A Brief History of: The Sodium Reactor Experiment Accident (short Documentary)

the journey of atomic power has left many a disaster by the roadside has different designs and working principles were tried out as well as the odd human error the subject of his video is an incident that would push forward reactor operation experience albeit at the expense of a partial meltdown it seems about a certain place keeps on popping up in the comments sections of my videos and after reading the title venue atomic aficionados will have a pretty good idea of where I mean today we are looking at the sodium reactor experiment at the infamous Santa Susana field laboratory trust me we'll be looking at this place as a whole in another video as there's too much to talk about in this one video about the sre the sodium reactor experiment was a proof-of-concept for a type of reactor that made use of liquid sodium as a coolant instead of the more common water the experiment sought to be able to provide enough heat for use in commercial electricity generating applications the benefits of this type of reactor is that the coolant does not act as a moderator as well as not needing the coolant to be held under pressure as liquid sodium has a wider total temperature range to water 785 K compared to a hundred K in a water-cooled reactor the water has to be held under pressure to avoid the coolant boiling off but before we get into the technicals let's have a brief history of the Santa Susana field laboratory which is where the sree was located BSS FL which is around here on a map was a government testing facility between 1949 and 2006 the site was used for testing of Rockets space program equipment most notably for the Apollo missions and what you are all here for nuclear reactors the site was divided into areas called 1 to 4 and also had to buffer zones the site was selected due to its remoteness somewhere away from the prying eyes of civilians and to reduce the risk of contaminating any populated areas due to the risk of explosions and the like in total 10 reactors were opened at Santa Susana over the years and along with them came various atomic related endeavors for example a fuel fabrication facility a hot lab used for cutting up a radiative fuel and possibly one the worst ideas ever an open sodium burn pit where radiated in chemically contaminated items or just burned in a massive open fire pit oh and the hot lab also caught fire at one point as well pretty much a massive radioactive dumpster fire the sites reactors which work is sitted experimental didn't have any type of containment in their buildings so you know the big fit concrete walls and domes that most modern reactors have so that was also a great idea for sites when it was wound down in 2006 created a horrendous headache that still continues today in terms of the cleanup efforts and as always with the internet the place has some pretty hilarious Google reviews now that we've addressed the wider area about the SRT was placed in let's finally get on to the subject of this video now plans to test liquid sodium called graphite moderated reactors were announced in 1954 by the Atomic Energy Agency and construction began on an atomic international designed facility the reactor was designed to be a flexible testbed for various different types of fuel materials and different levels of enrichment as well as experimental types of cell cladding construction began in 1955 and local energy company Southern California Edison installed a six point five megawatt steam electric power generating plant to make use of the heat created by the experiment the reactor building of the SL ecosystem of a high bay area a side bay area and a hot sell facility the side bay contained in control room administrative offices electrical shop and air conditioning equipment the high bay area known because of its high roof house the reactor and its primary and auxiliary cooling systems a new fuel storage irradiated fuel storage a fuel handling machine and a moderator handling machine which handled the graphite moderator cans the reactor undertook controlled fishing for the first time in April 1957 and in November a small town called Moorpark became fully powered from the reactor albeit for just an hour the design was different to most modern reactors as the whole unit was built in place instead of being prefabricated the reactor containment structure consisted of free main part and was below ground level the first of which was the cavity container the Catena was the outermost containment vessel for the reactor and was 23 feet high and 14 for eight inches in diameter and was constructed of quarter-inch carbon steel the cavity liner was bolted to a wall surrounded by four foot feet concrete forming the biological shield and the support for the whole reactor next came the outer tank made of quarter-inch vic alloy steel this vessel was 18 feet 11 inches high with a diameter of 12 feet six inches it was sealed to the cavity liner and underneath sat on insulated blocks a space created by li insulated blocks is called the insulation cavity and was filled with nitrogen gas to prevent the coolant from coming into contact with the outside air in the event of a coolant leak the outer tanks main job was to act as a secondary containment of the sodium coolant and finally is the core tank this was where the reactor core was situated and was sealed to the outer tank at the top of the tank helium was held under a pressure of free psi this was known as the cover gas excess gas was sent to a waste gas decay tank this is to stop contaminated guess is leaked into atmosphere the core tank was made of one and a half inch thick stainless steel and had a diameter of 11 feet three inches on top of this was the top shield plug which sat inside a ring shield this was rotatable and weighs 75 tons the top plug had 81 small plug holes and two 40 inch and 120 inch larger holes the SL reused graphite as its moderator this was used to slow down the neutrons to get more use out of fuel elements the graphite moderator elements consisted of hexagonal blocks just under 11 inches wide and around 10 feet high please were known as cans each cam was placed 11 inches center-to-center from one another allowing a small gap between each can for coolant to flow the gap was approximately point 0 1/3 of an inch the moderator cans were wrapped in zirconium alloy sheets to help enforce spacing as well as protected the graphite from the sodium penetrating it aside about to core there was space for 119 cans however not everyone was for a moderator around the outside of the core where reflector cans these were used to reflect stray neutrons back to all center of the core fruity reactor core an 81 vertical tubes please we use for fuel safety and control words and were accessible via small plugs on top of the rotating shield plug right whilst we're on the subject let's talk about the fuel assemblies and how they were made up each filled assembly is made up of seven fuel rods each rod was six feet long and had 12 fuel slugs inside each fuel assembly was lowered through one of the 81 openings in the reactors top shield and inserted into the core region of the reactor each assembly had a hanger rod connector on top of it there were in total 43 fuel rods used to in operation reactor had eight control rods four V's were safety rods which formed the automatic shutdown facility known as scram these rods contained a boron on nickel alloy the Scramble says he was controlled automatically but also had the ability to be activated by operators from the control room to enable quick activation of the scram facility the safety rods are held out of the reactor by magnets if disengaged the rods would enter the core by the power of gravity and during normal operation the safety roads were not inserted into the core region next we have for more control words bees were split into two groups of two but they did very similar actions and were limited in their total movement whilst the reactor was in operation the first amis were called the shim rods these were used for fine regulating adjustment of the power of the reactor the next two were regulating rods and these were use unsurprisingly to regulate the power of the reactor these were limited in their movement to only seven inches by the reactor control system the four rods are used to manage the Neutron population of the reactor core during operation I didn't have a scram facility but they did help keeping the reactor under control and when a main mechanism for safely bringing the reactor to initial criticality during start-up like the safety control was the regulating rods contained a boron nickel alloy right the final bit of the reactor I'm going to cover is the cooling system using liquid sodium had its benefits for instance not being a moderator however it had one big drawback veliko sodium becomes extremely dangerous when exposed to water or air by ever exploding or catching via the liquid sodium coolant was split into two parts a primary and secondary loop the reason for the two cooling loops is to prevent contamination due to the primary loop being in contact with directed materials inside the reactor the primary loop circulated around the reactor vessel taking with it heat from fission and passed through a heat exchanger inside the heat exchanger the primary loop coolant passed through metal tubes this in turn warmed up the liquid sodium inside the nonreactive secondary loop after miss the secondary loop coolant made its way for a steam generator which in turn powered a turbine connected to a generator if a leak in the secondary loop became apparent for use of two loops reduce the risk of radioactive sodium being released Reaktor didn't operate continuously due to the experimental nature of the project instead it was operated in runs in between each run data was reviewed and the reactor components were examined for potential improvements the operation of such a reactor as the sre meant that the operators were working to what could be done in theory however theoretical and operational realities were not the same thing and this would be found out over each subsequent run the first seven power runs between the 7th of July 1957 and the 25th of September 1958 soared a successful generation of electrical power as well as a number of tests involving checking out the effectiveness of the scram facility before run eight the primary sodium was pumped back and forth several times between the primary loop and its primary fill tank this introduced sodium oxide to the primary loop and ran the risk of causing blockages in the system during one eight operators noticed worrying inconsistencies in Inlet and outlet coolant temperatures this was put down to the oxide buildup in the coolant channels and on temperature sensors the reactor was shut down and the coolant was filtered and fuel rods 9 and 10 were removed for inspection as had been running too hot upon removal the rods were contaminated with a black residue very prominent and reinserted into the reactor core for a remainder a power run eight things didn't go to plan erratic temperatures sodium oxide in the core and the eventual confirmation of tetra lien in the primary loop showed that disaster was just down the road runs nine to twelve continued to be plagued with erratic Inlet and outlet temperatures and more black residue was found on fuel elements this leads us on to power run 13 the penultimate before disaster the run took place between the 27th of May and 3rd of June 1959 on a 29th of May a scram was triggered due to poor sodium flow rate the next ad reactor was restarted but things would go dramatically downhill from there after 113 again a number of fuel sales were examined and deemed to be contaminated enough to warrant cleaning but it chillin on the sales had blocked drain holes allowing some sodium to become trapped risk would not have great outcome whilst in the wash cell which was an area near the reactor around 18 US gallons of water came in contact with the trapped liquid sodium and the inevitable happened the explosion lifted the washed shell ceiling plug 18 feet into the air it was later found that no one had actually installed to hold down clips properly juicy explosion no more fuel cells were washed leading up to run 14 the confirmed tetryl in contamination had to be addressed this would be quite a large undertaking as nitrogen gas had to be bubbled through the primary sodium loop in preparation for a nitrogen gas purge all helium inside the reactor had to be removed and replaced after completion at 6:50 a.m. on the 12th of July the reactor has brought into criticality for run 14 the operators were cautious during start-up reaching only 500 kilowatts at 8:55 small but outer speck temperature fluctuations began within the moderator this was expected due to the Tetra lane contamination and operators saw similarities from runs eight to twelve fuel channel exit temperatures which normally should be similar began to diverge meaning that there were cooling blockages the power level of