Work hours for security guards at Grand Gulf Nuclear Station averaged more than 54 per week over six-week periods leading up to the current lockout, according to the workers’ union.

Security officers work 12-hour shifts at the Claiborne County plant and, by federal law, can’t exceed that average, said Desiree Sullivan, president of the United Government Security Officers of America. In the nuclear power industry, plant operators must send waivers to the Nuclear Regulatory Commission to justify the overage and maintain a security presence.

About 25 to 30 workers picketed this week near the access road to the plant and near the plant entrance since the union workers were locked out at midnight Sunday, when Entergy said a contract expired. Non-union workers and staff from its other nuclear plants were being employed during the lockout, Entergy said.

In June, a six-month effort was completed to refuel the boiling-water reactor and upgrade its generating capacity by 13 percent.

Also in June, union workers at the utility’s Pilgrim nuclear plant in Plymouth, Mass., were locked out after a tentative contract was rejected. The union has filed a complaint with the National Labor Relations Board over the alternative staffing plan.