Document 3e0rrG8avaEnp1O2KwvNDBRGD

IONIZ1NC RADIATION 2. Number of employees exposed to radia tion and then locations 3. Chemical and physical states of the radio active material and the nature of its use 4. Incidents likely to occur and their possi ble locations 5. Nonradiabon hazards involved 6 Nature of the probable radiation expo sure oi release of radioactive material, a A controlled or supervised release as m a disposal operation b. An accidental release or exposure which cannot be sensed by warning alarm signals generated by radiation detection instruments. c. A violent release of dust, droplets, gases, or vapors through fire, tem perature increase, or explosion. d. A contact spread of contamination as the result of its adherence to other material or of spillage 7. Inherent danger of the material because of its internal or external effect on man. (This danger depends upon the isotopic identification and chemical form of the material. See NBS Handbooks 59 and 89.) 8. Probability of detection of harmful situa tion by routine surveys or monitoring. (Current knowledge of conditions is es sential in order to determine the ac ceptability of the risks involved.) 9. Possible effects of accidents on opera tion, such as interruption of production, loss of occupancy of space, loss of equip ment, and cost of cleanup. Consider employee exposure potential The industrial accidents which may pro duce radioactive contamination are usually no more difficult to control than the com mon types of industrial accidents, but there is an a^dad, compelling reason to control them--the probability of absorption by hu mans of radioactive materials. External radiation. Under ordinary op erating conditions and barring accidents, the level of exposure to external radiation usually will be immediately known through constant monitoring alarm devices, the use of monitoring instruments, dosimeters, or previous measurements of radiation fields for identical operations The problem is then reduced to limiting the rate of ex posure or the length of exposure time Measurement of the exposure by instru ments will indicate what advantage is to be obtained by installing additional shielding or by having personnel work farther from the source Under emergency conditions with higbexposure levels, it is advisable to rotate personnel in order to reduce the exposure of any one individual to guide levels Emer gency exposure levels for extreme condi tions have been published in NBS Handbod: 59. These are essentially once-m-alifetime allowances for handling a really serious situation See also "Exposure to Radiation in an Emergency" by the Na tional Committee on Radiation and Meas urements, listed m "References " Occasionally, an unexpectedly high read ing will appear on a personal dosimeter For any one of a number of reasons, the reading may be invalid, but an accident in vestigation will determine the validity of the reading and indicate the corrections needed to prevent recurrences Internal emitters Commonly, the intro duction of radioactive materials into the body is most serious if entry is through the lungs. Subcutaneous rejection can even be worse. Inhalation of dusty or finely divided ra dioactive materials is possible if unknown to die employees, materials are released and become air-home Routine air sam pling may detect the concentration, hut a constant air-monltonng system will signal such releases More important, employees may recognize conditions which in the past have released materials, thus they can act promptly to minimize exposure (Fig 42-9) Simple calculations will show that if per sons working m dusty trades retained in their lungs all the insoluble dust particles that they breathe, their lungs would become filled. Fortunately, certain protective mech anisms of the lung prevent this result Except for air passages below a certain size, the interior walls of the lung's breath ing airways are constantly and rapidly being swept dear. Some inhaled parbdes are swept back out of the lung to be swallowed or coughed and expectorated. Also scaven ger blood cells remove foreign materials from the lung Some inhaled material is subsequently exhaled. 42-23