A Brief History of: The SL-1 Reactor Accident

this subject was suggested to me and i thought it was too interesting to pass up so i paused what i was doing and started to focus on this thank you for the suggestion it is likely that you may have discovered my channel from one of my nuclear disaster videos this story is most definitely not the deadliest i've covered in terms of environmental impact however it deserves to be remembered as it was the only nuclear reactor incident in the u.s that resulted in immediate deaths with one of the fatalities being impaled by a shielding plug to the ceiling the sl1 was an experimental nuclear reactor and stood for stationary low power reactor number one the idea for the reactor was part of a series of experimental nuclear power plants for use in remote radar outposts in the arctic where the only power source had been from diesel generators the army had been evaluating their use of diesel generators between 1954 and 1955 and decided on a more effective replacement the army reactors branch contacted the argonne national laboratory who had a proven track record in reactor development on the manhattan project to design build and test a prototype reactor the army has set out a shopping list of requirements for their new low power reactor some of the more important attributes were simple reliable easy to build operable in the harsh arctic environment must be air transportable all components limited to package sizes measuring 2.2 by 2.7 by 6 meters and no heavier than 9.1 kilos to use minimal proprietary parts and finally each call loading to have a three-year life cycle the prototype will be built at the national reactor testing station in idaho falls idaho which was pretty isolated with ground being broken in july 1957 after a year almost to the day july 1958 saw the construction complete and going critical in august and finally up and running in november with it formally being opened on the 2nd of december the reactor was held within a 15 meter high cylindrical building made out of quarter-inch steel and was known as ara 602 with a condenser fan room near the top of the building access to the plant was via a door through an enclosed stairwell from ara 603 the support building there was an emergency exit leading out to external stairs to ground level the reactor was embedded in gravel at the bottom the building didn't have the same protections as a plant in a built up area but it was thought that any incident could be contained within the main structure the reactor would use a boiling water design and used 93.2 percent highly enriched uranium fuel which would use light water in a natural circulation cycle for cooling the water system flowed through fuel plates of uranium aluminium alloy under a pressure of 300 pounds per square inch the reactor was built to house 59 fuel assemblies one source and nine control rods however in general operation it only used 40 fuel and 5 control components many of the blank spaces used dummy rods which were later fitted with test sensors after testing the reactor was handed over to the army for operation and training experience and combustion engineering incorporated working as the lead contractor from february 1958 many different personnel would train on the reactor from both military and civilian organizations with the plant operated by two crew members with cei staff monitoring any developments being able to step in as necessary as the reactor aged boron strips corroded and flaked off and by 1960 the cei had calculated that 18 had been lost within the core of the reactor in november 1960 cadmium sheets were added to try and bolster the corroded boron leading up to the christmas on the 21st december 1960 the reactor was shut down for maintenance for 11 days during this time the instruments were recalibrated and extra auxiliary components were installed flux wires were also installed these were used to monitor the neutron flux levels within the core on the 3rd of january 1961 the reactor was being readied by a free-man team in preparation for it to be brought back online each man was in their 20s and consisted of army specialists john a byrons richard leroy mckinley and navy cb construction electrician first class richard c legg as the team worked on the reactor two false fire alerts would be triggered both of which were responded to by the fire department part of the maintenance process meant that the main control rod in the center of the core had to be withdrawn manually to be reconnected to its drive mechanism as the evening drew in all three men were inside the reactor room with byron's and mckinley at the side and legs standing on top of the structure supervising the movement of the control rod at one minute past nine in the evening john byron's withdrew the control rod too far and were four milliseconds the rod became critical instantly creating enough heat to melt the fuel within the core vaporizing it as the heat caused the fuel to expand a pressure wave was ejected out of the reactor creating a water hammer which in turn lifted the whole reactor 2.77 meters in the air richard legg who was standing on top of the structure became impaled to the ceiling by one of the shield plugs which had been traveling at a speed of 26 meters a second a high pressure spray of radioactive steam water hit the two men who had been working to the side of the reactor killing byrons instantly and severely injuring mckinley from the control rod going critical to complete destruction only took between two and four seconds another fire alarm for the day was sounded and a slightly annoyed fire crew of six men turned up at first it seemed like another false alarm with the main building intact from the outside with only a little bit of steam emanating from the roof however as the crew moved towards the building and upon entering the stairwell they found their radiation gauges were going haywire the fire crew immediately retreated and after consulting with a doctor made a plan of spending no more than a minute for each person inside the structure to limit the exposure initially one crew member and a health physicist wearing protective equipment and gas masks attempted to enter the building however they were drew after seeing 25 rotagens on their radiation meters at 10 30 pm a supervisor working for the contractor cei and the head health physicist arrived on the scene and entered the reactor building at 10 45. two of the men were found soaked in radioactive water with byron's dead and mckinley slowly moving and groaning from a head injury prioritizing mckinley the rescue team focused on trying to save the injured operator with only one entry at one minute per person it would take until 10 50 before they could successfully place him on a stretcher and remove him from the structure mckinley would not regain consciousness and would succumb to his wounds at 11 pm although dead his body was still deadly measuring gamma