TMI-2 Core End-State Configuration 1) 2B inlet 2) 1A inlet 3) Cavity 4) Loose core debris 5) Crust 6) Previously molten material 7) Lower plenum debris 8) Possible region depleted in uranium 9) Ablated incore instrument guide 10) Hole in baffle plate 11) Coating of previously-molten material on bypass region interior surfaces 12) Upper grid damage A Hidden Indicator Light…ĭue to the loss of heat removal from the primary loop and the failure of the auxiliary system to activate, the primary loop pressure began to increase, triggering the pilot-operated relief valve (PORV) at the top of the pressurizer – a pressure active-regulator tank – to open automatically. However, because the valves had been closed for routine maintenance, the system was unable to pump any water. Once the secondary feedwater pumps stopped, three auxiliary pumps activated automatically. The reactor continued to generate decay heat and, because steam was no longer being used by the turbine, heat was no longer being removed from the reactor’s primary water loop. Within eight seconds, control rods were inserted into the core to halt the nuclear chain reaction. With the steam generators no longer receiving feedwater, heat and pressure increased in the reactor coolant system, causing the reactor to perform an emergency shutdown (SCRAM). These filters are designed to stop minerals and impurities in the water from accumulating in the steam generators and increasing corrosion rates in the secondary side. The initial cause of the accident happened eleven hours earlier, during an attempt by operators to fix a blockage in one of the eight condensate polishers, the sophisticated filters cleaning the secondary loop water.
In the nighttime hours preceding the incident, the TMI-2 reactor was running at 98% of full power, while the companion TMI-1 reactor was shut down for refueling. The accident began with failures in the non-nuclear secondary system on March 28, 1979.
The only difference was that TMI-2 was slightly larger and received its operating license in 1978.
The Three Mile Island Unit 2 was also a pressurized water reactor similar to Unit 1. TMI-1 is licensed to operate for 40 years from its first run, and in 2009, was extended 20 years, which means it may operate until 2034. The Three Mile Island Unit 1 is a pressurized water reactor with a net generating capacity of 852 MWe, which first came online on April 19, 1974.
The plant was originally built by General Public Utilities Corporation and consists of two separate units. Three Mile Island has got its name because it is located three miles downriver from Middletown, Pennsylvania. Three Miles Downriver from Middletown, Pennsylvania The so-called Three Mile Island Accident was the worst accident in U.S. On March 28, 1979, a partial nuclear meltdown occurred in one of the two Three Mile Island nuclear reactors in Dauphin County, Pennsylvania. A clean-up crew working to remove radioactive contamination at Three Mile Island.