What Happend Essay Research Paper In the

What Happend Essay, Research Paper

In the mid-1950s, nuclear physicists confidently predicted that nuclear energy would usher in a new age for humanity. The cost of energy would be so low it would be almost too cheap to meter. They predicted that by the year 2000 there would be thousands of commercial reactors producing unlimited amounts of power. Like the horse and buggy, oil and coal would become little more than historical curiosities. With such a bright outlook for the future the engineers and scientists started to get careless. Then on March 28, 1979, an event took place that rocked the nuclear power industry so badly that it has yet to recover. That event was the partial meltdown of one of the reactor cores at the Three Mile Island nuclear power plant in Londonderry Township, Pennsylvania. The accident at Three Mile Island was a combination of equipment failures, design problems, and human error. It was even more that though it was a complacent attitude that the industry had as a whole as Harold Denton former Nuclear Regulatory Commission official said, We thought the plant was too well designed to have a serious accident. It was kind of like the Titanic. (CNN) It may surprise some people to find out how close we came to a major disaster and the shear amount of problems that occurred.

To understand what went wrong you first need to understand how a nuclear power plant works. At the heart or every plant is it s radioactive core. The core is a nuclear furnace creating heat by the splitting of atoms during a controlled chain reaction. Control rods that are raised and lowered into the core to control the rate the atoms split and there by controlling the amount to heat produced. To slow down the reaction the rods are lowered into the core, to speed it up they are raised or taken out of the core. Surrounding the core is the water in the primary loop. This water removes the heat generated by the core as it is pumped through the loop. Because the water in the primary loop comes in contact with the core it becomes radioactive. The heat is then transferred from the water in the primary loop to the water in the secondary loop. The water in the secondary then turns in to steam that steam turns a turbine that is connected to a generator that produces electricity. Pumps move the water through the secondary loop and back to where the heat is exchanged. Because the water in the secondary loop never comes in contact with the radioactive water in the primary loop it is not radioactive. (PBS)

At 4:00 A.M. on March 28, 1979 the main pumps in the secondary non-nuclear loop of the unit 2 reactor stopped working caused by a slight malfunction. The turbine and then the reactor shut down according to their design. Because water is no longer flowing through the secondary loop, heat is no longer being transferred from the primary loop to the secondary loop. The water temperature and pressure in the reactor raise, this is normal and no cause for alarm. To prevent the pressure from getting too high, a pressure relief valve opens to relieve some of the pressure and water to a drain tank. (Raso) All according to what was supposed to happen in case of such an event.

This is when things start to go wrong. The back up pumps for the secondary loop had had a test run on them 42 hours before the indent. Part of this test included a valve being closed and then reopened at the end of the test. But this time the valve was not reopened after the test. The valve being closed prevented the backup system from functioning. The plant workers discovered the valve closed in about eight minutes and reopened. Once the valve was open the back up system started to work correctly. Cooling water then flowed into the steam generators. (NRC) This solved one problem but a bigger one existed.

Because the secondary loop was out of commission for about eight minuets the pressure relief valve had to open. The pressure relief valve should have closed after the pressure dropped but it did not. The emergency water injection system had also come on to inject water into the primary loop to prevent a loss of coolant accident. Plant workers were not concerned when this happened because it had come on in the past when there had been no leak. Operators seeing that the water level and pressure are going up turn the emergency water injection off. In reality the water level was still dropping but since the gauge that the workers saw was reading incorrectly they were unaware of this. Because of design shortcomings the plant operators also did not know that the pressure relief valve was stuck open. Allowing pressure to continue to drop and too much water to escape. Since so much water had escaped and it was no longer under as much pressure and there began to be pockets of steam in the primary loop. When these pockets of steam passed through the pumps it made them shake violently prompting the workers to shut two of the four pumps down. All this time steam is escaping through the pressure relief valve and going in to the drain tank.

Once the drain tank filled a component called a rupture disk broke spilling thousands of gallons of radioactive water in the basement of the containment building. Pumps start to transfer the water from the basement to waste-storage tanks in an auxiliary building, but the water overflowed these tanks and spilled to the floor. Because of the high water temperature some of the g