Wednesday, May 31, 2017

Fukushima Logging, Lumber, and Radiation Safety

The Japanese Forestry Agency is allowing logging to be resumed in Fukushima Prefecture. Before logging begins, the radiation level of the lumber will be evaluated:
Forestry Agency to log and ship Fukushima trees in trial starting this fall. JIJI, Kyodo May 16, 2017
The Forestry Agency said Monday that it will resume felling and shipping trees in Fukushima Prefecture this fall on a trial basis...

...Logged trees will be shipped after radiation checks. In the current fiscal year ending next March, the agency will also thin forests in the village of Katsurao and remove surplus trees in the town of Naraha, although they will not be shipped...

...In order to prevent wood with contamination levels higher than national standards from going on sale, the agency intends to ship only trees logged in forests with radiation levels below 0.5 microsievert per hour.

Tepco plans to build a new incinerator to dispose of radioactive logs that have piled up in the premises, company officials said. The logs amassed to about 78,000 cubic meters after the company felled trees to clear land in order to build containment tanks for contaminated water. Construction materials such as mortar was used to cover the soil to isolate radioactive materials. The new incinerator is slated to begin burning logs in fiscal 2020 through March 2021 and the ashes will be moved to storage warehouses by fiscal 2026, according to the company.

The nuclear plant has an incinerator to burn protective gear worn by workers but the fast-growing pile of logs prompted the company to seek a new facility, which would be able to burn 95 tons of waste per day, they said.
The method for evaluating the radioactivity of lumber in Fukushima is questionable. It seems from the article above that the radioactivity of the entire forest will be measured and the level of radioactivity for particular trees derived from that "forest" measurement level.

However, deriving individual measurement from population level measurement is NOT PREDICTIVE when it comes to contamination by radiation.

Individual trees vary in exposure based on their location. Radioactive hot spots occur naturally as the vagaries of terrain, wind and water run-off lead to concentrated areas of radionuclides. Some trees will be exposed to much greater concentrations of radionuclides than other trees.

Individual trees also vary in their concentration, or bio-accumulation, of radionuclides depending upon the nature of the soil within which they are embedded and in relation to the vagaries of their growth.

The proposed method for evaluating the radioactivity of lumber will not predict the radioactivity of individual trees. Instead, the proposed method offers a homogenized representation that, when symbolically spread across the population, represents "little to no" radiation risk.

So, the risk-assessment appears flawed because it extrapolates individual risk from a homogenized representation of collective risk.

In addition, the proposed risk management approach for radioactive forests - incineration - also raises concerns. Is it possible to trap all contaminants when incinerating radioactive waste?

Even if its possible to eliminate unwanted migration of radioactive materials, what happens with the remaining waste captured in the incineration process?

Highly radioactive waste remains.

Chernobyl's forests are still radioactive and every so often concerns are expressed about fire risks to its radioactive trees:
Braxton Little. June 24, 2013. At Chernobyl, Radioactive Danger Lurks in the Trees. Scientific American,

For almost three decades the forests around the shuttered nuclear power plant have been absorbing contamination left from the 1986 reactor explosion. Now climate change and lack of management present a troubling predicament: If these forests burn, strontium 90, cesium 137, plutonium 238 and other radioactive elements would be released, according to an analysis of the human health impacts of wildfire in Chernobyl's exclusion zone conducted by scientists in Germany, Scotland, Ukraine and the United States.

This contamination would be carried aloft in the smoke as inhalable aerosols, that 2011 study concluded.
Logging in Fukushima seems necessary to prevent unwanted forest fires. However, the risk-management system described in the news article doesn't appear to mitigate effectively against radiation risks.

Monday, May 29, 2017

Spent Fuel Pool Fire at US Could Dwarf Fukushima Impact

Fukushima Daiichi suffered three core meltdowns and one reported spent fuel pool fire (unit 4).

Nuclear fallout from the explosions and fires significantly increased the world’s “background” level of radionuclides: “During the passage of contaminated air masses from Fukushima, airborne 137Cs levels were globally enhanced by 2 to 3 orders of magnitude.”[i]

Fukushima precipitation in March 2011 immediately after the Fukushima accident was more than 3 orders of magnitude higher than the background level of this region [ii] 

Newer research has documented that 75 percent of the radiation released by the plant into the atmosphere occurred after March 15 because of ongoing melting of hot fuel in the cracked spent fuel pools,[iii] with subsequent episodes of increased atmospheric levels of emissions from Fukushima in November and December of 2011, April of 2012, and September of 2012, after which the Japanese researchers discontinued sampling.[iv]

The severe dangers of spent fuel pool fires in the US documented in a 2005 report by the National Academy of Sciences:

Committee on the Safety and Security of Commercial Spent Nuclear Fuel Storage, National Research Council, “Safety and Security of Commercial Spent Nuclear Fuel Storage,” (2006). Washington, DC: National Academies Press.
A new study by the Union of Concerned Scientists indicates that a fire at a US nuclear spent fuel pool could dwarf Fukushima because of the amount of fuel stored in US pools:
Richard Stone. May 24, 2016. Spent fuel fire on U.S. soil could dwarf impact of Fukushima. Science Magazine,

A fire from spent fuel stored at a U.S. nuclear power plant could have catastrophic consequences, according to new simulations of such an event.  A major fire “could dwarf the horrific consequences of the Fukushima accident,” says Edwin Lyman, a physicist at the Union of Concerned Scientists, a nonprofit in Washington, D.C. “We’re talking about trillion-dollar consequences,” says Frank von Hippel, a nuclear security expert at Princeton University, who teamed with Princeton’s Michael Schoeppner on the modeling exercise.
Here is a blast from the past: Blue Glow and Fire(?) at Fukushima: