Is Montana at Risk?
Identified Hazards for the State of Montana
Basic Disaster Information:
NUCLEAR ATTACK
Although it no longer holds the same threat it once did, nuclear attack is still a possibility. There are three primary potential effects experienced as the result of the explosion of a nuclear bomb.
- The direct effects from blast overpressure:
When a nuclear weapon explodes in the atmosphere, the air surrounding the detonation point is rapidly compressed and forced outward. A blast or shock wave is created that initially moves at speeds much higher than the speed of sound. The amount by which the pressure produced by this wave exceeds normal atmospheric pressure is know as overpressure.
Additional direct effects are initial nuclear radiation (INR) and the electromagnetic pulse (EMP). INR is that portion of nuclear radiation that appears during the first minute after the detonation of the weapon. This form of radiation may be hazardous to unprotected people within about 1.5 miles of a detonation.
EMP is a short energetic pulse of electromagnetic radiation released by the weapon. The EMP effect resulting from a nuclear detonation within the earth’s atmosphere is generally not significant. A surface or near surface burst generates an intense but mostly localized EMP near ground zero. The effects of blast, shock, nuclear and thermal radiation, however, usually outweigh any destructive capabilities of EMP in this region. High altitude bursts cause more extensive problems. When high yield weapons are detonated outside the earth’s atmosphere, an efficient conversion of nuclear energy into the electromagnetic frequency range occurs. This energy can affect the operation of unprotected electrical and electronic equipment over entire continents. Continued operation of the equipment is disrupted until it can be repaired or replaced. Equipment without electronic components, such as generators, motors and transformers, is less susceptible to EMP damage, while control systems and computers are highly susceptible to damage.
Many types of electrical/electronic equipment could be affected or even destroyed by the EMP from high-altitude detonations, but it is unlikely that anymore than a small percentage overall will be damaged. The direct effect of EMP on people is limited to those who are dependent upon electrical life support systems.
- The fire risk:
The combined effects of blast overpressure damage and the thermal pulse or fireball of a weapon can ignite exposed combustible materials, causing many sustained fires. Primary fires are those ignited directly by the thermal pulse of a nuclear detonation. Secondary fires are generated by damage and destruction from blast overpressures. These fires result from the disruption of building furnaces, gas lines, and electric lines.
- The fallout risk:
Fallout radiation generated by surface burst weapons presents unique problems that make civil defense today quite different from the civil defense practiced during World War II.
When a nuclear weapon explodes near the ground it makes a big crater, Earth from the crater is instantly changed from solids into hot gas and fine dust by the tremendous heat of the explosion. This hot gas and dust, together with vaporized materials from the bomb itself, form a giant fireball that rises rapidly high in the air. This becomes the top part of the mushroom cloud of a nuclear explosion. Dust and the heavier particles of earth make up the stem of the mushroom cloud. The dust and earth in the stem and in the mushroom cloud become radioactive mainly because radioactive materials created in the nuclear explosion stick to some of the dust and earth particles.
As the top of the mushroom spreads out and cools, it forms a cloud of fine particles of earth and debris. This cloud is carried for long distances by the wind and the particles gradually drift down to earth as fallout. The heavier, larger particles settle closer to the point of explosion, but the wind can carry small particles several hundred kilometers. Once fallout begins to settle, the first 24 hours is the most dangerous period. This initial fallout is highly radioactive. The lighter, delayed fallout particles would lose much of their radioactivity in the upper atmosphere. Delayed fallout reaches the earth in rain or snow over periods ranging from days to years. The decay of fallout radiation is described by the seven-ten rule. This rule states that for every sevenfold increase in time after detonation, there is a tenfold decrease in the radiation rate. For example, if the radiation intensity one hour after detonation is 1,000 Roentgens (measure of radiation exposure) per hour, after seven hours it will have decreased to one/tenth as much. In seven more time periods (7 X 7 = 49 hours or two days) the radiation level will be 1/100 of the original rate. After about a two-week period, the level of radiation will be at 1/1000 of the level at one hour after detonation.
There are three kinds of dangerous radiation in fallout from nuclear weapons: alpha, beta and gamma. All three types of radiation are dangerous, but gamma radiation poses the greatest threat to human life. Alpha radiation is stopped by the outer skin layers and does not usually present an external hazard. However, if contaminated air, food or water enters the body in sufficient quantity, by ingestion, inhalation or through skin abrasions, considerable internal damage can occur. Beta radiation is more penetrating and may cause burns where fallout particles have deposited on the skin. Gamma radiation is capable of penetrating the entire body and causing damage to organs, blood and bones. Large doses of gamma radiation can cause sickness or death, depending on the amount of the dose received and victim susceptibility. Small doses incurred over a long period of time may have no immediate effect, but could cause various forms of illness later in life. Genetic damage in subsequent generations may also result.
The above listed effects of a nuclear attack have varying consequences for the populations affected. Those people located near the explosion would be killed or seriously injured by the blast, heat, or initial nuclear radiation. People a few miles away would be subject to blast, heat and fires. A high percentage of the population residing in the lighter damager areas would probably survive these hazards, but might subsequently be endangered by radioactive fallout.
Obviously, Montana has no history of nuclear attack. The only experience the United States has had in dealing with the effects of nuclear detonation comes from the bombs dropped on Hiroshima and Nagasaki, Japan, weapon tests performed between 1945 and 1963 in the South Pacific, and at the test ranges in the southwestern United States.
Atmospheric tests conducted at the times of these detonations revealed that radioactive fallout could be carried great distances in the atmosphere. The potential seriousness of human exposure to fallout became apparent when studying the medical effects observed in some Marshallese Islanders and Japanese fishermen after the 1954 Bravo test. The controversies surrounding fallout effects on livestock and humans in southern Utah and Nevada further confirmed the dangers. Thyroid dysfunction was the primary effect observed in the Marshallese with children being the most susceptible.
The natural ecosystem surrounding detonation points was also adversely affected. At both the South Pacific and Nevada test ranges, perennial plants recovered more quickly from blast and thermal effects than species that rely on seeds for re-establishment. Seed availability limited re-establishment of some species on the South Pacific test islands. Abnormal plant growth was observed in fresh vegetative growth at both the Nevada and South Pacific test ranges. At the Nevada test range, lizards and small mammals exposed to long-term radiation suffered adverse effects to their individual lifespans, time of sexual maturity, population age distributions and other life-history characteristics.
Although this historical perspective in enlightening, it does not represent what could occur if a nuclear attack were launched today. Most nuclear war scenarios assume that 5,000 to 6,000 Megatons of explosive power would be detonated in a nuclear war over the Northern Hemisphere. Such a war would release an explosive yield of 109 to 1010 tons of TNT equivalent. Expressed another way, a 5,000 megaton war in which one Hiroshima sized bomb was dropped every second, would last four and a half days.
Predicting the time and extent of an attack is nearly impossible. The Federal Emergency Management Agency assumes that a surprise attack is very unlikely. A period of heightened international crisis will precede any conflict.
