Nuclear Plants and Grid Blackouts

On September 8, 2011 the electrical grid in and around San Diego, California experienced a blackout that lasted for more than 12 hours.  By some accounts more than 5 million people were effected.  The initiating event was a human error that caused a large transmission line from Arizona to turn off unexpectedly.  I recently discussed why a single failure as occurred that day should  not have caused such a widespread grid failure, and how New York City will be much more susceptible to similar events if Indian Point Nuclear Plant is shutdown prematurely. As it was designed to do, the San Onofre nuclear plant automatically disconnected itself from the grid and shut down then the blackout occurred.  This was done as part of the plant’s protective scheme to shield the plant from unintended consequences from the falling grid voltage and frequency.  A similar thing happened to nine nuclear plants in the eastern USA during the blackout of 2003. Why do nuclear plants trip off line when a blackout happens? While this is a somewhat simplified answer, it covers the fundamentals.  Please be aware my experience is with pressurized water reactors, but the same basic principles should apply to boiling water reactors. The nuclear plant’s generator, like that of any electrical generator supplying the grid, is electrically locked to the voltage and frequency of the grid. As grid voltage drops, so does the voltage sensed inside the plant. Most large electric loads inside nuclear plants are electric motors on pumps, valves, fans, and other such equipment.  To drive a fixed mechanical load connected to the shaft, a motor must draw a fixed amount of power from the power line. The amount of power the motor draws is roughly related to the voltage times current (amps). Thus, when voltage gets low, the current must get higher to provide the same amount of power.  Thus, as voltage drops, current inside the motors rises. This increase in current can cause overheating and short circuits.  Note: the paragraph above was revised to correct an oversimplification & error in my original post. The results are the same, my explanation was lacking. Also, normally the alternating current on the grid operates at 60 cycles per second (60 hertz).  As the grid collapses, the frequency begins to drop. If allowed to continue this would cause the nuclear plant’s reactor coolant pumps to run slower, thus moving less water through the reactor.  Less cooling water could potentially lead to higher than normal fuel temperatures.  To protect against the reactor operating with degraded cooling water flow, nuclear plants have various means of sensing low grid frequency or coolant flow.  When electrical frequency or reactor cooling...

Read More

Only the Energy Impoverished Run Towards a Gasoline Spill

There was a horrible accident in Kenya this week.  More than 100 people were burned to death, and hundreds more were injured when a gasoline pipeline began leaking and then exploded.  My heart goes out to the victims, and their families, and to all the people of Kenya who are dealing with the worst industrial disaster in their history.  Eyewitnesses reported seeing burning people leaping into a nearby river trying to extinguish the flames that engulfed them.  Rescue workers had to place a net across the river to catch the charred bodies of the dead so they would not wash down stream. The death toll continues to grow, and most of the 100+ injured including many children are not expected to survive. The pipeline runs through Sinai, a Nairobi ghetto of corrugated tin and cardboard huts.  When the pipe began leaking hundreds of people gathered around to scoop up the spilled gasoline.  As the crowd grew a spark from a cigarette butt or some other heat source ignited the fuel.  The blast incinerated scores of people nearby.  Flames cascaded down on nearby huts then raced through the crowded slum. Trying to image the chaotic and horrific scene, I realized there was something so far outside my own paradigm that I had to stop for moment to collect my thoughts…who runs TOWARDS a leaking gasoline pipeline?  Maybe that’s a silly question; but if anyone reading this came upon a leaking gasoline pipeline they would stop, back away, and call for help.  You would keep your distance while warning others not to go near for fear of igniting the leak and causing a fire or explosion.  If you were forced to approach the leak you would fear for your life and rightfully so! So what is different between you and the hundreds of people in Kenya that did the exact opposite?  As word spread through Sinai about the leaking pipeline hundreds of people grabbed every container they could find and rushed towards the explosive spill! You might settle on a simple socioeconomic answer: because they are poor they’ll risk their lives for a few dollars worth of anything of value.  The real answer is a lot more complicated.  These people are not only poor, they are super poor, and one of the factors that separates the poor from truly impoverished is the lack of access to even basic energy sources that human beings need to survive.  They are energy destitute. Another way of saying this is availability of plentiful, accessible energy is the greatest single factor that allows people to rise out of poverty.  All of the world’s developed economies got...

Read More

The San Diego Blackout – Is New York City Next?

