Japan’s magnitude 9.0 earthquake last week was the fifth-largest ever recorded. At press time, the death toll had climbed to more than 3,000 on the Japanese coast, where entire towns were washed away. Adding to the calamity there, and of some concern to residents on the West Coast of the U.S., are the explosions at nuclear reactors near the city of Sendai, which have released enough radiation there to justify mass evacuations of personnel and residents nearby.

As sketchy information from the Japanese government circulated this week and rumors made the rounds online, Americans struggled to get accurate data concerning the potential risk here, should prevailing winds push the radiation to our coast.

But as of Wednesday morning, major news outlets were reporting that there was virtually no threat to the U.S. — for now. Given the fluidity of the situation, that could change in the event of a complete “nuclear meltdown” similar to what happened at the Chernobyl disaster in 1986.

According to Susanne Garfield-Jones, a spokesperson for the California Energy Commission, the term “nuclear meltdown” is not actually recognized by the International Atomic Energy Agency. But what it essentially means is a “severe overheating of the core of a nuclear reactor.” When the core loses coolant, she explained, there is no way to keep the rods in the reactors from overheating, making it possible for them to burn or even “melt.” When this happens, radiation escapes.

Garfield-Jones said the best-case scenario during an incident at a nuclear facility is a “partial melt,” which happened at Three Mile Island in 1979. “The primary containment or the steel casing surrounding the reactor core held the overheated rods intact,” during that accident. Worst case, she said is when the rods breach the casing and become entirely exposed. Japanese officials have admitted to a partial exposure of rods in one facility but are still in the process of containing the situation, using sea water to keep them cool.

The Ventura County Sheriff’s Office of Emergency Services remains in contact with state and federal officials regarding the continuing developments in Japan. According to a press release from the Sheriff’s Office earlier this week, “All the available information indicates weather conditions have taken the small releases from the Fukushima reactors out to sea away from the population.  Given the thousands of miles between the two countries, Hawaii, Alaska, the U.S. Territories and the U.S. West Coast are not expected to experience any harmful levels of radioactivity.”

Meanwhile, the disaster in Japan has not only raised questions as to the safety of nuclear energy, but also about the placement of these facilities, which typically need to be built near large bodies of water. It’s now known that Japan’s reactors were not damaged by the massive earthquake, but by the tsunami. The two power plants situated on the West Coast — San Onofre and Diablo Canyon — are built to withstand earthquakes of magnitude 7 and 7.5, respectively. Both plants are near earthquake faults that aren’t known to generate quakes any larger than that, but there is always the possibility of previously undiscovered faults both on- and offshore.  

Were either of the reactors to fail completely, it’s been reported that the residents within at least a 30-mile radius would be at risk for radiation poisoning. The likelihood of this happening, officials have stated, is very slim and there would be some forewarning.