the impact of the fukushima daiichi nuclear power plant accident on the environment, and...
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The Impact of the Fukushima Daiichi Nuclear Power Plant Accident on the Environment, and Consequential Effects on Japanese Energy Policy
On March 11, 2011, the Great East Japan Earthquake triggered a tsunami that
traveled almost ten kilometers on land. The 9.0 magnitude earthquake and 40.5 meter-‐high tsunami were the highest recorded in Japanese history (Hamada and Ogino 2012). Tokyo Electric Power Company (TEPCO) had six boiling water type nuclear power reactors operating in the Fukushima Daiichi Nuclear Power Plant (FDNPP), which were equipped with sea defenses, but these defenses were not adequate for the tsunami that struck. The reactors were immediately shut down, but the tsunami demolished the reactor’s backup power system, causing the cooling system to malfunction (Ohta 2012). Despite efforts to inject water into the overheated reactor cores in an attempt to cool the system manually, hydrogen explosions occurred in three of the reactors, releasing a multitude of radionuclides into the atmosphere (Saito et al. 2014). The consequences of the FDNPP incident raised concerns regarding the well-‐being of the environment due to impacts from radionuclides, as well as questions of what direction Japan’s energy policy would head in after such a severe nuclear power related incident.
Of the radionuclides released, 131I, 133Xe, 134Cs, and 137Cs were detected, with half-‐lives of 5.24 days, 8.02 days, 2.07 years, and 30.17 years, respectively (Sohtome et al. 2014; Povinec et al. 2013; Ohta et al. 2012). 133Xe had the highest initial activity, estimated by Povinec (2013) to be between 13,000 to 20,000 PBq, but disappeared quickly due to its relatively short half-‐life. Additionally, 131I and 134Cs had the biggest effect on the external effective dose immediately following the accident, but when these concentrations started to diminish, 137Cs became the most prominently detected radionuclide. 137Cs has shown to be a significant concern due to its long half-‐life, which is substantially longer than that of any radionuclide emitted by the FDNPP and causes chronic, low-‐level exposure to radiation (Taira et al. 2012). Radionuclides entered the earth’s system via both dry and wet deposition from the atmosphere and also directly via waterways from the damaged reactors (Yasunari et al. 2011). FDNPP’s reactors were cooled with seawater, and due to the damage of the accident, large volumes of contaminated water was leaked into the ocean (Sohtome et al. 2014). TEPCO estimated that the 520-‐ton flow of water from the reactor to the open ocean contained 2.8 PBq 131I, .940 PBq 134Cs and .940 PBq of 137Cs in the period between 1 – 6 April, 2011 (Hamada and Ogino 2012). It is difficult to estimate the concentration of radionuclides in the ocean, as they dilute upon hitting the water.
Radiocesium from FDNPP was mostly deposited into the North Pacific Ocean, where it was then moved eastward by surface currents and then southward through the Kuroshio Extension Current (Kumamoto 2015). There is a significant concern in how the presence of radionuclides in the oceans will effect the safety of seafood. The Ayu Plecoglossus is a herbivorous fish that is a significant food source for both humans and bird species, and is thus a good indicator of how these radionuclides, particularly 137Cs, will travel through the food chain. Ayu graze on algae on the
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bottom of riverbeds, where particles of radiocesium had gathered after the Fukushima accident. While concentrations of radiocesium in the muscles and internal organs of Ayu have decreased since the accident in 2011, indicating a decrease in the risk of radiocesium moving up the food chain, the sediment at the bottom of rivers still act as a considerable source of radionuclide exposure. Radiocesium is highly insoluble and its granular nature interacts strongly with clay minerals, causing it to physically attach to sediment, making removal extremely difficult (Niimura et al. 2015; Tsuboi et al. 2015). It is estimated that the 22% of 137Cs emitted from the accident deposited over Japanese land is likely to stay there; radiocesium is strongly adsorbed by micaceous clay minerals, which tightly hold the radiocesium within the soil, causing it to stay there for many years (Kumamoto et al. 2015; Yasunari et al. 2011). Radiocesium has high biological availability and the primary pathway for exposure to cesium is through ingestion. Despite its tight adsorption to clay minerals, there is some transfer of radiocesium to edible parts of crops via plant root uptake (Takeda et al. 2014). However, this transfer has been shown to decrease rapidly in a short period of time. Fujimura et al.
