An American nuclear expert has warned that Westinghouse’s proposed reactor for Cumbria needs a $100m (£68m) filter to safeguard against a leak that would turn the region into “Chernobyl on steroids”.

Arnie Gundersen lifted the lid on safety violations at a nuclear firm in 1990 – he claimed to have found radioactive material in a safe – and was CNN’s resident expert during the Fukushima nuclear disaster in Japan in 2011.

Mr Gundersen told The Independent that he is concerned by designs for three reactors proposed for a new civil nuclear plant in Cumbria. A nuclear engineering graduate by background, Mr Gunderson believes that the AP1000, designed by the US-based giant Westinghouse, is susceptible to leaks. The reactor has been selected for the proposed £10bn Moorside plant, a Toshiba-GDF Suez joint venture that will power six million homes. It is going through an approval process with the Office for Nuclear Regulation (ONR).

Mr Gundersen, who visited the Sellafield nuclear facility in Cumbria last week, warned that any leak would be like “Chernobyl on steroids”, referring to the 1986 nuclear disaster that killed 28 workers within four months. He passed on some of these fears to MPs at an event in Parliament during his visit to the UK.

He said: “Evacuation of Moorside would have to be up to 50 miles. You could put a filter on the top of the AP1000 to trap the gases – that would cost about $100m, which is small potatoes.

“If this leaks it would be a leak worse than the one at Fukushima. Historically, there have been 66 containment leaks around the world.”

The aftermath of the Fukishima disaster Show all 14 1 /14 The aftermath of the Fukishima disaster The aftermath of the Fukishima disaster Fukishima Wearing white protective masks and suits, Yuzo Mihara (L) and his wife Yuko pose for photographs on a deserted street in the town of Namie, Fukushima prefecture. EPA The aftermath of the Fukishima disaster Fukishima Weeds grow around a seat in the abandoned town of Namie, outside the the nuclear exclusion zone surrounding the crippled Fukushima Dai-ichi nuclear plant in Japan. AP The aftermath of the Fukishima disaster Fukishima A single house remains at an area wiped out by the 11 March 2011 tsunami near Ukedo port in the town of Namie EPA The aftermath of the Fukishima disaster Fukishima View of the destroyed Tomioka station in the town of Tomioka, Fukushima prefecture EPA The aftermath of the Fukishima disaster Fukishima A time capsule is surrounded by weeds at the Tsushima Junior High School in Namie AP The aftermath of the Fukishima disaster Fukishima Protest slogans criticising Tepco, the company which ran the crippled Fukushima Dai-ichi nuclear plant, appear with a photo of residents on the window of the home they were forced to evacuate in Namie AP The aftermath of the Fukishima disaster Fukishima View of a deserted street in the town of Namie, Fukushima prefecture EPA The aftermath of the Fukishima disaster Fukishima A fishing vessel carried by the 11 March 2011 tsunami remains inland near Ukedo port of the town of Namie EPA The aftermath of the Fukishima disaster Fukishima Bags belonging to children remain hanging at the abandoned Namie elementary school in the town of Namie EPA The aftermath of the Fukishima disaster Fukishima A statue of a boy and a girl stands at the entrance of the abandoned Namie elementary school in the town of Namie EPA The aftermath of the Fukishima disaster Fukishima Wearing white protective mask and suit Yuzo Mihara looks at a collasped house in his neighborhood in the town of Namie EPA The aftermath of the Fukishima disaster Fukishima Policemen stand at checkpoint in Namie, Fukushima Prefecture, prior to the second anniversary commemoration of the tsunami and earthquake Getty Images The aftermath of the Fukishima disaster Fukishima Piles of radiation-contaminated waste sit in a field in the abandoned town of Namie, outside the exclusion zone surrounding the Fukushima Dai-ichi nuclear plant in Japan AP The aftermath of the Fukishima disaster Fukishima An empty gas station is seen in the abandoned town of Namie AP

A spokeswoman for the ONR said that the regulator is currently ensuring that the reactor will be safe. She said: “We have received revised plans from Westinghouse for 51 outstanding issues. These will have to be resolved before the ONR can make any decisions [to approve the reactor].”