Random values (0 and 1) with condition on each row and each column

Hi I am trying to create a dataframe of 600 rows and 18 columns in R BUT:

-each row has to have only three 1's randomly in the 18 columns (for example column A,E,F with 1 and the rest with 0's) -the sum of each column has to be equal to 100

I am really stuck with this problem :(