimated 3,000 fallout casualties out of the 130,000 potential casualties of an unsheltered population).
• For Regional evacuation planning, errors in identifying the centerline and boundaries of high-dose-rate regions can result in poor evacuation routes that eliminate the benefits of evacuation.
• Preplanned evacuation routes may not be the best evacuation route as they may follow the contamination centerline.
• The current federal guidance of sheltering for 12-24 hours in in a shelter is adequate.