Pittsburgh Played a Pivotal Role in Bringing Fukushima under Control
Tokyo, August 2011- Roy Brosi is collaborating with colleagues from the U.S. nuclear power industry and their counterparts from TEPCO, the Japanese company that owns the disabled nuclear power station at Fukushima Daiichi, to bring it to cold shut down conditions. Five months earlier three of the station’s six reactors had been crippled by the fourth largest earthquake on record and the 46-foot tsunami that followed it. Although the reactor structures successfully survived the pounding quake and the reactors themselves were automatically shut down when seismic sensors detected the tremors, the subsequent tsunami, combined with loss of electrical power from the grid, precipitated a chain of previously unimaginable events.
Despite the fact that Brosi and colleagues are among the most experienced professionals in the nuclear power industry, the scenario is unprecedented. Even with Chernobyl and Three Mile Island in the rearview mirror, nobody has ever dealt with a situation quite like this before. There is no standard procedure to follow. But until the residual heat is brought under control, clean up cannot begin.
Fukushima to Shippingport
Five months earlier – On the morning of the disaster Roy Brosi is intensely occupied at FirstEnergy Nuclear Operating Corporation’s (FENOC) Beaver Valley nuclear power station in Shippingport. As director of a scheduled refueling outage for one of the station’s two reactors, Brosi is charged with overseeing one thousand regular employees in their assigned refueling duties, in addition to one thousand temporary employees on site specifically for the outage. When he first learns of the earthquake and tsunami, his thoughts go to the well-being of the people of Japan. But when he learns about conditions at Fukushima he is deeply concerned about the previously unimaginable sequence of calamities – massive earthquake, monster tsunami, loss of grid power, flooded emergency generators, depleted backup batteries, hydrogen explosions, damaged reactor fuel, and spent fuel pools in dire need of replenished water for cooling. If anybody has a grasp of how to approach the disaster, Brosi does. Early in his career, he helped write the U.S. nuclear industry’s book on emergency and severe accident procedures. But under the weight of managing the scheduled outage at Beaver Valley, any notion of Brosi’s becoming involved in taming the reactors in Japan must remain just thoughts.
Pittsburgh to Tokyo
By the end of April refueling is complete and Brosi is back at his regular job as Beaver Valley’s Director of Performance Improvement. In June he moves to a new position – Fleet Director of Strategic Industry Initiatives. Shortly thereafter, the Institute of Nuclear Power Operators (INPO), the self-regulating industry organization for nuclear electric power the United States, asks him to join their advisory team in Japan.
By the time he arrives, the lingering heat of the Fukushima reactors is being cooled by a system of portable pumps and temporary pipes recirculating a stream of decontaminated and desalinated water drawn from flooded turbine buildings. Equipment damage, compounded by high levels of radiation, makes direct measurement of the temperature inside the reactors impossible, but surviving sensors on reactor components show metal temperatures hovering between 115 and 120°C – above the boiling point of water– too hot to contemplate a clean-up.
Anatomy of a Nucleus
The entire enterprise of nuclear energy is based upon the generation of heat by splitting atomic nuclei, a process known as nuclear fission. During normal operation a nuclear reactor employs the heat of fission to make steam to drive an electric generating turbine. But the heat that Roy Brosi and his compatriots are fighting is different. The fission process has been halted. This is decay heat – the residual heat generated by newly formed radioactive materials transmuted from one element to another during nuclear fission.
Because atomic nuclei are composed of positively charged protons and non-charged neutrons, the overall charge of a nucleus is positive. And although at larger scales bodies with like-charges naturally repel each other, inside an atomic nucleus the positively charged protons do just the opposite – they stick together due to the strongest and shortest attraction in nature, the strong nuclear force. So when a neutron from outside penetrates an atomic nucleus it usually pushes its nuclear boundary beyond the breaking point and liberates the tremendous energy that had been holding it together. Pound for pound, a splitting nucleus releases roughly 2.5 million times as much energy as an equivalent amount of fossil fuel.
While releasing that tremendous energy a splitting nucleus produces nuclear fragments, radiation, a lot of heat, and flying neutrons, which tend to split other nearby nuclei. The typical nucleus in a reactor emits an average of 2.4 neutrons when it splits. In turn, those newly split nuclei eject more neutrons that split more nuclei, in what becomes a continuing chain reaction.
But getting a nucleus to split on command is no easy matter. And getting a large number of them to engage in the fission process is downright tricky. It takes a concentration of atoms with ideal imbalances between the number of protons and neutrons in their nuclei to make nuclear fuel. Such atoms are known as isotopes. Those that split readily are called unstable. And those that engage in the fission chain reaction are called fissile.
As it turns out, a fissile isotope of Uranium, named U235, is ideal for use as nuclear fuel. But as with all things natural, it’s not quite that simple. In most cases fission produces unstable nuclear fragments which don’t engage in fission and actually interfere with the fission process. It is these fission products that are producing the decay heat that Brosi and colleagues are attempting to quench.
Certainties, Probabilities, Unknowables
In assessing the possibilities for bringing the reactors to a state of cold shutdown – in which lingering decay heat is sufficiently low to commence a physical clean up – the team assesses a vast array of certainties, probabilities, and one big unknowable – the condition of the reactor cores.
