One Year Later, What Does Fukushima Mean for Nuclear Research?

Map of nuclear power reactors in the USA (image from the U.S. Nuclear Regulatory Commission - http://www.nrc.gov)

How does a Canadian-American professor of uranium mineralogy living in the unassuming American Midwest respond to the one-year anniversary of Fukushima? He writes a calculated review of what?s known and not known about the behavior of nuclear fuel after a reactor accident. Then he goes back to writing grant proposals, reviewing journal articles and fielding questions from graduate students. How do I know this? He?s my boss.

Why should you care? This isn?t just any humdrum review. It showed up in Friday?s issue of Science, and it calls for a return to scientific research to solve big problems.

Peter Burns, the director of a federally funded Energy Frontier Research Center, has been studying uranium for almost 20 years. His earliest work was related to the disposal of commercial nuclear fuel in a geological repository. Remember Yucca Mountain? Burns studied the breakdown of nuclear fuel and the subsequent formation of uranium minerals.

In the years that followed, he served on Nuclear Regulatory Commission discussion panels, a National Academy of Sciences panel on nuclear waste and created a research center for the study of actinide materials. Now his review in Science suggests the need for a national research program to develop comprehensive predictive models of nuclear accidents?a direct response to the accident at Fukushima.

Understanding What Happens After We Know What Went Wrong

One year ago, news reports about a 9.0 earthquake, a nearly 50 foot high tsunami and a potential nuclear reactor meltdown in Japan began a cascade of confusion. Something serious was happening, and everyone watched as reporters struggled to sort out exactly what it would mean.

?Early in a reactor accident, the priority is to minimize [radioactive] release, but as time progresses, the public needs to know information about how much radioactivity has been released,? says Burns. ?What we saw coming out of Fukushima was problematic?we saw quite a few errors in radiation doses that were reported, we saw readings on some of the radiation detection systems that were unreliable. It took a little while for that to get sorted out.?

A review published in Science on Friday examines what happened at Fukushima last year and uses scientific literature from the last four decades to discuss the current understanding of nuclear fuel following a reactor accident. Burns and his co-authors also used reports from government and regulatory agencies along with advice and pre-print publications from other researchers to provide the most up-to-date information.

It may come as a surprise, but the work ahead seems to be in understanding what happens chemically once radioactive material is released into the surrounding environment. Although the modern study of radioactive elements began more than 70 years ago, the behavior of nuclear fuel after an accident remains uncertain.

In the review, Burns says that nuclear fuels are designed to perform under the extreme but well-defined conditions of a nuclear reactor operating normally. He says that studies have looked at irradiated fuel in the context of a geological repository, but little attention has been given to the interaction of irradiated fuel with the environment during and after a reactor accident.

To reduce the damage and potential for radioactive release, he calls for a better understanding of how damaged fuel interacts with ?local, rapidly changing conditions.?

Charting a Course for the Road Ahead

Burns and his colleagues want to understand the chemical breakdown of fuel materials. This includes how fuel dissolves in water and what factors increase the movement of radioactive materials away from a reactor accident and into the paths of those living nearby.

?When isotopes from a damaged radioactive fuel are dissolved in water, these isotopes can be transported and end up somewhere else,? says Burns. ?The radioactivity is now coming from those [transported isotopes] and may wind up in your pumpkin, squash or blueberry muffin. That?s a very different scenario than having them in a power plant.?

One of the challenges in studying nuclear fuel in the environment is the number of variables that can add up in a laboratory study. For example, the interaction of nuclear fuel with groundwater versus seawater can be remarkably different since groundwater would be very dilute compared to the seawater used and released at Fukushima.

There?s even a difference in behavior between fresh fuel, irradiated fuel and fuel following a meltdown.

?Studies of the release of radionuclides from undamaged fuel generally cannot be extrapolated to the extreme conditions of temperature and radiation field that occur during and subsequent to a core-melt event,? says Burns in the review.

Manhattan Project 2.0?

In the review, Burns emphasizes the importance of further study relative to cost and difficulty in order to ?reduce the risk associated with an increasing reliance on nuclear energy.? Can understanding the release of radioactivity after an accident prevent an accident in the future? He thinks so?by updating the design of fuel and reactors to better withstand damage.

?The Fukushima reactors were not designed to withstand the natural events that occurred,? says Burns. ?When the Fukushima reactors were designed and built approximately 40 years ago, there wasn?t a particularly well-developed theory of plate tectonics. We know so much more now about plate tectonics and seismicity than we did then.?

Even with an understanding of low-probability events, Burns doesn?t believe that our nuclear problems will be solved.

?At the end of the day, if you have enough reactors operating in the world, sooner or later you will have another accident,? he says. ?This is why we need to spend effort to understand the actual processes that take place during a core-melt accident and understanding the release mechanisms of radionuclides so that we can reduce the risk of the next accident that takes place.?

Like all big problems worth solving: it won?t be cheap, and it won?t be easy.

Source: http://rss.sciam.com/click.phdo?i=fc071568ce050bdbfb80a4d4757e5bcd

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