Nuclear-Powered Submarines for Australia? Maybe Not So Fast.

But Britain’s submarines have come relatively slowly off its production line, and often behind schedule. Britain’s submarine maker, BAE Systems, is also busy building Dreadnought submarines to carry the country’s nuclear deterrent.

“Spare capacity is very limited,” Trevor Taylor, a professorial research fellow in defense management at the Royal United Services Institute, a research institute, wrote in an email. “The U.K. cannot afford to impose delay on its Dreadnought program in order to divert effort to Australia.”

Adding to the complications, Britain has been phasing out the PWR2 reactor that powers the Astute, after officials agreed that the model would “not be acceptable going forward,” an audit report said in 2018. The Astute is not designed to fit the next-generation reactor, and that issue could make it difficult to restart building the submarine for Australia, Mr. Taylor and other experts said.

Britain’s successor to the Astute is still on the drawing board; the government said last month that it would spend three years on design work for it. A naval official in the British Ministry of Defense said that the planned new submarine could fit Australia’s timetable well. Several experts were less sure.

“Waiting for the next-generation U.K. or U.S. attack submarine would mean an extended capability gap” for Australia, Mr. Taylor wrote in an assessment.

The challenge does not stop with building the submarines. Safeguards to protect sailors and populations, and meet nonproliferation obligations, will require a big buildup of Australia’s nuclear safety expertise.

Residents in some parts of Barrow-in-Furness, the town of 67,000 that is home to Britain’s submarine-building shipyard, are handed iodine tablets as a precaution against possible leaks when reactors are tested. The Osborne shipyard in South Australia, where Mr. Morrison wants to build the nuclear submarines, sits on the edge of Adelaide, a city of 1.4 million.