Tuesday, March 15, 2011

The third explosion.

It seems cautious optimism may have been out of order. Reactor 2 just had an explosion described as being significantly larger than the other two, this suggests that it was a steam explosion within the containment vessel.  They have been having problems with the pressure relief valves on this plant, and such an explosion would be consistent with this.  Early reports suggest that there is some dispersion of radioactive material across the site as a result.

This raises the possibility that the site becomes not merely unsafe, but unworkable.  Not a pleasant thought with a significant number of other reactors in need of supervision, as well as fuel storage pools requiring cooling etc.

There may be some very significant technical challenges ahead.

Monday, March 14, 2011

Thoughts on Fukushima, 14th Mar.

Comments on “Why I am not worried about Japan’s nuclear reactors”


re-blogged at


This very well written account of the possible causes and consequences of the nuclear accidents in Japan at fukushima has stormed to the top of Google search and has already garnered over 220,000 readers. The author is not a nuclear engineer, although he is clearly quite familiar with the technology involved and seems to have a very pragmatic approach to the risks involved.

The arguments and reassurances put forward are based in general on sound science, and do not need the backing of an appropriately qualified authority to back them up. The science is straight forward and is in general un-contentious.

There are a number of points in the account which I would like to comment on.

1) Fukushima reactor 1 does not have a core catcher assembly. This issue has come up in the comments to the post and means that if the core did melt the result would be less controlled than as described in the post. Having said that, this scenario seems unlikely as the core is cooling and is being moderated effectively by boron containing seawater.

2) It has been reported that radioactive Iodine and Caesium are contained in the released products. This is worrying as it may imply that the cladding on some of the fuel elements has been breached. Radioactive Iodine is taken up by the thyroid gland and can lead to cancer of the thyroid. Prompt Administration of Iodine to the affected population is an effective preventative measure at the levels which one would expect given current information. I don’t know about the health consequences of Caesium.

3) Some of the terminology used in the article is not standard. Thus as described in the article there are four levels of containment. It is more normal to describe the “stainless steel kettle” with its concrete surround as the primary containment.

Events have moved on, and we have seen what appears to be a further hydrogen explosion in Fukushima 3. Fukushima 3 is a later version of the same boiling water design and this version seems to have a “suppression pool” underneath the main reactor vessel.

My conclusion is be cautiously optimistic. The picture changes if it turns out that either of the reactors is leaking cooling water, or if significant amounts of the core becomes exposed and heat up in either reactor. One issue which has not been discussed extensively is the status of any spent or irradiated fuel which may be stored on site. Issues surround this have to potential to cause more widespread site contamination, jeopardising continuing operation of the other reactors present.

Selected references:

A trailmeme with some more technical documents is here

Thursday, March 3, 2011

Through a glass darkly metrics and modalities

Metrics for blogging.

Any form of measurement for which there is a preferred outcome creates distortions, whether its school completions, or listings of the best performing schools in terms of students proceeding to college or any other thing. For the two school based metrics mentioned above: in one case we retain students when their time might be better spent elsewhere, in the other case we teach to the interview or teach to the test depending on the college entry requirements in the country concerned. This distorts the system and moves us away from a well rounded education appropriate for the entire educational cohort concerned.

It’s the same in the blog-o-sphere. The search for traffic whether the numbers are important for cash or self esteem reasons distorts the medium.

Distortion is not all bad, the classic Haiku or the sonnet are literary forms where a very constricted format leads to great art.

Stephen Downes in this post http://www.downes.ca/cgi-bin/page.cgi?post=54933 describes  describes many of the tricks Bloggers use to drive traffic to their sites. He is deeply critical. giving out that the result is neither deep, well aruged or authentic. These are all good points, but may misrepresent how many of us use blogs.
Often we are not looking for a long and deeply intellectual discourse which will leave us pondering for the rest of the day, we are looking for the short “edu bite”, fast food for thinkers on the run trying to clear the in-stack on their Google reader page.