What+failed+and+what+di+we+learn

 Mike Alden

Chernobyl the worst nuclear disaster the world has ever seen even today there are still parts of the Ukraine are still to radioactive to have anyone live there. But what happened to reactor number 4 to make it explode. There are many factors both mechanical and operator errors that precluded and helped cause this terrible technological disaster. The most serious of which was a flaw in the design of the RBMK reactor one major one is that it was built without a containment shell which would keep almost all the radioactive material in just in case of an accident. The reason the RBMK reactor has no shell is because it was too tall and not only used for power but also used to collect military grade plutonium. The reactor also had something called a positive void coefficient Which John McCarthy states is “the water in the reactor boils in some spot a bubble of steam is produced. In PWR and BWR reactors, this reduces reactivity, causing the nuclear reaction to slow down. In RBMK reactors it can cause the nuclear reaction to speed up.”(McCarthy). The operators at the time also turned of several safety features including the emergency shut off to the reactor that could have stopped this disaster from happening. On the day of the accident there was and experiment was being done to see how long the turbines were to spin and supply power to the circulation pumps. The same test was carried out the year before but power ran out to quickly. So they were testing a new voltage regulator to keep the water continually going to the reactor incase of power failure. Reactors have an interesting characteristic if they is shut down a build of a poison keeps the reactor from being able to be restarted for many hours. This made it difficult to get the 25% of full power needed to run the test. So in order to get as much power as they could most of the control rods for the reactor were pulled out and even then the power level only reached 6%. Strictly against the rules of the planet it was done anyway. The test went ahead anyway and additional water pumps were turned on and were driven under the inertia of the turbine. This provided too far to much water to the reactor a problem in the design increased the water flow even. This additional water flow made it so they had to remove the manual control rods making it extremely dangerous if water was ever to slow around the reactor as it did would make the reactor go critical in seconds. At around 1:20 computers print out read that the reactor was unsafe and should be shut down immediately. The operators choose to ignore it though it isn’t understood why this was done. The normal electrical drive of the water pumps were switched off slowing the water flow to the reactor causing a build up of steam. Making the reactors chain reaction speed making the automatic control rods go down but because of design flaws there insertion was slow. Before they could get all the way down damage occurred preventing them from being fully inserted. Making the chain reaction continue to accelerate producing heat 100 times greater than the reactor was designed for. No one knows the exact cause of the reactors exploding but two loud explosions were heard and glowing material was seen flying out of the top of the structure. Because of Chernobyl and the USA’s near disaster of Three Mile Island two new large organizations were established by the nuclear industry. One of them is Nuclear Safety Analysis Center also known as the (NSAC).What NSAC does is “NSAC carries out very intensive technical analyses ”. The other organization is The Institute of Nuclear Power Operations or INOP “INPO has established an impressive electronic communication network among power plants, reactor vendors, and centers of expertise all over the world. It also conducts inspections of power plants, offering suggestions and criticisms that are taken very seriously”. Now there is substantial contact between the former Soviet and American reactor safety experts, including many visits in both directions, personal friendships, and lots of informal discussions over cocktails. The above question has been asked and discussed many times, and the Soviet reply runs along the following lines.