DRESDEN LICENCE RENEWAL | LIFE EXTENSION Enhanced electrical insulation programmes manage the


effects of reduced insulation resistance at various voltage levels.


Insulation material is visually inspected and may be subject to other tests including thermography. The management programme will be enhanced to evaluate operating experience to confirm that insulation can still perform its function despite the cumulative effect of mitigated ageing, and testing a sample population when a large number of cables are identified as degraded. Inaccessible medium voltage cables exposed to


significant moisture undergo periodic testing to assess insulation condition. Enhancements will include cable testing of circuits in


scope at least once every six years. If there are events that could result in water accumulation and cable submergence there will be additional inspections. Two manholes (MH-16 and SBO-4) have been identified for regular inspection in case of water accumulation. The metal enclosed bus programme involves visual inspection for age-related cracks, corrosion, foreign debris, excessive dust build-up and evidence of moisture, covering insulation as well as other equipment. This will now include periodic inspections of the 4kV switchgear accessible bus duct and a sample of metal-enclosed bus bolted connections.


Balance of plant Enhancements to the aging management programme include several that relate to systems and technologies that are familiar in non-nuclear and even in domestic contexts. Their inclusion illustrates the interconnected nature of complex nuclear power plants. Familiarity cannot be a reason for complacency over safety. The compressed air monitoring programme will add opportunistic visual inspections of internal surfaces exposed to a dry air environment for signs of loss of material. The fire water system programme applies sprinklers,


fittings, valves, hydrants, hose stations, standpipes, pumps, and aboveground and buried piping and components. It will additionally include a a one-time volumetric wall thickness inspection on a representative sample of piping that is periodically subject to flow but is normally dry. It will also include biennial external visual inspections of sprinkler systems in accessible and inaccessible areas and internal visual inspections of sprinkler and pre- action system piping to identify internal corrosion, foreign material and obstructions to flow. Follow-up volumetric wall thickness examinations will be performed if internal visual inspections detect an unexpected level of degradation due to corrosion and corrosion product deposition. The hydrant flushing procedure will be revised to require


that hydrants drain within one hour. The testing frequency of the transformer deluge systems will be increased to a biennial basis and the flow test and main drain test procedures will be revised to perform additional tests after each failed test. An outdoor and large atmospheric metallic storage


tanks programme includes two contaminated condensate storage tanks, and contaminated and clean demineralised water storage tanks. These tanks contain treated water, and are constructed of aluminium. They are not insulated and are supported on a concrete and sand foundation. This


means that the bottoms of the tanks are inaccessible for direct visual inspection. The programme is being enhanced to apply sealant to provide a moisture barrier at the perimeter of the bases of both the clean and contaminated demineralised water storage tanks. The programme will also perform an inspection of the sealant at the perimeter of the base of the contaminated condensate storage tanks and demineralised water storage tanks for signs of degradation every two years and perform periodic volumetric inspections of the contaminated condensate storage tanks, clean demineralised water storage tank, and contaminated demineralised water storage tank bottoms. The fuel oil chemistry aging management programme


relies on a combination of surveillance and maintenance procedures. It will be enhanced to perform periodic internal inspections of the emergency diesel generator fuel oil day tanks and fire pump fuel oil day tank at least once during each 10-year period. Each tank will be drained and cleaned and the internal


surfaces visually inspected. If there is evidence of degradation they will be volumetrically inspected. There will be quarterly particulate contamination, water and sediment checks, and microbiological activity checks for the isolation condenser makeup pump fuel oil day tanks. The fuel oil sampling and draining of accumulated water will use a new route to the existing drain valves that are connected to the flush drain connections of these tanks. The structures monitoring programme relates to concrete


and steel structures, steel edge supports, and steel bracings associated with masonry walls, groundwater chemistry and inspections of below grade concrete. It will be expanded to include the turbine and control buildings and include manholes, sliding surfaces and trash racks. Clarified procedures will be required for cracking,


spalling, scaling and leaching, while sliding surfaces will be examined for wear or corrosion and accumulation of debris. The programme will be expanded to sealants, seismic joint fillers, vibration isolators and bearing pads. New procedures will also be written to address aging management of areas exposed to raw water and groundwater/soil environments. After ground water testing adverse water chemistry results will be entered in a corrective action programme. If degraded concrete is identified it will be exposed for further inspection and possible repair. Inspection of water-control structures includes


structures such as intake canals and the discharge outfall structure.


Inspections will be performed at least once every five


years for submerged components and every 10 years for those that are not. The programme will be expanded to include several new areas including canal bridges and embankments, as well as equipment such trash racks. Water chemistry analysis will be used to model


degradation. In a recent statement, Constellation noted that renewing


the NRC license for Dresden will give the company the ability to keep the plant operating through 2051. Although future policy and market conditions will ultimately determine how long the plant operates, renewal of its license would provide Illinois with an estimated 305 TWh of additional electricity over the 20-year extended lifespan. Constallation says this adds up to more low-carbon energy than all of the state’s wind and solar facilities have produced to date. ■


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