Period+3+-+TMI

 Three Mile Island (TMI)  http://www.atomicarchive.com/History/coldwar/images/tmi.jpg

Three Mile Island is a Nuclear Power Plant located in Harrisburg, Pennsylvania.

Major Details
 * Accident occured on March 28, 1979 at 4 a.m.
 * The first problem was that the secondary, non-nuclear part of the plant failed with a cooling malfunction
 * Then the main feedwater plant stopped running, which meant that the steam generators shut off
 * After the heat rose, the pressure in the nuclear section of the plant rose, which caused the operator to open the relief valve, but it failed to shut off after the pressure went down
 * Resulting from the open valve the cooling water poured out from the open valve and caused the reactor to overheat
 * As the coolent flowed through the pressurizer, the instuments became confused and gave back crazy readings showing the core was pressurized when it was not
 * This made matters worse because the plant had no clue it was experiencing a loss-of-coolent accident
 * Because there was no cooling the nuclear fuel overheated enough that the zirconium pipes ruptured and the fuel pellets began to melt
 * The authorities were caught off-gaurd and were not aware the core melted, but were worried about the small amount of radioactive gasses the plant had let off
 * After the gas leak they immediatly knew something serious had happened to the core and tried desperatly to cool it until authorities from Washington D.C. arrived
 * When the experts arrived they knew that the plant needed more coolant, which was applied until the plant seemed in a somewhat stable condition
 * That evening the governor of Pennsylvania Richard L. Thornburgh called for an evacuation of women and pre-school aged children within a five mile radius of the plant to be on the safe side
 * Thoughts of safety ended when a large hydrogen bubble was discovered in the dome of the pressure vessal. The bubble could have exploded or burnt destroying the pressure vessel. Then the containment of the core would have been destroyed and the core would have melt. This worried authorities until March 31 when the bubble dissapeared and the disaster was finally avoided.

Causes
 * There are a number of reasons Three Mile Island occured, but the main causes were:
 * Mechanical Failure
 * Human Error
 * The mechanical failure that "cascaded" into a core meltdown as human errors and other mechanical failures combined to prevent the operators from correctly recognizing the problem and adequately dealing with it.
 * The worst part is there are a number of ways the incident could have been avoided if the operators where more aware of their surroundings
 * The people were under the pressure of making a critical decision and they reacted the wrong way under stress.



Laws or Policies Changed after TMI
 * The accident at Three Mile Island permanently changed both the nuclear industry and the NRC (Nuclear Regulatory Commision) forever
 * Public fear and distrust increased as a result of the event.
 * NRC's regulations and oversight became broader and more robust
 * Management of the plants was scrutinized more carefully
 * <span style="COLOR: rgb(15,0,0)">Many changes have occured to increase safety of nuclear power plants including:
 * <span style="COLOR: rgb(0,12,255)"><span style="COLOR: rgb(15,0,0)">Upgrading and strengthening the plant design and equipment requirements
 * <span style="COLOR: rgb(0,12,255)"><span style="COLOR: rgb(15,0,0)">Human performance evaluations
 * <span style="COLOR: rgb(0,12,255)"><span style="COLOR: rgb(15,0,0)">Regular analysis of plant equipment preformances and inspections
 * <span style="COLOR: rgb(0,12,255)"><span style="COLOR: rgb(15,0,0)">Expansion of NRC's resident inspector program where at least two people live or work nearby to watch plant activity
 * <span style="COLOR: rgb(0,12,255)"><span style="COLOR: rgb(15,0,0)">Strengthening and reorganization of enforcement as a separate office within the NRC
 * <span style="COLOR: rgb(0,12,255)"><span style="COLOR: rgb(15,0,0)">The establishment of the Institute of Nuclear Power Operations (INPO), which is a group that makes a unified approach to generic nuclear regulatory issues
 * <span style="COLOR: rgb(0,12,255)"><span style="COLOR: rgb(15,0,0)">Lastly installing additional equipment to deter accident conditions and to moniter overall plant status

<span style="DISPLAY: block; FONT-SIZE: 170%; FONT-FAMILY: Arial,Helvetica,sans-serif; TEXT-ALIGN: center"><span style="COLOR: rgb(0,20,255)">References http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html http://wiki.answers.com/Q/What_were_the_causes_of_the_Three_Mile_Island_accident    http://www.world-nuclear.org/info/inf36.html


 * Comments:

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