A discussion on the lingering effects of three mile island

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A discussion on the lingering effects of three mile island

The TMI-2 reactor was destroyed. Some radioactive gas was released a couple of days after the accident, but not enough to cause any dose above background levels to local residents. It had two pressurized water reactors. It involved a relatively minor malfunction in the secondary cooling circuit which caused the temperature in the primary coolant to rise.

This in turn caused the reactor to shut down automatically. Shut down took about one second. At this point a relief valve failed to close, but instrumentation did not reveal the fact, and so much of the primary coolant drained away that the residual decay heat in the reactor core was not removed.

The core suffered severe damage as a result. The operators were unable to diagnose or respond properly to the unplanned automatic shutdown of the reactor.

Deficient control room instrumentation and inadequate emergency response training proved to be root causes of the accident The chain of events during the Three Mile Island accident Within seconds of the shutdown, the pilot-operated relief valve PORV on the reactor cooling system opened, as it was supposed to.

About 10 seconds later it should have closed. But it remained open, leaking vital reactor coolant water to the reactor coolant drain tank. The operators believed the relief valve had shut because instruments showed them that a "close" signal was sent to the valve. However, they did not have an instrument indicating the valve's actual position.

Responding to the loss of cooling water, high-pressure injection pumps automatically pushed replacement water into the reactor system. As water and steam escaped through the relief valve, cooling water surged into the pressuriser, raising the water level in it.

A discussion on the lingering effects of three mile island

The pressuriser is a tank which is part of the primary reactor cooling system, maintaining proper pressure in the system. The relief valve is located on the pressuriser.

In a PWR like TMI-2, water in the primary cooling system around the core is kept under very high pressure to keep it from boiling. Operators responded by reducing the flow of replacement water. Their training told them that the pressuriser water level was the only dependable indication of the amount of cooling water in the system.

Because the pressuriser level was increasing, they thought the reactor system was too full of water. Their training told them to do all they could to keep the pressuriser from filling with water.

If it filled, they could not control pressure in the cooling system and it might rupture. Steam then formed in the reactor primary cooling system. Pumping a mixture of steam and water caused the reactor cooling pumps to vibrate.

Because the severe vibrations could have damaged the pumps and made them unusable, operators shut down the pumps. This ended forced cooling of the reactor core. The operators still believed the system was nearly full of water because the pressuriser level remained high.

However, as reactor coolant water boiled away, the reactor's fuel core was uncovered and became even hotter. The fuel rods were damaged and released radioactive material into the cooling water. This action stopped the loss of coolant water through the relief valve.

However, superheated steam and gases blocked the flow of water through the core cooling system. Throughout the morning, operators attempted to force more water into the reactor system to condense steam bubbles that they believed were blocking the flow of cooling water.

During the afternoon, operators attempted to decrease the pressure in the reactor system to allow a low pressure cooling system to be used and emergency water supplies to be put into the system.

Cooling restored, radioactive releases to air By late afternoon, operators began high-pressure injection of water into the reactor cooling system to increase pressure and to collapse steam bubbles. They had condensed steam so that the pump could run without severe vibrations.[Content warning: Discussion of social justice, discussion of violence, spoilers for Jacqueline Carey books.] [Edit 10/ This post was inspired by a debate with a friend of a friend on Facebook who has since become somewhat famous.

The best opinions, comments and analysis from The Telegraph. The Lingering Effects of Three Mile Island The Three Mile Island accident took place in Middletown, Pennsylvania, on March 28, During this accident even though there was no meltdown, there was some radioactive gas that was let out into the air.

As a result more than 50, people were evacuated from their homes (Levine ). In the early hours of Wednesday, March 28th, , before the first rays of the early spring sun had crossed the banks of the Susquehanna River, the $ million dollar Unit Two of Three Mile Island’s nuclear generating station, completed only three months earlier, experienced a minor malfunction.

As a result more than 50, people were evacuated from their homes (Levine ). The Three Mile Island incident had a major impact on public opinion, the construction of nuclear plants, and the future of nuclear power.

Three Mile Island was a three month old nuclear power plant located in . A group of geologists have drawn my attention to the / Geological Society of London‘s statement on climate change and asked if I could arrange an on-line discussion about it.

The lead author of the statements is Dr Colin Summerhayes who has participated as guest blogger and commenter on Energy Matters before.

And so I .

A discussion on the lingering effects of three mile island
Jesse Kropelnicki