Scientists Assess Radioactivity in the Ocean from Japan Nuclear Power Facility

With current news of additional radioactive leaks from the Fukushima nuclear power plants, the impact on the ocean of releases of radioactivity from the plants remains unclear.

But a new study by U.S. and Japanese researchers analyzes the levels of radioactivity discharged in the first four months after the accident.

It draws some basic conclusions about the history of contaminant releases to the ocean.

The study was conducted by Woods Hole Oceanographic Institution chemist Ken Buesseler and two colleagues based in Japan, Michio Aoyama of the Meteorological Research Institute and Masao Fukasawa of the Japan Agency for Marine-Earth Science and Technology.

They report that discharges from the Fukushima Dai-Ichi nuclear power plants peaked one month after the March 11 earthquake and tsunami that precipitated the nuclear accident, and continued through at least July.

Their study finds that the levels of radioactivity, while high, are not a direct threat to humans or marine life, but cautions that the effect of accumulated radionuclides in marine sediments is poorly known.

The release of radioactivity from Fukushima--both as atmospheric fallout and direct discharges to the ocean--represents the largest accidental release of radiation to the ocean in history.

Concentrations of cesium-137, a radioactive isotope with a 30-year half-life, at the plants' discharge points to the ocean peaked at more than 50 million times normal/previous levels.

Concentrations 18 miles offshore were higher than those measured in the ocean after the Chernobyl accident 25 years ago.

This is largely related to the fact, says Buesseler, that the Fukushima nuclear power plants are located along the coast, whereas Chernobyl was several hundred miles from the nearest salt water basins, the Baltic and Black Seas.

However, due to ocean mixing processes, the levels are rapidly diluted off the northwest coast of Japan.

The study used data on the concentrations of cesium-137, cesium-134 and iodine-131 as a basis to compare the levels of radionuclides released into the ocean with known levels in the sea surrounding Japan prior to the accident.

The resulting paper, Impacts of the Fukushima Nuclear Power Plants on Marine Radioactivity, is published in the current issue of the journal Environmental Science & Technology.

Buesseler was awarded a rapid-response grant from the National Science Foundation's (NSF) Division of Ocean Sciences to establish baseline concentrations of radionuclides in the Atlantic and Pacific Oceans.

"Understanding and management of the long-term geochemical fate and ecological consequences of radiochemical contamination of the sea is dependent on our knowledge of the initial conditions," says Don Rice, director of NSF's Chemical Oceanography Program. "Acquiring that knowledge depends on our ability to deploy experts to the scene with minimal delay."

The investigators compiled and analyzed data on concentrations of cesium and iodine in ocean water near the plants' discharge points.

The data were made public by TEPCO, the electric utility that owns the plants, and the Japanese Ministry of Culture, Sports, Science and Technology.

The team found that releases to the ocean peaked in April, a fact they attribute to "the complicated pattern of discharge of seawater and freshwater used to cool the reactors and spent fuel rods, interactions with groundwater, and intentional and unintentional releases of mixed radioactive material from the reactor facility."

The scientists also found that the releases decreased in May by a factor of 1,000, "a consequence of ocean mixing and a primary radionuclide source that had dramatically abated," they report.

While concentrations of some radionuclides continued to decrease, by July they were still 10,000 times higher than levels measured in 2010 off the coast of Japan.

This indicates that the plants "remain a significant source of contamination to the coastal waters off Japan," the researchers report.

"There is currently no data that allow us to distinguish between several possible sources of continued releases," says Buesseler.

"These most likely include some combination of direct releases from the reactors, or storage tanks or indirect releases from groundwater beneath the reactors or coastal sediments, both of which are likely contaminated from the period of maximum releases."

Buesseler says that at levels indicated by these data, the releases are not likely to be a direct threat to humans or marine biota in the surrounding ocean waters.

There could be an issue, however, if the source remains high and radiation accumulates in marine sediments.

"We don't know how this might affect benthic marine life, and with a half-life of 30 years, any cesium-137 accumulating in sediments or groundwater could be a concern for decades to come," he says.

While international collaborations for comprehensive field measurements to determine the full range of radioactive isotopes released are underway, says Buesseler, it will take some time before results are available to fully evaluate the impacts of this accident on the ocean.

The Gordon and Betty Moore Foundation also funded the research.

-NSF-

DHS's First Patent: A Citizen's Dosimeter!

It fits in your wallet and can save your life.

No matter how many plastic cards currently crowd your wallet, one day you may wish to make room for one more. The Department of Homeland Security(DHS)’s Science and Technology Directorate (S&T) has developed a miniaturized version of a dosimeter, a portable device used for measuring exposure to ionizing radiation, which can provide life-saving early detection in the unlikely event of a nuclear accident or dirty bomb.

