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Category Archives: nuclearpower

Lots of radioactivity, but little risk in oceans, seafood near Fukushima

Although the land near the Fukushima nuclear reactors was heavily contaminated by the aerial release of radioisotopes, the majority of the radioactive releases drifted out over the Pacific. There, they were joined by substantial amounts of water that were discharged from the reactors directly into the ocean. A new study, based on data from a NOAA research vessel, takes a look at radioactivity levels near Japan a few months after the disaster. The data suggests that the highest estimates of radioactive discharges are likely to be accurate, but the rapid dilution of the water has kept the levels from Fukushima's isotopes below those of the naturally occurring radioactivity.

Although the peak of discharge into the ocean occurred in early April, NOAA didn't manage to get a vessel in place until June. For the first half of the month, the Ka'imikai-o-Kanaloa (Hawaiian for "Heavenly Searcher of the Sea") sampled the waters and oceanic life off Japan (between 30km and 600km), all while releasing floats that helped researchers identify the predominate currents in the region. Most of the radioactivity was released in the form of cesium isotopes that have half-lives of over two years, so the time needed to get a vessel in place did not allow for a significant decay of the discharged material.

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Dept. of Energy signs agreements to develop small nuclear generators

The Obama administration's Department of Energy, led by Steven Chu, has taken a "portfolio" approach to easing the country into a future in which we're less reliant on fossil fuels. Instead of betting on a single technology to solve all our problems, the DOE has been pushing a mix of renewables, efficiency measures, and nuclear power. After having licensed the first new nuclear plant in decades, the DOE has now reached agreements with companies that are trying to develop an alternative to these large facilities.

Rather than building large, Gigawatt-scale reactor buildings, several companies are developing what are termed small, modular nuclear reactors that produce a few hundred Megawatts of power. These are typically designed to be sealed units that simply deliver heat for use either directly or to generate electricity. When the fuel starts to run down, the reactors will be shipped back to a central facility for refueling. Since they will never be opened on site, many of the issues associated with large plants don't come into play.

The new agreements, set up with Hyperion Power Generation, SMR, and NuScale Power, will give the companies access to the DOE's Savannah River National Lab, with the intention of having them develop sites there for a test installation. Ultimately, the test installations are intended to provide data that will go into the licensing of these new designs. Chu, in announcing the agreement, stated, "We are committed to restarting the nation’s nuclear industry and advancing the next generation of these technologies."

We'll be running a feature on the future of nuclear power in the US early next week.

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US approves new nuclear reactor design

On Thursday, the US Nuclear Regulatory Commission voted to approve a new nuclear reactor design, the AP1000 from Westinghouse. As Energy Secretary Steven Chu put it, the "decision certifying the AP1000 reactor design marks an important milestone towards constructing the first U.S. nuclear reactors in three decades." The administration has already offered over $8 billion in loan guarantees to a project in Georgia that would feature two of these reactors as part of its push for domestic, low-carbon energy.

The Westinghouse design is a pressurized water reactor that includes numerous features that would allow it to continue to cool the reactors even if the site were to lose power—a key design feature, given what happened at Fukushima. Mindful of public perception, the company's website for the design features an entire section that provides a timeline for shutdown following a blackout.

It has been several decades since the US last built a nuclear reactor, and a lot of the country's existing facilities are pushing the edge of their designed lifespans. A significant amount of new construction is going to be needed if the country is to retain nuclear as a source of low-carbon baseline power. At the same time, the lack of recent construction leaves us without a good picture of the economics of building new plants in the US, something the Georgia project could help clarify.

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Fukushima radiation spread: wide dispersion and localized hot spots

Yesterday's issue of PNAS contains two papers that are first steps in tracking the radiation released by the meltdowns at the Fukushima nuclear plant. Both contain bits of good news: a substantial amount of the radiation went out over the Pacific, and most of the remainder is concentrated immediately northwest of the crippled reactors. However, they also indicate that some isotopes released by the damaged reactors were spread fairly widely across the country, raising the prospect of localized hot spots.

The two papers take somewhat different approaches to understanding where the radiation went. One of them actually involves environmental sampling of the radiation emitted by five different isotopes that were released from Fukushima. The second builds an atmospheric model of the isotopes' spread, and calibrates the model against real-world data.

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