91698
Cobalt-60 , , is preferred for radiography , since it is chemically a rather nonreactive metal offering higher energy gamma-ray photon s. Caesium-137 can be found in some moisture and density gauges , flow meters , and related sensors .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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