A mathematical model and Monte-Carlo simulation method of radon exhala-tion from uranium tailings were developed based on the nuclear recoil theory .The grain size effect on radon exhalation under different moisture contents was simulated .When radium is distributed on grain surface , K increases with grain size and then remains a constant value under moisture contents of 5% ,20% ,50% and 75% .When radium is distributed to a depth of 34 nm or 68 nm from the surface ,K firstly increases with grain size and then reaches a constant value under moisture contents of 5% and 20% ,and K decreases with...