(2015) studied the transfer factor (a measurement estimating the concentration of radionuclides in plants) of 137Cs in rice, and found
that it decreased 67% in one year, and it decreased exponentially to 0 in just 3 to 4 years, suggesting that clay minerals prevented the uptake of the radiocesium.
Figure 1. Distribution of air dose rates taken by car-‐borne surveys from June 4 – 13, 2011 (Andoh et al. 2015)
Figure 2. Distribution of air dose rates taken by car-‐borne surveys from November 5 – December 10, 2012 (Andoh et al. 2015)
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Due to the adsorption of 137Cs by micaceous clay minerals, it has a very low chance of seeping from the soil into the groundwater. Studies done after the Chernobyl nuclear power plant accident (CNPP) and from atmospheric weapons tests in the 50s and 60s have shown that the downward movement of 137Cs decreases significantly within a matter of years due to its fixation to soil particles (Takahashi et al. 2015). A majority of the radiocesium becomes trapped within the top 1 cm of soil and will not travel much further downwards (Yasunari et al. 2011). Due to this
limited movement, the 137Cs is likely to only move 18 cm within 300 years, which constitutes 10 half-‐lives. This is comparatively less movement than was seen after the dropping of the atomic bomb at Nagasaki, where 137Cs moved downward 30 cm within 40 years (Ohta 2012). Car-‐borne surveys enabled the compilation of very precise data relating to the airborne spread of radionucldies after the accident and the air dose rate. Figures 1 and 2 show how the areas of high dose rates, with Figure 1 showing movement from June 4 -‐13, 2011 and Figure 2 illustrating November 5 – December 10, 2012. The difference in these illustrations highlights the dissipation of radionuclides out away from Fukushima and the decrease in severity of dose rates over time (Andoh et al. 2015).
When compared to a map showing the deposition of 137Cs on June 14, 2011 (Figure 3), it is clear to see that there is marked overlap between areas of high dose rate and high concentrations of 137Cs (measured in kBq/m2). This follows with conclusions made by Saito et al. (2015), whom stated that radiocesium had substantially higher radiation doses than the other radionuclides emitted from FDNPP, and was found to create an external effective dose rate greater than the public dose limit of 1 mSv y-‐1, (Taira et al. 2012).
The Chernobyl Nuclear Power Plant (CNPP) accident of 1986 and previous radionuclide emissions from atomic weapons testing in the 50s and 60s provide critical information on the behavior and movements of radiocesium through time. Povinec et al. (2013) created a model using 137Cs patterns from the CNPP accident and nuclear weapons testing to predict what path FDNPP radiocesium would take. This model concluded that 137Cs activity would not exceed 20 Bq/m3, a level of activity similar to the observed activity from atmospheric nuclear weapons tests. This information enabled the conclusion that the global population does not face a risk of radiation from consumption of seafood from the Fukushima region.
Based on conclusions from the literature on the environmental impacts of the FDNPP accident, it can be determined that the environmental risks posed by
Figure 3 Deposition density of 137Cs on June 14, 2011
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radionuclides are substantial, but not astronomical. While there is still a significant concern over the long-‐term presence of 137Cs, there are recorded decreases in air dose rates, concentrations of radionuclides in marine biota, and in edible portions of crops, and there is evidence showing that groundwater is highly unlikely to become contaminated.
