 In 1947, a rather average fishing boat was launched in Wakayama Prefecture, Japan. Little was it known at the time that the post-war fishing vessel would become an important footnote in US atomic weapons history. Just seven years after its construction, the Daigo Fuku Ryu Maru, working near Bikini Atoll became exposed to deadly radiation, resulting in all her crew experiencing varying levels of acute radiation sickness, with one dying. The crew of the 140 ton fishing boat out of Yaizu Jizuka Prefecture became an interesting opportunity at the time to study the effects and treatment of acute radiation syndrome. Although relatively unknown incident today, it was a direct influence on one of the 20th century's most recognisable movie franchises, Godzilla. The film was a mirror of the Japanese psyche in regards to the effects of the atomic age, tracing its roots back to Hiroshima and Nagasaki, but also in the accidental fallout of nuclear weapons. As such, I'm going to rate the incident here for on my Patience in Plain Difficult Disaster Scale, but here, 8 on my Historical Legacy Scale. Today we're looking at the Daigo Fuku Ryu Maru, or the Lucky Dragon No. 5 Radiation Incident. The wooden fishing vessel built in 1947 was originally designed as a bonito fishing boat, intended to be used in shallow waters carrying the name Diana Koutoshiru Maru, but the vessel was reworked for deep sea tuna fishing in 1953 and it moved to Yaizu Port, Shizuka Prefecture. As part of this, she was renamed the Daigo Fuku Ryu Maru, or the Lucky Dragon No. 5. The vessel had a length of 28.56 meters, a beam of 5.9 meters, and a 250 horsepower engine, all of which resulted in a fairly slow 5 knots. In January 1954, the crew of the boat prepared for another voyage under the captain ship of 22-year-old Hizaki-chi Suzui. Lucky Dragon No. 5 set sail on the 22nd January with a crew of 23 on route to Midway Island on the hunt for some tuna. The voyage reached its destination three weeks later, but lost many of its nets to the reef yielding little fish caught. Not wanting to admit defeat, Suzui altered the vessel's destination towards the Marshall Islands. To make the decision, that was hoped to change the voyage's fortunes, but would actually be the complete opposite. Little did they know, but a small test called Castle Bravo was about to be undertaken just off of Bikini Atoll. Let's pause here to talk quickly about the test and its implications for the area surrounding the epicentre. Castle Bravo was the first experimental high yield thermonuclear weapons test in Operation Castle. The blast was to be an atmospheric test at Bikini Atoll in the Marshall Islands, using the Tella Ulam design. The type was intended to be a stepping stone to develop an aircraft-deliverable thermonuclear device. The bomb worked in multiple stages and had two parts, a primary and a secondary. The primary consisted of a fission bomb. The secondary consisted of a uranium-235 tamper with lithium deuteride fuel within. In the centre of this was a plutonium rod called a spark plug. Both parts were cased in polystyrene foam, surrounded within a reflective case. When detonation is initiated, high explosive fires within the primary compressing the plutonium core into supercriticality and beginning a fission reaction. The fission reaction emits x-rays that are scattered along the inside of the bomb casing, irradiating the polystyrene foam. The foam becomes plasma, compressing the secondary and the plutonium spark plug begins to fission. Compressed and heated, the lithium deuteride fuel produces tritium and begins the fusion reaction. The neutron flux produced causes the uranium-238 tamper to fission and the fireball in shoes. The detonation was only intended to yield an explosion of around 6 megatons, but the actual output would be 15 megatons of TNT. The extra power was due to the unforeseen extra reactions involving lithium-7. The resulting explosion far exceeded the calculations set out by the US military, and this included the exclusion zone that the lucky dragon number 5 was slowly approaching. The vessel towards the end of February was low on fuel and supplies. The captain decided on one last roll of the dice, on the 1st of March before turning around to return back to port. The lucky dragon should have been safe as it sailed just outside the exclusion zone, but this would not be the case at 6.45am on the 1st of March 1954. In a scene that would directly inspire the 1954 Godzilla movie, the morning darkness was interrupted by a man-made sun. As the crew watched the sky turn into flames, they didn't realise the danger they were in. The explosion was the largest man-made at that time and was a thousand times more powerful than Nagasaki or Hiroshima. The vessel was rocked by the shockwave but survived, so far so lucky I suppose, but a strange ash-like substance started raining down covering everything and everyone on board. A towering mushroom cloud rose above Bikini Atoll at 47,000 feet and a diameter of 7 miles. A crater around 