Anti Political Dynasty Bill 15.pdf
Joyce Buzard
Public sentiment in many states has turned against nuclear energy following the March 2011 accident at Japan's Fukushima Daiichi Nuclear Power Station. The Fukushima accident was, however, preventable.
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In the final analysis, the Fukushima accident does not reveal a previously unknown fatal flaw associated with nuclear power. Rather, it underscores the importance of periodically reevaluating plant safety in light of dynamic external threats and of evolving best practices, as well as the need for an effective regulator to oversee this process.
The accident at Fukushima Daiichi Nuclear Power Station on March 11, 2011, has put safety concerns front and center of the ever-contentious debate about nuclear energy. With large quantities of radioactivity released into the environment, over three hundred thousand residents evacuated from the vicinity of the plants,1 and a cleanup operation that will take decades and cost tens, if not hundreds of billions of dollars, critics have argued that nuclear power is too dangerous to be acceptable. But are they right? Can nuclear power be made significantly safer? The answer depends in no small part on whether nuclear power plants are inherently susceptible to uncommon but extreme external events or whether it is possible to predict such hazards and defend against them.
On March 11, 2011, at 2:46 pm local time, Japan was struck by a magnitude 9.0 earthquake, centered in the Pacific Ocean about 80 kilometers east of the city of Sendai, that set a powerful tsunami in motion.3 This was the largest earthquake ever recorded in Japan and, according to the United States Geological Survey, the fourth largest recorded worldwide since 1900.4
Nonetheless, complete remediation of the site is likely to take three or four decades, and the biggest challenge will probably be removing all the melted fuel. The road to complete recovery will be an extremely long and expensive one.
There is still much to be learned about the accident sequence, including the actions of the plant operators to mitigate it. In contrast to the report by an IAEA fact-finding mission (which was highly complimentary of the plant operators), an interim report by a commission appointed by the Japanese government to investigate the accident expressed direct and significant criticism of plant operators in units 1 and 3 for delays in implementing emergency cooling procedures.13 The commission, however, stopped short of asserting that a swifter response would have prevented the explosions in those units, withholding judgment until more information becomes available. The actions of the operators will undoubtedly come under considerable scrutiny in the months ahead. In assessing these actions, it is necessary to keep two points in mind.
First, the accident progressed extremely quickly. The table below shows estimates, by both the Japanese regulator, the Nuclear and Industrial Safety Agency (NISA), and TEPCO of the length of time that passed after the earthquake until (i) fuel became exposed, (ii) fuel started to melt, and (iii) molten fuel started to damage the reactor pressure vessels. At unit 1, it appears that the emergency cooling system became inoperative immediately after the tsunami and fuel damage began two or three hours later (that is, three or four hours after the earthquake).14 However, the operators were flying blind for much of that time. All instrumentation in the main control room of units 1 and 2 was lost following the tsunami, and it was almost three hours before some instrumentation had been restored and the operators had reason to suppose that the emergency cooling system had failed.15 By the time operators could reasonably have known there was a problem, fuel damage was already imminent.
The accident progressed somewhat more slowly in units 2 and 3. The emergency cooling systems in those units failed after about seventy and thirty-five hours, respectively, and in each case fuel damage began about seven or eight hours later (that is, about seventy-seven and forty-three hours, respectively, after the earthquake).16
[d]uring the initial response, work was conducted in extremely poor conditions, with uncovered manholes and cracks and depressions in the ground. Work at night was conducted in the dark. There were many obstacles blocking access to the road such as debris from the tsunami and rubble that was produced by the explosions that occurred in Units 1, 3 and 4. All work was conducted with respirators and protective clothing and mostly in high radiation fields.17
These two observations have important implications for assessing the Fukushima Daiichi accident. Given the short time that might be available for operators to take action in the event of a station blackout and the extraordinary stress under which they are likely to be working, actions to be taken after an extreme external event and measures to prevent fuel damage must be prepared in advance, must have been practiced extensively, and must rely only on local resources if they are to have a realistic chance of success. None of these criteria was met at Fukushima Daiichi.21
As a result, we believe it would be unfair to apportion significant blame for the accident on the actions the operators took (or failed to take) after the tsunami, as the official investigation committee has done. Furthermore, given the potential challenges of a complete loss of AC power, it is clear that prevention is the best form of management. To this end, the key questions raised by the accident are why was the tsunami hazard at Fukushima Daiichi so dramatically underestimated? And could changes in plant design (resulting from effective safety reviews) have prevented a severe accident in the event that a tsunami struck the plant? The answers to these questions help shed light on whether the accident could have been prevented.
Because the underlying geophysical phenomena are extremely complicated, accurate hazard assessment for earthquakes and tsunamis is exceedingly challenging. But it is becoming increasingly evident that there were significant flaws in the methodology used to assess hazards to the Fukushima Daiichi plant.
Notwithstanding the intrinsic difficulties of hazard prediction, the approach to hazard prediction for Fukushima Daiichi appears to have been at variance, in three important areas, with both international best practices and, in some cases, with Japanese best practices.
Second, there appear to have been deficiencies in tsunami modeling procedures, resulting in an insufficient margin of safety at Fukushima Daiichi. A nuclear power plant built on a slope by the sea must be designed so that it is not damaged as a tsunami runs up the slope. In 2002, the Japan Society of Civil Engineers developed a detailed methodology for determining the maximum run-up of a tsunami.40 This methodology prompted TEPCO, voluntarily, to revise the design-basis tsunami at Fukushima Daiichi from 3.1 meters to 5.7 meters. However, in at least one important respect, TEPCO does not appear to have implemented the relevant procedures in full.
To be fair, it appears that there were no suitable tools available in Japan for TEPCO to analyze the full range of effects of a tsunami. But given the prevalence of tsunamis in Japan, NISA should have encouraged the development of such instruments in keeping with international standards.
These simulations assumed a repeat of the 869 AD earthquake.49 Because this event was larger than the earthquake on which previous simulations were based, the resulting tsunami was predicted to be higher. Given the new simulations were based on an actual historical earthquake, they should have been followed up on immediately. Had the results been verified, TEPCO may have been able to take corrective action in time to avert the disaster of March 11, 2011.
In theory, during the decade before the accident, NISA might have urged or required TEPCO to significantly strengthen the design of the Fukushima Daiichi Nuclear Power Station. NISA had been reviewing the safety of unit 1 related to a TEPCO request to extend its operating lifetime. Just a few weeks before the accident, NISA gave unit 1 the green light to operate for an additional ten years.
According to these experts, on the basis of international knowledge accumulated during the four-decade operating lifetime of the Fukushima Daiichi Nuclear Power Station and put into practice at nuclear power plants elsewhere, TEPCO, encouraged by Japanese regulators, could have taken some or all of the following actions to have protected the plants against a tsunami:
When the Fukushima Daiichi station was constructed, the emergency diesel generators and emergency batteries were installed on the floor inside the plant building to afford protection against earthquakes. Ventilation ducts in the compartments where this equipment was located were not waterproofed. Moving this emergency power equipment to higher ground, safety experts said, would not have increased its vulnerability to seismic shock, provided it was fixed to a platform designed to resist earthquakes.62
During the four decades that the Fukushima Daiichi Nuclear Power Station was in operation, nuclear safety authorities and nuclear power plant owners in several countries were establishing requirements and configuring nuclear power plants in ways that could potentially have saved the Fukushima Daiichi nuclear station from disaster had they been heeded. In particular, some regulatory bodies outside of Japan reassessed the safety of installations in the event of extreme flood hazards, a station blackout, and the loss of the ultimate heat sink. In the view of safety experts participating in such assessments, had Japan acted on these developments, the plant could have survived the tsunami that struck in March 2011.
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