Is Diablo Canyon Safe?

By Steve Kliewer

Many fears have been raised about the safety of the Diablo Canyon Power Plant (DCPP).   While risks and uncertainties always exist, the probability of any failure mode and the subsequent potential damage are both greatly exaggerated. 

Visiting the plant and talking with any of the personnel, one cannot but be impressed with the “culture of safety” that permeates every level of job and task.   This is the most highly regulated and watched over industry in the country, the employees are the most highly trained in compliance with these regulations, with ongoing training, and safety is the top priority.

Nuclear Bomb explosion:   Fear of a nuclear explosion at a nuclear power plant is still rampant despite the absence of any evidence that this has or might occur.   This issue is no longer raised by reasonable journalists but is still in the public consciousness and often implied in anti-nuclear rhetoric. 

Earthquake:  Fear of failure of key safety systems due to earthquake has been the most common fear throughout the history of this plant.  Here in California, there is no spot free of faults and the risk of seismic activity.   We live with it.   The greatest threat is unreinforced buildings.   Diablo Canyon is one of the most strongly reinforced buildings in the world, engineered to withstand enormous quakes and to not only remain standing but intact and completely functional.  

The region around DCPP has been subjected to the most detailed seismic studies of any location on earth.  Many leading geologists and engineers have reviewed all of this data and have ruled that there is minimal chance of any seismic event beyond what the plant is engineered to withstand. (Central Coast California Seismic Imaging Project, 2014)  Ironically, since these professional judgments are often discounted on the presumption that hired experts lie, opinions and fears of those least qualified are often accepted in their place. 

Tsunami: Failure of key safety systems due to a tsunami is the latest fear following the Fukushima disaster.   Japan suffered an enormous earthquake and a huge tsunami.  The number of people who died in these natural disasters has been tallied at 25,000, the financial loss at $235 billion. (2011 Tohoku Earthquake and Tsunami, 2012)   This is now known as the Fukushima Nuclear disaster despite the fact that the subsequent dramatic failure of the Daiichi nuclear power plant was a much smaller disaster with no one killed, no one expected to die (WHO, 2013) (UNSCEAR, 2013), and a large but much less significant financial loss.

Early predictions of thousands dying in Japan of radiation exposure and of deadly radioactive fallout reaching the U.S. have not materialized and have been quietly discredited.  (Banse, 2014)

There is no question that the Daiichi reactor suffered a large quake and a huge 46 foot tsunami.  However, Japan had 50 other reactors that suffered no damage even though several were closer to the epicenter.  The utility company, Tepco, clearly made particularly glaring errors in the design of Daiichi and in their preparation for natural disasters.  

The region surrounding DCPP has a much smaller probability of such seismic and tsunami events and DCPP has a much larger safety margin, being built 85 feet above sea level and backup safety systems are in place to handle inundations even higher.   However, the devastation to our entire region due to a tsunami even 85 feet high is virtually unimaginable.     In short, the probability that DCPP would experience this level of an event is extremely small.  It is also true that the risk from even this level of nuclear accident is tiny compared to the risk associated with a natural disaster that might generate it. 

If such improbable events should ever occur in this area — about the same probability as an asteroid strike — then we should be much more concerned with surviving the devastation such an event would create throughout the area than any potential failure of the power plant. 

Radiation: Cancer due to leaks and ongoing radiation exposure remains the presumptive result of power plant operation even without a disaster. (SLO Tribune, 2014) (Adams, 2011)  Radiation from U.S. nuclear power plants is well below natural background radiation and is virtually indistinguishable from natural sources.   Three Mile Island was the worst accident at a domestic nuclear power plant in U.S. history. (List of Nuclear and Radiation Accidents by Death Toll, 2014)   The maximum exposure was equivalent to a medical chest x-ray and was limited to a very few people. (Three-Mile Island Cancer Rates Probed, 2002) (Three Mile Island Accident Health Effects)

Spent Fuel: The long-term storage of spent fuel is a problem, but mostly this is a political problem.  First: because the total volume of spent fuel is very small compared to other sources of energy (e.g. coal).   Second:  most of the waste (97%) can be separated out and need not be stored. Third: because the Federal government committed to a long term solution (Yucca Mountain) and then reneged. 

The burning of coal in the U.S. alone produces 240,000 tons of toxic waste each year. (Clean Energy, 2014)  Coal and other fossil fuels release a terrible burden of climate changing greenhouse gases.  They also release many hazardous elements (e.g. mercury, arsenic, and cadmium) into our air through combustion and into our water supply through huge landfills and spills. (Coal Waste)   According to an article in Scientific American, studies show that the coal plants each release 100 times more radioactivity through fly ash into our air and water than the same size nuclear power plant (Hvistendahl, 2007)  

All of the nuclear power plants in the U.S. combined, produce about 2000 tons of radioactive waste per year (EPA, 2014).  If placed on a football field this would cover the first 3 yards.   For a family of four, using power generated only by a nuclear power plant, after 20 years the resulting used fuel would fit in a shoe box. 