the reactor was kept below 1 megawatt however 1142 the primary system automatically initiated a scram this was due to a loss of auxiliary primary sodium flow just over half an hour later the reactor was restarted at 12:15 and for the next few hours the power was increased to 2.7 megawatts around 3 p.m. something worrying was discovered an increased radiation level in the high bay area of the reactor building the pressure on the cover gas was reduced to try and slow down any leak a member of staff in protective clothing entered the high bay area to take readings to try and locate the source of the radiation a measurement of 500 milli REMS an hour was discovered over the shield plug near channel 7 by 5:00 p.m. 25 REMS an hour was recorded over channel 7 after the replacement of his shield plug and at 5:30 p.m. the reactor was shut down the next day on the 13th the reactor started to act even more erratically by experiencing and of excursions and rows in power without any operator action at 528 p.m. the reactor was set at one point through megawatts and as the operators gradually try to increase power the levels went higher than expected the controllers who inserted to try and get back control over necks our operators struggled to keep control over the fluctuating power as 6:24 p.m. s Ari's power level began doubling every eight seconds the operators manly scram to the reactor at 6:25 p.m. for the next few days the reactor was started up and shut down several times as power excursions and erratic temperatures were recorded on the 23rd at 9:50 p.m. the reactor shut down automatically due to an indication that the power was increasing too sharply it was restarted again at 10:15 p.m. the 24th saw some rather dangerous behavior has operated attempted to try and free up blockages in some of the fuel channels by jiggling the fuel elements up and down however four elements seemed to be stuck in place again the sre was shut down automatically at 1250 due to an uncontrolled increase in power however the indication of fuel cell damage was ignored by the operators who had been convinced it was a faulty signal he reacted continue to act erratically and on the 26th it was shut down for inspection of the fuel elements that had shown highest temperature increases a camera is inserted into the troubled fuel channels and the results were whirring a total 13 fuel elements have been damaged and whilst removal for inspection took place channel 69 s rod broke off leaving over half of its stuck inside the reactor core but damage had been done over the course of run 14 and numerous chances to prevent disaster were IVA ignored or avoided multiple missed opportunities meant that the experimental reactor released radioactive elements into the building housing the unit it will be later thought that the main fuel cell damage took place after the 22nd of July but signs were clear to see in the parens leading up to the event how is easy to say this after finishing reading a report into the whole event sixty years after the fact it's important to note that clearly unsafe practices by today's standards such as wiggling fuel rods were not really thought of like that in the late 1950s and whilst operating an experimental reactor radioactive materials were released from the damaged fuel cells to the sodium coolant and in turn to the helium cover gas the cover gas would run for a filter and was stored into decay tanks before being vented to atmosphere an internal document produced after the event stated that over a two-month period around 28 careese oarfish and gases were released into the atmosphere which was within federal government limits however conflicting reports claimed that up to 6500 Curie's of iodine-131 and 1,300 Curie's of caesium-137 were released but the poor data collection and recording at the time means it's very hard to know for certain how a rocket Dean at the time claimed nothing was released which does seem a bit hard to believe due to lack of proper confinement about the s re building hat now you think this might have spelled the end for the s re but if you did you'd be wrong as the whole reactor building was cleaned up and pressed back into work in 1960 albeit with a new and improved reactor core the event damaged around a quarter of the reactor core and many lessons will be learned from this including improvements to the sodium circulation system wash cells use steam instead of water it proved cladding alloys and better fuel geometry was utilized the sree was shut down and decommissioned finally in February 1964 the cleanup of the experiment was rolled into the wider cleanup efforts at Santa Susana field over the coming decades due to nature of the field laboratory so much contamination both chemical and radioactive has been reported over the last 60 years I mean it's pretty much expected when open sodium burn pits were used at the site this makes it very difficult to pinpoint the damage to the environment caused by just one of the reactor incidents on the site over the years in 2006 a board made up of independent doctors and scientists Rover over the years around 260 cancer related deaths are linked to the test laboratory as a whole the same panel also concluded that the SRA meltdown released 458 x him of radioactivity released into the atmosphere by the free mile island accident even early event actually created 10 times less contamination this was due to a lack of confinement buildings at the site and other experimental reactors bearing in mind that the TMI accident was fairly well contained within its confinement building however this is widely disputed in several conflicting reports so you may have to believe what you want on this one for cleanup efforts at Santa Susana as a whole still continue to this day as all sorts of nasty materials have to be safely removed and disposed of but miss will most likely be a subject of a future video as the SRE incident is only scratching the surface thank you for watching I hope you enjoyed the video I wasn't expecting this one to be this long but there was just too much to cover would you like to see my videos before we're up on this channel then you're in luck as for $1 / creation on patreon you can do you have any future video suggestions let me know in the comments I've got a Twitter so check me out on there and always left to say is thank you for watching

Channel: Plainly Difficult

Views: 1,522,697

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Id: 7-NKdWV5SCg

Length: 20min 11sec (1211 seconds)

Published: Thu Mar 05 2020