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ORAU characterizes radioactivity levels on six ships one year after Fukushima nuclear crisis

Radiological surveys help crews of ships involved in Japanese relief efforts return to normal operations

Ship at sea

After the March 2011 Japan earthquake and tsunami, ORAU’s environmental assessment team was tasked with the unique challenge of performing a characterization survey of a maritime transport ship that had sailed through airborne radioactive materials leaking from the crippled Fukushima Daiichi Nuclear Power Plant. The results of the survey determined that the ship’s onboard air filtration system trapped the vast majority of contamination, but questions still lingered about the radiological condition of other vessels that had also traveled through the Pacific Ocean in the days and weeks following the disaster.

To help alleviate these concerns, ORAU agreed to survey six additional ships that had also played various roles during the U.S. response effort. Similar to the mission of the first ship characterized by ORAU, these new ships had also delivered thousands of pallets of humanitarian relief supplies to Japanese cities affected by the tsunami and helped to replenish nearly 10 million gallons of fuel. Uniquely, one ship surveyed 4.5 million square yards of ocean floor and removed five tons of wreckage that had been washed out to sea from the unprecedented tsunami and that was blocking shipping channels.

Accomplishing these ship surveys took rapid planning and precise coordination. The ORAU team had to mobilize quickly and dispatch health physicists to various parts of the world. They were to each rendezvous with their assigned ships in suitable port areas like Singapore, Thailand and Djibouti. Once aboard, ORAU health physicists sailed with the ships’ crews on their predetermined courses while engaging in survey activities—working seven days per week and sometimes up to 12 hours a day. Ultimately, ORAU would provide clear recommendations for how to release any equipment parts that may have been contaminated.

After completing the survey work for the six additional ships in 2012, the team determined that three of the ships were found to satisfy the criteria for release. The other three ships, plus the original ship first characterized by ORAU immediately following the disaster, underwent further investigation in 2013.

In FY13, ORAU’s environmental assessment team successfully cleared a fourth maritime support ship that had been exposed to radioactive materials leaking from Japan’s Fukushima Daiichi Nuclear Power Plant. ORAU also received approval from the Naval Sea Systems Command for a technical basis document that outlines an innovative approach for quantifying the total amount contamination found within the ships air-handling systems. As the only team cleared with an approved process for surveying and decontaminating ventilation systems, ORAU and its partners expect to have all seven ships fully released by end of FY14.

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Innovating on the run

ORAU health physicists have had become very adept at customizing their tools on the run to adjust for environmental or spatial considerations. For example, when surveying the seven maritime support ships, the team built light-weight frameworks for their equipment to replace the floor monitor carts they typically use during a survey. This adaptation enabled the health physicists to safely carry their equipment up and down the ladders connecting the various decks of the ship while surveying those areas.