A nulcear watchdog has slapped an 'improvement notice' on Sellafield Ltd over the condition of a cooling tower on site.

The Office for Nuclear Regulation (ONR) says that improvements must be made in the management and control of the legionella bacteria in the tower at its Highly Active Liquid Effluent and Storage (HALES) facility.

Both the ONR and Sellafield Ltd say there has not been an outbreak of legionnaires' disease, but regulators say that steps must be taken before January 27, 2017, to "minimise the likelihood" of the bacteria spreading and being released. Sellafield Ltd accepts that its cleaning regime was not sufficiently "robust".

Dr Richard Savage, ONR's chief nuclear inspector, said: "We are here to ensure the nuclear industry meets the high standards of safety and security required by the law and will always take appropriate enforcement action where necessary. This includes management of risks to health and safety arising from legionella.

"We are satisfied that this issue does not impact nuclear safety and there has been no outbreak of legionnaires' disease. This is about requiring improvements to ensure that the risks arising from legionella are being appropriately controlled and managed."

A Sellafield Ltd spokesman said: "The notice formalises an improvement programme we had already identified. In this instance, our cleaning regime wasn’t as robust as it should have been and we have already started work on an improvement plan.

"The age and nature of the Sellafield site means that some of our facilities are more difficult to maintain than they might be elsewhere, but that is not an excuse; we will learn from this and implement our improvement plan promptly.

"The legionella bacteria found in the towers during routine tests does not cause legionnaires’ disease."