Devonport has a long queue of submarine refits

As part of the application, the yard wanted to decrease discharges of cobalt by three times.

The Environment Agency has told it to reduce them by eight times.

Cobalt is more radioactive than tritium, so the Environment Agency said, overall, there will be a decrease in the radioactive discharges.

DML's plan prompted local people to form opposition groups and hold protest marches.

Dr Sandy Matthews, a member of the pressure group Campaign Against Nuclear Storage And Radiation (CANSAR), is unhappy about the river's future.

He said of the decision: "My reaction is one of disappointment."

Provisional permission

Dr Matthews said: "Tritium is, as the scientists are telling us, a poison, meaning that the Tamar will be more polluted in future."

The Environment Agency's permission is provisional.

In reaching its decision, it concluded the radiation doses from the discharges would be extremely low and well within national and international limits set to protect both people and the environment.

The levels will also much lower than the doses from natural background radiation.

Government approval

Anil Koshti from the Environment Agency said: "We have examined the application very carefully, taken expert advice and considered all the points raised during the public consultation."

"We are satisfied that the health risks from DML's discharges at our proposed limits are not significant in radiological terms.

"The new authorisation will see an overall improvement for the environment and, in addition, the agency will be seeking further reductions in radioactive discharges."

The decision now goes to the government for approval.

The first submarine refit is planned for next year.