U.S. President Barack Obama has plans to try to bring rationality to the nation’s nuclear weapons program and thereby take the lead in attempting to rein in nuclear proliferation.

He set the stage for the effort with his brief statement in Feb. 12’s State of the Union address: “We’ll engage Russia to seek further reductions in our nuclear arsenals.”

Sad to say, his timing may be wrong. Reaching any new agreement with Moscow will be a problem.

But that won’t compare with what Obama would face from some Senate Republicans. Just listen to what was said during Feb. 12’s Senate Armed Services Committee hearing before the party-line vote — Democrats, yes; Republicans, no — to confirm the nomination of former Nebraska Republican Sen. Chuck Hagel to be secretary of defense.

Alabama Republican Sen. Jeff Sessions, the ranking minority member of that panel’s subcommittee on strategic forces, said, “We are facing and going to be debating the nuclear posture of the United States a great deal” because he had heard Obama would be seeking to reduce numbers.

Then Sessions added: “It does not totally surprise me, because I believe he comes out of the anti-nuclear left.”

He also noted that Hagel was one of five signers to a study on U.S. nuclear policy sponsored by Global Zero, which calls itself an “international movement for the elimination of all nuclear weapons.”

The study said it presented “an illustrative U.S. nuclear force structure” that in 10 years could be an “alternative deterrence construct for the 21st century.”

It lays out some “illustrative” possible future steps over the next decade, including reduction of U.S. nuclear warheads to 900 — 450 deployed but in a nonalert status and requiring a day or two to become launch ready. The other 450 in reserve would be deployable within weeks or longer. In addition, there could be elimination of land-based ICBMs. Such a step would halt the possibility of the ICBMs being launched on an erroneous warning or the possibility they would be a target of an enemy’s first strike.

New Hampshire Republican Sen. Kelly Ayotte, who had sharply questioned Hagel on the Global Zero study during the confirmation hearing, referred last week to the suggested elimination of land-based ICBMs and said, “with the North Koreans testing, with Iran marching toward a nuclear weapon, that’s a deep concern that our secretary of defense less than a year ago would sign onto a report that would state that position.”

While Hagel’s part in the study was the Republicans’ focus, no one pointed out that the study group’s chairman was retired Gen. James Cartwright, former vice chairman of the Joint Chiefs of Staff, who also headed the Strategic Command from 2004 to 2007 during the George W. Bush administration. Another signer was retired Gen. Jack Sheehan, a former NATO commander, along with two retired U.S. ambassadors, Thomas Pickering and Richard Burt.

Nor did anyone note the current posture, or what it will be in 2018. That’s when the 1,550 warhead limit of the 2010 New Strategic Arms Reduction Treaty (START) kicks in. Today’s 450 U.S. ICBMs — strategic intercontinental ballistic missiles — are armed primarily with single nuclear warheads, each of which has an explosive power more than 10 times that of the bombs that destroyed Hiroshima and Nagasaki. In 2018 that will probably drop to 420 ICBMs.

These weapons remain on alert status 24-7, under an early-warning and presidential-decision time schedule born out of the old fear that Soviet Union leaders would launch a first strike to knock out the entire U.S. nuclear force and giving a president 30 minutes to respond.

The U.S. also has 14 Ohio-class strategic submarines, each with 24 sub-launched ICBMs, most armed with up to five warheads with at least three times the explosive power of the bombs dropped on Japan. The navy normally has four or five on active patrol, making some 480 sub-launched warheads available for use at any one time. Those numbers will also be cut to 2018 limits.

Meanwhile, back on U.S. soil, there are 118 B-52 and B-2 strategic bombers, capable of delivering nuclear bombs anywhere in the world, though they are not on Cold War alert.

Just how much destructive power does the U.S. nuclear force represent?

One practical measure can be found in that controversial Global Zero study’s “illustrative categories of targets and warhead assignments” based on Cold War targeting principles.

For Russia, it describes 325 warheads directed against every one of their missile silos, with two for each silo; 110 warheads against leadership command posts; 136 warheads against war-supporting industries. Under the latter two categories, roughly 80 warheads would be directed solely against Moscow.

Think about 80 nuclear explosions, each more powerful than Hiroshima, hitting Moscow.

The Global Zero study also says, with just 900 warheads, the U.S. would still be able to send 250 warheads against China’s missile silos, leadership command posts and war industries — and still have at least 75 warheads left for use against North Korea, Iran or Syria.

Still, I believe Obama would have difficulty selling any new reductions to Republicans in Congress given the partisan politics poisoning Washington.

Two years ago Arizona Republican Sen. Jon Kyl virtually alone, forced the White House to promise to spend $80 billion to upgrade the nuclear weapons complex and at least $100 billion more to replace the strategic delivery systems in return for GOP votes to pass START.

Maybe Obama ought to begin reminding lawmakers and the public what one nuclear weapon would do. He ought to use footage from past atmospheric tests and perhaps newsreels from Hiroshima and Nagasaki.

In the 1970s, I traveled to a South Pacific atoll named Rongelap that in the 1950s got doused with radioactive coral from a hydrogen bomb test 124 miles away. Homes built with cement using sand on the atoll were still too radioactive and had to be destroyed.

Just think of what any country would be like after being hit by just one or two nuclear weapons. That should make people wonder why we even need 1,000 of them, which is close to the new number the Obama administration is considering.

Walter Pincus reports on intelligence, defense and foreign policy for The Washingon Post and writes the Fine Print column.