Electric Boat, best known for its expertise in developing nuclear-powered submarines, may help design the next generation of nuclear plants to produce electricity. The Groton-based General Dynamics division has a tentative agreement with San Diego-based General Atomics, leading one of the two teams that have been awarded $40 million by the U.S. Department of Energy to design and plan for new nuclear plants. "This is a relatively small effort that could involve a limited number of EB engineers and designers through this summer, whose task it would be to ensure that any design is producible and affordable," EB spokesman Robert A. Hamilton said.