Japan Fukushima Reactor Catastrophe: Problems and Solutions

A serious earthquake (9.0) and a major tsunami hit the Pacific coastline of eastern Japan on 11 March 2011. The earthquake resulted in the complete closure of six nuclear power plants in total. Also, external control was lost.[1] The earthquake and resulting tsunami began $235 billion of dollars in damage. Rehabilitation in the wake of the devastation is expected to take five years. Destruction on such a scale is unexpected in the face of normal and optimal protection steps. This research paper analyses the Fukushima tragedy, concerns that existed during the accidents, their remedies, and potential steps that can be taken to avoid those problems in order to dive deeper into the subject.

Incident of Fukushima: Background

The Fukushima Diachi nuclear disaster was the result of a tsunami and earthquake. It proved to be Japan’s worst natural disaster in recent history, destroying more than 20,000 lives and more than $300 billion in damage. Magnitude of the initial incidents was unexpectedly extraordinary. Earthquake was 9.0 on rector scale as opposed to the designed made for 8.2 levels. Moreover, tsunami wave was 14 meters high in comparison to the building designed for 5.7 meters. IAEA nuclear event scale has rated Fukushima disaster at highest level of 7 which refers that the incident has been resulted in huge amounts of radioactive emissions which will lead to health and environmental hazards on large scale.[2]

Emergency diesel generators and reactor cooling systems started functioning after the station blackout as a result of earthquake. An hour later, tsunami damaged seawater cooling system and the last option to regulate heat through seawater was also lost. Electric insulation collapse caused the failure of diesel generators and unavailability of the AC power. The situation led to a severe accident that went beyond the plant’s design standards. The systems which were designed for it worked to provide water to the reactors without AC control, however, they also stopped after the loss of DC power supply after two hours of the incident. [3]

The water temperature and pressure of the reactors rose in the absence of the last-resort source of heat dissipation. In addition, reactor water levels continued to decline after the shutdown of heat emissions from the decay of fuel. AC power and heat dissipation source failure was occurred in all reactors, therefore, reactors 1-4 were switched into crisis state one after the other. Reactors 5 and 6 didn’t switch to crisis mode because their emergency diesel generators kept functioning and providing power to the cooling systems. Fire extinguishing tools were utilized to soak the reactors in order to cool them from the nuclear fuel’s generated heat. During the 1990s, such major accident response initiatives were introduced at the Fukushima facility (Figure.1).[4]

                    Figure.1-Massive accident management system (Waseda University)

Development of the Catastrophe: Hydrogen Generation

Reactor pressure exceeded the capacity of fire extinguishing system; therefore, water from external source could not be supplied properly. The process of pressure release was continuously hampered by power failures; the rectors’ fuel rods were exposed. As a result, rods temperature increased and zirconium oxidation in fuel cladding tubes has resulted in the reduction of water and consequent hydrogen production. Emission of radiation was also high that hindered the activity.[5]

            Due to non-condensability of hydrogen, the pressures within the containment vessels heightened. The gas was discharged from the inside to decrease their pressure and keep them running for containment. At the top of the reactor houses, hydrogen gathered with the reduced pressure in reactors and vessels. Hydrogen exploded and destroyed the reactor buildings in units one and three. The pressure vessels of the reactor and their respective tanks were covered by 2 metres of concrete, so the blast was contained and the reactors stopped running. Another explosion occurred at the bottom of the weakened reactor and containment vessels of containment vessel Unit 2, both as seen in Figure 2.[6]However, IAEA’s key findings highlighted that hydrogen risk must be evaluated in a detailed manner and essential mitigation systems must be provided in case of other plants’ hydrogen venting capacities.[7]

          Figure.2– by Waseda University

TEPCO Solution: Water Injection

After internal cooling systems failed, water was injected into the reactors from outside in order to cool them. One of the critical things to prevent radiation emission was to keep the fuel under water. Though the system of cooling by water injection and steam condensation was not steady, external power supply was resumed in order to ensure the minimum chances of failure of long-term fuel exposure. TEPCO revealed the accident resolution and concurrent measures on April 17.Other steps they took included steady cooling of reactors and fuel-pool, containment, management, storage of polluted water and its utilization for cooling process, and regulation of radioactive material.[8]

Emergency Cooling System Used and Emergency Shutdown Plane

In Fukushima disaster complete station blackout was observed due to two major reasons. Firstly, the offsite power failure due to earthquake. Secondly, onsite power failure due to tsunami. Both of these power failures, in addition to rapid discharge of DC batteries led to this situation. Emergency Core Cooling System (ECCS) was immediately disabled after station blackout that led to future problems in regulating serious parameters, for instance, controlling reactors’ water level and opening significant safety valves, such as, isolation condenser return valves, safety and relief valves, and containment vent valves. Station blackout led to the failure in opening these valves which resulted in the damage and overheating of fuel and containment.[9]

TEPCO Safety Measures

For their insufficient response and public contact, the Japanese government and TEPCO have continuously been blamed. Throughout the disaster, there were fears that if a significant division of local workers were killed or damaged by earthquakes and tsunamis, TEPCO could not supply a sufficient amount of staff at the factory. In the Fukushima plant district, the U.S. NRC requested a large relocation area for U.S. residents. It was a precautionary measure; this demand, however, was not compatible with the radioactive exposure magnitude. It not only destabilized Japanese regulator’s reliability but also created confusion and apprehension among local people, general public, and media.[10]

TEPCO has quite a long history of not only manipulating safety standards, but also falsifying data and covering up inspection activity. Regardless of the issues in gaining and vulnerable reactors, severe earthquakes, tsunamis, inadequate barriers, existence of fuel-ponds in the reactor area, power issues, and backup generators’ low placement, TEPCO has not imagined that possibility of such massive accident.[11]Moreover, TEPCO underestimated the scope of the disaster and arranged one stretcher, one satellite phone, and only 50 suits for emergency to which 100 workers were exposed.[12]After a month of disaster, TEPCO came up with the restoration plan that deals with plant stabilization and radioactive emission control, and plant reactors’ “cold shutdown” in next 9 months. However, experts are skeptical of the claim.[13]

Global Impact

Japan is planning to go for floating wind power turbines on Fukushima coast for providing power to the damaged area.[14] The incident triggered worldwide concerns about the consequences of this disaster and future of nuclear power in general. After Fukushima disaster, some governments are revising their nuclear energy policies, in particular, Japan and Germany. Future nuclear construction plans and plant reevaluation for license extension have also been called for cancellation. Following this incident, global nuclear enterprise may suffer due to the perception that nuclear energy is unsafe.[15]Japanese government is has concerns about Japan’s economic future in the absence of nuclear power, therefore, they are struggling to ease safety concerns.[16]

Future Considerations

To prevent station blackout or control such situations in future in order to ensure minimal damages without depending on external intervention, a combination of safety mechanisms which are passive and active should be installed. The right combination of such mix should be assessed through analysis, such as, risk assessment. The risk assessment must consider the occurrence of external incidents and resulting potential disability modes of the passive systems.[17]According IAEA findings, for Fukushima reactors, tsunami threats were underestimated. Measures for deapth, separation on physical level, diversity, and redundancy needs must be considered on the basis of extreme possible levels.[18]Fukushima incident provide an opportunity for the whole world to reconsider their nuclear plans and reevaluate their safety to the optimum levels.

Conclusion

an unusually big tsunami was the primary cause of the Fukushima disaster as a result of earthquake. Earthquake was undoubtedly the most severe on the records, however, Fukushima plant stood against it and emergency management handled it efficiently. Future measure may include the optimized version of emergency supply and heat exchanging system for cooling. It must be at an altitude which is untouchable for tsunami. The incident has taught most costly lessons; however, the regulations must not be as detailed as it seemed to be practiced by institutions. The most critical measures are to be taken against tsunami incidents. There have been many regulating bodies and institutions working in Japan since the incidence of tsunamis, however, this incident proved their inability to deal with the incident of such scale. The failure does not imply that there must be some new regulating bodies; existing institutions must reevaluate their policies and systems that need a complete overhaul in the light of Fukushima disaster.[19]No doubt, Fukushima disaster is a great opportunity to learn and get prepared for the extreme conditions that a nuclear reactor can be exposed to. It is critical to enhance safety standards to the optimum level in order to ensure a safer world in future.

Bibliography

• Buongiorno, j. et al., “Technical Lessons Learned from the Fukushima-Daichii Accident and Possible Corrective Actions for the Nuclear Industry: An Initial Evaluation.”Centre for Advanced Nuclear Energy System (CANES).26 July 2011. http://canes.mit.edu/sites/default/files/pdf/NSP-025_rev1.pdf.
• Breakbulk. “Japan Plans Floating Wind Power Plant.” Bearbulk Online, September 16, 2011. http://www.breakbulk.com/wind-renewables/japan-plans-floating-wind-power-plant
• Dvorak, Phred, and Peter Landers. “Japanese Plant had Barebones Risk Plan.”Wall Street Journal, March 31, 201.http://online.wsj.com/article/SB10001424052748703712504576232961004646464.html.
• Fraser, Malcolm. “From Fukushima to Disarmament.” ABC Environment. July 5, 2011. http://www.abc.net.au/environment/articles/2011/07/05/3260732.htm
• Kim, Victoria. “Japan damage could reach $235 billion, World Bank estimates,” Los Angeles Times, March 21, 2011. http://www.calendarlive.com/la-fgw-japan-quake-world-bank-20110322,1,5161198.story
• Mitnse, “The IAEA Publishes a Preliminary Report of Its Fact Finding Mission for Fukushima,” MIT NSE Nuclear Information Hub (blog), June 16, 2011(3:14 am UTC), http://mitnse.com/2011/06/16/the-iaea-publishes-a-preliminary-report-of-its-fact-finding-mission-for-fukushima/
• McCurry, Justin. “Japan’s Nuclear Energy Debate: Some See Spur for a Renewable Revolution.” The Christian Science Monitor, May 3, 2011. http://www.csmonitor.com/World/Asia-Pacific/2011/0503/Japan-s-nuclear-energy-debate-some-see-spur-for-a-renewable-revolution.
• Oka, Yoshiaki, “The Fukushima Daiichi Nuclear Plant Accident Caused by the Massive Tsunami-Improvement of Safety Mechanism.”Waseda University. May 30, 2011. http://www.researchsea.com/html/article.php/aid/6137/cid/2/research/the_fukushima_daiichi_nuclear_plant_accident_caused_by_the_massive_tsunami_-_improvement_of_safety_mechanism.html?PHPSESSID=l7acfq80pkr6squg7kkofivop2
• Strickland, Eliza. “Explainer: What Went Wrong in Japan’s Nuclear Reactor.” IEEE spectrum, May 13, 201. http://spectrum.ieee.org/tech-talk/energy/nuclear/explainer-what-went-wrong-in-japans-nuclear-reactors.
• Wagner, Wieland. “Japanese Leaders Leave People in Dark,” Spiegel Online International, March 15, 2011, http://www.spiegel.de/international/world/0,1518,751109,00.html
• [1] Oka,Yoshiaki, “The Fukushima Daiichi Nuclear Plant Accident Caused by the Massive Tsunami-Improvement of Safety Mechanism,” Waseda University, May 30, 2011, http://www.researchsea.com/html/article.php/aid/6137/cid/2/research/the_fukushima_daiichi_nuclear_plant_accident_caused_by_the_massive_tsunami_-_improvement_of_safety_mechanism.html?PHPSESSID=l7acfq80pkr6squg7kkofivop2
• [2] J.Buongiorno et al., “Technical Lessons Learned from the Fukushima-Daichii Accident and Possible Corrective Actions for the Nuclear Industry: An Initial Evaluation,” Centre for Advanced Nuclear Energy System(CANES),26 July 2011, http://canes.mit.edu/sites/default/files/pdf/NSP-025_rev1.pdf.
• [3] Oka, Improvement of Safety Mechanism
• [4] Ibid
• [5] Ibid
• [6] Ibid
• [7] Mitnse, “The IAEA Publishes a Preliminary Report of Its Fact Finding Mission for Fukushima,” MIT NSE Nuclear Information Hub(blog),June 16,2011(3:14 am UTC), http://mitnse.com/2011/06/16/the-iaea-publishes-a-preliminary-report-of-its-fact-finding-mission-for-fukushima/
• [8] Ibid
• [9]Buongiorno, 5
• [10]Buongiorno,6
• [11] Malcolm, Fraser, “From Fukushima to Disarmament,” ABC Environment, July 5,2011, http://www.abc.net.au/environment/articles/2011/07/05/3260732.htm
• [12] Phred Dvorak and Peter Landers, “Japanese Plant had Barebones Risk Plan,” Wall Street Journal, March 31, 2011, http://online.wsj.com/article/SB10001424052748703712504576232961004646464.html.
• [13] Eliza Strickland, “Explainer: What Went Wrong in Japan’s Nuclear Reactor,” ieee spectrum, May 13,2011, http://spectrum.ieee.org/tech-talk/energy/nuclear/explainer-what-went-wrong-in-japans-nuclear-reactors
• [14] Breakbulk, “Japan Plans Floating Wind Power Plant,” Bearbulk Online, September 16,2011, http://www.breakbulk.com/wind-renewables/japan-plans-floating-wind-power-plant
• [15] Buongiorno, 3
• [16] Justin McCurry, “Japan’s Nuclear Energy Debate: Some See Spur for a Renewable Revolution,” The Christian Science Monitor, May 3, 2011, http://www.csmonitor.com/World/Asia-Pacific/2011/0503/Japan-s-nuclear-energy-debate-some-see-spur-for-a-renewable-revolution.
• [17] Buongiorno, 5
• [18] MITNSE
• [19] Oka, Improvement of Safety Mechanism