EDF said the improvements to a flood barrier at the plant were “arguably unnecessary”, although it said the scheme would increase resilience to flooding.
Details of the work have come to light after it emerged the French company shut one of two reactors at Dungeness power station on the Kent coast for five months.
The move was made following concerns raised in a report carried out after the Fukushima disaster in Japan that its shingle bank flood defences could be breached during a catastrophic weather event.
Commenting on the Hartlepool improvements, the company said it had worked on the scheme with the Environment Agency and the Office for Nuclear Regulation.
EDF said that there was no requirement for general improvements to the site’s flooding defences.
However, a spokesman added: “We are always looking at ways to improve and enhance our plants, and so we have looked at additional flooding defence work at the Hartlepool site.
“We have made some very minor changes to a flood barrier to give ourselves even more margin against water ingress onto the station, we decided to do this, even though it was arguably unnecessary, to increase resilience against the most extreme flooding events that we could envisage.”
Flood risk maps produced by the Environment Agency show the nuclear power plant could be surrounded by flood water after extreme weather, but the site would not be at risk.
The agency calculated that the access roads to the plant could become flooded, but only in a one in a 1,000 years event.
Even then, the plant itself would not be at risk, a spokesman added.
In December, an RAF Chinook helicopter was used to move tonnes of boulders from the sea front at Seal Sands to prevent further flooding at nearby Port Clarence after bad weather damaged flood defences.
In 2011, an earthquake struck Japan, killing 20,000 people and resulting in a tsunami to crash over the Fukushima nuclear plant’s sea wall.
Hundreds of workers at EDF are to go on strike next month in a dispute over pay.
Unite said almost 500 of its members will walk out on May 6 and 8.