Platt’s news service reported today:
US nuclear plant operators must provide information to the Nuclear Regulatory Commission by February about an electrical vulnerability that could affect safety systems and how each plant plans to mitigate it, the agency said in a letter made public Friday.
The vulnerability affects almost all US nuclear stations and has received regulatory attention since January 2012, when Exelon’s 1,210-MW Byron-2 reactor near Rockford, Illinois, lost power to its safety systems after a partial loss of off-site power known as an open phase condition.
The event revealed what the NRC called a “design vulnerability” in nuclear plant power systems related to power provided to them from the grid to feed internal plant loads.
Addressing the vulnerability may be a costly problem:
All US nuclear plant operators, by a formal vote of their chief nuclear officers, agreed in September to a binding industry initiative that will resolve the issue by making permanent plant modifications by the end of 2016, NEI’s senior director of engineering John Butler told NRC in November. Those modifications, which may involve the addition of relays that can detect the open phases, could cost $1 million or more per site, he said.
Exelon, which has begun installing the new relays, has said costs to protect seven of its nuclear plants could be $27 million.
The problem is not limited to the United States, Platts reported:
Sweden’s 1,208-MW Fosmark-3 on May 30 experienced the loss of two phases of offsite power as a result of an error during maintenance. Systems providing cooling to the reactor core briefly lost power and stopped, and some equipment was damaged, officials of operator Vattenfall said in June.