The Kori unit 1 plant is a Pressurized Water Reactor type reactor (PWR). The membranes are used to remove dissolved oxygen from water in the Primary Make-up Water Storage Tank. The water is continuously recirculated through the membrane contactor system in an effort to keep the dissolved oxygen level low. Dissolved oxygen is controlled to very low levels in this system in order to prevent corrosion of piping and equipment. Dissolved nitrogen is also controlled to prevent the formation of Carbon 14.
Kori Unit 1: Reducing Production of C14 and Replacing Hydrazine Injection
Kori unit 1 is a Pressure Water Reactor (PWR). The reactor is continuously fed boronated water which is used to control the neutron flux inside the reactor. The boron is continuously consumed and is replenished from the primary make-up water system.
The water in this primary feed tank is typically blanketed with nitrogen or covered with a rubber bladder to prevent oxygen from entering the storage tank. Before Liqui-Cel Contactors were installed, hydrazine was typically used to control the dissolved oxygen level in the DI water system feeding this tank. The breakdown of hydrazine and the nitrogen blanket increased the amount of dissolved nitrogen in the water.
Researchers at KEPRI have found that dissolved nitrogen in the reactor feed water leads to an increased production of carbon 14 in the power plant. The nitrogen forms carbon 14 when it absorbs neutrons in the reactor. Carbon 14 is a long-term environmental contaminant and the engineers sought ways to minimize its production at the plant.
Engineers at the facility investigated new ways to control the dissolved oxygen and nitrogen in the water feeding the reactor. Membrane contactors were installed because they simultaneously remove both dissolved nitrogen and oxygen from the water.
As illustrated in Fig. 2, the Kori plant uses a deep vacuum. This operating condition lowers the partial pressure of all gasses that are in contact with the water. This creates a driving force to remove all gasses that are dissolved in the water.