Certainty: There have been three reactor building explosions.
Probability: The likely cause of the explosions was hydrogen gas liberated by a chemical reaction between overheated zirconium fuel rods and emergency cooling water.
Probability: Since the likely cause of the explosions was overheated zirconium fuel rods, there is a better than average chance that at least some of the fuel rods have failed, releasing a mass of molten fuel into the reactor vessel.
Probability: In the interests of conservative thinking, the hypothesized molten fuel is presumed to have burned through the reactor bottoms and possibly, their heavy steel containment vessels, resulting in radioactive puddles of molten nuclear fuel re-solidifying on the concrete floors of the reactor buildings.
Unknowable: Due to high levels of heat and radiation, nobody can get close enough to know whether or not their expert assumptions are correct.
Certainty: There is no question in anyone’s mind that before any cleanup can proceed, reactor temperatures must be brought below 100°C.
The current cooling system is keeping the reactors from getting hotter, but the team believes they can do it faster. They consider switching cooling systems. The currently employed system, feed water injection, cools the core from the bottom up with a stream of water injected through the side of the reactor vessel, a relatively slow process. The proposed method, core spray, will utilize each of the reactors’ built-in emergency spray systems to cool the core from the top down, a more direct, hence faster, process. The core spray system had been rendered inoperable during the earthquake due to the loss of electric power.
While everybody agrees that making the transition to core spray cooling is essential to stabilizing the reactor, they also realize that, given the unknown extent of reactor damage, the procedure is not free of risk. They work through the theoretical problems: Could overheated zirconium fuel rods react with spray water and cause another hydrogen explosion? Could the introduction of cool water from above shock the zirconium fuel rods into fracture and release more molten fuel? Might some sequence of events lead to criticality – the conditions necessary to re-initiate fission? Will the spray water dislodge radioactive material from the inside surfaces of the reactor and transport it in water or steam to the outside environment? After going through the requisite calculations, the team concludes that while the procedure is likely to succeed, given the unprecedented nature of the situation, caution is in order. Of lingering concern is the possibility of dislodging radioactive material from inside the reactor and contaminating the outside environment.
They employ a giraffe, a piece of construction equipment used to pump concrete to high-rise buildings under construction. They rig the giraffe with a video camera to observe the environment immediately surrounding the reactor, a radiation detector to monitor the air for any increase in radiation as they proceed and – in the event the process results in an increase in radiation – a nozzle to suppress it with a water spray which will carry any radioactive particles to the ground.
They initiate the first reactor’s core-spray system at a rate of one cubic meter (264 gallons) of water per hour for the first day. When they detect no increase in radiation they double the rate of spray for another day; then increase it to 3 cubic meters per hour for two weeks and finally, 8 cubic meters per hour for three months. They initiate core spray inside the other reactors with no adverse affects. Happily, the radiation suppression nozzle on the giraffe is never called into action.
The plan works. With the assistance of Roy Brosi and the INPO team, TEPCO has reduced reactor temperatures to below 90°C. By mid-December all three crippled reactors at Fukushima have reached cold shutdown conditions. TEPCO announces plans to begin spent fuel removal within in two years; damaged fuel within 10 years, and ultimately; to clean up and decommission the site within 40 years. It’s a long time, but it’s not forever. By dint of international collaboration, engineering creativity and unswerving determination, FirstEnergy’s Roy Brosi and his colleagues at INPO and TEPCO have brought a previously unimaginable disaster under control.
It is no accident that Roy Brosi was dispatched to Fukushima. At various times over the past 31 years the University of Pittsburgh mechanical engineering alum has served as manager for almost every operating position at the Beaver Valley station in Shippingport. Located just 34 miles from downtown Pittsburgh, Shippingport’s legacy as the site of the United States’ first commercial-scale nuclear power plant extends back to 1957. The impetus for the facility started in 1948, when Admiral Hyman Rickover commissioned Westinghouse Electric to design a power plant for The Nautilus, the world’s first nuclear submarine. Researchers and instructors from the University of Pittsburgh and Carnegie Technical Institute (now CMU) staffed the project. Then, when the time came for commercial nuclear electric power, Pittsburgh had the proven engineering horsepower to convert the energy from a controlled nuclear reaction into electricity. As a result, today, Western Pennsylvania remains a global center of nuclear energy expertise.
A Mecca for Nuclear Power
“Pittsburgh is a Mecca for nuclear power in the United States,” Dr. Larry Foulke, former head of the University of Pittsburgh’s nuclear program, said. “We have the Bettis Atomic Power Laboratory in West Mifflin – one of the greatest concentrations of nuclear engineering talent in the United States, Westinghouse Nuclear in Cranberry designing today’s facilities and working on the next generation of reactors, Curtiss-Wright Flow Control in Cheswick making the pumps; Bechtel Plant Machinery, contractor for the Navy’s Nuclear Propulsion Program, and FirstEnergy’s two nuclear power plants on the Ohio River. Nuclear power offers Pittsburgh jobs, infrastructure and technology development. I think the technology development going on at Bettis and Westinghouse will make them major players in the world.”
FirstEnergy’s Roy Brosi has certainly contributed more than his share to the effort.
This story first appeared in the Spring 2012 issue of The Pittsburgh Technology Council’s TEQ Magazine.