A Brief History of: The Three Mile Island Accident (Short Documentary) (Part 1)

[Music] it is 228 of March 1979 James Callaghan loses a vote of no-confidence by one MP in Westminster laying the path for a fat check govern and in Londonderry Township Pennsylvania a reactor cooling malfunction would cause the USA's most significant commercial reactor incident as you may know I've covered free of the four international nuclear Event Scale level five incidents on this channel and today completes the set as we will look at the free mail Island incident if you want to know more about the I in ES and you can click here for a video I did about it don't worry I'll wait for you the accident would lead to clean up efforts running well into the early 90s costing around 1 billion dollars Vincent although not directly to cause saw the end of a historic growth of the atomic energy industry in the USA and it would spare on a growing anti-nuclear movement in a bizarre coincidence the event would take place only a number of days after the release of the film but China Syndrome which is based around a nuclear reactor accident a free Mile Island nuclear generating station or TMI for short up until just a few weeks ago at the time of writing a script was a nuclear power station based in Pennsylvania on a sandbar next to the Susquehanna River which is here on a map being just free miles downstream from Middleton Pennsylvania with a population of around 9,000 it was decided that a nuclear power station would be beneficial to the region being close to Harrisburg York and Lancaster metropolitan Edison owned by General Public Utilities began construction of TMI 1 on the 18th of May 1968 a pressurized water reactor designed by Babcock & Wilcox with a net generating capacity of 819 megawatts going online in 1974 who acted was built with a cost of around 400 million which is equal to around 2 billion in today's money TMI one would have a relatively trouble-free career up until 2019 apart from a couple of incidents one which was a radiation release into the reactor containment building with 20 workers being treated for mild radiation exposure another incident involved someone driving into the site eventually being apprehended in the turbine building which sounds like a great subject for a future video however this video isn't really about TMI one and instead the ill-fated TMI two construction began on TMI 2 on the 1st november 1969 unit 2 was similar in design to the original reactor however it boasted an increased output of 906 megawatts construction was delayed due to running over budget at 700 million in 1978 money due to delays the reactor wasn't brought online until 34 December 1978 a combined power generating capacity of both TMI 1 and TMI 2 was around 1700 megawatts or enough to electrically supply 300,000 homes the reactor was a PWR type like TMI one however just four months after commissioning disaster would strike but before we get into that let's look at how the reactor at TMI 2 works now I'm a fan of an ie a report both of my commute is spent reading either one of those or an RA IB report I know I live an exciting life so because of my not at all boring reading habits needs to say mattress videos based on the IAEA report but a free Mile Island incident right so TMI 2 reactor was of a pressurized water type and it produced steam from heat created from fission to drive a turbine to generate electricity to be distributed to the public you had to use uranium oxide as its fuel source inserted into the reactor core via fuel rods and the reactor also had control rods with a scram facility TMI too used free calling circuits the first or primary circuit circulated water through the core acting as a moderator by letting neutrons undergo multiple collisions with the light hydrogen atoms in the water towards use in the PWR is simply ordinary water but does not contain large amounts of dilute reom making it distinct from heavy water used in reactors like the nrx in Canada the primary circuit picks up heat from fission and carries it out of the core to two steam generators inside the 30 feet two generators is many small diameter tubes of which primary water flows the heat for the primary water inside the tubes is used to boil the secondary circuit of water inside the generators creating steam being sent to the turbines after being used to turn the turbine blades the steam from the secondary circuit is condensed in a condenser called by a novel water circuit using the site's iconic cooling towers for use again all the water circuits are kept separate to stop any radioactive cross contamination meaning the primary circuit is the only one to have direct contact with the reactor core also to prevent the primary circuit from boiling the water is kept our high pressure of around 2200 PSI connected to the primary circuit our pressurizes filled about halfway full of water with a steam cushion on top the pressure in a system can be controlled by Eva heating up the electric heaters or cooling down with a water spray on the pressurizes miscibility to change the pressure can be done either by the control system or the plant operators to Brent over pressuring the pressurizer a pilot relief valve is provided if this valve is open to relieve pressure steam and or water flows into a drain tank to prevent the tank from over filling a rupture disc is provided the redundancy and extra valve is provided in case the relief valve becomes stuck this extra valve is called the block valve several hours leading up to the accident the operators were attempting to fix a blockage in a secondary cooling system the system uses eight condensate polishes to filter out any minerals from the water any impurities in the water loop can cause premature damage to the steam generators much like the rubbish you find in your kettle it's not uncommon for the resin from the filters to cause blockages in the system and I usually cleared by compressed air how this time the simple fix was providing more of a challenge compressed air was used to instead blow water through the system to try and clear it up and in doing so pushing water past an open check valve into an instrument airline this would cause a vital piece of equipment to trip out right let's get on to the accident on the 28th for March at around 4 a.m. TMI 2 was operating at 97% whilst TMI 1 was shut down for refueling a secondary cooling system condensate pump tripped out causing it to stop working lacking a water supply the two feed pumps also tripped out due to the pumps on the secondary cooling system being shut down a safety circuit automatically shut down the turbine generators free Oxley Larry feedwater pumps started up as designed these pumps should have been enough to start the turbine generators however valve downstream have been left closed by an earlier test operation duty auxilary pumps not being able to pump water the steam generators were unable to remove enough heat from the primary cooling circuit due to lack of heat reduction from the secondary cooling system the temperature in the primary system increased and subsequently expanded in volume the expansion led to the pressurizer beginning to fill up compressing the steam cushion inside leading to a higher pressure in the primary system four seconds after initial tripping of the condensate pump the pressure in the pressurizer had reached such a level that the pilot relief valve opened as it was designed to do the pressure continued to increase leading to at around nine seconds after initial pump trip four Cottrell roads being inserted into the reactor shutting down the chain reaction the shutdown caused the pressure in the primary system to decrease operators were expecting this to happen and in currents with the rules and procedures turned on the high pressure injection system would you rectus shut down and a relief valve open the pressure continue to drop off so far so normal however at a certain point once the pressure was sufficiently low enough the valve should have closed stabilizing the pressure on this occasion however the valve stuck open causing more and more pressure to be lost in the system as steam and water escaped through to stuck open valve with not enough pressure in the primary system staying started to generate inside the reactor core which it was not designed to accommodate and in turn started to fill the pressurizer with water thinking that the system was filling with water and accordance with their rules and procedures the operators switched off the pressure injection system as an attempt to prevent the overflow of water however pressure continue to rise inside the system due to the steam buildup inside the reactor core with the pressurizer filling with water and pockets of steam forming inside the reactor core cooling channel's the heat increased the fuel cladding temperature the operators had a confusing event unfolding in front of him something that they hadn't trained for rising water level in the pressurizer and a decreasing primary system pressure this was due to the lack of proper instrumentation inside the control room the control room had some confusing design quirks one of which being the indicator light for the pilot operated valve the one stuck open allowing coolant to escape a light was provided to signify the status of the relief valve light on means open light off means closed well that wasn't the case the operators weren't aware that the light only signifies the state of the electronic solenoid as the bulb was white at circuit when the valve was working correctly the light bulb would give an indication as echo power to the solenoid reversing the valve to a closed state and the operators had been conditioned to think light off valve closed herve this morning the valve had a mechanical issue meaning it was stuck open but power had been cut to the solenoid extinguishing the indicator bulb giving an assumed closed valve state to the operators whilst the confusion in the control and continued water had begun to fill up the drain tank eventually causing the rupture disc to burst water and steam from the reactor was now being ejected into the reactor building unknowing of this the operators continue to try and managed to rising water level in the pressurizer at around eighty minutes into the incident the primary loops for pumps began to cavitate from the water and steam mixture to try and counteract this the pumps were shut off it was fought when the water would continue flowing through the core from natural circulation however the steam buildup in the core prevented this and in turn caused the trap water to boil itself creating more steam with the pumps running there was just enough water cooling for the core however without this forced flow of water there was nothing stopping the fuel from being damaged by overheating the operators tried several different passages to try and get a hold of the situation however the stuck valve was still not discovered but Fiona steam filled regions of the core boil dry heating to temperatures high enough to create a chemical reaction the dessert calorie cladding anestine producing as a by-product hydrogen which we will look at later the fading cladding allowed uranium dioxide efficient product to escape and after mixing with hydrogen water and steam were expelled into reactor building by the stuck valve and broke a rupture disc thanks for watching part one I'm hoping to get out part two really soon if you get a chance to check out my teespring store as well as my patreon for early access to videos and always left to say is thank you for watching and I'll see you back here shortly [Music]

Channel: Plainly Difficult

Views: 1,278,912

Keywords: three mile island, nuclear history, atomic history, education, history, plainly difficult, atomic, chernobyl, qxir, zepherus, learning education, the demon core, demon core

Id: oXxeHNA2JcE

Length: 11min 59sec (719 seconds)

Published: Thu Nov 14 2019