Two Massachusetts Democrats are urging nuclear regulators not to renew operating licenses for nuclear plants -- namely, the Seabrook plant in New Hampshire -- if operators request the renewals years or even decades before the current license expires.

Rep. Ed Markey, ranking member of the House Natural Resources Committee, and John Tierney, a senior member of the House Oversight and Government Reform Committee, asked Nuclear Regulatory Commission Chairman Gregory Jaczko today to deny a 20-year license renewal for the Seabrook nuclear plant in Seabrook, N.H.

NextEra Energy Seabrook LLC, which operates the plant 40 miles north of Boston, requested a renewal last year to operate the plant from 2030 to 2050. The plant first received its operating license in 1986 and the license expires in 2030, the company said.

Scott Burnell, a spokesman for the agency, said NRC is expected to complete a review of the application in January and an environmental review in March.

The lawmakers pointed out that inspections at the plant uncovered a tunnel related to the cooling system had been weakened from water saturation during the past decade. Two 3-mile-long tunnels are used to carry water to the plant from the Atlantic Ocean, according to the company's website. "There is simply no way that the NRC can guarantee that it will remain safe until it enters its 'golden years' almost 40 years from now," they wrote.

NextEra said it self-identified the issue and prolonged groundwater intrusion is only potentially affecting a small section of the wall in the electrical tunnel that is not related to the plant's cooling system. The plant is built to high safety standards and is well above its design safety requirements, the company said.

NRC said yesterday that a team of international nuclear safety experts will visit the Seabrook plant from June 7 through June 23 to conduct a voluntary peer safety review of the facility. The team will issue a report identifying best practices and suggesting possible safety improvements, NRC said.

Markey and Tierney are also asking NRC to adopt a more general policy to block requests for 20-year license extensions up to 20 years before a license expires. The commission is currently considering such applications for 16 existing reactors at 11 power plants, they said.

The commission should also hold off on approving the applications until lessons are learned from the crisis at Japan's Fukushima Daiichi nuclear complex, which was struck by an earthquake and tsunami on March 11. NRC has approved four license extensions since the Japan disaster without incorporating findings from the Fukushima accident into the applications, they said.

Burnell said the agency's regulations regarding license renewal have a reasonable technical and legal basis for allowing plants to apply for renewed licenses once a plant has been in operation for 20 years. Several plants have already applied at or very near the 20-year mark, he added.

Click here to read the lawmakers' letter.