radiation at 500 rotations an hour even after being stripped of his contaminated clothing it would take until 11 38 pm for the discovery of the final victim richard legge whom had been impaled to the ceiling above their heads after the discovery of all the victims the rescue efforts slowed down as to protect the safety of the recovery team the next night byron's body was recovered by a team of six volunteers it wouldn't be until the 9th that an attempt could be made to recover leg's body the process to remove leg's body would be practiced in the safety of the dugway proving ground as it would involve a 1.5 by 6.1 meter stretcher attached to a crane this process would take 10 men each working in intervals of 65 seconds to pull leg's body off the shield plug by using hooks on long poles eventually his body became free and fell onto the stretcher suspended from the crane originally it was thought that the disaster was caused by a chemical explosion believing the reactor to be safe however gold watch worn by one of the operators showed evidence that the buckle had reactive gold and other items in the men's possession showed neutron activated element the bodies had to be treated as if they were nuclear waste due to their potential for polluting the environment and were buried in lead line coffins placed inside metal vaults with some of the more radioactive parts being buried in the idaho desert with other nuclear waste the cleanup efforts would take 475 people 18 months it was decided that to transport all the contaminated waste to the radioactive waste management complex 16 miles away would cause too much risk of radiation exposure as the journey would travel over public roads instead a burial site was established 500 meters from the reactor the first main hurdle was cleaning up the contaminated reactor room of all dangerous materials once this was done a 60 ton crane was employed to remove the reactor vessel from the building as a reactor building was deconstructed any contaminated materials got disposed of in the burial site however any parts of the structure and reactor core that would be needed in a later investigation were sent separately to the aircraft nuclear programs hotshot inspection center after which were sent to the radioactive waste complex in total after completion of the cleanup efforts in september 1962 2800 meters of dangerous material was placed in the burial site up to a depth of 4.3 meters with half a meter of clean soil placed above the site is now known as united states environmental protection agency operational unit 5-0-5 the cause of the incident would be a mystery over the following two years of the investigation they knew the reactor went critical but they didn't know why the control rod was pulled out so far maintenance procedures stated that the rod would only be needed to be manually moved 10 centimeters however it is estimated that byron's actually withdrew it 66 centimeters causing the reactor to go critical setting off the steam and water hammer that would destroy the vessel much of the damage to the building and the impaling of leg was put down to the high pressure water jet initiated by the vaporized fuel using scratches on the control rods and analyzing the newly installed flux wires investigators managed to establish any movement under 58.4 centimeters of the rod would not have caused the reactor to go critical however it would have only taken bayen's 500 milliseconds to move the rod between 58.4 and the eventual 66 centimeters unfortunately he had no time to correct his action however still a mystery was while a rod had been moved over the 10 centimeters needed in the first place as there were no logs made during the process some worrying theories were proposed here are the main theories from least to most likely a suicide murder because of an affair with one of the other crew members wives plain old suicide sabotage accidental withdrawal and finally an attempt to make the rod travel freely within the core by working it backwards and forwards there is some weight unfortunately behind the murder suicide theories as byron's and leg were from the same training class and leg had surpassed him becoming a supervisor and the third of january was the first shift leg had worked being in charge of his old classmate also on the day of the critical event byrons had been informed that his wife wanted a divorce whether an intentional mistake or not it's not unthinkable to think that byron's mind was not on the job at hand the last theory is thought to be the most likely case as the design of the sl1 had an unwanted side effect sticky control rods this meant that over the three years that the reactor was operational 40 events of a stuck control rod had been reported and the number had dramatically increased over the latter part of 1960 with four happening in the month leading up to the incident it was thought that the reason for the problem of stuck controllers were caused by corrosion clutch and drive bearing issues on the rotation assembly in the core and a misalignment issue the rod that went critical number nine was in the center of the core a bearing or clutch issue would be unlikely as sticking only occurred during rotation this would affect the other non-central controllers more even though the cause was highlighted the rapid removal of control rod number nine the reason for the movement will likely still remain a mystery the aftermath of the sl1 incident caused the design to be abandoned and for future reactors to not have the ability to go critical after removal of just one control rod other low power reactors would be made during the army reactors branches project however the outbreak of the vietnam war would divert army resources stopping the program in 1965. during a cleanup around 790 people were exposed to dangerous levels of radiation the area would be monitored for decades to come 32 workers would receive commendation for heroism for their role during the recovery and cleanup operation is lucky that the reactor was situated in a relatively isolated area and the building itself did well to contain a lot of contaminants however in 1995 the environmental protection agency recommended a cap be built over the burial sites as these were still hot spots of radiation the cat was made out of local rocks and rubble and was completed in 2000 thank you very much for watching i hope you enjoyed the video do you have any suggestions for future videos let me know in the comments below help the channel grow by liking sharing and subscribing if you'd like to support the channel financially i also have a patreon and the link is in the description and always left to say is thank you for [Music] watching you

Channel: Plainly Difficult

Views: 1,034,400

Keywords: SL-1, sl1, reactor, nuclear, power, plainly difficult, education, learning, history guy, history, accident

Id: IYle_eI5j78

Length: 14min 17sec (857 seconds)

Published: Thu Nov 15 2018