Nuclear Power Plant Radioactive Water Remediation
New Logic Research headquarters is based fifteen minutes outside of San Francisco, and has experienced the devastation caused by earthquakes and their subsequent disasters. The page serves as a reference on our experience with nuclear remediation and cleanup of radioactive wastewater.
NLR acknowledges the work done by Roger Asay of Centec XXI, from Gilroy, California. Asay is a world-renowned expert in the field of power plant decommissioning and has worked with NLR over the last fifteen years to evaluate VSEP for the treatment of radioactive waste at nuclear generating facilities.
VSEP in Japan
Historically, VSEP has been successful in treating radioactive water and concentrating waste material. Kashiwazaki-Kariwa is the largest nuclear power plant in the world and is owned by TEPCO, the parent company of the Fukushima plant. Testing conducted at the Kashiwazaki-Kariwa power plant in western Japan proved successful. VSEP treated the radioactive cobalt wastewater, producing non-toxic water suitable for discharge.
NLR also provided VSEP testing equipment for the decommissioned Rancho Seco nuclear facility in California. The Rancho Seco testing evaluated the removal of radioactive particles from water with the goal of producing water for reuse or discharge. This test was also successful, with VSEP producing a clean filtrate while reducing the radwaste materials.
Simulation testing was also completed for several other power plants in the Eastern United States.
Nuclear Power Plant Operation: The Basics
Electricity can be created by steam turbines. Heat is needed to boil water to make steam. Conventional power plants burn coal, natural gas, or some other hydrocarbon to make the heat to create steam. In the process known as “nuclear fission”, atoms are split into smaller particles and as this happens, heat is created. Nuclear power plants use the heat from this process to create steam. Combustion gases are generated when hydrocarbons are burned, but no emissions are created with the fission of atoms. Unstable atoms with large amounts of stored energy known as radioactive nuclides are used in the process and as these atoms break down, many forms of radioactive materials can be generated. These waste materials must be sequestered and eventually disposed of.
Uranium is enriched and then used to make rods of the proper composition and geometry and then this is used as the fuel rod where fission takes place. These fuel rods are used for about six years when about three percent of the uranium has been fissioned. The rods are then moved to spent fuel pools. Water is used to cool the rods for approximately five years, and when they are cool enough they are moved to dry storage. Water is also used to keep the reactor core cool and prevent overheating. Large pumps are used to circulate cooling water and cooling towers are used to evaporate the heat from this water.
As three percent of the uranium rods are fissioned away, fission products are created, which are radioactive isotopes of different forms, such as cesium-137, iodine 131, strontium-90, barium-140 and many other isotopes. Some are short-lived in their radioactivity like iodine-131, while others like cesium-137 can be dangerous for a long time.
Under normal operations, there is little radioactivity in cooling water and other process water used. However water can become contaminated during decommissioning where used tanks and equipment are washed prior to disposal. Water can also become contaminated from leaks at the reactor core where water can contact the fuel rods, or from leaks in the containment areas around spent fuel rods. With normal decommissioning, there is usually time to plan for disposal of this water. In the case of unexpected leaks, however, there is not time for such planning and contingency plans are deployed.
Whether radioactive water is generated in a planned fashion or in an unexpected release, membrane filtration can be used to effectively separate the radioactive materials from the water. The biggest challenge in both leaks and decommissioning is volume. The amount of spent cooling water contaminated can quickly deplete storage capacity and therefore require discharge or removal from the site. Unfortunately, the volume of space available for radioactive disposal is usually limited, and maximum volume reduction must be achieved to minimize the cost and the risk to the environment.
Wastewater Treatment Methods
Testing completed using conventional spiral RO membranes on radioactive water showed typical volume reductions of 50%. Other testing using VSEP RO on concentrated waste streams showed volume reductions of 90-95%. This increased volume reduction is a critical difference between the two technologies. VSEP is capable of higher volume reductions because it has a more open feed channel and can handle suspended solids with no limitations. Furthermore, VSEP is not limited by solubility saturation where scaling could occur in conventional spiral RO modules.
Other methods of remediation can include settling and adsorption. The problem with adsorption methods is breakthrough, where the adsorbing material can become saturated and cease to function. Also, the percentage removal may not be high enough to ensure sufficiently treated water. While settling is effective for larger particles, neither small suspended solids nor soluble radioactive materials (such as iodine) will settle.
Because decommissioning and accidental releases are rare, limited work has been performed in radioactive wastewater treatment. VSEP technology has multiple advantages in treating radioactive water:
- Very high volume reduction
- Small footprint
- Remote access for controls and operation
- No additional waste material volume is added as with adsorbents
- Virtually complete removal of radioactive materials
- No bleed-through once saturated
- Proven industrial design used in refineries and chemical manufacturing plants
- Options for selectivity with choice of various membranes
NLR will update this reference to inform interested parties about the both the history and capabilities of VSEP for treating radioactive wastewater.
For more information about VSEP and its capabilities, or to discuss a particular application, please contact us.
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