The Salem Generating Station is among the industry's top water users, pumping a trillion gallons a year from the Delaware River.

At issue is whether plants such as Salem should be required to install expensive, fish-protecting cooling systems or whether they'll be allowed to implement cheaper fish protection measures.

A Bush administration regulation set to take effect next month gives nuclear plants wider latitude to choose how they protect fish. Attorneys general from six states, including New Jersey, filed suit last month to block the rule.

"The EPA is once again putting the profit margin of power companies ahead of protecting the environment and the public," New Jersey Attorney General Peter C. Harvey told The Philadelphia Inquirer for Monday's editions.

PSEG Power, the operator and majority owner of the Salem plant, said it has spent $100 million over more than a decade trying to solve the fish-kill problem. Under state Department of Environmental Protection requirements, the owners have installed rotating screens to keep out larger fish, and have restored 21,000 acres of nearby tidal marshes to help boost the fish population.

PSEG Power says the amount of water and fish it extracts is a small fraction of the resources in the Delaware River and Delaware Bay estuaries, where an estimated 46 trillion bay anchovies live and an estimated 0.01 percent are killed by Salem.

Environmentalists want to force the plant to install a "closed- cycle" cooling system, which reuses water instead of using it just once. PSEG estimates the cost of such a system at $1 billion. Hope Creek, a newer PSEG nuclear plant next to Salem, already has such a system.