Nuclear Tragedy on Three Mile Island

Nuclear Tragedy on Three Mile Island

The Three Mile Island accident can be attributed to both human error and mechanical failure. This story begins on March 28, 1979 at about four o'clock in the morning. Every thing seemed to be running efficiently down at the nuclear power plant in Three Mile Island. Little did anyone know the catastrophe that was about to occur.

The problem started in the secondary loop. There was a slight malfunction, which caused the pumps to shut down automatically. The alarms sounded immediately within the control room. Water pressure and water temperature began to build in the primary loop, because the heat could no longer be transferred to the secondary loop. However, this seemed normal and was no cause for immediate concern.

At this point, the pressure relief valve (PORV) had opened automatically and released the steam into a holding tank. The backup pumps, which are located in the secondary loop, automatically turned on. Then, the cut-off valves disconnected the pumps from

the system. The operators in the control room still felt that everything was running normal and there was nothing to worry about.

Then, the PORV light went out indicating that the valves were then closed; however they were not. The steam and water continued to be released causing a loss of coolant accident (LOCA). The emergency injection water (EIW) was set in motion in the primary loop. The EIW is activated in the case of a LOCA. This did not concern the operators because it had happened before during numerous false alarms. However, they kept their eye on it, and noticed that the water in the primary loop was rising, while the pressure was decreasing. They turned off the EIW, but the water still appeared to be rising. However, that was not the case at all. The water along with the steam was being released through the PORV, without the operators knowing.

By this time, over three thousand gallons had escaped from the primary loop. The instrument that checks the level of radioactivity levels was not functioning, so the operators had no reason to suspect a LOCA. The gauges in the control room continued to falsely state that the water levels were up.

At this time, two of the four pumps were turned off in the primary loop caused by the amount of pressure from the steam traveling through them. Then, the last two pumps in the primary loop shut off.