Nuclear Power Plants Disasters and their possible meltdowns

A little about nuclear power plants  Most reactors have a “core” where the reaction takes place. Inside the core are fuel rods and assemblies, the control rods, the moderator, and the coolant.  Outside the core are the turbines, the heat exchanger, and the cooling system.

Nuclear power plant diagram

Chernobyl  Located in the Ukraine, the Chernobyl nuclear power plant was the site of the worst nuclear disaster to date.

Chernobyl  On April 25 th -26 th, 1986 the World's worst nuclear power accident occurred at Chernobyl in the former USSR (now Ukraine).  The Chernobyl nuclear power plant located 80 miles north of Kiev had 4 reactors and while testing reactor number 4. Numerous safety procedures were ignored.  At 1:23 am the chain reaction in the reactor became out of control creating explosions and a fireball which blew off the reactor's heavy steel and concrete lid.

The radiation cloud  The Chernobyl accident killed more than 30 people immediately.  As a result of the high radiation levels in the surrounding 20-mile radius 135,00 people had to be evacuated.  The picture to the right shows how far radiation had spread by May 6 th.

Area of radiation cloud  How much land was affected by the original radiation cloud on April 26 th ? There was a radius of 20 miles, so how can you calculate the square miles affected by the original blast?

Effects on the environment  In some local ecosystems lethal doses were reached particularly for coniferous trees and small mammals within a 10 km radius of the reactor.  However in 1989 the natural environment of these ecosystems began to recover but there is the possibility of long term genetic effects.  Increased cancer was often seen. Researchers also found that 64% of all Ukrainian thyroid cancer patients age 15 or younger lived in the most contaminated regions the provinces of  Kiev, Chernigov, Zhitomir, Cherkassy

Other long term effects?  Can you find anymore long term effects that the accident might have caused? Either in humans, animals, or on just the environment itself. There have been many other sicknesses linked to the disaster, discuss some of the possibilities based on radiation poisoning.

Closure of the plant  The Chernobyl plant was closed on December 15 th,  More than 8,000 deaths have been blamed on the accident.  The concrete tomb built to encase the exploded reactor is leaking, threatening the world with another catastrophe.  Forty tons of radioactive dust has accumulated inside, and some experts believe that it could lead to an even bigger explosion than the one that occurred before.

Three mile island  A nuclear power plant located near Harrisburg, Pennsylvania.  On March 27 th, 1979 there was a near meltdown.

The near miss  The plants main feed water pumps in the secondary non-nuclear cooling system failed.  From that point there was a series of events that occurred from either a mechanical or electrical failure.  A large part of the core melted and the system was highly radioactive.  Over the next week the steam and hydrogen were removed from the reactor using a recombiner and, more controversially, by venting straight to the atmosphere  Over the next week the steam and hydrogen were removed from the reactor using a recombiner and, more controversially, by venting straight to the atmosphere.

Clean up efforts  The reactor cleanup started in August 1979 and officially ended in December 1993 at a cost of around $975 million.  From 1985 to 1990 almost 100 tons of radioactive fuel were removed from the site. TMI-2 had been online only three months. TMI-1 was restarted in 1985.

What’s used?  See if you can find what radioactive materials nuclear power plants use in their processes. There maybe more than one correct answer. What radioactive material was used at the Three Mile Island plant?

After the accident  Approval ratings for nuclear power dropped from near 70% to about 50% with the accident. Write a paper on how you feel about nuclear power.  Give the pros and cons and make a strong argument as to your opinion and why you feel that way.

South Texas Project  Located 13 miles southwest of Bay City, Texas or 90 miles southwest of Houston.  The plant and surrounding areas are home to many wildlife species.

The plant itself  South Texas Project (STP) reactors went online in August 1988 and June  The plant contains two identical steam generating units.  The permits for these units expire in 2027 and  Located on 11,000 acres of land adjacent to the Colorado river

More plant facts  Largest nuclear plant in the U.S.  Ownership of the units is divided between  Texas Genco (30.8%), San Antonio City Public Service Board (28.0%), Texas Central Co. (25.2%) and Austin Energy (16.0%).

Find the location of the plant  On the map where would this plant most likely be located? Look at a Texas map and guess where you think the plant is located. (Remember 90 miles southwest of Houston, 13 miles southwest of Bay City, and 12 miles Northeast of Palacios). Use the map on the next slide to guess the location of the plant.

If there was a meltdown  Guesstimating that if there was a meltdown, that it would be of equivalence to that in Chernobyl, what surrounding areas would be effected?  Do you think that since the power plant is so close to the Gulf of Mexico, that it would do more or less damage to the environment than when the Chernobyl accident happened?