BOSTON (AP) — Activists who say federal regulators must do more to fix nuclear plant weaknesses exposed by the meltdowns last year in Japan argued Thursday that a safety board should hear their concerns.

The Atomic Safety and Licensing Board met in a federal courthouse in Boston to hear from attorneys for Pilgrim Watch, a citizens group that opposes Entergy Corp.'s Pilgrim Nuclear Power Station in Plymouth.

Pilgrim Watch has filed the only remaining challenge to the Nuclear Regulatory Commission's attempts to correct possible weaknesses at nuclear power plants that came to light after the disaster in Japan.

The safety board is trying to determine if it should hold a broader evidentiary hearing on Pilgrim Watch's claims. It adjourned Thursday with plans to release its decision at a later date.

Carrie Safford, an attorney at the NRC, argued Pilgrim Watch has no legal ground to bring its claims before the board and the board no authority to make several changes the group is demanding.

But Pilgrim Watch attorneys said a board hearing of broader scope is the group's only recourse to demonstrate that NRC changes for the plant don't sufficiently guarantee public safety.

"We would be better off without these changes," said Pilgrim Watch attorney Richard Webster. "It makes us worse off because it forecloses other remedies."

The hearing had no bearing on last month's relicensing of Pilgrim, which allows the plant to operate 20 more years. It came amid an ongoing lockout of union workers over a contract dispute at Pilgrim, the state's only nuclear power plant.

Outside the courthouse, several workers lined a sidewalk to protest plant owner Entergy, while about 25 activists chanted and held anti-Pilgrim signs at another corner of the city square.

Twelve floors above, the main issue was Pilgrim Watch's objection to two enforcement orders that the NRC released in March. The orders aimed to correct possible weaknesses at U.S. plants that came to light after the March 2011 accident at the Fukushima Dai-ichi nuclear plant in Japan. An earthquake and tsunami there sent three reactors into meltdown.

Pilgrim Watch claims the fixes don't eliminate serious problems in two areas. They allegedly don't require a venting system that would be reliable and sufficiently trap lethal contaminants in an emergency. And the group claims the measures to contain spent fuel rods, currently cooled in pools of water at Pilgrim, are inadequate.

The NRC has repeatedly said Pilgrim is safe. On Thursday, Safford said the commission continues to work to reduce risks at nuclear plants, including by considering issues Pilgrim Watch has raised.

But Safford said no one disputes — not even Pilgrim Watch — that the two March orders make U.S. plants safer. She argued the law doesn't allow petitioners to intervene and possibly delay such safety measures.

Entergy attorney Daniel Stenger argued that, by law, the NRC defines the scope of any hearings before the atomic safety board. In this case, that scope is limited to whether the recent orders should be sustained, not whether they should be improved on.

"The petitioners are asking for a number of things the board can't grant," Stenger said.

Webster responded that while the NRC orders may make Pilgrim somewhat safer, they fall far short of meeting the required standard of providing "adequate protection" to the public. Sticking with the flawed orders ultimately puts the public at risk and Pilgrim Watch is entitled to a hearing on the issue, he said.

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