Australia's nuclear submarines may not be ready for 15 years due to how long it will take to train the extra personnel required to operate them, according to retired Rear Admiral Peter Briggs. “One of the most challenging bits of the transition is the personnel. Not only do you need more submariners, but the mix is quite different as well,” he told Sky News host Andrew Bolt. “From the manpower training perspective, I think you’re looking at something like 15 years till the first commissioning. “You can probably shorten that with a pile of cooperation from both the US and the UK. “In particular, the senior technical personnel supervising the capability ashore who take 15 or 20 years to train - we won’t be able to do that from scratch. “So, borrowing those qualifications and that experience would enable us to fast track it.”