A former national serviceman involved in a 1950s nuclear test in Australia is pleading for his lifetime healthcare application to be reconsidered.

Key points: Operation Hurricane was the first British nuclear test in Australia and took place at the Montebello Islands

Operation Hurricane was the first British nuclear test in Australia and took place at the Montebello Islands Ken Palmer believes exposure to radiation from a nuclear blast contributed to his illnesses

Ken Palmer believes exposure to radiation from a nuclear blast contributed to his illnesses The national servicemen are now pleading to have their cases reviewed by Dan Tehan

Ken Palmer, 83, believes exposure to radiation from the blast has contributed to illnesses, including cancers.

"Please Mr Minister … you'll still be in the job for a little while, make a clean breast of things, let your guard down a bit," he said, referring to Veterans' Affairs Minister Dan Tehan.

"Please Mr Dan, please."

Mr Palmer was a teenager aboard HMAS Murchison in October 1952 when he saw "a big mushroom cloud" form on the horizon.

Operation Hurricane was the first British nuclear test in Australia and took place at the Montebello Islands, off Western Australia's coast.

"It's about five operations I could safely put down to being at Montebello," Mr Palmer said.

He attributed having both thyroid glands removed to the nuclear test, along with two hip procedures, back surgery, and having his prostate removed.

This year's federal budget included $133 million to give nuclear veterans gold cards, providing lifelong no-gap medical care.

But Mr Palmer's application was rejected by the Department of Veterans' Affairs.

"That decision was made because they weren't within the required distance of the blast," Mr Tehan said.

"This has been looked at comprehensively."

Servicemen had to be within 10km of blast to qualify

Ken Palmer says photos of the blast taken aboard HMAS Murchison prove it was closer to the explosion than records indicate. ( Supplied )

Government records place HMAS Murchison about 130 kilometres from the blast.

Those aboard the ship have long argued they were as close as nine kilometres away, saying photographs taken moments after detonation prove their claims.

To qualify for gold cards, the national servicemen had to be within 10 kilometres.

"Was there a curtain they put up to stop the radiation heading towards our ship? I doubt it. I didn't see it," Mr Palmer said.

Veterans advocates estimate about 60 national servicemen were on the navy ship.

Another former 'nasho' aboard the HMAS Murchison, who has also been knocked back, estimated fewer than a dozen of his crewmates were still alive.

Mr Palmer, who is in hospital ahead of surgery on Tuesday, said: "This is our last stand."

Applications 'should be re-examined'

Ken Palmer (centre) and crewmates days before the atomic blast at the Montebello Islands. ( Supplied )

Mr Tehan hinted he could review their cases.

"If there is any new evidence that suggests that the circumstances were different, I would definitely be prepared to look at it," he said.

"We were the first government to enable the British nuclear test [participants], and the British and Commonwealth Occupied Forces, to get gold cards.

"This had been something that they'd been battling for over 40 years.

"We've showed that we want to do what we can to help those who were involved."

At 25 kilotons, the explosion was more powerful than the bomb dropped on Nagasaki during World War II.

The Murchison's role was to patrol the area around the Montebello Islands, including to intercept any commercial vessels.

Western Australian Greens senator Rachel Siewert said the applications should be re-examined.

"I think we need to give them the benefit of the doubt," she said.

"If they are being excluded, there needs to be an independent review to look at the accounts, but I certainly wouldn't be trusting the records."