Period+8+-+TMI


 * Three Mile Islan[[image:4-1408.jpg width="366" height="194" align="left"]]d (TMI)

//__Major Causes__//

The accident at three mile island was with unit 2 nuclear power plant near middletown, Pennsylvania on March 28 1979. The accident began at about 4 o'clock am on March 28 1979, the plant experienced a failure in the secondary which was a non nuclear section of the plant. One of the first problems they noticed was the main feed water pump stopped running,which was caused by either a machanical or electrical failure, because of this it prevented the steam generators from removing heat from the plant. Immediately pressure in the primary system began to increase. The pressure valuve should close when the pressure decreases but it didn't. The signals to the operator showing that it was open was never sent, and the cooling water came out of the valvue, which caused the reactor to overheat. No instrument existed to show the level of coolant in the core, so the operators judged the level of water by the pressurizer, because it was high they assumed the core was properly covered with coolant. Since there was no clear signal that the valuve was open alarms rang and lights flashed but the operators didn't realize that the plant was experiencing a loss-of-coolant reaction. Actions were made that just reduced the flow of coolant making the situation worse. Since cooling was not available the nuclear fuel overheated to the point where the zirconium cladding( the long metal tubes which hold the nuclear fuel pellets) burst and the fuel pellets melted.

//__Laws and Policies__// **
 * Identify human performance,by doing operator training and staffing requierments, also improved instruments and controls for running the plant, making sure they are fit for the duty, and be checked for drug and alcohol abuse
 * Expansion of NRC's resident inspector program-two inspectors have to live nearby and work nonstop at the plant to provide daily surveillance
 * Regular ananlysis of performance by senior NRC managers who say the plants need regular attention
 * Improved instruction so the workers aren't confused by the signals
 * Expansion of performance and safety oriented inspection, so the risk of vulnerabilities is less
 * Additional equipment was installed that mitigate accident conditions and monitor radiation levels
 * Upgrade of plant design and equipment requirements including: fire protection, piping systems, auxilary feedwater system, and the ablitly for the plant to shut down automatically



Three Mile Island is located on an island that coveres 814 acres of the Susquehanna River in the city of Harrisburg, PA. Three Mile Island is the most widely known power plant in the United States due to the accident that happened to the Unit 2 reactor on March 28 1979. It was immediately shut down due to a coolant accident. It still remains the most signifigant power plant reaction on record in the U.S. The accident lead to enhancement in training procedures and safety operations. **
 * //__Major Details__//

 **The TMI accident had a psychological effect on the nation. Before the accident, 70 percent of the general public approved of nuclear power. After it, support for nuclear power across the country fell to about 50 percent, where it remained for decades. The TMI cleanup started in August 1979 and officially ended in December 1993, having cost around US$975 million. From 1985 to 1990 almost 100 tons of radioactive fuel were removed from the site. In the end, a few simple water level gauges on the reactor vessel might have prevented the accident. The operators' focus on a single misleading indication, the level in the pressurizer, was a significant contributing factor to the meltdown.**
 * //__Aftermath__//**

Sources Sited: http://www.world-nuclear.org/info/inf36.html http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Aftermath Images Sited: http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/tmi-2.gif http://morrillmajority.org/tmicancer.jpg


 * Comments: You guys did a fair job organizing the information. You guys could add a little bit more about what happened after the TMI accident. But overall, great job!! I really like the pictures you guys added.

IT is good and everything, but it doesn't say anything about what happen after the melt down. It is good that you put laws that they have in place now.** This page looks really good overall with the pictures and the layout. You could have added a little more information about what happened after the accident. All in all, you guys did a great job.