As you are reading this, I have officially commenced my refueling outage duties. This entails reporting to the Outage Command Center each morning at 5:30 A.M. for turnover, and then putting in a twelve hour shift. That, along with the one hour commute each way, six days a week, makes for a long week. So if I am not around reading and commenting for the next five weeks, please understand.For some of my Blogger readers, who did not see some of my nuclear power entires over in AOL J-Land, the rest of this entry describes what a nuclear power plan refueling outage is all about.
What you are looking at in this picture is a fuel assembly being removed from the reactor. The fuel is removed from the reactor using all remote handling equipment completely under water due to the extreme high radiation levels of the fuel. Water is a very effective shield source of radiation. The characteristic blue glow is Cerenkov radiation - attributed to radioactive particles moving faster than the speed of light in water. With time the blue glow diminishes.
The fuel is picked up by a manipulator crane that has a mechanical arm that extends down into the reactor vessel. The round structure you see with all of the little round holes in it is actually the reactor vessel flange. The top of the reactor and all of the control rods have already been removed in these pictures to allow access to the fuel. The arm of the manipulator crane has a fuel assembly attached to it. The fuel assembly is approximately 17" X 17" square and about 12 feet long. There are 193 fuel assemblies inside the reactor. All fuel assemblies are removed from the reactor and transferred underwater into the spent fuel pool which is in another building. Approximately 1/3 of the fuel is replaced each refueling outage.
To put things in perspective the crane is about 40 feet above the top of the reactor vessel and the water level is 23 feet deep to the top of the reactor vessel flange. The fuel sits about 20 feet below the reactor vessel flange (so the technician's are about 60 feet above the top of the fuel as it sits inside the reactor).
There is enough low enriched uranium in the fuel to allow operation for 18 months. New fuel is not radioactive until it is placed in the reactor and activated via neutron bombardment, which causes the uranium atoms inside the fuel to become unstable, splitting millions of times per second (fission) and releasing energy in the form of heat, and subsequently this heat is transferred to a secondary water source to produce steam, and this steam then spins the turbines and attached generator to produce electricity.
