Japanese Nuclear Crisis - Do We Need to Worry?

The recent earthquake and tsunami off Japan have created a nuclear reactor crisis that concerns everyone.  I’ve asked my friend and fellow Osher instructor Dr. Jerry Clifford to provide his insight and answer questions that many are asking.  Jerry is a Ph.D. physicist and expert in nuclear energy plants. What follows is a collaborative effort.


What caused the nuclear reactor crisis?

The earthquake did no significant damage to the reactors, which shut down properly following the shaking.  Even when reactors are “off”—no longer producing electricity—they still have to be cooled.  Nuclear reactors create heat by fission, breaking uranium nuclei into smaller nuclei called fission products.  These fission products are radioactive and continue to produce heat, diminishing rapidly at first, then more gradually over decades. 


The earthquake disrupted the electric power grid, cutting power to the water pumps that cool the reactors.  Emergency diesel generators immediately started to keep the pumps running.  But when the tsunami hit about ten minutes later, the generator building flooded, shutting off power to the pumps.  Emergency back-up batteries were engaged, but ran out after several hours.  After that, there was no cooling for the reactors.


Water in the reactors and the spent-fuel cooling pools heated up and ultimately boiled into steam, leaving the fuel exposed to air.  Steam (H2O) decomposed, oxidizing the fuel rod casings, leaving hydrogen gas, which exploded—remember the Hindenburg? 


The remedy is to cool the fuel rods with water as rapidly as possible. This is difficult because the exposed fuel rods have increased radiation within the facility to dangerous levels.  Water cannons are being used to fill the cooling pools, hoping to eventually cover the rods and provide shielding to protect the workers. Boron is being added to the water to absorb free neutrons thus reducing further nuclear reactions.


How serious is the situation and how bad can it get?

The situation is very serious because hydrogen and/or steam explosions could rupture the containment vessels, which are still believed to be essentially intact and which prevent radiation escaping the facility and becoming airborne, as happened in Chernobyl.   


If the reactor or pools dry out and sufficient heat is generated, then, hypothetically the fuel rods could melt into a liquid and restart the fission process, as in an operating reactor.  This would increase the problem immensely with huge amounts of radiation.  The scenario is scary but improbable. 


The facility operators are trying to restore electrical power to the pumps, hoping these will be operable, but no one currently knows the exact extent of damage caused by the explosions and tsunami.


What are the health dangers?

The main danger is radiation from aerosolized fission products.  As of March 18, 2011, the radiation levels were only high within the facility.  Monitoring is also ongoing at many places, both near the reactors and throughout Japan. Current radiation readings are available at http://www.mext.go.jp/english/.  Luckily, the winds are generally off shore taking any effluents out over the Pacific. 


Only a barely detectable level of radiation has reached California.  Our Department of Energy reports that radiation levels in Sacramento are elevated by one-millionth of the normal background—a testament to the precision of their instruments. Any radiation plume will be greatly diminished by our distance from Japan.  The EPA is monitoring radiation levels along the coast; see http://www.epa.gov/japan2011/


There is no need to do anything now.  If you want to worry, worry about driving to the supermarket because that is much more dangerous than the radiation from Japan.


Radiation Levels and Backgrounds

The Japanese reactors are inherently safer than the Chernobyl reactor.  Chernobyl had no containment vessel and used graphite for cooling rather than water.  The graphite caught fire and quickly spread radioactive fission products, killing about 50 workers almost immediately.  An official international investigation concluded that 150,000 people were exposed to over 20 times normal background radiation from Chernobyl, which might result in 4,000 premature deaths (this number is strongly contested).


Everyone on Earth is exposed to background radiation; on average each of us gets 2.4 millisieverts (mSv) per year. About half of that is from radon gas seeping up from the ground and being trapped within our buildings. We also get 0.5 mSv from radioactive elements in the ground, 0.4 mSv from cosmic rays from outer space, and 0.3 mSv from food.  Man-made radiation, from past nuclear weapons testing, nuclear power plant operations and accidents (almost entirely Chernobyl) add 0.005 mSv, on average.


However, background radiation varies greatly. Those in well-insulated buildings can get up to 4 times the normal dose, as do people in Denver, with less atmosphere shielding them from cosmic rays. And, in Ramsar, Iran, radiation levels are 200 times normal. Yet, residents of Denver and Ramsar show no adverse health effects.


Flying also increases radiation exposure (particularly polar routes): one round trip between New York and Tokyo boosts your dose by 0.2 mSv. And eating a banana every day will boost your annual dose by 30 mSv, over 12 times normal, due to the potassium in bananas. Our bodies need potassium, but it is radioactive, as is the carbon in everything we eat.


Medical procedure can also expose us to radiation. With modern equipment and properly trained staff, a chest x-ray delivers 0.02 mSv, dental x-rays deliver 0.003 mSv, and a CT chest scan delivers 7 mSv.


Life is Risky

We all want our loved ones and ourselves to be safe, but the reality is that the world is full of risks.


In 2008, 37,261 people died in motor vehicle accidents in the U.S. (much lower than many prior years) — yet we drive. Do we really have a choice?


Our society consumes vast amounts of energy, and wherever that energy is produced or stored there will be life-threatening risks. The BP oilrig explosion in the Gulf killed 11 workers, and a BP refinery explosion in Texas killed 15. No one has ever died due to a commercial nuclear reactor accident in the U.S.


According to Dana Christensen, associate director of Oak Ridge National Lab, the effluent from burning coal releases 100 times as much radiation into the biosphere as does a nuclear reactor producing the same amount of energy.


When the final grim statistics are reported, the number of Japanese killed by the earthquake, the tsunami, and by the explosions and fires from gas systems will probably be hundreds of times higher than the number lost due to their nuclear reactors.


Yes, we can and should do better. Year-by-year technology advances and step-by-step we reduce those risks that we can. That effort will proceed more effectively if we are rational about our risks and our options. Hysteria promotes media revenue, but not good public policy.


Best Regards,



Dr. Robert Piccioni

Author of "Everyone's Guide to Atoms, Einstein, and the Universe"
and "Can Life Be Merely An Accident?"