Document 6Rne6wVO7Yje1QN99EpemRbqd

tion of barriers and warning signs, stationing of attendants to keep personnel out of re stricted localities, and, in extreme cases, complete closing of the areas Safe exposure times and safe practices can be established through measurement and control, and by profiting from past experience Work with radiation can and should be so planned and managed that radiation ex posures of employees and of the general public are kept to a minimum No radio active matenals which can result in exposures above guide levels should be released through contaminated air or water, through loss of control over contaminated waste materials, equipment or shipments, or by employees unknowingly leaving the place of work with contamination on their persons, clothing, or shoes Consider the type of work involving radiation The literature on radiation protection is an invaluable aid (see "References" at the end of this chapter) It is important to realize that any one of a wide range of operations may be under discussion, and that safety measures applying in one case may be inappropriate for another The following examples point this out Processing of feed matenals for nuclear reactors and operations includes large-scale mining and processing of ores containing useful radioactive matenals Feed streams for separation and punfication involve tons of matenals, with a small percentage of radio active matenals which are then further proc essed and punfied The Atomic Energy Commission is closely associated with this Certain kinds of work involve appli cations using radiation from radium, thonum, and other naturally occurring matenals which are not controlled exclusively by the AEC Some of these matenals are used, for example, in luminous instrument dials, in gas mantles, in certain ceramic colors, and as radiation sources Radiation fields occur in the operation of such devices as industrial, fnedical, and dental X-ray machines and X-ray diffraction machines, and cyclotrons and other particle accelerators Relatively small amounts of radiation are emitted in electronic tubes, television receivers, and electron micro scopes (See NBS Handbooks 55, 76, 93 Protection Against Betatron-synchrotron Radiation up to 100 men. Medical X-Ray protection up to 3 Million Volts, and Safety Standard for Non-Medical X-Ray and Sealed Gamma-Ray Sources ) Industrial operations m which radio active matenals are of pnme importance in clude fuel fabncation, shipment and trans portation of radioactive matenals, construc tion or operation of reactors, and chemical processing to recover or separate radioiso topes from spent fuel elements (See Safety Series No 6 Regulations for the Safe Trans port of Radioactive Materials, published by the International Atomic Energy Agency, Vienna, 1961, and also Nuclear Energy Ma tenals Handling Manual, Helm's Express, Inc , P O Box 268, Pittsburgh, Pa 15230 ) Radiation is used in various operations to assist in quality control Thickness gauges using X rays or gamma rays (Fig 44-5), or beta rays (Fig 44-6) have been used with great success to maintain tolerances on the thickness of continuous sheet strips These devices are so mounted that the external field is a very minor source of exposure Some static eliminators contain alpha emitters and are used in high-speed rolling of sheet material or in operations such as calendering that involve the evaporation of flammable solvents Radioactive tracers are used in analytical chemistry and to trace the flow of fluids in process Parts of equipment may be irradi ated to facilitate wear studies Other ma terial may be irradiated for purposes of ster ilization or for use in chemical reactions Consider the sources of radiation One must always consider the amount and kind of radiation sources which will be used in a contemplated operation Then, suit able radiation safety operating standards can be decided upon to make sure proce dures are safe A number of examples of operations are presented m the following pages and may help to point out some basic 1451