All 3,000 pages of Entergy’s plan to make Grand Gulf Nuclear Station the nation’s single most powerful reactor have been submitted to federal regulators for approval, moving a step ahead in one process and further slamming the hammer on another.

The reactor boost, approved by the Mississippi Public Service Commission in November, is a cap on plans to build additional reactors at Grand Gulf in Claiborne County and at River Bend Station in St. Francisville, La., about 30 miles north of Baton Rouge.

The detailed plan for the reactor boost was submitted on Sept. 10, Entergy officials said.

A decision on whether the utility will be allowed to increase its output by 13 percent is expected in late 2011, though the company might learn within 60 days whether the agency has accepted the plans for a full study, Entergy Mississippi spokesman Mara Hartmann said.

In 2007, when a new nuclear reactor at one of Entergy’s 10 plants nationwide looked certain, the company pushed Mississippi and Louisiana legislators successfully to “front load” future construction costs and pass it on to customers. Sites at each facility had been studied for each to have new reactors built, though building a pair of 1,500-megawatt reactors would have taken nearly a decade and cost Entergy about $10 billion. Both projects, however, were put on the back burner in January 2009 as design costs on the new reactor’s core reportedly tripled. Details on the $510 million “uprate” at Grand Gulf were sent to the Mississippi Public Service Commission four months later.

If approved by NRC, Grand Gulf probably will be “powered up” during a spring 2012 refueling outage. It will result in capacity rising to 1,443 megawatts from 1,265 — enough to keep electricity flowing for an extra 200,000 homes and more productive than any of Arizona’s Palo Verde station’s three units, still the nation’s most productive station. Customers in Mississippi, Louisiana and Arkansas who receive electricity generated at the plant would pay about $6 more in 2013, then pay about $5 less by 2017, according to estimates by the state Public Utilities Staff.

Projections are based on average monthly usage of about 1,000 kilowatts and could vary depending on the price of natural gas, which is the source of about 60 percent of Entergy’s power.

Estimated savings would start the first year for customers of South Mississippi Electric Power Association, according to the Hattiesburg-based utility, which owns 10 percent of Grand Gulf and receives 10 percent of the energy.

In July, the Louisiana PSC permitted a $1 hike in power bills charged by Entergy Louisiana LLC and Entergy Gulf States Louisiana LLC, the latter of which owns River Bend, and together serve about 1 million electric customers in 58 of Louisiana’s 64 parishes. The increase is geared to help the utility catch up on contributions to a trust fund set up to decommission the plant once its license expires in August 2025.

Previous decisions by the state’s utility oversight panel led to a shortfall of more than $300 million and no payments at all since 2002, according to published reports. Entergy Corp. began a two-part, $1 billion bond sale Monday, with much of the sale reportedly going to retire various debts.

River Bend was put into service in June 1986, nearly a year after Grand Gulf began generating in July 1985.

Entergy Louisiana has sought a procedural schedule to evaluate costs of developing plant plans, such as building a new reactor if the utility believes it’s cost-efficient to do so.

Developing plans at River Bend has cost the two Louisiana subsidiaries more than $50.5 million, which the utility has said will continue to be deferred. No plans to boost capacity at River Bend exist now, Entergy spokesman Mike Bowling said.

Extending Grand Gulf’s license beyond 2024 should begin next year with an application, Entergy Mississippi CEO Haley Fisackerly said in June, just before the plant marked its 25th year of power generation.