DAVIS-BESSE IS AN ELECTRIC EXPERIENCE
January 5, 2000, article one

PIX#1 - Cooling Tower. This 500 foot structure is the most visible feature at First Energy's Davis-Besse Nuclear Power Station near Oak Harbor. It is not the Reactor. It's a cooling tower and its purpose is to dissipate waste heat from the nuclear reaction. The plume rising from the tower is simple, non-radioactive water vapor. Davis-Besse has been producing electrical energy for northwest Ohio for 22 years.

In 600 B.C., the Greek philosopher Thales of Miletus discovered that amber becomes charged by rubbing. Consequently, our word "electricity" comes from the Greek for amber.

Thales had no idea where his discovery would lead.

Today, electricity powers our lives in so many ways that it's easy to take it for granted. Locally much of our electricity is generated at the Davis-Besse nuclear power plant near Oak Harbor operated by. Locally, much of our electricity is generated at the Davis-Besse nuclear power plant near Oak Harbor operated by First Energy.

To make electricity a magnetic field and a conductor are required and relative motion between the two motion supplied by a turbine.

Nuclear power plants use atomic fission to generate the heat necessary to produce the steam that drives a turbine.

Fission occurs when fissionable nuclei of uranium 235 absorb neutrons, become unstable, split in two and release energy. Particles released by the fussioning in the core of a nuclear reactor are such that they split other atoms in a self-sustaining nuclear chain reaction.

Fission occurs in the reactor's 177 fuel assemblies. Each is 14 foot long, weighs 1,550 pounds, and contains 208 fuel rods.

Each rod contains 300 uranium pellets. Each assembly is fitted with control rods which can be lowered into the assembly to moderate or stop the reaction.

Davis-Besse is a pressurized water reactor.

"Water is pumped through the reactor vessel through four reactor pumps powered by 9,000 hp motors," said Fostorian Randy Burk, a plant operator.

"The water is pumped down the wall, then up through the reactor core where it picks up the heat from the nuclear chain reaction. The water coming out is 606 degrees. The water is pressurized to about 2,155 pounds so it doesn't boil."

That's important, because 606 degrees is nearly three times the boiling point of water.

The water is then pumped through a steam generator, or heat exchanger, with 13,000 tubes.

"The idea is for the water to give up the heat from the reactor into another system," said Randy. "It's called the feed water system."

The feed water boils from contact with the superheated water in the heat exchanger's tubes, turns to steam and is sent to the 150 foot long, 30 foot tall turbine which turns at 1,800 rpms.

The water in the reactor core is radioactive, but circulates in a closed loop. It doesn't come into contact with the water used to produce the steam.

Since the inception of commercial nuclear power in the late 1950s, there have been concerns about its safety. The plant is designed with many safety features.

The fuel rods are made of a pressurized zirconium alloy, welded shut after the fuel pellets have been inserted. The rods are the first physical barrier against radiation release. The second barrier is the pipe system containing the reactor coolant water.

The third is the reactor's steel containment vessel. The final barrier is the three foot thick concrete containment building (not to be confused with the 500 foot cooling tower which dominates the landscape).

Operators in the control room continuously monitor every aspect of the plant's operation.

In the event of an emergency, Davis-Besse can be shut down with astonishing speed. Once the control rods have been fully deployed, energy output in the core drops to 6% in one second.

Safety valves open automatically in the event of a malfunction to allow pumps to move water into the containment building.

The control rods are held in place by a motor that is always energized so the rods are ready to be inserted into the core immediately if needed. The rods are made of silver, cadmium and indium -- three elements that absorb high-energy neutrons.

A tank containing thousands of gallons of water with a 5-7 percent solution of boric acid stands ready to flood the reactor in the event of an emergency.

Boron also absorbs neutrons and slows the atomic reaction.

The water used in the reactor is purer than ordinary drinking water. If the water contains any impurities, those can become irradiated and damage the pipes.

Finally, every system at Davis-Besse is redundant. That is, it has a back-up. In emergencies, the plant's safety wouldn't depend on any single valve, pipe or pump.

In addition, one system can be in operation while the other is undergoing maintenance.

Each fuel assembly costs roughly $1 million. New fuel assemblies are stored in individual hatches awaiting refueling. One-third of the fuel is replaced at each refueling.

If $1 million seems expensive, consider that a single fuel pellet (as small around as your finger and maybe an inch long) packs an energy punch equivalent to 17,000 cu.ft. of natural gas or three 42 gallon barrels of oil.

Davis-Besse sends the final product out over transmission lines to the Lemoyne, Bayshore and Ohio Edison stations for distribution. Davis-Besse is a 2,772 mega-watt plant. One megawatt equals one million watts.

When a fuel assembly's useful life is finished, it's stored in the spent fuel storage pool. A depth of 23 feet of water with a 2,000 parts per million concentration of boron covers the assemblies.

The pool's 700 assembly capacity has only recently been reached after 22 years of operation. The water in the pool is continuously a re-circulated at the rate of 1,000 gallons per minute to carry away the heat still being produced.

The atom may be imperfectly understood and issues regarding the disposal and treatment of radioactive waste remain unsolved. Nonetheless, it says much for human inventiveness that we split particles as tiny as atoms, rend the very fabric of matter, and harness the energy to productive use.

It is a prodigious accomplishment.

(Many thanks to Randy Burk for taking me along on his tour of Davis Besse on Nov. 20. It was a remarkable educational experience - LKS.)