Assertion: gamma ray's source | /r/HasProperty | protective internal shield
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Source sentences:
text: A teletherapy radiation capsule composed of the following:A.) an international standard source holder (usually lead),B.) a retaining ring, andC.) a teletherapy "source" composed ofD.) two nested stainless steel canisters welded toE.) two stainless steel lids surroundingF.) a protective internal shield (usually uranium metal or a tungsten alloy) andG.) a cylinder of radioactive source material, often but not always cobalt-60 .