Sellafield safety incidents revealed in new ONR report

Workers at Sellafield were forced to carry out an emergency evacuation after both a breathing-air compressor and its backup supply failed, a newly published nuclear safety report has revealed.

The incident was among a series of safety concerns and near misses detailed by the Office for Nuclear Regulation (ONR) in its latest report covering the nuclear site between April and September 2026.

The regulator also revealed that heavy lead shielding blocks fell approximately six metres, a container holding special nuclear material was found damaged, and a steel crane rope fell from height near workers.

Breathing-air failure

The ONR said: "In September, Sellafield Ltd reported failure of a mobile breathing-air compressor during work involving an air-fed suit entry.

"The back-up air supply also failed and the operators carried out an emergency evacuation.

"Subsequent monitoring identified no contamination of the operatives."

The regulator said Sellafield had suspended the use of mobile breathing-air compressors while investigating the circumstances of the failures.

It added: "We considered the immediate information provided and are continuing to engage with Sellafield Ltd as they investigate the event and implement improvement actions."

Falling shielding blocks

In another incident in June, lead shielding blocks fell approximately six metres at the Highly Active Liquor Evaporation and Storage facility after a retaining bracket failed.

The ONR described it as a 'significant conventional safety near miss'.

It said: "Although there were no injuries or radiological consequences, there was a credible potential for serious injury to workers."

The regulator identified concerns responsibility for the affected area and arrangements for inspection and maintenance. An enforcement letter was issued.

Meanwhile, a can containing special nuclear material was found damaged during retrieval operations in September.

The ONR said: "There was no damage to the internal containment hence no release of the contents and there was no contamination to operators."

An investigation was launched and remained ongoing at the time of the report.

Further safety concerns

The report also detailed an incident in April at Encapsulation Product Store 1, where a steel crane rope fell from height during routine maintenance while workers were nearby.

No injuries resulted and there was no nuclear safety risk, but the ONR issued an Improvement Notice.

The regulator said: "We found that Sellafield Ltd had failed to ensure that persons appointed as competent supervisors of maintenance activities had sufficient training and experience to enable them to undertake the role."

In a separate June incident, a trailer carrying an unloaded radioactive-waste flask was moved unsafely, damaging the trailer and equipment.

The ONR said its follow-up had identified 'gaps in implementation of Sellafield Ltd's arrangements for operating instructions'.

The report also recorded two minor electric shocks involving workers, neither of whom suffered lasting effects.

The findings appear in the ONR's site report for the six months ending September 30, published in November 2026.