Reaction to Fukushima

On March 11, a devastating earthquake hit Japan and triggered a massive tsunami that left a wake of destruction, including major damage to the Fukushima Daiichi nuclear power plant. The aging plant consisted of six boiling-water reactors powering electrical generators. The 45-foot waves halted power and disabled a number of reactor cooling systems, leading to nuclear radiation leaks, hydrogen explosions, and most likely, significant core melting. Radiological contamination ensued and Japan mandated a 12.5-mile-radius exclusion zone around the plant.

In response to the radioactive iodine emanating from the power plant, the Japanese government tested water from various cities across its nation and announced that the level of radioactivity exceeded legal limits. Around the world, people feared another Chernobyl—the 1986 reactor explosion that spread carcinogens across Eastern Europe, killed thousands, and left towns uninhabitable—and they needed answers quickly. Los Alamos scientists, experts in nuclear reactions, heeded the call.

Tsunami waves approach the Number 5 reactor of the Daiichi

Tsunami waves approach the Number 5 reactor of the Daiichi nuclear power plant in Fukushima, Japan on March 11.

During the first several weeks following the earthquake, the U.S. Department of Energy (DOE) provided analysis to support the response to events at the Daiichi plant. This support involved a broad set of institutions with more than 200 people contributing. The DOE sought help from Los Alamos, as it did previously for the Three Mile Island and Chernobyl incidents, on issues related to materials, health physics, nonproliferation safeguards, and reactor design. Dozens of experts in electrical power restoration, cooling systems, nuclear and radiochemistry, spent fuel pools, and robotics provided near- and long-term support to Japan.

Los Alamos teams characterized and modeled events during the nuclear accident, hoping to learn more about the safety of reactor cores while simultaneously providing insight to mitigate potential similar events on U.S. soil. Researchers provided technical perspectives regarding hydrogen explosion avoidance, burn-up calculations for isotope release, fission product calculations for coolant systems and worker exposure predictions, corrosion perspectives, heat-transfer analysis, criticality, and methods to decontaminate water. To verify data, Los Alamos colleagues also peer-reviewed calculations performed externally. Additionally, Los Alamos scientist Cas Milner proposed to Japan a technique called muon scattering tomography to help locate and quantify nuclear material. Milner's team constructed a mock reactor in Los Alamos and successfully demonstrated how the technique depicts where the uranium fuel resides within the reactors. [See "Dial µ for Assistance" for more on this effort.]

Los Alamos air specialist Michael McNaughton and colleagues quickly deployed high-volume air samplers to see if radioactive emissions from Japan could be detected in Los Alamos, New Mexico. Detectors in Los Alamos picked up traces of radioactive iodine and cesium, among other isotopes. Levels were higher than those detected after the Three Mile Island incident, but lower than Chernobyl, McNaughton said.

What is the real risk of this type of disaster happening again? Have we appropriately quantified the risk to our own citizens? It's hard to be certain. However, Los Alamos researchers have helped to mitigate the risk by proposing rigorous new regulations to the Nuclear Regulatory Commission (NRC). The accident in Japan was caused by a combination of extraordinary natural forces far more severe than the Fukushima Daiichi plant was designed to accommodate, according to the NRC. Fortunately, as Los Alamos nuclear engineer David Dixon points out, "New reactors address a lot of the problems."

—Kirsten Fox

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