"I was hit by a thunderous flash and an explosion of sound," she recalled in a children's book she wrote so even the youngest in our society would know the dangers of nuclear weapons. "My eyes burnt — everything went black. I held my sister. Everything faded away — I thought I was dying."

The then 13-year-old's home was flattened. The neighbourhood destroyed. Everything and nearly everyone she knew was torn apart, burnt or destroyed. The thunderous crash killed 360 of her school friends who went to classes on that hot August day. Skin fell like rags from those burnt in the blast. A neighbour was trapped in a drain when he died, only to remain there for weeks. Within five years, half a million people had died in Hiroshima and Nagasaki, which was destroyed three days later on August 9, 1945, by a nuclear bomb with the codename of Fat Man. Both were dropped by US Air Force B-29 Superfortress bombers, the first by the Enola Gay and the second on Nagasaki by Bock's Car (often called the forgotten plane).

New Red Cross data released on Thursday shows that even 70 years after the atomic blasts, Japanese hospitals treat thousands of survivors each year, mostly for cancer which has caused two-thirds of deaths. In the past 12 months, the Red Cross hospitals treated nearly 11,000 survivors.

The full impact of the blast on the survivors and their children who are now reaching 50 years of age, is still not fully known, Dr Masao Tomonaga, the director of the Japanese Red Cross Nagasaki Atomic Bomb Hospital and a survivor told Fairfax Media this week.

As well as suffering higher rates of cancer, new research by the Red Cross hospitals showed survivors who had lived close to the epicentres were also 1.5 times more likely to suffer from heart attacks and angina.

"I couldn't imagine (these results) before we started this research some 65 years ago (when the hospitals were built.) This means atomic bomb radiation is a life-long effect, with evidence of a life-long susceptibility to cancers, leukaemia and heart attacks," Dr Tomonaga said.

Of the 16,000 nuclear weapons held today, 1800 are launch ready and any one would make Little Boy or Fat Man "look tiny" and wipe out a city like Sydney, said Robert Tickner, the CEO of the Australian Red Cross. No country or medical service could handle the immediate or long-term impacts, including the millions who would go hungry, Red Cross research has found.

Mr Tickner is calling on Australians and their leaders to support a ban on nuclear weapons for humanitarian reasons.

"If the world has moved on biological and chemical weapons as illegal weapons of war, if we have moved on clusters, landmines and had conventions to tackle those to deal with them as a weapon of war, what madness is it that we have not taken a similar stand on nuclear weapons.They are the standout greatest threat to the planet," he said.

Around 113 countries have now signed the Austrian Pledge to prohibit and eliminate nuclear weapons because of their unacceptable humanitarian consequences. The federal government hasn't signed, but the ALP 's new party platform, amended at last month's conference, agrees to "prohibiting and eliminating nuclear weapons is a humanitarian imperative."

Until that ban, the 83-year-old Mrs Morimoto - who with her older sister are the only two known survivors of the blasts in Australia - will keep telling and retelling her story whenever and wherever she can. After she reads the story to schoolchildren, she makes them promise to never make or go to war.

Writing My Hiroshima, the sixth of 14 children's books she has written, was the hardest thing she had done, she said, bringing tears as she drew her younger self. With a non-malignant brain tumour causing her to lose balance, she is increasingly aware that time is running out for all the hibakusha or bomb-affected people.

Aware that many of the 190,000 living survivors of Hiroshima and Nagasaki are dying or ill, Mrs Morimoto feels compelled to tell her story while she can. "Very few of those (survivors who are still living) can tell what happened. So it is very important to share my experience on every opportunity," said Mrs Morimoto at her home in Sydney across from a busy primary school.