The shutdown of the Three Mile Island (TMI) reactor #2 involved the successful insertion of control rods despite significant core damage. The reactor was scrammed before overheating, allowing control rods to be inserted without obstruction. In cases of reactor cooling, boron can be utilized, as demonstrated in the Fukushima incident where borated seawater was employed to maintain subcritical conditions. The TMI reactor core was removed from the site years ago, and the containment structure was designed to withstand extreme conditions, although it did sustain damage during the incident.
PREREQUISITESNuclear engineers, safety analysts, and anyone involved in reactor operations or emergency response planning will benefit from this discussion.
FishmanGeertz said:I believe that a cooling valve at the TMI NPP malfunctioned, closed, and water was unable to flow to the core. And this valve had malfunctioned at least a dozen times at other plants.
FishmanGeertz said:I believe that a cooling valve at the TMI NPP malfunctioned, closed, and water was unable to flow to the core. And this valve had malfunctioned at least a dozen times at other plants.
Morbius said:Fisherman,
There are no valves in the TMI cooling system that when closed prevent coolant flow.
The valve in question failed in the open position after it relieved a pressure spike. The continued outflow from that valve dropped the pressure in the TMI primary system. As the pressure went down, so did the boiling point of the water. It got to a point at which the temperature in the core which is not high enough to boil the water at nominal pressure was able to boil the coolant at the reduced pressure. The core was being cooled by a two-phase mixture of steam and water.
However, the core was undamaged at that point, and the TMI accident was totally reversible up to 90 minutes into the accident. It was at that time that the operators, who were unaware of the fact that the coolant was boiling because they never checked their steam tables, decided that the primary coolant pumps should be stopped because they were making strange noises.
Those strange noises were a badly needed clue that the operators ignored. The reason the pumps were complaining is because they were pumping a two-phase steam and water mixture. The operators missed that.
They decided to "save" the pumps, and in so doing "lost" the reactor.
Dr. Gregory Greenman
QuantumPion said:Not only did they turn off the reactor coolant pumps due to cavitation, but they also turned off the automatically-actuated safety injection pumps because they thought the system was TOO full of water (due to the pressurizer level indication).