Dismantlement Work Begins on Turbine Deck
On most days, it's one of the best job locations you can find. The turbine deck at SONGS sits 72-feet above the Pacific Ocean and offers tantalizing views of the water and San Onofre State Beach to the north and south.
The job of dismantling the turbine deck structures is not as glamorous and requires a focused attention on safety, with many heavy lifts taking place and torch cutting on the cold, hard steel of the turbine system components.
Each nuclear reactor at SONGS had a turbine and generator to make electricity. The turbine system contained one high pressure unit and three low pressure units on a single shaft leading to the generator. When both units were operating, these machines provided enough carbon-free electricity for 1.4 million homes.
Crews have been removing the heavy steel coverings that encased the turbines during plant operation, as well as the moisture separator reheaters, valves, upper and lower turbine casings, turbine fans and generator stators.
The system worked like this. First the steam generated in the containment building would travel to the high pressure turbine, then to moisture separator reheaters, which removed water from the steam that could damage turbine blades, before going to the low pressure turbines. The steam would then travel through the condenser, turning back into water, and cycle through the process again. The single shaft would spin at 1800 RPM to generate electricity.
In pressurized water reactors like those at SONGS, the steam is non-radioactive. However, during the demolition project, radiation protection surveys are performed prior to removing any material, and during the downsizing of materials in the crane bay located below the turbine building structure. All radiological surveys are reviewed and approved by SCE oversight before material is cleared for removal from the site.
Tackling the turbine building will be different from other demolition that has taken place on site.
“Whereas the Diesel Generator buildings, and other major structures on site primarily consist of structural reinforced concrete, the turbine buildings primarily consist of large quantities of plate and structural steel, piping and heat exchangers,” said Frank Pavia, SCE field engineer.
A lot of the metals taken from the turbine building will be cut down to shippable size for recycling outside of California.
The main condensers contain 2 million pounds of titanium tubes. The Unit 2 and Unit 3 turbine structures contain an estimated 62 million pounds of recyclable ferrous (steel) and nonferrous materials (metals with low iron content, such as titanium).
The turbine building also housed the intake structure that brought in sea water for cooling. The large gantry cranes on each end of the turbine deck will be used to remove heavy components from the intake structure areas including fish screens, saltwater pumps, and motors. After the gantry cranes are no longer needed, they will be placed onto the ground using controlled procedures. The crane will then be downsized using torch cutting and loaded onto trucks for offsite recycling.
“At that point, the turbine superstructure building will be prepared for demolition by engineered pre-cutting of heavy systems, structures, and components with torches within the turbine buildings below the turbine deck,” Pavia said.
A very large excavator with long reach attachments consisting of shears, grapples and hydraulic hammers will be mobilized to allow wrecking of the structure from the ground.
After both turbine building structures have been demolished, the demolition crew will turn its attention to the Unit 2 and Unit 3 intake structure. Once that is completed, likely in mid-2023, crews will have access to allow demolition of the control building and other buildings that sit at the center of the site, including the containment domes.
This computer animation provides an overview of the general dismantlement process.