Thursday, July 18, 2013

Nuclear Leaks 28: The Devil is in the Details

Image Source: Snippets and Snappets.

There are a few unsettling nuclear headlines circulating at present. Bill Gates is set to spend billions of dollars of his own money on the development of mini nuclear reactors which will operate continuously for 30 years. Presumably, this means that he expects to make many more billions back on his investment. After a leak at a Swiss nuclear plant which contaminated drinking water from Lake Biel, attention returned to Japan.

Steam was seen rising today from reactor #3 at Fukushima (you can see a video of the steam entering open air below the jump). This is a cause for "alarm" since reactor #3 contains deadly MOX fuel, which combines plutonium and uranium; the vapour is coming from the fifth floor near the MOX fuel pool; at the same time, local groundwater has unbelievable levels of contamination:
The steam was noticed at 8:20am by repair crews tasked with removing contaminated debris from the building, which was badly damaged by the magnitude-9 earthquake that struck on March 11, 2011, and further battered by the subsequent tsunami.

The roof and walls of the upper stories of the building were torn off by a hydrogen explosion in the days after the disaster.

"All work to remove debris in and around Unit 3 was stopped," a spokesperson for Tokyo Electric Power Co. told The Daily Telegraph. "We have confirmed that radiation levels around the pressure chamber have not changed and at 9:20am we were able to confirm that the reactor has not reached criticality."

Tepco is collecting samples of air above Unit 3 and the assumption at the moment is that the steam is from rain that entered the reactor building and collected in the well beneath the pressure chamber where it became heated.

The incident is likely to raise new concerns about progress to bring the situation under control at the Fukushima plant.

Tepco confirmed recently that high levels of radioactivity had been detected in ground water in a well drilled to determine the spread of radioactivity beneath the plant.

Some 900,000 becquerels of radioactive substances were found per litre (0.22 gallon) in a sample taken from the well, which is just 80 feet from the coast. The radioactivity included strontium and Japan's Nuclear Regulatory Agency has set the safety level for radioactivity in drinking water at 10 becquerels per litre.

The authorities have said it is highly likely that the radioactivity is already leaking into the sea around the plant, despite efforts by Tepco to complete a concrete wall set deep into the ground to restrict the flow of groundwater.
There is some concern that there is an uncontrolled nuclear reaction taking place in reactor #3 (see The Japan Times and AFP). NYT:
[W]orkers were ready to inject water containing boric acid into the reactor from the outside at any signs of further trouble, like a rapid rise in temperature or radiation parameters, the company said in an e-mailed statement. Such spikes would raise the chilling possibility of criticality in the reactor’s damaged fuel, most which is thought to have melted and slumped to the bottom of its containment structure after the hydrogen explosion, one of several at the site in 2011. Boric acid would slow that rate of fission, preventing the worst-case scenario of uncontrolled nuclear chain reactions in the core.
In other words, if the core in reactor #3 were to reach criticality, we would have a nuclear reaction open to the environment, as happened at Chernobyl. However, officials urge calm, because the steam is apparently coming from between the Device Storage Pool (DSP), or from an area between the DSP and the containment lid. The most recent guess from TEPCO is that rainwater was heated and steaming on the containment lid. Should the lid really be that hot?
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