Three Mile Island

By peknazellena

  • 6:00 am

    6:00 am
    • A reaction in the overheating reactor core damaged the fuel rod cladding and the nuclear fuel.
    • An operator, arriving for the start of their shift, noticed the irregular temperature of one of the valves, so used a backup valve to prevent any further leakage of coolant.
    • Thus far, more than 100,000 liters of coolant had leaked.

  • 6:45 - 7:00 am

    6:45 - 7:00 am
    • 6:45 AM: Radiation alarms started ringing due to detectors finally registering the contaminated water.
    • 6:56 AM: A site-wide emergency was declared.
    • Image: A Three Mile Island employee has their hand checked for radioactive contamination

  • 10:30 am

    10:30 am
    • 10:30 AM: Three Mile Island’s owners, the company Metropolitan Edison (MetEd), had released a statement insisting that radiation had not yet been detected off-site.
    • 11:00 AM - 5:00 PM: MetEd consultants vented radioactive steam from the plant.
    • This material was said to have a short-half life and was ‘biologically inert’ so did not pose a threat to the public.

  • 4:15 - 5:20

    4:15 - 5:20
    • 4:15 AM: The leaking, contaminated water ruptured its tank and spills into the surrounding building.
    • 5 AM: This released radioactive gas into the plant and the atmosphere. The degree of contamination not lethal, but increased the threat posed by the incident. Efforts were taken to protect plant workers. Meanwhile, the core’s temperature continued to rise.
    • 5:20 AM: Two pumps around the core were turned off, contributing to the buildup of a hydrogen bubble in the reactor.

  • 8 pm

    8 pm
    • The plant’s pumps were turned back on, and water was passed around the reactors again, lowering the temperature and easing the pressure levels.
    • The reactor was brought back from the brink of total meltdown: at its most volatile, the core had reached 4,000°c, meaning it was 1,000°c – or about an hour of continued temperature rise – from meltdown.
    • The core was partially destroyed, but it hadn’t ruptured and didn’t appear to be leaking radiation.

  • 4:00 am

    4:00 am
    • Increased reactor temperature and pressure in Unit 2 led to a pressure valve opening - it then ‘scrammed’ - control rods were lowered to stop the nuclear fission reaction.
    • The valve didn't close, as it should, when the pressure dropped. Contaminated cooling water leaked from the open valve, filling the surrounding tank and the nuclear core temp continued to rise.
    • The emergency cooling system activated, but operators misinterpreted their readings and shut down the backup cooling system.

  • 8:00 - 9:00 am

    8:00 - 9:00 am
    • 8:00 AM: News of the incident had leaked beyond the plant by this point. The Federal Emergency Management Agency had started to put an evacuation plan into action but had cancelled it by around 8:10 am.
    • The state governor, Dick Thornburgh, also contemplated ordering an evacuation.
    • 9:00 AM: Journalists and news crews started arriving at the scene.

  • 8:00 - 11:45 am

    8:00 - 11:45 am
    • 8:00 AM: More radioactive gas was vented from the plant during the continued cooldown operation. A plane monitoring the incident detected contaminants in the atmosphere.
    • 10:30 AM: Governor Thornburgh’s staff insisted local residents didn’t need to evacuate but should shut their windows and remain indoors.
    • 11:45 AM: A press conference was held in Middletown, in which officials suggested that a bubble of potentially volatile hydrogen gas had been detected in the pressure vessel of the plant.

  • 12:30 - 1:00 pm

    12:30 - 1:00 pm
    • 12:30 PM: Governor Thornburgh advised that pre-school children and pregnant women evacuate the area, closing various local schools.
    • This, amongst other warnings and rumors, triggered widescale panic. In the following days, some 100,000 people evacuated the region.
    • 1:00 PM: Schools started to close and evacuate students from within a 5-mile radius of the plant.

  • The China Syndrome & Jimmy Carter

    The China Syndrome & Jimmy Carter
    • No oxygen in the pressure vessel = slim likelihood of the hydrogen bubble exploding. The bubble was vented and reduced and the threat of meltdown was brought under control.
    • The China Syndrome, came out in March of 1979. The film dealt with the aftermath of nuclear meltdown. The nuclear industry dismissed the plot as far-fetched and claimed meltdowns were almost impossible.
    • President Jimmy Carter, in a bid to abate the public’s fears, visited Three Mile Island and toured the control room.

  • 1985 - 2019

    1985 - 2019
    • The huge cleanup operation of Unit 2 took over 11 years, finishing in 1990, and cost $973 million. The damaged reactor was permanently closed and entombed in concrete. 15 tons of nuclear waste was removed.
    • In 1985, while the clean-up continued nearby, Unit 1 started operating again and was ranked the most productive nuclear power plant in the world by the decades end.
    • The plant was shut down on 20 September 2019, having failed to turn a substantial profit for several years.