6,500 feet in diameter and 250 feet in depth was made at the epicentre. The ash particles were inhaled by the vessel's inhabitants as they continued to fish in the area. 6 hours later they were finished and set about weighing their catch and making preparations to return home. Although a strange experience, the crew thought little more of the second sun they saw and of the dangers of the radioactive particles that lay all around them. By the evening, all was not well as the first signs of acute radiation sickness began to present themselves in the crew members. The voyage back would be a painful and arduous endeavour for the crew as any part of their skin that had come into contact with the ash were covered with burns. Not only that, but bleeding gums and severe sickness and nausea were also experienced. 14 days later, the lucky dragon returned to port Yaizu and her crew were sent to hospital. It was not really known by the doctors at the Yaizu Public Hospital what the actual cause of their injuries were. Some of the older crew members were sent to Tokyo University Hospital, where one of the men had their bone marrow sampled and the results showed his white blood cell count to be lower than expected. After further inspections of the crew and the lucky dragon, radiation exposure was concluded and a diagnosis of ARS was issued to all 23 men. The vessel gave off radiation that could be detected up to 100 feet away. Later, a Geiger counter detected 120 million ronkins on the deck of the ship. Because of the public health risk, the lucky dragon was moored at Yaizu's north pier and guarded by police. The hull aboard the vessel was buried, but some of the tuna aboard was thought to have made it to local fish markets never to be seen again. The younger men were quarantined in Yaizu Hospital, but their hair was shaved and their clothes were confiscated for disposal. This was due to radioactive particles still being present amongst the fibres. Two American medical scientists were sent to keep an eye on the treatment of the crew members. I should say that during the whole event, the actual bomb test wasn't officially acknowledged by the US, as the Castle Bravo test was top secret. After the ARS diagnosis, all 23 men were sent to Tokyo University Hospital for treatment for the next year, where constant monitoring and blood sampling took place. Their red and white blood cells dropped significantly, causing internal bleeding and blood stools, necessitating multiple transfusions and regular doses of antibiotics. By August, one of the men, 40-year-old Kubuyama Akichi's situation had severely deteriorated. Towards the end of the month, he had developed meningitis and later on in September, he developed pneumonia eventually going into a coma and passing away on the 23rd of September, 1954. The surviving members of the crew were released from hospital on the 20th of May, 1955, although the men would continue to receive yearly check-ups to monitor the progression of their recoveries. Many of the crew would develop cancer post-event, with several dying in their 50s and 60s, however a few did live to a good age. Tizumu Mizaki lived to the age of 92, and Oishi Matasichi died in March 2021 at the age of 87. Many of the crew tried to keep their experience a secret, as social isolation usually followed if someone had been discovered to have been exposed to radiation. This was due to radiophobia, which was unsurprising in a country that had actually been nuked before. Eventually, each of the survivors would receive a payout of roughly today's money of about $52,900 from the US government. The event had wider implications to the Japanese economy as it is thought that up to 800 fishing vessels had been affected in the 1950s from the tests at Bikini Atoll. Around 490 tons of fish caught by these boats had to be discarded, leading to a loss of confidence in Japanese caught fish, which got the very unappealing nickname a bomb tuner. But what happened to the lucky dragon number 5 after such a dramatic chapter in her history? Well surprisingly, the boats still exist today. After the event, her future ownership was debated with the United States military, proposing to move the ship to their base in Yoko Suka to be disposed of, but the Japanese government refused, instead taking it to Tokyo for training purposes, but Daigu Fukuiu Maru was deemed safe for public viewing in 1976 and was kept for preservation. It is now on display in Tokyo at the Tokyo Metropolitan Daigu Fukuiu Maru Exhibition Hall, where she acts as a visual aid to the dangers of nuclear proliferation. This video is a plain-difficult production, all videos on the channel are Creative Commons attribution share alike licensed, plain-difficult videos are produced by me, John, in a currently not sunny southeastern corner of London, UK. Help the channel grow by liking, commenting and subscribing, check out my Twitter for all sorts of photos and nods and sods as well as hints on future videos. 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