Monday, January 09, 2012

Japan Discusses Policy To Shutdown 40-Year-Old Reactors

MihamaNuclearPlant_Jan92012Over the weekend, Japan’s government began discussing a new policy that would shut down the country’s nuclear reactors after they reach their 40th birthday. Some say the move stems from the fact that the Fukushima Daiichi reactors were built starting in 1967, implying that older reactors may not be as safe as newer reactors. Whereas others say the action stems from the government’s plan to eventually phase-out its nuclear energy facilities.

An editorial in The Daily Yomiuri takes the latter view:

Elsewhere in the world, it is rare for a country, except for those advocating abandonment of nuclear power generation, to stipulate by law the life span of a nuclear power station.

Meanwhile, discussion is still under way within the government as to what kind of power supply the nation should have in the future. It seems too abrupt for the government to come up with such a policy now.

Describing the new policy as “abrupt” may be right, given that there currently is not enough evidence to support Fukushima Daiichi’s age being a contributing factor to the reactor accident. The Associated Press explains:

It is unclear whether the age of the reactors was related to the nuclear crisis. The location of the generators, absence of alternative backup power and inadequate venting are believed to be more direct causes, but some critics have said the Fukushima plant showed signs of age, such as cracks in piping and walls.

Without factual basis, it seems premature for Japan to pursue a policy that would likely force many of its 54 reactors to shutdown. This action would likely result in a 36 percent gap in Japan’s power generating capacity by 2030 if alternative energy sources and solutions to cutting demand are not realized.

However, if the law mirrors the United States’ model for license renewals, as The AP indicates that it might, the country could be on a path to better ensuring that its plants are safer and more equipped to operate beyond the 40-year mark.

In the United States, the Nuclear Regulatory Commission has a systematic process that analyzes both the safety and environmental issues that are involved with certifying that a licensee can operate a nuclear plant for an additional 20 years beyond the original license of 40 years. The process takes on average two years to complete and costs the owners of the facility between $10 million and $20 million.

A common misperception that I hear from members of the public is that older nuclear plants are not safe. In fact, an article in today’s SmartPlanet substantiates this myth:

The problems arise from America’s aging nuclear infrastructure, where plants are operating decades past their intended lifespans.

The NRC debunks this claim on its website by stating that there was never a set lifespan for operating a nuclear plant and that the 40-year license is somewhat arbitrary:

A 40-year license term was selected on the basis of economic and antitrust considerations, not technical limitations.

NEI’s fact sheet on relicensing nuclear plants further explains:

The 40‐year term of a nuclear power plant license has nothing to do with aging plant components or a belief that safety needs to be reviewed on a 40‐year cycle. Instead, the period was chosen to parallel the financing amortization period for a plant. Exceeding federal safety standards is an ongoing activity for companies that operate nuclear power plants.

Of the 71 U.S. nuclear reactors that have been granted 20-year license extensions by the NRC, it is important to note that the regulatory agency at any time has the authority to shut down a reactor—regardless of its age—if it feels that the reactor is not fully meeting all of its safety standards. It is also worthwhile to note that the date a nuclear plant starts operating is not a reliable indication of its age or condition because the industry’s sustained maintenance and improvement programs help to routinely reconfirm the plant’s safe operation.

As more is learned about the Fukushima Daiichi accident, and the significance—if any—that the reactor’s age played, the global nuclear industry undoubtedly will incorporate those lessons into how they both operate and regulate today’s operating nuclear plants to ensure that a plant’s age is never a compromising factor to public health and safety.

Photo credits: The Mihama nuclear plant in Fukui Prefecture will enter its 43rd year of operation this year. From The Asahi Shimbun.


Shreejana said...

Yet government is not willing to shut all the nuclear plants down. They are only interested in shutting down those plants running over 40 years. This initiative will hardly Japan to get rid off further disasters.

I recently discovered the following dispersion model, which someone had linked to Berkeley’s discussion page. It uses TEPCO emission data to model possible dispersion patterns for Neptunium and Plutonium

If this model is accurate, it is very disturbing. Where are all of the so-called experts who claimed these elements were too heavy to travel far from the plant site?

Anonymous said...


Setting aside the issue of whether the model is accurate, take a look at what it shows:

I looked at the projections for April 1st, in Chicago IL, which looks pretty close to where the highest intensity of Np/Pu is predicted in this model.

It shows 1.2*10^-7 becquerels per cubic meter of Pu-239. Not an easy thing to understand for the layperson, so let me convert it to mass:

5.2*10^17 grams per cubic meter. A block of air one meter to a side was therefore projected to contain:
0.000000000000000052 grams of Pu-239.

Said another way, the model predicted one single atom of plutonium for every 7-8 cubic centimeters of air. Let's say you take a breath and breathe in a half liter of air (avg according to wikipedia), which is 500 cubic centimeters. You'd breathe in about 66 atoms of plutonium.

Let's say you didn't exhale those atoms right back out (in reality you probably would--at least most of them). Those 66 atoms of plutonium would have an activity of 6*10^-11 becquerels (or disintegrations per seconds). Take the inverse of these and you find that there would be 16 billion seconds between each disintegration. (A disintegration meaning one of those Pu-239 atoms decays and emits its alpha particle into your lungs).

In other words, those 66 atoms from that breath would need to reside in your lungs for 527 years before emitting a single alpha particle! This is because the half life of plutonium-239 is 24110 years, meaning it would take 24110 years for those 66 atoms to decay into 33 atoms, releasing 33 alpha particles.

Now this is a random/statistical thing, so it's certainly possible that one of those 66 atoms would hit you with an alpha particle before you die of natural causes and your body completely decomposes, but odds are they won't.

Is this really "very disturbing"? I think there are more important things to be concerned about.