THE BULLETIN OF THE ATOMIC SCIENTIST<\/p>\n
Nuclear safety lessons from Japan’s summer earthquake<\/p>\n
BY ASHWIN KUMAR AND M. V. RAMANA | 4 DECEMBER 2007<\/p>\n
On July 16, 2007, an earthquake with a magnitude of somewhere between 6.6 and 6.8
\nstruck Japan. Its epicenter was about 16 kilometers north of the Kashiwazaki-Kariwa
\nNuclear Power Plant (KKNPP), the biggest such plant in the world. The known results of
\nthe earthquake include a fire and leaks of radioactivity. However, news of damage to the
\nreactors continues to emerge, the most recent being the discovery of a jammed control
\nrod in Unit-7. Though there was no major release of radioactivity, the many failures and
\nunanticipated events that occurred at the reactor after the earthquake have important
\nimplications for nuclear safety worldwide.<\/p>\n
To start, the Japanese nuclear establishment never anticipated the magnitude of the After the recent earthquake, Takashi Nakata at the Hiroshima Institute of Technology and Such differences in conclusions suggest that there were organizational pressures to ignore The July earthquake also points to how actual accidents could result in unexpected modes Finally, the earthquake showed how emergency plans that look great on paper can fail Throughout, TEPCO’s primary aim seemed to be to quell fear rather than accurately The prevention of accidents at nuclear facilities depends on both technological and
\nearthquake. Under Japan’s old guidelines, which formed the basis of the KKNPP design,
\nthe seismic hazard for each nuclear site is defined in terms of two intensities, termed S1
\nand S2. (See “Status Report on Seismic Re-Evaluation”.)<\/em> The S1 earthquake, referred to
\nas the “maximum design earthquake,” is less intense and determined by historical events
\nand current and past fault activity. The S2 earthquake, called the “extreme design
\nearthquake” and supposedly an impossibility, is derived from seismo-tectonic structures
\nand active faults. These requirements were believed to provide a “sufficient range of
\nearthquakes to assure reactor safety for any potential earthquake shaking.” (See “A
\nDeveloping Risk-Informed Design Basis Earthquake Ground Motion Methodology”<\/em>.) But
\nclearly the S2 design earthquake wasn’t extreme enough: The peak ground acceleration of
\nthe July 16 earthquake was two-and-a-half times greater than what was assumed for the
\nS2 earthquake.<\/p>\n
\nYasuhiro Suzuki at Nagoya University analyzed the data in the Tokyo Electric Power
\nCo.’s (TEPCO) license application and concluded that it indicated a fault five times
\nlonger than the one TEPCO identified. Between 1979 and 1985, TEPCO found four small
\nfaults off the coast of Kashiwazaki-Kariwa, but it concluded that they were either inactive
\nor unimportant. However, Nakata and Suzuki believe that three of these small faults
\nconstitute one 36-kilometer long fault, which is probably active, too.<\/p>\n
\ninconvenient data or interpret it to ensure it supported vested interests–in this case,
\nbuilding the reactor at a specific site. A similar example (albeit from a different
\ntechnological arena) is the 1986 Challenger space shuttle explosion. In her 1996 book,
\nThe Challenger Launch Decision: Risky Technology, Culture, and Deviance at NASA,
\nsociologist Diane Vaughan observed that the ultimate origins of the accident “were in
\nroutine and taken-for-granted aspects of organizational life that created a way of seeing
\nthat was simultaneously a way of not seeing.”<\/p>\n
\nof failure. Nuclear reactors are based on complex interactive technologies, operating at
\nhigh temperatures or pressures, with tightly coupled events occurring at a rapid pace, and
\ntherefore, prone to accidents. (See Charles Perrow’s 1984 book, Normal Accidents:
\nLiving with High-Risk Technologies<\/em>.) By simultaneously affecting large parts of a nuclear
\npower plant, earthquakes increase the possibility of accidents. The Japanese earthquake
\ndamaged KKNPP’s switchyards and water piping for the fire-suppression systems. It also
\ncaused a fire when electrical equipment near a transformer slipped, causing separated
\ncables to short-circuit. There are reports that leaking oil was involved in this fire.
\nSome events were unexpected: For example, underground electric cables were pulled
\ndown by ground subsidence, creating a large opening in the outer wall of the reactor’s
\nbasement–a so-called “radiation-controlled area” that must be completely shut off from
\nthe outside. According to a TEPCO official, “It was beyond our imagination that a space
\ncould be made in the hole on the outer wall for the electric cables.”<\/p>\n
\nwhen disaster strikes, with KKNPP managers admitting that “disaster-prevention
\nmeasures did not function successfully.” For example, the fire-extinguishing system at
\none reactor couldn’t be used because of pipe damage, resulting in the water hose only
\nbeing able to spray water at a distance of a meter rather than the normal dozens of meters.
\nSince the plant didn’t have chemical fire extinguishers, workers had no choice but to
\nwatch the fire burn. The earthquake also knocked out a hotline to the local fire station.
\nMeanwhile, Plant Director Akio Takahashi was told of the fire immediately after the
\nearthquake, but didn’t dispatch the facility’s firefighters because he thought management
\nwould have already done so–an example of the human error even high-level officials are
\ncapable of during stressful moments. When they were notified, the fire brigade struggled
\nto reach the plant because of the area’s other damage. So although the transformer fire
\nwas detected at 10:15 a.m., firefighters didn’t start fighting it until more than an hour
\nlater. Takahashi also admitted to problems in the facility’s primary firefighting system
\nand cooperation between related organizations.<\/p>\n
\nreport facts. For example, TEPCO employees knew about the leak by 12:50 p.m., but the
\ncompany didn’t publicly report it until 8:28 p.m. Similarly, the initial estimates of
\nradioactivity TEPCO released were significantly smaller than the final figure. If this was
\nthe case during a relatively major accident that was displayed on television screens
\naround the world, it’s easy to imagine the paucity of information nuclear authorities
\nwould make available during a smaller accident.<\/p>\n
\norganizational factors. The efficacy of these factors is contingent upon them performing
\naccording to design. Though there wasn’t a large-scale release of radioactivity, events at
\nKKNPP after the July earthquake demonstrate both technological and organizational
\nfailures. Discussions about nuclear safety should begin by acknowledging the possibility
\nof such failures.<\/p>\n