The Nuclear Regulatory Commission, after careful analysis of inspection findings and related information, has concluded Dominion Generation’s North Anna Unit 1 and 2 reactors can be restarted. The North Anna reactors (1800MW), in Louisa, Virgina, have been shut down since 23 August when a magnitude 5.8 earthquake occurred about 11 miles from the plant.
“The earthquake shook the reactors more strongly than the plant’s design anticipated, so Dominion had to prove to us that the quake caused no functional damage to the reactors’ safety systems,” said Eric Leeds, director of the NRC’s Office of Nuclear Reactor Regulation.
Immediately after the earthquake plant operator Dominion immediately began a programme of inspections, testing and analysis to make sure the station was undamaged and capable of being safely restarted. The programme involved more than 100,000 man-hours of work and cost more than $21 million.
The NRC’s independent actions included an Augmented Inspection Team (AIT) that examined the plant shortly after the quake, as well as a restart readiness inspection in mid-October. Both Dominion and NRC’s results showed only minor damage that did not affect North Anna’s safety systems.
“We’ve asked Dominion dozens of detailed questions, and our experts have examined Dominion’s answers as well as information from our own inspections. We’re satisfied the plant meets our requirements to restart safely, and we’ll monitor Dominion’s ongoing tests and inspections during startup of both reactors,” Leeds added.
Control room operators, under the oversight of both Dominion nuclear officials and NRC inspectors, initiated the restart process for North Anna unit 1 on 11 November. Dominion will bring unit 1 online safely and then begin the same process with Unit 2. It is expected to take about 10 days to return both units to full power.
The restart process for each unit normally takes about four days from cold shutdown to normal power operations, however it will be prolonged to allow for additional equipment tests that can only be performed when the units are in various stages of start-up as an extra, deliberate safety precaution.
As part of its restart agreement with the NRC, the Dominion will perform a number of actions after restart to analyze and confirm North Anna's capability to withstand seismic events now and in the future. This will include:
- Updating North Anna’s Final Safety Analysis Report to incorporate information from the quake and subsequent analysis;
- Additional characterization of the fault responsible for the Aug. 23 quake, as well as any special ground motion effects at North Anna;
- Re-evaluating plant equipment (including an assessment of potential improvements) identified in earlier seismic reviews;
- Developing any needed inspections or evaluations for components within the North Anna reactor vessels; and
- Permanently updating seismic monitoring equipment for the North Anna reactors and dry-cask spent fuel storage facility.