A power station at Heysham has closed two reactors as a precaution after a fault was found.
EDF Energy has closed both reactors at Heysham 1, as well as at its sister station in Hartlepool.
An inspection of reactor 1 at Heysham 1, in June this year, showed a defect in one of its boilers.
As a precaution the company has shut all reactors they operate which are of the same design.
Concerned resident Mo Kelly said: “If two of the safety measures are starting to malfunction its slightly worrying.
“It begs the question of the long term feasibility of keeping them running.
“There are over 180,000 of us living within a 10 mile radius of the four elderly AGR reactors at Heysham 1 and 2.
“EDF should place public safety paramount above any desire to continue the operation of failing, unsafe and inefficient out of date AGR nuclear reactors.
A spokesman for EDF said: “Although routine inspections of other boiler spines have not previously indicated any similar defects, EDF Energy has taken the conservative decision to shut down Heysham 1 Reactor 2 and Hartlepool Reactors 1 and 2 that are of similar design over the next few days to carry out further inspections in order to satisfy itself and the regulator that the reactors can be safely returned to service.
“The two reactors won’t be supplying electricity but National Grid have said that demand is low in summertime and there will be no impact on customers.”
The investigations will take eight weeks, said EDF Energy.