Lethal dose from radiation

The lethal effects of inhalation exposure to uranium have been investigated in humans in epidemiological studies and in animal studies under controlled conditions. Epidemiological studies indicate that routine exposure of humans (in the worlq)lace and the environment at large) to airborne uranium is not associated with increased mortality. Brief accidental exposures to very high concentrations of uranium hexafluoride have caused fatalities in humans. Laboratory studies in animals indicate that inhalation exposure to certain uranium compounds can be fatal. These deaths are believed to result from renal failure caused by absorbed uranium. The low specific activity of uranium precludes the possibility of absorbing enough uranium to deliver a lethal dose of radiation. 

The sole purpose of the shield cask is to provide protection for workers from potentially lethal doses of radiation emitted by irradiated material during transfer operations. The shield cask also provides limited physical protection to the radioacrive material should a mishap occur in transport. 

In the event of a maximum accident producing a total of lO fissions in a single burst, it is likely feat most of the persons within a radius of 100 meters of fee source would be killed by the explosive blast, flying debris, or by direct radiation. Lethal doses from exposure to the radioactive cloud may be received downwind from fee source as far as 300 meters. One-AED doses from the direct radiation and cloud exposure could be received at distances of 300 and 1800 meters, respectively. 

Computers are now increasingly being introduced into safety-critical systems like nuclear power plants and aircraft and, as a consequence, have been involved in a number of deadly mishaps. A particularly noteworthy medical example concerns a computerized radiation therapy machine called the Therac-25 used to treat cancer patients. In 1986, two cancer patients died when they received lethal doses of radiation from the Therac-25 system utilizing a computer-based controller. An investigation revealed that one contributor to this catastrophe was failure of the design team to recognize a race condition, a miscoordination between concurrent tasks. 

The final column presents the radius of 50% mortality from fallout 1 hour after the explosion. Of all of the threats described, fallout is the hardest to predict because of the influence of local, regional, or even global weather patterns. The mushroom cloud can rise into the atmosphere as far as 80,000 feet, where wind and rain influence the time and location for fallout to occur.2 Individuals several miles from ground zero and well outside any radius presented in Table 5.1 can receive significant or even lethal radiation doses from fallout. However, while the air blast, thermal burns, and initial radiation are threats in all directions, fallout is a threat downwind from ground zero. Wind speed and direction vary at different altitudes, and it is safest to assume that fallout is a potential threat in all directions from ground zero. Individuals outside the blast zone generally will have several minutes to an hour or more to seek shelter before fallout arrives. 

The 1,3-dioxolane ring is found in a major antifungal drug, ketoconazole (123). Ketoconazole is a broad spectrum, orally active antifungal agent and is used to treat a wide variety of superficial or deep fungal infections. Various workers, especially in Russia, have explored the use of simple oxathiolanes as radioprotectants. For example, the survival rate of mice irradiated with lethal doses of X- or -y-rays was 40% when they were pretreated with 2,2-dimethyl-l,3-oxathiolane. Other oxathiolanes were less active. 1,3-Oxathiolane, administered intravenously to dogs 2 or 3 times daily for 2-4 days before chronic irradiation with polonium-210, increased their life expectancy from 9 months to 3-7 years and alleviated radiation sickness. Some blood indicators were also restored to normal. 

Purpose 2 serves a worker protection function by providing barriers to potentially lethal doses of ionizing radiation from radioactive material operations conducted within the facility. 

An indication of the lethality of a given substance or type of radiation. Because resistance varies from one individual to another, the lethal dose represents a dose (usually recorded as dose per kilogram of subject body weight) at which for a given percentage of subjects a fatality will occur. The most commonly used lethality indicator is the LD50, a dose at which 50 percent of subjects will die. 

During the first few days of the Chernobyl accident, 28 emergency workers and plant staff received lethal doses and then died from radiation exposure. This was a result of workers not monitoring their exposure and not being properly trained and equipped. Inhalation and external exposure were important sources of doses, and bums to the skin resulting from beta contamination were a major contributor to many of the fatalities. 

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