The cranes have been assembled on the Sellafield SIXEP Continuity Plant site.
It means that the project is able to accelerate into the construction phase, with the pouring of concrete and erection of re-enforcing steel.
The plant is one of a portfolio of projects being delivered under the Programme and Projects Partnership model.
The model, which is unique in the UK construction industry, is transforming major project delivery at Sellafield. It brings together KBR, Jacobs, Morgan Sindall Infrastructure Ltd, Doosan Babcock and Sellafield Ltd as the fifth partner.
It is helping to drive improvements in procurement,and job creation, amongst other benefits.