The commission believes that the new requirements will allow plant staff to operate the vents safely if the reactor core is damaged.
The nuclear industry commended the rule.
In a statement to The Hill, Nuclear Energy Institute spokesman Steve Kerekes said it was "in line with the industry’s ideas on the most effective means to address the venting issue, and we consider the timing of the phased approach to be achievable."
Plants will have different deadlines to comply with the requirements depending on their refueling schedules, but the first plants will need to have completed some improvements by June 2014.
The new regulation is part of a series of orders developed after the 2011 disaster at the Fukushima Daiichi nuclear plant. A Platts survey of companies released on Thursday estimated that power plant operators could spend up to $3.6 billion over the next three to five years in response to the tragedy.
In March, the NRC delayed issuing new standards for systems to filter out radioactive material from any gases vented during an accident.
Those systems could cost as much as $45 million each, according to industry groups, though proponents say they are necessary to prevent the kind of catastrophe that occurred at Fukushima.