Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.
Apparently she said to the public via radio. That said, I found no transcript or recording that proves that. So make what you will of that.
Regardless, Marie Curie could be such a cool person. I've came in contact with her on more detail by reading La ridÃcula idea de no volver a verte (which is a very nice book on grief). Thoroughly recommend getting to know her better.