It sounds to me like your doing homework? If you have a NEC code book you can look it up by looking at the index in back of the book.
If you don't have a code book you should get one ASAP.
It's has all your answers in it.
The minimum as I understand it is 5/8 of an inch for 1/2 inch conduit. As FC has put it the index might help you through the code. Generally the sealant should be no less than the diameter of the raceway.