 History has a habit of repeating itself when you don't learn from your mistakes. For a second time, the plutonium facility at Rocky Flats would experience a devastating fire. The event would be another chapter in the saga of pollution at the site. The Rocky Flats plant is up there as one of the worst nuclear industry sites for long-term contamination. The facility would experience not one but two plutonium fires. Now, before I start, I strongly recommend that you watch my video about the 1957 Rocky Flats fire as it gives a bit more background to the site and was the worst of the two fires in regards to contamination release. Although it less a disaster, today's subject, the 1969 fire, was the catalyst for the wider public being aware of the site's shortcomings with radioactive containment. As such, I'm going to rate the Rocky Flats plant as a whole as seven on the painted, plainly difficult disaster scale. The Rocky Flats nuclear bomb factory was located 16 miles northwest of Central Denver. Our story begins in 1957, around the same time as the remediation works to clean up the first fire were undertaken. A new trigger design was beginning to be employed in US nuclear weapons. The new triggers had different shapes of plutonium with closer tolerances, necessitating more rolling, forming and machining than early years of weapons production at the damaged building 77. With the main fabrication building running at reduced capacity, a new complex was decided to be constructed, completed in 1958. The complex was two buildings, 776 and 777, one for manufacturing and the other for inspection. The new building was able to cope with the more intricate manufacturing process for plutonium triggers. After a couple of years of operation, the dividing wall between the two buildings was removed for ease of production. The building was a two-storey structure with a partial basement. The main floor had 135,000 square feet, the second floor contained 88,000 square feet and the basement boasted 600 square feet. Similar to the process used in building 77, the plutonium triggers had to be founded and milled to the correct shape, all of which was done within shielded glove boxes with plexiglass windows. Releases of radiation wasn't just confined to the two rocky flat fires. As between 1964 and 1967, toxic cutting fluid contaminated with particulates of plutonium and uranium were stored in 55 gallon drums on pad 903. Over the years, the drums had corroded on their underside, leaking the contaminated effluent into the soil around the storage area. With some of the waste mixed with dust, between 1.4 and 15ci, or 19 to 208 grams of plutonium dust, was released contaminating offsite areas to the south and east, necessitating the pad to be paved over with asphalt. Leading up to 1969, over 10 modifications to the complex were undertaken as production grew. Four principal glove box systems existed at building 776-777. These included North Foundry Line, the South Foundry Line, the Centre Line and the North-South East Machining Line. All production operations were carried out in glove boxes that were interconnected. This leads us onto the 11th of May 1969, and a small smouldering fire in one of building 776 or 777's glove boxes that were turned into one of the most costly industrial accidents up until that point in US history. At around 2pm, a smouldering began in an open plastic can containing plutonium. As we saw in 1957, the material slowly burns, much like charcoal, and again the cause of the spontaneous ignition is not completely known. Eventually, the smouldering ignited the plastic, causing a much bigger fire as other materials set a light. The fire was spread about by the glove box ventilation systems. There were very few fire breaks in the line, causing damage to a large proportion of the building. The filters employed in building 776 and 777 were different from the ones in the 1957 fire, and were less flammable, and had six banks of high-efficiency particulate air filters, or HEPAs. This time round, the filters worked more efficiently, capturing a large amount of contaminants. By 6pm, the fire was largely contained and fully extinguished by 8. During the fire, four filters were severely damaged, leading to a release of material out of the building vent stack. It was estimated that between 0.14 and 0.9g or 10 and 60mci of plutonium 239-240 had escaped into the atmosphere during the fire. The most contaminated area was behind the vent stack on the building's roof, with plutonium all over the structure. And some was tracked in and out of the building by firefighters during the fire. Some plutonium was carried off site by winds, although it was not known by the exact amount. Again, like in 1957, the most exposed were people outside exercising at the time of the release. This is because plutonium predominantly emits alpha particles, which are only damaging to the human body if ingested, for example through breathing. The fire drew the attention of independent radiochemists at the National Centre for Atmospheric Research. Samples of soil on site were taken, and unsurprisingly, plutonium traces were found to be 400 times above the average levels. Officials at the plant were questioned, strangely denied the contamination was from the fire, and instead admitted to the 1957 fire and the release at area 903. And thus the 1957 fire and contamination were now known by the public. After the fire, a two-year path for remediation was laid out, and production was moved to another building, and waste disposal operations began. Cleanup activities were completed on October 18, 1971, and by 1972, all manufacturing was transferred to building 707, with 776 and 777 converted to a waste disposal area. No serious injuries were reported from the fire, apart from one firefighter who inhaled a sizable amount of plutonium and 32 other employees, all of whom were treated for contamination. All were reported to have made a full recovery, although the effects would have been long-term illnesses such as cancer long after the incident. So take that with a pinch of salt. The damage to building 776, 777 would cost upwards of $26 million to dispose and repair. The disaster had a positive change, however, in the way that Rocky Flats operated. The event pushed forward safety system improvements, including the installation of water sprinklers, firewalls to control the spread of fire, and the use of inert gas for plutonium operations to prevent spontaneous ignition. It's just a shame that all that wasn't brought in after the 1957 fire. Thanks for watching. I hope you enjoyed the video. This video is a plainly difficult production. 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