What is up with Fukuishima Spent Nuclear Fuel Pond Unit 4?

There is a recent report by R. Alvarez, former Policy Adviser to the Secretary of Energy, under the Clinton administration which claims that an earthquake at Fukushima Unit 4 could cause a widespread disaster by the release of Cs-137 from the spent nuclear fuel stored in the cooling pond. Let’s examine some of the information and see if this has any factual or technical basis.

According to the Former Japanese Ambassador to Switzerland and Senegal:

"It is no exaggeration to say that the fate of Japan and the whole world depends on No.4 reactor." A Former Japanese Ambassador to Switzerland and Senegal Mitsuhei Murata.

Is this an exaggeration?

Robert Alvarez an Institute for Policy Studies analyst and a former Senior Policy Adviser to the Secretary of Energy during the Clinton Administration has recently been issuing dire warnings as well.

Per a May 1, 2012 letter sent to UN Secretary Ki-moon:

Robert Alvarez, Senior Scholar at the Institute for Policy Studies (IPS), who is one of the best-known experts on spent nuclear fuel, stated that in Unit 4 there is spent nuclear fuel which contains Cesium-137 (Cs-137) that is equivalent to 10 times the amount that was released at the time of the Chernobyl nuclear accident. Thus, if an earthquake or other event were to cause this pool to drain, this could result in a catastrophic radiological fire involving nearly 10 times the amount of Cs-137 released by the Chernobyl accident.

Alvarez’ 2011 report primarily addresses issues with US SNF but also makes some rather large claims about Japan's Fukushima Daiichi spent nuclear fuel. What he does not address are some of the key questions that need to be answered to complete a technical assessment:

1. How is the fuel at Fukushima Unit 4 stacked – low, medium, or high density fuel storage? This makes a significant difference in accident assessments (see NRC NUREG 1380). As part of fuel management at the Fukushima site there is also a common spent nuclear fuel pond where fuel from the four reactors can be stored that has been in operation since 1997 and dry cask storage in operation since 1994 (report).
2. The Fukushima Unit 4 is a boiling water reactor (BWR) rather than a Pressured Water Reactor (PWR). This is an important distinction to make since the results of the analysis show very different results based upon whether or not the system is a BWR versus a PWR. NRC NUREG 1353.
3. The most recent fuel discharged from the reactor has been cooling for over a year. This significantly decreases the amount of radioactivity and therefore the resulting decay heat as shown in the figure to the right.
4. How was the most recently removed fuel stored relatively to other “cooler” fuel – according to the 2006 National Academy of Sciences report this makes a significant different in heat removal between fuel assemblies.
5. What is the assessment of the structural integrity of Unit 4? According to US Senator Ron Wyden, a senior member of the Senate’s energy committee“Another big earthquake or tsunami could send Fukushima Daiichi’s fragile reactor buildings tumbling down, resulting in “an even greater release of radiation than the initial accident yet neglects to mention that TEPCO has already evaluated the damage and reinforced the structure:
   

• Tepco says an analysis it conducted on the Unit 4 pool showed the building didn’t need reinforcing, but it went ahead and reinforced the structure anyway, increasing its safety margin by 20%. Tepco says it’s working to remove the fuel rods as fast as it can. If all goes according to its timetable, the utility could start taking the rods out in 2014. (WSJ 4/17/12)(special thank you to http://neutroneconomy.blogspot.com/ for this information)

Therefore before I take Robert Alvarez’ comments on face value, or those of even former Japanese Ambassadors – there are a few key questions that if answered could provide a clear estimate of risk over exaggerated claims with little or no real information or assessment.

Ciao Susan Voss