But first the industry needs more information from the NRC, Heymer adds. For example, before utilities harden vents on Mark 1 and Mark 2 reactors, the NEI says, the NRC should issue a letter to require licensees to review plant operational procedures and guidelines. Further, the industry needs NRC guidance on what equipment and instruments are acceptable to monitor water levels and conditions in spent-fuel pools, according to Heymer.

To complicate matters further still, utilities must go off-line to refuel before starting the vent work, NEI notes.

"We are dealing with safety equipment. We have to undertake [those tasks] hand-in-glove with the NRC," Heymer said. "We can't do that without acknowledgement or approval from the NRC."

The agency is expected to issue a generic letter this year that will set in motion analysis of the individual units and scope of work.

The NRC has developed two other tiers of recommendations. The second tier consists of recommendations that cannot be started immediately, including an examination of capability to restore water to spent-fuel pools and additional emergency prepatory actions.

The third tier requires longer-term studies and includes an examination of potential enhancements to prevent or mitigate seismic and flooding hazards, hardened vents for other reactor designs, hydrogen control and mitigation inside containment or other buildings, emergency preparedness for prolonged station blackout and for events that impact multiple nuclear units, public education, changes to reactor oversight and staff training for severe accidents.

Workforce Issues

When the work begins in earnest, Heymer and others say that, for the most part, there will be plenty of talent available to work on modifications, despite competition from new nuclear construction and power upgrades already under way.

Engineers specializing in flooding and seismic analysis could be in short supply, however. "NRC and [NEI] joke that who ever gets out there first, captures the consultants," Heymer says. A shortage could mean the seismic and flooding work would stretch out over several years, according to NEI.

While the companies that service nuclear plants do not want to appear overeager to do the work, "we certainly are trying to make sure the utilities are aware of our capability," says Jeff Merrifield, senior vice president for Baton Rouge-based Shaw Group.