There were never a lot of burnable resources in Japan, so generating power using steam was challenging. Liquid natural gas and fuel oil had to be imported, and this was not only polluting the air, it was extremely costly. Despite resistance from atomic bomb survivors, Japan would have to “make a deal with the devil” and embrace nuclear fission if it was to compete in the industrial world. Construction on the first plant, a British Magnox graphite pile, was begun by the Japan Atomic Power Company (JAPC) on March 1, 1961. They put it at Tokai, halfway down the east coast, and it had no cooling towers. The race to provide Japan with nuclear power was on.
TEPCO began its part of the nuclear expansion with the Fukushima I Power plant. Construction began on a single General Electric BWR/3 reactor with a Mark I containment on July 25, 1967. It would be the first of six boiling-water reactors built on the same property in the small towns of Okuma and Futaba in the Fukushima Prefecture, and it would become one of the world’s biggest nuclear power facilities. With everything running simultaneously, it could produce 4.7 billion watts of electricity. A second plant, Fukushima II, was built a few miles down the coast, and, by the turn of the 21st century, two more GE BWRs were planned for Fukushima I. Unit 1, the first completed reactor in the new plant, was switched into the power grid on March 26, 1971.
At the time, General Electric was competing vigorously with Westinghouse for the hearts and minds of nuclear power-plant consumers, and the goal was to make the most economical plant with the least accident potential. Westinghouse was pushing their upscaled version of Rickover’s flawless submarine engine, and GE was hooked on Untermyer’s dead-simple BWR. To optimize these designs for the civilian market, there were several engineering modifications to make.
The Westinghouse reactor is comparatively small, and neutron flux is controlled by a concentration of boric acid in the coolant. Secondary protection from fission-product escape into the environment is a thick concrete building constructed around the reactor. As was demonstrated at Three Mile Island in 1979, the building is strong enough to withstand a hydrogen explosion inside.
The GE reactor had to be big and tall, about 60 feet high, because the engineers had simplified the structure to include the steam separators and dryers in the top of the reactor vessel. To use external separators would involve a lot of complicated plumbing, and an engineering goal for these civilian reactors was to minimize the pipes.[259] The separators and dryers kept water droplets, which could quickly destroy a steam turbine, out of the steam pipes. The resulting integrated reactor/separator vessel, made of six-inch steel, was so tall, there was no way to construct a sealed, reinforced concrete building around it thick enough to contain a possible steam explosion. There would be a stout, rectangular structure covering the reactor, the refueling pool, and the traveling crane above, but it could not be specified as pressure-tight.
Not having a separate building as the secondary containment structure meant that something else would have to encapsulate the reactor vessel, so a large pressure-resistant container with a bolt-down lid, made of inch-thick steel, was designed to be built around the reactor. This “dry well” is shaped like an inverted light bulb, being a vertical cylinder surrounding the reactor with a spherical bulge at the bottom. The dry well is supported off the floor of the reactor building by a large concrete pillar.
In a Westinghouse reactor, a steam explosion due to a major pipe rupture is controlled by letting the steam expand into the building that houses it without letting the steam breach the walls. The steam has enough room to dissipate its explosive energy in the process and condense into water, which runs down the inside walls and into the sump. With this arrangement, no fission products dissolved in the steam are able to contaminate the countryside. Under extreme conditions, overpressure from steam trips a relief valve and it goes up the vent stack. In this worst case, radioactive steam is released, but the building remains intact and able to contain further contamination.
The dry well is not of sufficient size to contain such a steam explosion. To deal with this maximum accident, there are eight large pipes connected to the spherical bulge and pointed down. Circling the reactor at the bottom of the dry well is the “wet well,” which is a large torus or a doughnut-shaped steel tank, 140 feet in outside diameter, into which the connecting pipes terminate. The doughnut-tube is 30 feet in diameter, or slightly larger than the pressure hull of an early nuclear submarine.
This wet well is half filled with water, 15 feet deep, and it is held off the floor by steel supports. In the event of a sudden high-pressure steam release, the hot gas rushes down the eight pipes and blows out under water in the torus. This tames the steam by cooling it. It condenses into water, which is then pumped back into the reactor vessel to keep the fuel from melting. The GE invention, the Mark I containment structure, is thus able to do in a relatively small space what a Westinghouse reactor needs an entire building to accomplish.
It seemed an exceedingly clever workaround for the problem of otherwise needing an impossibly large reactor building, but the General Electric Mark I containment turned out to be the most controversial engineered object in the 20th century. Disagreements of an academic nature concerning the design may have been flying around at GE for a few years, but the problems became semi-public at a “reactor meeting” in Karlsruhe, Germany, on April 10, 1973, when a paper was presented by O. Voigt and E. Koch, “Incident in the Wuergassen Nuclear Power Plant.”
Wuergassen was the first commercial reactor built in Germany, on the River Wesser between Bad Karlshafen and Beverungen. It was an early BWR/3 with a Mark I containment. The Germans had spent four years building the plant, and they connected it into the power distribution system in December 1971.[260] They were aware of rumblings of possible discontent concerning the Mark I containment coming from many directions, and they decided to put the speculations to rest by performing a simple test. Responsible engineers at GE claimed that the Mark I “did not take into account the dynamic loads that could be experienced with a loss of coolant.” It was great design on paper, and it looked wonderful standing still in the basement of the reactor building, but would the steel torus stand up to live steam being suddenly blown down into it, or would it experience transient forces for which it was not prepared? The Germans ran the reactor up to power, making a good head of steam, and then sprang all eight steam-relief valves open at the same time.
Behavior of the torus under this “worst case” condition had not been predicted by even its strongest detractors. It quenched the steam under the water in the half-filled torus as it was supposed to, but not thoroughly, and the steam started to swap sides, first showing up on the north side of the torus, and then on the south side. The torus became possessed by “condensation oscillation,” and it started rocking, tearing the support irons out of the floor and terrifying the reactor operators. It finally settled down, but not before causing expensive damage.
On February 2, 1976, General Electric engineers in the Nuclear Energy Division, Gregory C. Minor, Richard B. Hubbard, and Dale G. Bridenbaugh, the “GE Three,” resigned from the company and held a press conference.[261] They were dismayed by their design of the Mark I containment and wished to come clean. The structure was just too fragile to stay together and prevent what it was supposed to prevent in an unlikely but not impossible reactor breakdown, they announced. It was not a good day in San Jose, home of GE Nuclear. A Mark I Owners Group was formed by concerned power companies.
259
The GE BWR/1, designed in 1955 and installed at the Dresden Generating Station in Illinois, used an external steam separator/dryer. The Soviet RBMK reactors, such as Reactor no. 4 at Chernobyl, were boiling-water reactors using multiple external steam separators.
260
Technically, the Wuergassen plant was not a GE, as it was built by AEG. AEG, however, did not design the reactor itself, but paid for a license from GE to build their latest model BWR. If there was something wrong with the Mark I, it was not the fault of AEG.
261
The three merry whistleblowers formed a consulting company, MHB Technical Associates. They were hired as technical experts for, of all things, Jane Fonda’s movie