VERNON, Vt. — The Nuclear Regulatory Commission has upheld an Entergy Nuclear “zero tolerance” policy for alcohol at Vermont Yankee nuclear power plant, which resulted in the firing of an employee who had unopened bottles of alcohol in their car.

The NRC, in releasing the conclusions of an investigation, upheld an Entergy decision to immediately suspend the access to the nuclear plant by the employee who had the alcohol in his or her vehicle in May 2014, when the plant was still in full operation. According to the investigation, after the employee was suspended and denied access, another Entergy Nuclear manager decided to convene a three­manager panel to review the situation, and that panel recommended a revision to the Entergy procedures.

The three-manager panel voted to overturn the employee’s access denial to the grounds of Vermont Yankee. But after another review, Entergy reinstated the original decision, following the original Entergy “zero­tolerance” procedure.

The NRC’s decision, released Thursday, upheld Entergy’s final decision, firing the employee.

Martin Cohn, Entergy Nuclear spokesman, said the company had a “zero­tolerance” policy, and it even included empty alcohol bottles that were headed toward a redemption center. He confirmed that the employee who had been denied access to the plant was ultimately fired.

“I don’t know how many bottles there were. We have a policy in place of zero tolerance,” Cohn said.

Employees are told not to bring anything on the site, even empty bottles.

“You can’t even have the perception,” Cohn said.

Guards are free to search employees’ vehicles at the guard­house and later when they are parked inside the controlled area next to the power plant, Cohn said.

According to the NRC investigation, the bottles were discovered in a parked car.

At the time of the incident, Cohn said, the plant was in full operation with 636 employees.

Vermont Yankee shut down in December 2014 after 42 years of operation. It currently employs about 150 people as the plant prepares for decommissioning and long­term storage of its highly radioactive spent nuclear fuel.