Hamilton and Rhea Counties, Tennessee and Limestone County, Alabama
On March 15, 2013, the Tennessee Valley Authority (TVA) issued a final environmental assessment (EA) and finding of no significant impact (FONSI) for implementing its response strategy for recent Nuclear Regulatory Commission requirements following the March 2011 earthquake and tsunami that struck the Fukushima Dai-ichi electrical power station in Japan. The Nuclear Regulatory Commission directed operators of nuclear power plants, including TVA, to review their procedures, equipment, and facilities and to develop strategies to improve their ability to maintain or restore core cooling, containment, and spent fuel pool cooling capabilities in the event of a severe accident.
TVA has proposed a strategy for addressing these issues at its Watts Bar Nuclear Plant (WBN), Sequoyah Nuclear Plant (SQN), and Browns Ferry Nuclear Plant (BFN). Components of the strategy include evaluating current procedures and facilities and undertaking the following physical actions:
- Replace certain transformers at SQN.
- Construct concrete equipment storage buildings (known as “FESBs”) at BFN, SQN, and WBN to house large emergency generators and other emergency equipment and supplies.
- Install as many as three 225-kVA diesel-powered generators on the roofs of existing buildings at BFN, SQN, and WBN.
- Harden the condensate storage tanks and associated equipment at SQN and WBN by constructing a concrete or metal housing around the condensate storage tanks, constructing new tanks with a more robust design, or implementing other mitigating measures to ensure reactor pressure vessel cooling water is available.
- Conduct general construction-type activities, including soil-disturbing actions, for minor upgrades to existing systems.
- Modify the vent system at BFN and install filters in the vents.
- At BFN, provide a remote station for a pneumatic supply to allow manual operation of the vent system from a safe location and modify the effluent radiation monitor to ensure prolonged operation or install a new monitoring system with an uninterruptible power source.
Since the issuance of the FONSI, TVA has reconsidered portions of its Fukushima Response Strategy as described in the 2013 EA. Consequently, TVA proposes to modify its Fukushima Response Strategy. The proposed measures include the following actions:
- Install one or two 1-MW diesel-powered generators (rather than two 3-MW generators originally proposed) in the FESB at BFN.
- Construct a second FESB at BFN.
- Construct emergency staging areas at BFN, SQN, and WBN to serve as the initial delivery point for equipment arriving from offsite in an emergency.
- At all three plants, validate potential haul routes for the onsite transfer of equipment from the emergency staging areas and FESB(s) to various onsite deployment sites. Validation would involve core borings at approximately 500- to 1,000-foot intervals along existing roadways at BFN and SQN.
- Construct an approximately 1,200-foot hard-surface haul road, including an 80-foot long bridge over the switchyard drainage ditch at BFN.
- Establish deployment sites for emergency pumps and install associated equipment for deploying emergency pumps and equipment at BFN, SQN, and WBN. A hard-surface pad would be constructed at deployment sites that are not already paved.
- Rather than constructing a single FESB at SQN, emergency equipment would be stored in other appropriate onsite structures and in a new storage structure.
- Include more than one tow vehicle as part of the emergency equipment to be stored onsite at SQN and WBN.
- Eliminate hardening the condensate storage tank at SQN.
- Construct one or two 1,000,000-gallon water storage tanks and associated piping at SQN and WBN to supply emergency cooling water. Install wells to replenish these 1,000,000-gallon water tanks.
Some of the actions listed above were not considered in the 2013 EA. Other actions would occur outside of the geographic scope of the 2013 EA. Thus, TVA conducted a supplemental environmental assessment of the actions within the modified strategy and issued a revised FONSI. TVA has determined that the findings in the original EA remain valid and that implementing the optional actions listed above would not result in significant environmental effects.