Nuclear - Energy Policy Analysis: A Conceptual Framework - page 49

disaster (WHO 2005). Yet lack of American interest in events overseas, coupled with differences in
design between the nuclear reactor at Chernobyl and those located in the United States—stressed
by the U.S. nuclear industry—resulted in only short-term increased concern over nuclear reactor
safety in the United States.
The Fukushima I nuclear disaster was based on a series of equipment failures, reactor core
meltdowns, and releases of radioactive materials following the 9.0 magnitude Tōhuku earthquake
and tsunami on March 11, 2011, in Japan (DiSavino 2011). The Fukushima I Nuclear Power
Plant, operated by the Tokyo Electric Power Company (TEPCO), contained six boiling-water
reactors (BWR) designed by General Electric, similar to many in the United States. Its electrical
generators had a combined capacity of 4,700 MWe, making Fukushima I one of the twenty-five
largest nuclear power stations in the world. Unit 1 was a 439 MWe reactor that began commercial
operation in 1971. Units 2, 3, 4 and 5 were all 784 MWe reactors, and Unit 6 had 1,100 MWe of
generating capacity.
At the time of the quake, only Units 1, 2, and 3 were operating, and they shut down automati-
cally after the earthquake, while emergency generators started up to run control electronics and
water pumps needed to cool reactors. Fuel had previously been removed from Unit 4, and Units
5 and 6 were in cold shutdown for scheduled maintenance (CNN Wire Staff 2011). The plant was
protected by a seawall designed to withstand a 5.7-meter (19-foot) tsunami but not the 14-meter
(46-foot) maximum wave that arrived about an hour after the earthquake (IAEA 2011b). The en-
tire plant was flooded, including low-lying generators, electrical switchgear in reactor basements,
and external pumps for supplying cooling seawater. Diesel fuel tanks for backup generators were
swept away. The connection to the electrical grid was broken. All power for cooling was lost and
reactors started to overheat.
In the next few days, Units 1, 2, and 3 experienced a full meltdown (IAEA 2011b). Hydrogen
explosions destroyed the upper level of buildings housing Units 1, 3, and 4; an explosion damaged
the containment of Unit 2; and multiple fires broke out at Unit 4. Fuel rods in all three reactors
and in spent fuel storage pools were exposed to air, and temperatures were uncontrolled. With the
remnants of its reactor core fallen to the bottom of its damaged reactor vessel, Unit 1 continued
to leak cooling water three months after the initial events, and similar conditions were believed
to exist at the other two melted-down reactors (CNN Wire Staff 2011).
Despite being shut down, fuel rods stored in pools at Units 5 and 6 began to overheat as water
levels dropped. Unit 6 was restarted on March 17, allowing some cooling at Units 5 and 6, which
were least damaged. Grid power was restored to parts of the plant on March 20, but machinery
for Units 1 through 4, damaged by floods, fires, and explosions, remained inoperable (Makinen
and Vartabedian 2011). On May 5, two months after the earthquake, workers were able to enter
reactor buildings for the first time (MacKenzie 2011a).
Worldwide measurements of iodine-131 and cesium-137 suggested that releases of those iso-
topes from Fukushima were of the same magnitude as those from Chernobyl in 1986 (MacKenzie
2011b). Plutonium contamination was detected in soil at two sites in the plant.
Japanese officials initially assessed the accident as Level 4 on the International Nuclear Event
Scale, and it was eventually raised to Level 7, the maximum scale value (Shears 2011). Only
Chernobyl is rated as high. Experts consider Fukushima the second-largest nuclear disaster after
Chernobyl, but more complex because multiple reactors were involved. A workforce in the hun-
dreds or even thousands will take years or decades to clean up the area (Makinen and Vartabedian
2011).
The Fukushima II Nuclear Power Plant, located about seven miles north of Fukushima I, has
four BWR of 1,100 MWe each, totaling 4,400 MWe capacity, which automatically shut down