23391
U has a much higher fission efficiency by low-energy ( thermal ) neutrons , compared e.g. with U. Most uranium chemistry studies were carried out on uranium-238 owing to its long half-life of 4.4 years .
 location: U
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: U 
Answer:
 location: U