Reprocessing is done very effectively in France, reducing the amount of waste needing to be stored to less than 3% at the same time producing much reusable fuel. 

Deaths per kWh of energy produced: In general, there is a gut conviction that nuclear energy is more dangerous than other sources of energy production and that it should be replaced with renewable sources, especially Solar.   Actual facts do not support this belief.   With a history of over 50 years in commercial use and not counting the projected death toll from climate change, nuclear has recorded fewer deaths per unit of energy produced than any other source of energy.  (Conca, 2014)   Solar is a worthwhile source to develop.  However, solar simply cannot replace nuclear because it is inherently more expensive, but mostly because it can only be produced when the Sun is shining and not when it is most needed. (Baker, 2013)
The U.S. Navy has been using nuclear power plants for over 50 years.   Navy personnel live within feet of these reactors.  In all this time, no one has died and no one has even received a dangerous dose. (Powering the Nuclear Navy, Protection of People, 2014) (Conca, America's Navy The Unsung Heroes of Nuclear Energy, 2014)

Once Through Cooling:  Entrainment of fish larvae and impingement of adult fish on the sea water cooling system at DCPP is presumed by many opponents to adversely affect the ocean environment and the local fisheries industry. (Once-Through Cooling, 2014)    Momentary warming of the ocean water as it flows through the plant has been shown in a lab to kill about 20% of the fish larvae.  Normally 99.5% of all fish larvae die due to natural causes.   On average one adult fish per day is caught against the incoming screen.  The warmed water in the discharge flows across the top of the ocean and the heat is rapidly dissipated into the open ocean.   Ongoing biological surveys show that the ecosystem is flourishing and the fisheries industry has seen only an increase in fish since the plant began operations.  Nonetheless the California State Water Resources Control Board at the prodding of several anti-nuclear groups is strongly considering ordering DCPP to build cooling towers in place of the OTC system currently in use.   This modification is expected to cost up to $10 billion, up to 400 acres of scenic land buried, a 20% reduction in rated power output, 2 million gallons of fresh water evaporated daily, and major disruption in safety systems for plant operation.
Despite the enormous costs and the fact that there is no actual adverse impact on the ocean, proponents of this plan blithely advocate for these modification.   This is NOT because of any adverse impact on our marine environment.  Instead it is as several have disingenuously and publicly announced because they “want the plant shut down”.


2011 Tohoku Earthquake and Tsunami. (2012). Retrieved from Wikipedia:

Adams, R. (2011, Dec 20). Mangano and Sherman Have Released Another Bogus Study Seeking to Scare People About Radiation. Retrieved from
Baker, D. (2013, Feb 12). Future of Solar Unclear as Big Plant Comes Online. Retrieved from San Francisco Chronicle:
Banse, T. (2014, Nov 12). Traces of Fukushima Radioactivity Detected in West Coast Waters. Retrieved from NorthWest Public Radio:
Central Coast California Seismic Imaging Project. (2014). Retrieved from PG&E:
Clean Energy. (2014). Retrieved from EPA:
Coal Waste. (n.d.). Retrieved from Source Watch:
Conca, J. (2014, Oct 28). America's Navy The Unsung Heroes of Nuclear Energy. Retrieved from
Conca, J. (2014, Oct 28). How deadly is Your Kilowatt? Retrieved from Forbes:
Hvistendahl, M. (2007, Dec 13). Coal Ash is More Radioactive than Nuclear Waste. Retrieved from Scientific American:
List of Nuclear and Radiation Accidents by Death Toll. (2014). Retrieved from Wikipedia:
Once-Through Cooling. (2014). Retrieved from State Water Resources Control Board:
Powering the Nuclear Navy, Protection of People. (2014). Retrieved from NNSA:
SLO Tribune. (2014, Aor 7). Study Saying Diablo Canyon Radiation Poses Health Risk is Disputed. Retrieved from San Luis Obispo Tribune:
Three Mile Island Accident Health Effects. (n.d.). Retrieved from Wikipedia:
Three-Mile Island Cancer Rates Probed. (2002, Nov 1). Retrieved from BBC News:
UNSCEAR. (2013). Retrieved from United Nations Scientific Committee on the Effects of Atomic Radiation:
WHO. (2013). Health Risk Assessment from the Nuclear Accident After the 2011 Great East Japan Earthquake and Tsunami. Retrieved from World Health Organization: