My Point of View on the Japanese Nuclear Situation

This is a user-friendly edition of an article I wrote earlier.  Essentially, I believe there is still too much we don't know about the Japanese nuclear situation to draw any type of technical conclusions.  Instead, we should focus our attentions toward the philosophical reasons behind the failure of a nuclear facility.  In my opinion, we should spend more time considering the people of Japan until it is appropriate to speculate about nuclear fallout. **Note: this point of view is only current with the date on which it was written.


In light of the recent debate hovering over the nuclear situation in Japan, it is appropriate to assess how well the Japanese Fukushima Daiichi and Daini Nuclear Power Stations have actually responded to the March 11 accident.  Are the facilities performing consistent with design specifications, or did they break down unexpectedly under the string of violent natural phenomena?  It is important to ask if the current auxiliary effects of the disaster are due to a safety performance response to natural phenomena. To appropriately make a decision about nuclear safety performance, one needs to understand the basis for safely designing and building a nuclear facility.

 Regulating nuclear safety is a national responsibility. It is carried out by the Nuclear Safety Commission and Japan Nuclear Safety Organization in Japan, and the Nuclear Regulatory Commission and to a lesser degree, by the Department of Energy (DOE), in the United States.  Regulatory standards are established to protect three primary areas: 1) the worker nearest to a possible radiation source; 2) a ‘co-located’ worker within 100 meters of the radiation source; and 3) the public and environment. Regulation is generally accomplished by setting safety standards of all kinds that consider each of the three primary areas.  Safety measures against natural phenomena are broken down into subcategories such as seismic (including earthquake), wind, and flood (including tsunami) safety.  

Engineers and design personnel look at all the components in nuclear facilities that are necessary to maintain safe operation on both a daily basis, and in the event of an accident. Some obvious safety components could be the pumping system responsible for circulating coolant through a reactor core, or the pressure vessel containment room that hermitizes potential radiation leaks.  Each component is categorized in a hierarchy, where components which are absolutely essential to maintaining safety are ranked at the top rung of the hierarchy.  Those high-ranked and integral-to-safety components, along with the facilities that house them, undergo rigorous and completely in-depth safety analyses, and are regarded with only the highest levels of required safety confidence.

As an example of the type of safety regulations currently in place, US facilities classified as DOE PC-4 (which would be the equivalent superiority of ranking of the Fukushima Daiichi and Daini nuclear power stations) have been built or retrofitted to withstand potential natural phenomena accidents.  The PC-4 facility safety basis is prepared to mitigate the worst seismic activity expected in 10,000 years (the “10,000 year event”), and the worst tsunami event expected in 100,000 years (the “100,000 year event”).  The 10,000 and 100,000 year events have a 0.01% and 0.001% chance of occurring—probabilities that are incredibly low, and almost difficult to visualize. If they occurred, they would be catastrophically unprecedented; this catastrophic nature was witnessed in Japan on March 11, 2011.

Nuclear facilities of all types are designed and built to withstand cataclysmic accidents.  Standards are delivered by the nuclear national regulating body, and project the responsibility to individual facilities to produce a design, or upgrade an existing facility, to meet safety standards.  It is the duty of the facility to determine specific case-scenarios of each probable accident, and enact commensurate safety precautions.  Facility specifics of seismic and tsunami events (and all natural phenomena events) are generated by considering a variety of factors.  Seismic analyses include considerations of ground acceleration or velocity, natural ground and structural frequency movement and amplification, and the inelastic energy absorption capacity of structures (toughness, ductility, and redundancy). Tsunami analyses include agents such as tidal wave height effects, storm surges, and tides. One of the products of the tsunami analysis is a flooding depth that the facility must be designed or retrofitted to withstand. 

The Daiichi and Daini Nuclear Power Stations were built and regulated to withstand and mitigate the effects of a magnitude 8.2 design basis earthquake, and to withstand a degree of flooding a little more than two foot below the estimated March 11 tsunami level.

