December 03, 2009

Japan Starts MOX Burning Reactor and Small Dose Radiation Risks Are Lower

1. Japan's first ever nuclear power reactor to use mixed oxide (MOX) fuel assemblies is now operating at full capacity, fuel supplier Areva has announced. Kyushu's Genkai 3 was loaded with the fuel fabricated from uranium and the plutonium recovered from previously used nuclear fuel in October.

Recycling of plutonium in MOX is to play a key role in Japan's future nuclear fuel cycle, and two other utilities - Shikoku Electric Power Co and Chubu Electric Power Co – plan to introduce MOX fuel into their reactors in or after 2010.

2. The risks of small radiation doses could have been exaggerated, the Electric Power Research Institute (EPRI) has found. This matters because we should not waste money trying to protect against things that are not actually dangerous. We do not spend money trying to protect against 2 mile per hour collisions or lower because those kind of collisions are not dangerous. Trying to protect against those kinds of collisions would mean spending trillions of dollars without any increase in safety.

The risks from small doses over longer periods have been largely assumed under the 'linear-no threshold' model, which implies that any level of radiation exposure - no matter how small - would cause a corresponding level of biological damage.

After collating more than 200 peer-reviewed publications on the topic, EPRI was able to conclude that this methodology may have been over-estimating the risks. Different mechanisms are at work at each end of the scale, EPRI found from recent studies, and "when radiation is delivered at a low dose rate (i.e. over a longer time period), it is much less effective in producing biological changes than when the same dose is delivered in a short time period."

The data covers more than 100,000 workers per year at US nuclear power plants. Nobody has been exposed to more than the US regulatory annual limit of 50 rem (0.5 Sv) since 1989. "Doses of less than 10 rem (0.1 Sv) in a single exposure are too small to allow detection of any statistically significant excess cancers," said EPRI.

The Ritch letter focused on the currently ongoing revision of the IAEA Basic Safety Standards and a proposal to reduce dose limits for the public from 1 mSv per year to 0.3 mSv. Ritch warned that a "wholly theoretical gain in radiation safety could take precedence over, and act to the detriment of, the real gains in public health and environmental protection that can be achieved through a worldwide expansion of nuclear power."

The tendency to strive for ever-lower radiation doses in the absence of evidence of real health gains "undercuts the fundamental, well-established principle of optimisation of doses, which entails that a judicious balance be struck among real risks and benefits," said Ritch.

In practical terms, a constant drive for lower doses would lead to increasing cost and complication for nuclear operators and regulators, with no measurable benefit for workers or the public.

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