Sens. Barbara Boxer, D-Calif., and Tom Carper, D-Del., in a letter urged the chairman of the U.S. Nuclear Regulatory Commission (NRC) to conduct a comprehensive investigation of all U.S. nuclear facilities "to assess their capacity to withstand catastrophic natural or man-made disasters including scenarios that may be considered remote like the recent events in Japan."

Boxer, chairwoman of the Committee on Environment and Public Works, and Carper, chairman of the Subcommittee on Clean Air and Nuclear Safety, sent the letter March 17 to NRC Chairman Gregory B. Jaczko.

"[T]he multiple simultaneous failures of backup coolant systems at nuclear reactors in Japan are a clear warning that we must step up efforts to ensure that every precaution is taken to safeguard the American people from a similar incident at a U.S. nuclear facility," they wrote.

They particularly urged that special attention be paid to U.S. nuclear reactors that share "similar characteristics as the failing reactors in Japan, including similar designs or located near a coastline or seismic fault line."

The NRC is required to update the two committees that the senators chair. In addition to those updates, the senators outlined six requests they want answers to "as soon as possible:"

1. Please identify all U.S. nuclear facilities subject to significant seismic activity and/or tsunamis.
2. What extra safety features does the NRC currently require for facilities that have a credible threat of an earthquake and/or tsunami? In light of the recent events in Japan, we would also like the NRC to re-examine the assumptions used to determine the maximum credible threat and suggest additional options that could provide a greater margin for safety at plants nationwide that might be subject to challenges similar to those currently being seen in Japan following the earthquake and tsunami.
3. Which U.S. nuclear power plants share similar design features with the affected Japanese reactor facilities? Do these facilities have design vulnerabilities that should be addressed to ensure their cooling systems do not fail when confronted by stresses including those similar to what we have seen in Japan following the earthquake and tsunami?
4. How comprehensive is the radiation monitoring system in Japan? Would the U.S. take a similar monitoring approach if a serious accident were to occur here? What increased risk is associated with exposure to mixed oxide fuel?
5. Given what has happened at the Japanese facilities, please describe how the NRC currently ensures the safety of spent fuel pools at U.S. facilities and identify additional steps the NRC could take to better address the vulnerabilities of spent fuel pools at plants in the U.S.
6. Has the NRC modeled what could happen if the U.S. had multiple nuclear accidents simultaneously? If so, how would the NRC respond to such a disaster?

The U.S. has 65 nuclear plants and 104 reactors in 31 states. Thirty-five of U.S. reactors are the "boiling water" type, similar to the troubled reactors in Japan, according to Jaczko, who was questioned by Boxer and others on March 16.

At that hearing, Boxer expressed safety concerns about two nuclear power plants in California that are located near the ocean and within close proximity to earthquake fault lines.

Jaczko said that all the U.S. reactors have been reviewed for various safety concerns including seismologic activity. He expressed confidence in the safety of U.S. nuclear plants.