Thoughts about the Fukushima incident

By Daniele Pestilli on March 19, 2011
Japan, with aid from US, is struggling to cool down those quake-hit reactors in Fukushima Daiichi Nuclear Plant. Image by United States Navy.

Contributing writer: Andreas Rosendahl Hansen 

The catastrophic quake and following tsunami that hit Japan the 11th of March has received extensive media coverage all around the globe. The scope of the catastrophe is enormous and thousands of Japanese along the Northeastern coast and even the inland have lost their homes and have limited access to water, food and shelter due to broken down infrastructure; aid agencies from all around the world are struggling to to reach those in need and assess the scope of the situation.

One incident in particular has captured the attention of worldwide media: the situation at the Japanese Fukushima Daiichi nuclear power plant. While the media coverage has been intensive with numerous pictures of collapsing structures and interviews with nervous Japanese officials, the information flow as to what has really happened and to what extent Japan is experiencing a nuclear hazard has been very nontransparent and fraught with exaggerations and hyperbole.

To explicate my point, I will firstly compare the situation at Fukushima with the biggest nuclear disaster in human history – Chernobyl – and in doing so, I will evince whether or not a disaster of the same magnitude could occur in Japan. Second, I will look into the media coverage of the situation and assess whether or not the media has a bias in cases such as this.

Technicalities

If one wants to compare Chernobyl and Fukushima, the overall construction and layout of the plants is a good place to start. Dr. Josef Oehman, Ph.D and research assistant at MIT writes the following about the construction of the Fukushima plant:

    The plants at Fukushima are Boiling Water Reactors (BWR for short). A BWR produces electricity by boiling water, and spinning a turbine with that steam. The nuclear fuel heats water, the water boils and creates steam, the steam then drives turbines that create the electricity, and the steam is then cooled and condensed back to water, and the water returns to be heated by the nuclear fuel. The reactor operates at about 285 °C. (…)

    The core is then placed in the pressure vessel. The pressure vessel is a thick steel vessel that operates at a pressure of about 7 MPa (~1000 psi), and is designed to withstand the high pressures that may occur during an accident. The pressure vessel is the third barrier to radioactive material release.

    The entire primary loop of the nuclear reactor – the pressure vessel, pipes, and pumps that contain the coolant (water) – are housed in the containment structure. This structure is the fourth barrier to radioactive material release. The containment structure is a hermetically (air tight) sealed, very thick structure made of steel and concrete. This structure is designed, built and tested for one single purpose: To contain, indefinitely, a complete core meltdown. To aid in this purpose, a large, thick concrete structure is poured around the containment structure and is referred to as the secondary containment.

Source

In other words, the containment structure is built to withstand and contain a meltdown indefinitely. The nuclear power plant of Chernobyl had no such containment, as all Soviet nuclear power plants were built with the development of plutonium in mind. The plutonium was from the uranium fuel rods of the power plant, but in order to avoid contamination of the plutonium, the rods had to be changed relatively often, which made a hermetically sealed containment inconvenient. This meant that when disaster struck, radiation was leaked directly into the atmosphere.

Another difference is the system of moderation in the two reactors. All nuclear power plants today operate using nuclear fission, wherein a neutron is absorbed into the nucleus of a uranium isotope causing it to split, releasing heat in the process. This heat is then used to boil water, which drives turbines producing power. In order to control the reaction, control rods that absorb neutrons are inserted between the fuel rods (this is what moderation means). That is not all: in water-based reactors like Fukushima, the coolant itself helps absorbing neutrons. However, in Chernobyl, the reactor was moderated with flammable graphite. That meant that when an explosion shattered the outer casing, graphite fell into the reactor and fueled the fire causing radioactive smoke to spread. This fire lasted for thirteen days and all the while radioactive material was released into the atmosphere.

Also, it is important to stress that all the reactors at the Fukushima plant have been shut down and this happened as soon as warnings about the earthquake started to come in. The reason why the reactors still need cooling is the residual heat generated by the fission products.

Essentially, the chance that the Fukushima incident will evolve into something as bad as Chernobyl is virtually null. The containment is built for the sole purpose of keeping radiation and heat from a meltdown inside. Also, the whole construction of the Fukushima reactor is such that a meltdown (a situation, where all the fuel melts together and start generating huge amounts of heat and radiation) cannot happen. I encourage anybody interested in the matter to read Dr. Josef Oehmans assessment of the situation, which also explains the explosions that has happened in all three reactors. Even if the containment should fail, the release of radiation will be greatly retarded by the fact that the Fukushima reactors are moderated by water and not flammable graphite.

Media coverage

Anyone following the situation in Japan closely will undoubtedly have noticed the strong one-sidedness and anti-nuclear bias in the media coverage. While some critique, such as Iouli Andeevs critique of the spent fuel deposit, and former member of the Japanese Nuclear Safety Committee, Dr. Katsuhiko Ishibashi's critique of building plants near fault zones are undoubtedly justified, reactions to the situation have been verging on the hysterical. Even before the damage and hazard level of Fukushima had been properly determined, German chancellor Angela Merkel announced that she plans to shut down all German nuclear power plants built before 1980 and Japanese are migrating south from Tokyo in the thousands due to a marginal rise in radiation levels. The Fukushima plant has endured the fifth largest earthquake in the history of man and a following 10 meter tsunami and while the situation remain uncertain and Japanese authorities are struggling to keep the situation under control, the IAEA is, at the time of writing, yet to disclose any information that there has been any radiation leakage that poses any major health hazard to even the local area. In any case, even if the Fukushima incident should turn out to be a major health hazard, there is virtually zero chance that any German plant, or any European plant for that matter, would ever be subject to a natural disaster of such magnitude. Furthermore, use of terminology in the press such as ‘nuclear explosion’ when referring to the explosions due to hydrogen buildups in the vented steam and the frequent mentioning of radiation danger without assessing its hazard level has contributed with nothing other than undue panic and taken the focus away from the thousands of Japanese who are in real danger and immediate need of shelter, medical attention and aid.

There is no doubt that the situation at Fukushima remains extremely serious. Workers are still struggling to keep water levels sufficiently high and unconfirmed rumors hints at a leakage from the containment shell of one of the reactors and cooling by helicopters were canceled due to rising radiation levels above reactor three. However, no matter what the situation in Fukushima will evolve into, the population of Japan has the right to unbiased and accurate radiation hazard assessments and information related to the incident, so they do not have to endure unnecessary worries in an already excruciatingly difficult situation.