Cancellation Of Tickets Where Railway Administration Is Unable To Provide Accommodation
Where a railway administration is unable to provide accommodation for any reason whatsoever to passengers holding reserved tickets, no cancellation charge shall be levied and full refund of fare shall be granted to them if such tickets are surrendered for refund within three hours from the actual departure of the train.
Provided that when the train is cancelled due to unforeseen circumstances such as accident, breach or flood, the ticket is surrendered within three days excluding the scheduled day of departure of the train.
Source: http://contents.irctc.co.in