A Republican member of the Nuclear Regulatory Commission up for re-nomination today before a key Senate committee provided a grim update on the status of damaged nuclear reactors at Japan's Fukushima Daiichi complex.

The plant on Japan's east coast was rocked by a magnitude-9 earthquake and tsunami on March 11, and Republican William Ostendorff said 55 percent of the nuclear core at Unit 1 has been damaged, 30 percent at Unit 2 has been damaged, and 35 percent at Unit 3 has been damaged.

Japanese officials are struggling to handle massive amounts of radioactive water at the nuclear complex, but Ostendorff said he's reasonably confident the plant can be shut down within six to nine months.

Members of the Senate Committee on Environment and Public Works called for Ostendorff's nomination to be swiftly ushered through the Senate and confirmed to ensure the NRC is fully staffed and able to review its own internal policies and safety requirements in the aftermath of the Japanese disaster.

Among his many achievements, Ostendorff has more than 26 years of experience with the U.S. Navy and was elevated to the rank of captain. He also commanded a squadron of attack submarines while serving and is a former Capitol Hill staffer with the House Armed Services Subcommittee on Strategic Forces.

President Obama appointed Ostendorff as a Republican member of the NRC last April to serve out the prior commissioner's term, and he is slated to only be at the agency through June 30 unless he is confirmed for an additional five years. Today, a bipartisan group of senators indicated his confirmation will be seamless.

The full complement of five commission members is needed to conduct safety reviews and checks of the country's 104 nuclear reactors, an effort the commission launched in March that has already uncovered deficiencies at a number of plants, lawmakers said. All commission members are also needed to ensure the agency is making appropriate calls on when and how Americans are evacuated during nuclear emergencies in the United States.

Sen. Frank Lautenberg (D-N.J.) said he was troubled when NRC Chairman Gregory Jaczko recommended in March that Americans in Japan be evacuated 50 miles from the damaged reactors, even though the NRC only evacuates residents 10 miles from crippled plants in the United States.

"We shouldn't be sending mixed signals to the public; the stakes are too high," Lautenberg said. "This is one reason why it's so important to ensure that all the seats on the NRC are filled."

Ostendorff said the recommendation from the NRC came from the chairman alone, but it was also made in the context of interagency discussions with the White House, the Energy Department, the Defense Department, U.S. EPA and other federal agencies that he was not privy to.

"I was not part of those discussions, but my understanding is there were significant interchanges with the other federal branch, executive branch groups" before the recommendation was made, he said.

But Ostendorff said incomplete information and uncertainty around information the commission did have also fed into that decision. This included the fact that three reactors and spent fuel pools were damaged and that there was massive disruption to infrastructure and roads, all of which crippled the information flow and contributed to the agency's very "conservative" call.

The NRC was also assuming that spent fuel in the fourth unit's pool was almost dry, which would have exacerbated the dangerous situation, but Japanese officials at the utility said last week that the pool was never dry, he said. But Ostendorff wouldn't second-guess the chairman's recommendation.

"The best information we had as of last Monday was that pool was never dry," Ostendorff said, adding that the agency may ultimately have some information gaps around what happened in Japan.