That will yield a boost for businesses in East Lothian and Berwickshire too as more than 600 additional staff will be joining the 750-strong workforce at the EDF Energy power station.
One of the two reactors at the power plant was taken offline last Friday for the nine-week duration of the works.
EDF Energy carries out a statutory outage on each of its reactors every three years.
These are planned in advance with the National Grid to ensure that there is no impact on the national electricity supply.
The other reactor at Torness is due to continue operating normally throughout the maintenance period.
During the outage, workers will carry out more than 12,000 separate pieces of work, all carefully planned during the last two years of preparation.
The biggest projects include inspections of the reactor vessel internals, exchange of the turbine high-pressure rotor and replacement of auxiliary cooling water pipework systems.
Station director, Paul Winkle, said: “This is the first statutory outage since we announced last year that Torness will continue to produce low carbon electricity until 2030 – an additional seven years.
“The outage will give us the chance to do inspections and carry out pieces of work that are not possible when the reactor is operating.
“It is also a great boost for the local economy.
“We are bringing in an additional 600 workers who will be staying in local hotels and B&Bs, eating in the area’s restaurants and using taxi firms.
“It is great that our investment in the power station can also benefit the local community.”
Torness power station’s two nuclear reactors generate enough electricity to power more than two million homes.
It employs more than 500 full-time staff and around 250 full-time contract partners to ensure the safe reliable generation of electricity.
Over the past 28 years, it has produced enough low-carbon electricity to save the equivalent of 80 million tonnes of CO2e, the same as taking all passenger-carrying cars off the UK’s roads for a year.
Last year it was given permission to extend its operational life from 35 to 42 years.
Although opposed to the building of new nuclear power stations, the Scottish Government made clear that its policy did not include the operating life of existing nuclear power stations being extended to help maintain security of supply “while the transition to renewables and cleaner thermal generation takes place”.
Torness is one of two EDF Energy power stations in Scotland, the other being Hunterston B in North Ayrshire.
Torness is the last second-generation nuclear power plant commissioned in the UK. Initially owned by South of Scotland Electricity Board, EDF Energy has been operating it since 2009.
It also runs two wind farms in the Borders – Fallago Rig in the Lammermuirs and Longpark, near Stow, and it provides nuclear-backed Blue energy to the UK’s electric rail network, including the main lines from London to Edinburgh and Glasgow.