In short, nuclear facilities are designed and maintained to meet certain performance criteria under the event of a postulated accident occurring at a postulated frequency (the 100,000 year event). Consider a statement given by the Federation of Electric Power Companies of Japan (FEPC) Washington DC Office as of 4:30pm (EST), March 13, 2011,

“Japanese nuclear facilities are built to exacting safety standards. They are designed to withstand powerful seismic events, such as earthquakes. In this earthquake—the strongest recorded over the past 100 years in Japan—the containment structures of Fukushima Daiichi maintained their structural integrity. These facilities were designed to withstand tsunamis within a range of assumed strength. In this event, however, the force of the tsunami exceeded the assumed range and flooded diesel generators at Fukushima Daiichi power station, thus precipitating the loss of power for the reactor cooling systems.”

The Fukushima Daiichi nuclear facilities met their design standards. The above reference also states that the Fukushima Daiichi and Daini Stations “shut down automatically in response to the earthquake.”  The power stations were designed to shut down in the event of an earthquake, and indeed, this is what they did. After shutdown, diesel generators kicked in to supply DC electricity to the plant, exactly as designed.  The nuclear facilities withstood the effects of a 6.0 magnitude earthquake (it was ranked a magnitude 9 at the epicenter, and magnitude 6 at the plant site), just as designed.

However, the facility safety design range was insufficient to mitigate the effects of the tsunami. Had the nuclear facility been designed to safely consider a larger tsunami or greater flooding depths comparable to the March 11 phenomena, it is reasonable to believe one wouldn’t see the presently-emerging ancillary effects (loss of electrical power, interaction of hydrogen and oxygen vapor). 

If the Fukushima Daiichi nuclear facilities performed according to design under the stresses of the accidents, where is the safety performance problem?  There was no safety performance problem. The problem lies in the safety performance design range.  Again, in the Japanese situation, structures withstood the affects of the 6.0 magnitude earthquake: they performed as intended. This is a triumph for the nuclear safety industry: facilities are standing up to the hazards they were designed to withstand.  The current tragedy was precipitated because the safety performance design range didn’t regulate up to the March 11 tsunami, hence the flooding of the diesel-generators powering the coolant pumping system.

Could we expect a similar triumph of hazard mitigation in a US nuclear facility?  Of course.  If an accident falls within the basis of safety design, or the safety performance design range, it is legitimate to assume it will be mitigated, exactly as was just witnessed at Daiichi with its proper response to seismic activity. What if a natural phenomena accident occurred outside the safety design basis of the facility (consider how improbable it would be to have the actual occurrence of the worse-case-scenario tsunami predicted in 100,000 years)? Nobody can say.  It is only speculation.

The reason for concern at the Daiichi station was not the safe design of the reactor, but the initial regulatory standards on which the design was based.  The concern was the safety performance design range. This lends the very legitimate question: how is the safety range determined? 

The safety performance design basis range is a compromise negotiated between the perceived or calculated cost of researching and implementing safety, and the commensurate safety risks or benefits.  A simple cost-benefit analysis. Theoretically, a nuclear power plant could be built to withstand the worst perceivable earthquake or tsunami in a million years.  However, implementing such stringent safety procedures could be financially irrational and even irresponsible. 

The question.  Where does one draw the line between the cost of researching and implementing safety design, and the perceived benefits of a more stringent implemented safety design?

That is the true question the media and public should be asking.  The Fukushima Daiichi and Daini Nuclear Power Stations responded in the ways they were designed to respond. Greater tsunami affects could potentially have been predicted and even compensated for.  If sufficient funds and time were spent in designing and implementing more stringent safety processes, we potentially wouldn’t be witnessing white plumes of steam ascending from Daiichi Reactors 1 and 3.  The current Japanese state of emergency is not an issue of technological adeptness. The state of emergency, and our future nuclear performance, is more about choosing an appropriate safety performance design range.

The future of nuclear energy should target finding the compromise between cost and safety, and then live with the conscience and consequences of that decision.