MPs had questions for those at the top of the project in charge of dismantling decommissioned submarines on Wednesday.
The commitment to dispose of more than 20 decommissioned submarines berthed at Devonport and Rosyth is almost four decades old.
MPs wanted to know why the dismantling is taking so long and costing so much.
The Submarine Dismantling Project aimed to provide a safe, environmentally responsible and cost-effective way to dismantle 27 nuclear-powered submarines leaving service from the Royal Navy.
Since 1980, £500 million has been spent storing and maintaining 20 already retired - nine of which still need their nuclear fuel rods to be removed.
Latest estimates predict that defueling is unlikely before 2023 - 11 years later than planned.
Complete dismantling is not expected to start until 2026 - 15 years late and at £1.6bn over the original budget.
There were concerns over whether the funding to do it would definitely be available, with more submarines set to come out of service in the mid-2020s. Dismantling delays bring the risk that there will be not enough available space to store them.