Radiations exposure levels

Marks, S., F.T. Cross, D.H. Denham, and W.E. Kennedy Jr., Estimation of Health Effects due to Elevated Radiation Exposure Levels in Structures, Sci. Total Environ. 45 543-550 (1985b). 

How much lead shielding will it take to reduce the radiation exposure level to <10 mrem/h 1 ft from a 5-mCi 60Co source ... 

An example of a common situation that leads to greater radiation exposure levels than would be expected occurs with some uranium compounds. Depleted uranium is an a-emitting isotope with an extremely long half-hfe, 4 billion years. As a result of this long half-life, is generally not considered to present a significant radiation hazard. However, uranium fluorides, a typical synthetic starting material, can... 

Duenas, C., Frenandez, M.C., Canete, S., Carretero, J. Liger, E. (1999) 222Rn concentrations, natural flow rate and the radiation exposure levels in the Nerja Cave. Atmospheric Environment 33, 501-510. 

Safety Standards. Protection from laser beams involves not allowing laser radiation at a level higher than a maximum permissible exposure level to strike the human body. Maximum permissible exposure levels for both eyes and skin have been defined (55—57). One of the most common safety measures is the use of protective eyewear. Manufacturers of laser safety eyewear commonly specify the attenuation at various laser wavelengths. Under some conditions safety eyewear has been known to shatter or to be burned through (58), and it is not adequate to protect a wearer staring directly into the beam. 

Thousands of studies of radiation and its risks have been conducted. Yet there is no conclusive evidence that low levels of radiation exposure cause either cancer or birth defects. The nuclear iadustry operates oa the coaservative ALARA approval, assumiag that any exposure iavolves some risk. 

Answer The automobile death rate is about lE-7/passenger mile. If 25,000 people evacuate 20 miles, this is 5E5 passenger miles, hence, the risk is 5E5 IE-7 = 0.05 deaths. The radiation exposure is 2.5E4 5E-4 48 = 600 person-rem. Using information from problem 4, the estimated deaths from radiation is 600 lE-4 = 0.06. About the same. The risk from radiation may be over estimated because the radiation level was measured close to the plant on the other hand, the traffic fatality estimate may be high because of police presence and slow driving. 

The presence of radiation in the workplace - which is an inevitable consequence of the radioactivity of uranium - requires that additional safety precautions be taken over and above those observed in other similar workplaces. There are generally three sources from which radiation exposure may occur (i) radiation emitted from uranium ore in-situ and/or during handling (ii) airborne radiation resulting from the decay of radon gas released from the ore and uranium dust and (iii) contamination by ore dust or concentrate. Radiation levels around uranium mining and milling facilities are quite low - for the most part only a few times the natural background levels - and they decrease rapidly as the distance from... 

Some years ago it was realized that the indoor inhalation of the short-lived radon daughters constitutes the most important contribution to the radiation exposure of the general population (Unscear, 1982). The working level concept has been introduced in the domestic environment due to the success of the concept in the occupational environment and due to a lack of experimental data on the relative and absolute magnitudes of the transformation and... 

Many states in the U.S. are currently involved in large scale surveys to measure radon levels in homes in an attempt to assess the environmental risk from radon and radon daughter exposure. Radon daughters deliver the largest radiation exposure to the population and it is estimated that 0.01% of the U.S. population (23,000 persons) are exposed from natural sources to greater than those levels allowed occupationally (4 WLM/yr) (NCRP, 1984). 

Individual dose assessment requires radiological data on all external and internal sources contributing to occupational and non-occupational radiation exposure (Steinhausler and Pohl, 1983). This is of particular importance in the case of low level Rn-d exposure, as man is always exposed to Rn-d at varying levels through all stages of life, e.g. at school, home or work. The resulting lifetime risk from this chronic exposure is influenced by the latent... 

This very long half-life (1.25x1(r years) isotope comprises 0.0117 percent of all potassium. Thus, this isotope is present in all of us and has always been so. In addition, the materials around us, including the soil and the building materials, contain both potassium and the heavy naturally occurring radioactive elements thorium and uranium that contribute to a level of radiation to which we are all continuously exposed. Thus, there is always radiation exposure to the general public and we must understand the exposure due to radon in this context. The amount of radioactivity is described in units of activity. The activity is the number of decay events per unit time and is calculated as follows... 

When relatively insoluble forms of l44Ce are inhaled, the primary effects are observed in the lungs and tracheobronchial lymph nodes. With large quantities of 144Ce, animals die of radiation pneumonitis and pulmonary fibrosis. The tracheobronchial lymph nodes are atrophic and fibrotic. At lower exposure levels pulmonary neoplasms are a prominent finding. 

Thermal burns result from the radiant heat emitted by a hydrogen fire and absorbed by a person, which is directly proportional to many factors including exposure time, burning rate, heat of combustion, size of the burning surface, and atmospheric conditions (mainly wind and humidity). For instance, thermal radiation flux exposure level of 0.95 W/cm2 may cause skin burns in 30 s. Cryogenic burns may result from contact with cold fluids or cold vessel surfaces. Exposure to large liquefied hydrogen spills could result in hypothermia, if proper precautions are not taken [17]. 

After the nuclear explosion at Chernobyl in 1986, Anatoly and other professors and physicians created a foundation, For the Children of Chernobyl. Their goal was to send children abroad for the summers for a reprieve from radiation exposure which impairs their immune systems and has resulted in unprecedented levels of thyroid cancer in children and adults. The first host country to respond to their call for help was India. Before long, the foundation was sending 30,000 children every summer to host families and programs in many countries, including Germany, England, Japan, the U.S., Spain, Italy and France. 

The effect of radiation on the thermal expansion of this toughened composite (T300/CE 339) is shown (191 in Figure 24. The thermal strains measured during the cool-down portion of the first thermal cycle (cooling from RT to -150°C) are shown for the baseline composite (no radiation exposure) and for samples exposed to total doses as high as 10 0 rads. Radiation levels, as low as 10 rads... 

Radiation dose Level of exposure to radiation, expressed in units called Roentgen equivalents in man (rem) a dose of approximately 400 rem is fatal in 50% of cases when medical treatment is not available. No health effects are typically observed at doses below 10 rem. 

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