Floating dry docks are structures that can be submerged to allow a ship or submarine to enter. They are then raised and emptied of water, enabling inspections, maintenance and repair.
Unlike their land-based equivalents, their ability to float means they can be towed to different locations.
The last floating dry dock to be manufactured in the UK is believed to be Admiralty Dock 60, built in the 1960s and based at HMNB Clyde at Faslane until the late 1990s when it was sold for commercial use.
Currently the base has to rely on a single shiplift, an elevator-type device which hoists submarines out of the water inside a large maintenance building.
The Spanish state-owned shipbuilder Navantia has been lobbying hard to build the new floating docks for Faslane, through its UK division.
The company owns the Harland & Wolff shipyard in Belfast, along with fabrication sites at Arnish on the Isle of Lewis, Methil in Fife and Appledore in Devon.
Following Healey’s speech, Navantia said it hoped to lead the project, using the Methil and Belfast facilities.
The GMB Scotland union has previously written to Healey, external asking for the work to be shared between the Methil site and Belfast.
Other possible contenders include the Cammell Laird shipyard in Merseyside, now owned by Balaena, and Babcock which has facilities at Rosyth.