T.O. 33B-1-16-140continuous with external cooling. The end-anode type of X-ray tube is shielded with a 1-inch lead collar with a circularaperture for the primary beam. Typical tube housing leakage radiation exposure rates range from 500 to 1000 mR/hr (5to 10 mSv/hr) at one meter from the tube target. The 1000 mR/hr (10 mSv/hr) exposure rates generally occur at 90degrees to the major tube axis at the high-voltage-input end of the tube housing.6.9.16.5 Sperry300-KVPUnit.The maximum output of the 300-kVp unit is about 117 R/min (1.17 Sv/min) in the beam at 1 meter from the tubetarget with the tube operating at 300 kVp and 10 mA. Filtration of the primary X-ray beam is 2.36 mm beryllium forthe 35-degree tube heads and 0.5 mm nickel for the 360-degree tube heads.6.9.17 ClassificationandSelectionofRadiographicInstallations.6.9.17.1 Summary.Basically any installation which so constructed and operated as to meet the basic radiation protection standards isacceptable. However, if this were the only requisite, the assumptions as to the use of the equipment and degree ofoccupancy might be subject to widely divergent interpretations.6.9.17.1.1AirForce:TheAirForcedefinestwotypesofNDIinstallations.a. ShieldedInstallation. A facility designed with sufficient shielding so that exposure limit requirementsare met.b. UnshieldedInstallation. Applies where fixed shielding cannot be used (i.e. flight line, open hangers,make-shift buildings, etc.)ARMY: In order to ensure certain minimum standards of protection without needless expenditures, it has been foundadvisable to divide installations into three different classes.a. Protective Installation. Provides the highest level of inherent safety; exposure limit requirements aremetb. Enclosed Installation. Provides fixed shielding for low use and low radiation levels (“Protective"radiographic facilities generally will be used within the Army rather than "Enclosed" facilities.)c. Unshielded Installation. Applies where fixed shielding cannot be used (i.e. flight line, open hangers,make-shift buildings, etc.)6.9.17.1.2NewFacilities.New radiation facilities shall be constructed to meet the requirements of one of these classes of installations. Theclasses differ in the relative dependence on inherent shielding, operating restrictions and supervision necessary tosecure the required degree of protection. In addition, each class has certain advantages and limitations. The abovereferenced paragraphs contain details of the respective installation classes.6.9.17.2 HighRadiationAreas.Each of the types of installations specified herein involves the creation of "High Radiation Areas". Access to all highradiation areas created by radiographic operations with sealed sources shall be controlled in accordance with 10 CFR20.1601. To insure high levels of safety, these rules will also be applied to radiographic operations performed with x-ray sources. Requirements include:a. Control devices that, upon entry into the area, cause the level of radiation to be reduced (below thatlevel at which an individual might receive a deep-dose equivalent of 100 mrem (1 mSv) in 1 hour at 30centimeters from the source (or from any surface that the radiation penetrates).
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