A day after a company hoping to build a new breed of nuclear reactors in the UK hailed a development in shield design, that very design was called into question by the Health and Safety Executive’s nuclear directorate.

Last week, Ric Perez, senior vice-president of nuclear power plants at Westinghouse, told the Marketforce Nuclear Industry Forum that technology from Japan and South Korea had been utilised in the company’s AP1000 model to withstand a plane crashing – or being crashed into – a reactor.

The design employed a steel composite rather than the usual concrete because, Mr Perez said, concrete shatters on impact.

But within 24 hours of Mr Perez’s speech, the UK’s nuclear directorate raised a regulatory issue against Westinghouse’s AP1000.

In a statement, the HSE said: “Westinghouse is proposing to use a new construction methodology for key structures … essentially using a sandwich of steel plates filled with concrete, rather than using more conventional reinforced concrete, which is strengthened with internal steel bars.

“This is new and we need to be reassured that key structures would be sufficiently robust to protect the reactor’s safety systems under normal conditions, and also from severe weather and other external hazards, such as physical impacts. In order to get that reassurance, we need to see appropriate evidence to demonstrate the strength and durability of the structures. In essence, we want to be assured that the structure will hold together.”

The regulator stressed that fact that it had issued a regulatory issue “does not mean that the design is unsafe” and added that the nuclear directorate “is still assessing designs on paper, so any safety detriment is still in the design stage”.

Westinghouse is said to be considering a number of possible solutions, such as further analysis, testing and possible changes to the design, and intends to provide detailed proposals and supporting evidence to the HSE by the end of October.