Profound mitotic delay occurs when the doses are:
Radiation is especially damaging to rapidly dividing cell systems, such as skin and intestinal mucosa and hematopoietic tissues. Irradiation of such cell populations causes a reduction in size of the irradiated tissue as a result of mitotic delay (inhibition of progression of the cells through the cell cycle) and reproductive cell death (usually during mitosis).
The three mechanisms of reproductive death are:

DNA damage 
Bystander effect
Apoptosis

Note: Large dose of irradiation causes mitotic delay.
Smaller
Larger
Intermediate
No effect of doses