Dubbed the Citizen’s Dosimeter, this high-tech plastic card would be as convenient and affordable as a subway card, with the capability to measure the amount of radiation on a person or in a given area. The National Urban Security Technologies Laboratory (or NUSTL, pronounced new STEEL) located in New York City and managed by DHS S&T, has been awarded a patent that covers the development of radiation dosimetry technologies – DHS’s first patent.

Currently, personal radiation dosimeter badges are worn in nuclear plants, but a plant dosimeter cannot be read on the spot; it must be sent to a processing lab to determine an individual’s radiation dose. While a final prototype has not yet been built, a workable blueprint for a wallet-sized card that can detect radiation in real time is now in place.

“We were inspired by the Metro cards we use every day to get around Manhattan, and envisioned a dosimeter with that level of convenience,” says Gladys Klemic, a NUSTL physicist who managed the project from Illinois. Klemic believes a dosimeter in this form could benefit both emergency responders and the general public.

Klemic and her team at NUSTL set out to create a dosimeter that would meet American National Standards Institute (ANSI) requirements for personal radiation dosimeter badges, and incorporate commercially available components to decrease the size and lower the price tag.

NUSTL began by using radiation-sensitive material from Landauer, Inc., a commercial dosimetry provider in Illinois, testing materials of varying thicknesses and combinations to determine how thin they could make the card while still achieving the targeted performance. After testing nearly a half a dozen materials, the NUSTL scientists determined that using the chemical element tantalum allowed them to obtain accurate readings with minimal thickness. Combining this element in a unique double-layer, stainless steel filter helped to reduce false positives. It was this unique design that led to the patent award.

The next step is to develop a card reader to reveal the radiation dose measured by the Citizen’s Dosimeter. In the event of a nuclear incident, first responders equipped with a card reader would immediately be able to measure radiation exposure for anyone carrying the Citizen’s Dosimeter. While it will be years before a card and reader can be prototyped, tested, certified and wallet-ready, NUSTL has lined up a team to support the effort, including:

•Engineers at StorCard, a California-based group that has previously developed a prototype credit-card floppy disk and reader

•Nomadics, an Oklahoma engineering firm

•Radiation detection experts at Landauer and Oklahoma State University

The Citizen’s Dosimeter represents a technological breakthrough and the next generation in radiation detection. It also demonstrates how public-private partnerships can work to produce life-saving solutions – in this case, protecting the nation from radiation resulting from an act of terrorism or natural disaster.

Unlocking Research on Nuclear and Radiological Threats

By John Ohab

This blog post was shared with us by the Chemical, Biological, Radiological and Nuclear Defense Information Analysis Center (CBRNIAC).

The Chemical, Biological, Radiological and Nuclear (CBRN) history of the United States exists in sealed documents and gated buildings. Part of The Chemical, Biological, Radiological and Nuclear Defense Information Analysis Center’s (CBRNIAC) goal is cataloging historical CBRN research for future use. Although most people are not familiar with the exact studies that occur at CBRN labs, you may be familiar with some of the sites.

Einstein buffs may be aware of the famed Trinity site, home to the first nuclear explosion. Other sites, like the One-Million-Liter Test Sphere, played a major role in biodefense experimentation during the Cold War. Or perhaps you’re familiar with the Air Force Weapons Lab Transmission Line Aircraft Simulator, which was used to test aircraft against electromagnetic pulses to simulate nuclear detonations.

CBRNIAC takes studies, conducted at sites similar to these, and catalogues the work to increase its accessibility across the DoD and government agencies. We are one of ten IACs that work with the Defense Technical Information Center (DTIC). Like the other IACs, we track and analyze research that has been conducted specific to our technical focus area (for us, CBRN defense); our staff of subject matter experts makes this research accessible to those who may not have the time to sift through the mountains of data themselves, and is available to provide answers to specific questions.

This capability is particularly important when world events necessitate a quick response to a complex problem. The current situation in Japan is one example. CBRNIAC has developed a diverse collection of data on radiological threats, including our own original research as well as studies conducted by others with expertise across government, industry, and academia. DoD and government agencies interested in past CBRN research have access to the reports directly through DTIC, or can call our experts for assistance. If applicable studies cannot be found, we have the capability to perform new research ourselves. Agencies may be interested in viewing studies on the radioactive nuclear fallout on ships, methods to properly measure radioactive fallout in the air, and testing on protective equipment used in nuclear facilities.

The Chemical, Biological, Radiological and Nuclear Defense Information Analysis Center (CBRNIAC) is one of ten Information Analysis Centers (IACs) chartered by DOD and managed by the Defense Technical Information Center (DTIC). CBRNIAC is the DOD Center of Excellence responsible for acquiring, archiving, analyzing, synthesizing, and disseminating scientific and technical information related to Chemical, Biological, Radiological and Nuclear (CBRN) Defense.