California politicians and utilities were quick to assign blame for Thursday’s blackout of 6 million customers on a single unfortunate utility worker in Arizona.  In reality, they need to look a lot deeper at the root cause of the major electrical system failure that lasted about 12 hours.  Why? Properly designed, maintained, and operated electrical grids just don’t collapse when a single error takes place or a single piece of equipment fails. If things are running properly there are redundant transmission lines, spinning reserves, and power plants on standby.  When a failure happens a single transmission line may go down, but system operators can reroute power around the failure and if necessary order standby power plants to pick up the load.   What happened in San Diego is likely a symptom of a much bigger problem.  Strategies focusing on conservation and expanding intermittent renewable energy sources, while ignoring the need for base load power plants close to population centers may have weakened the California grid. In southern California there exists insufficient electrical generating capacity close to electrical loads; the cities.  Instead, utilities rely heavily on power imported over long distances from neighboring states, and there may be too few power plants inside transmission “bottle necks.”  This places cities like San Diego at much greater risk of blackouts.  When the umbilical cord from Arizona was unexpectedly severed, the few power plants close to the city simply could not provide enough power to maintain grid voltage.  As voltage dropped those power plants automatically disconnected to protect themselves from the low voltage condition.  The result?  A major blackout. If the San Diego grid had sufficient local power they should have been able to isolate a small part of the grid and continue to run on their own power plants.  Even if the local grid lost power, they should have been able to call reserve power plants into operation to repower the grid within a few minutes.  Unfortunately, the power plants were over loaded; there simply wasn’t enough capacity to repower the grid without assistance from the outside. California’s much touted renewables were of no use.  The wind was blowing only 8 mph at the time, and skies were partly cloudy.  Any tiny wind and solar capacity that was available was out-gunned thousands to one. New York had better take notice!  Shutting down Indian Point Nuclear plant would have exactly the same impact on the electrical grid.  This is because Indian Point’s 2100 megawatts are physically located INSIDE the transmission bottleneck feeding New York City.  In a future without Indian Point operating, a similar failure of a single transmission line could easily black out New...

Read More

TEPCO Did Not Adopt a Key Lesson Learned from the Accident at Three Mile Island

Unlike their American counterparts, not all control room operators in Japan have access to plant specific training simulators.  Instead, according to a report by NPR, they use “generic” simulators that are similar to, but not identical to their plant.  This difference may have contributed to the difficulties operators had at Fukushima Dai-ichi when responding to complex events that followed the catastrophic earthquake and tsunami on March 11, 2011. The differences between a generic simulator and a plant-specific one are often in precisely the systems the Fukushima operators were struggling with: electrical power supplies, cooling water, and building ventilation.  These differences matter little when training for events within the design basis of the reactor, but when events stray outside the design basis, include “cascading” failures, and involve severe accident response, generic simulators can’t accurately model the events.  When training for situations that exceed the capabilities of a simulator, instructors are left with fewer, less realistic options like classroom training or “table top” walkthroughs of operator actions. In my 20+ years as a nuclear plant senior reactor operator, instructor, and manager I spent thousands of hours on plant specific simulators as a student, instructor, and management evaluator.  I can say with certainty the differences between a generic and plant specific simulator matter greatly in the quality of training received by operators! This higher quality training results in operators with greater proficiency in dealing with plant upsets and complex events.  In fact, training on generic simulators is a practice the USA abandoned more than 20 years ago. This shift was but one of  many improvements in training for nuclear workers adopted following the 1979 accident at the Three Mile Island plant.  Today no nuclear plant can be built in the USA without it’s own plant specific simulator, and no operator can be granted a reactor operator’s license without exhaustive training and examination on a plant specific simulator. My peers from other nations often have not agreed.  Many I have met view plant specific simulators as a costly extravagance, and they still rely on generic simulators.  In addition, generic simulators are often located at some central or distant location rather than on the plant site.  This makes simulator training less frequent and more time consuming because of the travel involved. As a result, operators get far less simulator time per year than their counterparts with local plant specific simulators. In the USA, nuclear plant control room operators routinely spend one of every five or six weeks in full time training.  Each training week is typically composed of 20 hours of simulator time and 20 hours in the classroom, and includes both written examinations...

Read More

Gas Speculators are Licking Their Chops in New York

With New York Governor reaffirming his opposition to Indian Point, natural gas speculators are lining up to position themselves to fill the enormous energy gap that would be left if the plant shuts down. One such speculator is a privately owned Swiss-based company, Advanced Power Services.  They have begun preliminary work to build a 1000 MW gas fired power plant in Dutchess County New York, about 40 miles north of Indian Point.  There was a front page article in the Poughkeepsie Journal today describing how shutting down the 2100 MW nuclear plant could help the local project gain traction. News that Gov. Andrew Cuomo has issued his strongest statement yet in favor of closing the Indian Point nuclear power plant has improved the chances that a proposed plant in Dutchess County would be built. I know something about Dutchess County, NY because I lived there for several years while working at Indian Point.  In reading the story, I wondered if the editors of the Poughkeepsie Journal gave one moments thought to the fact that many of the people who work at Indian Point live in Dutchess County?  There’s no mention in the article of the serious economic impact that would befall the county shold Indian Point be prematurely shut down. Here’s a copy of the comment I posted on the online version of the article: This article seems to imply there would be a silver lining for Dutchess County if Gov. Coumo has his way and shuts down Indian Point. In reality, trading Indian Point for a 1000 MW gas fired power plant is a terrible idea and would harm Dutchess County. A large number, probably at least 300 of the 1100 men and women who work at Indian Point live in Dutchess County. They earn good paychecks and spend most of it in the county. Most own homes and pay property and school taxes. Sure, the new plant would hire a few people, but nuclear plants pay WAY MORE than gas plants, and it takes ten times as many people to run a nuclear plant as a gas plant. The net effect would be a huge loss of jobs. If Indian Point is shut down, hundreds of families will leave Dutchess County. As they go they will flood the already depressed real estate market with homes for sale. Do you remember the impact of the IBM layoffs of the 1990’s on housing prices? It took a decade for home prices to begin to recover. Then there’s the impact on electricity rates. While natural gas is relatively inexpensive now, nuclear energy is still cheaper. More gas power and less...

Read More