Additionally, information on radionuclide concentration and activity from the CDNPP accident and atmospheric atomic weapons testing enables the comparison of the detriment of the FDNPP accident. When put into perspective with the CDNPP accident and weapons testing, the impact of the FDNPP accident seems less severe; the Nuclear and Industrial Safety Agency (NISA) estimated that the total emitted radiation of the CNPP accident measured to be about 5,200 PBq (Hamada and Ogino 2012), while radiation from atmospheric nuclear weapons testing was measured at about 2,000 PBq (Povinec et al. 2013). Recently, TEPCO released a statement stating that more radionuclides were released from the accident than previously imagined, reporting radiation levels of just over 1,000 PBq (TEPCO 2012).
Since the accident, all nuclear reactors were decommissioned and Japanese citizens have firmly opposed resuming nuclear operations. As the world’s fifth-‐largest energy consumer (Vivoda 2012), it stands in a precarious position as an importer of 95% of total energy consumption (Hong et al. 2013). Previously, 30% of the country’s electricity was generated from nuclear power (Hayashi and Hughes 2013), and prices in electricity experienced an incredulous increase in the absence of nuclear power. The Japanese government is now left with the daunting task of creating an energy scheme that is affordable, substantial, and sustainable.
In June of 2010, the Japanese government devised the Basic Energy Plan, which devised a set of energy and emissions goals, including a goal to increase its use of nuclear energy to 50%, while receiving 70% of its electricity through zero-‐emission sources by 2030, which would cut its emissions by 25% (Hayashi and Hughes 2013). These goals became unrealistic with the decommissioning of the 54 nuclear power plants. While nuclear power constituted only 30% of the nation’s power, 28% was from liquid natural gas (LNG), 25% from coal, and 13% from petroleum (Meltzer 2011). In a scenario whereby Japan completely abandons nuclear, one or more of these sources would need to be greatly increased to meet the energy deficit, placing economic pressures on the country and backpedaling on environmental goals.
In the wake of the FDNPP accident in 2011, the former prime minister, Naoto Kan declared that Japan’s energy policy would receive a complete overhaul. He proposed a new energy scheme that would promote solar and renewable energies, having them generate 20% of the nation’s power by 2020 (Vivoda 2012). Zero-‐carbon sources such as photovoltaics or wind turbines are highly appealing, but are severely costly; in Japan, the price of electricity from photovoltaic panels is twice as high for homeowners and five times as high for businesses, diminishing the practicality of the source. While more economically feasible, wind turbines face a tipping risk in an area that experiences a multitude of hurricanes (Meltzer 2011).
Recently, in the absence of nuclear power generation, Japan has been forced to increase reliance on LNG and coal, which greatly interferes with its climate
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change goals. These imported fuel sources are costly and have caused the price of electricity in Japan to greatly increase (The Economist 2014).
Japan has several options for proceeding with its future energy plan: it can play it safe and choose to turn its back on nuclear completely, it can reopen some of its nuclear reactors to help lessen the blow of its energy struggles, or it can continue down the path it forged with nuclear power.
If Japan chooses to abandon nuclear power all together, it will have to increase its dependence on other energy sources to make up for the 30% of electricity previously generated by nuclear energy. Hong et al. (2013) estimates that if Japan moves away from nuclear power, it will have to increase its electricity production by renewable sources to 35% (with natural gas as a backup source), and meet the rest of the country’s energy demand with fossil fuels.
Problems with this projection immediately become evident; photovoltaics and wind turbines are costly and impractical for Japan (Meltzer 2011), the levelized cost of electricity will skyrocket to £16/MWh (Hayashi and Hughes 2013), new infrastructure supporting these sources will need to be built, and it will greatly increase greenhouse gas emissions. The Intergovernmental Panel on Climate Change (IPCC) set forward an emissions goal of 50 -‐150 kg CO2 MWh-‐1, and the hypothetical nuclear-‐free energy scheme would likely emit 262 kg CO2 MWh-‐1 due to the increased reliance on fossil fuels (Hayashi and Hughes 2013; Hong et al. 2013).
These issues can largely be avoided if Japan chooses to reopen its nuclear reactors. Hong et al. (2013) estimates that if Japan were to increase its nuclear power generation to 35%, greenhouse gas emissions would be 40% lower than in the nuclear-‐free scenario (only 262 kg CO2 MWh-‐1). According to a study by the IEA, Japan will need to double its generation of nuclear power by 2050 in order for the world to achieve the “international 2 degree C warming goal” (IEA 2015). Doing so would decrease Japan’s dependence on imported energy, while decreasing the cost of electricity.
The literature suggests that a move toward nuclear would be strongly in Japan’s favor. The rolling blackouts, extremely high cost of electricity, and increased fossil fuel emissions that are occurring as a result of a lack of nuclear power is in no way in the best interest of Japanese citizens (Hiranuma 2014; Hayashi and Hughes 2013). Additionally, there are few energy sources that are more suitable to Japan’s needs than nuclear power, and relying less on imported sources such as LNG and coal would increase Japan’s energy independence and ensure that fuel prices remain low (Economist, 2014a).
The Japanese government seems to be in agreement with a shift back towards nuclear power. In April 2013, Prime Minister Shinzo Abe adopted the Policy on Electricity System Reform, which outlined goals of a stable supply of electricity with low rates. Almost a year later in April of 2014, the Strategic Energy Plan was updated to include the “3E + S” strategy, which aims to enhance energy security while striving for economic efficiency and environmental sustainability, all while emphasizing the importance of safety (Hiranuma 2014). Since the accident, the Nuclear Regulation Authority (NRA) of Japan has been creating new standards on nuclear reactors in hopes of restoring public faith in nuclear.
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Despite the government’s goals to increase safety move towards a secure energy future, there is still strong public opposition of nuclear power. Regardless, the Japanese government is pursuing the reactivation of nuclear reactors. A city in the Kagoshima prefecture voted to reopen two nuclear reactors in the local Sendai power plant, despite disapproval from the local citizenry, and is expected to resume operations by the end of 2015 (The Economist 2014a). Prime Minister Shinzo Abe recognizes that total reliance on nuclear power is still risky, and although he has come out as a supporter of reopening nuclear reactors, he has done so while also stating that he would like to reduce reliance on the energy source as much as possible (Tsukimori and Saito 2015). The NRA approved the reactors in Sendai despite its location in an active volcano area. Although the NRA has the self-‐proclaimed most-‐strict safety regulations in the world, citizens are skeptical of the agency; it seems unclear as to whether the agency is simply driving the Abe administration’s ambitious agenda, or if it is truly proceeding with the public’s best interests in mind (The Economist 2014b)
Japan does not have many options when it comes to the fate of its idled reactors. The factors of electricity cost, emissions goals, and energy availability are all pushing the Japanese government back towards nuclear power. If it chooses to disregard nuclear power completely, Japan will be faced with an unreasonable cost of electricity while spewing an irresponsible amount of greenhouse gasses from costly imported fossil fuel sources into the atmosphere. It seems, then, that the Japanese government is now stuck in a situation where it can gamble the livelihood of its citizens with nuclear operations, or dig itself into an environmental and economic sinkhole.
Public opposition to resuming nuclear operations is reasonable; the risks associated with nuclear power are severe, long-‐lasting, and dangerous. In an area so susceptible to natural disasters, it is not inconceivable that another string of natural disasters could cause more complications with nuclear reactors. However, a comprehensive look at the evidence shows that, while the FDNPP accident was serious and had a series of impacts on the integrity of the environment, scientific studies have shown that these impacts are diminishing and are less severe than previously realized. The CNPP accident and atmospheric weapons testing both had more negative consequences on humans and the environment than the FDNPP accident. In order to make meaningful steps towards energy security, the Japanese government must take these environmental impacts into account when considering its stance on nuclear power. Word Count: 2,743
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