Fukushima Nuclear Disaster 2011: A look at the past and the present

Nuclear power is one hell of a way to boil water!” ~ Albert Einstein

On March 11, 2011, Japan experienced a devastating ‘triple-disaster’ that culminated into the world’s worst nuclear accident since Chernobyl. The 9.0 magnitude earthquake, with an epicenter about 80 miles off the Northeast Coast of Japan, triggered a 15-metre-high tsunami. These two natural disasters disabled the power back-up and emergency cooling systems of nuclear reactors at the Fukushima Daiichi nuclear power plant – initiating a chain of events that caused three active reactors to experience meltdown.

The unexpected situation caused the emergency crews to use seawater to cool the damaged reactors. Consequently, much of the water washed into the Pacific Ocean – resulting in the largest release of radiation into the sea that has ever been recorded. As the crew struggled to cool the reactors and bring back power to the coolant systems, a number of hydrogen explosions occurred at the plant – causing an exceptionally large amount of radioactive material to release into the air and also to fell onto the ocean surface.

And a look at what followed……and still continues

It may have been five years since the Fukushima nuclear meltdown but the ruins are still smouldering with continued leakage of radioactive isotopes. The disaster site is, in fact, an ongoing source of these radionuclides entering the sea. With the containment vessels spewing radioactivity every day, the situation indeed has far-reaching consequences.

A 2015 Green Cross report published that, “Reports on the Fukushima disaster timeline indicate that nine months following the earthquake and tsunami, radiation was still being released from the reactors as uncooled fuel rods reacted with air, explosions occurred within the plant, and water containing radioactive material leaked from the plant” and that “The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported that radioactive material was still being released into the ocean as late as May 2013.” [1]

According to very recent news published in The Asahi Shimbun, Tokyo Electric Power Co. (TEPCO) is still struggling with contaminated water at the Fukushima plant. Initially TEPCO constructed seaside walls in attempts to block the radioactive groundwater flowing out of contaminated reactor buildings and leaking into the ocean. The plan was to pump up groundwater from five wells that were dug between these walls and the plant’s reactor buildings, and to release the less contaminated water into the sea after the purification process. But it turned out that the water still had large amounts of radiation and “the water from four of the wells was discovered to have high levels of tritium–a radioactive substance that is hard to remove–at levels higher than 1,500 becquerels per litre, which means the water cannot be released into the sea.” [2]

What does this mean? As of now, TEPCO is temporarily transferring the groundwater into highly contaminated reactor buildings – leading to further contamination of water when exposed to melted nuclear fuel. As a result, an increasingly large amount of radioactive water is still being accumulated at the power plant with no assurance of things turning around anytime soon. 

What radioactive material was released from the Fukushima reactors?

The Fukushima Daiichi Nuclear disaster resulted in the release of many different radioactive isotopes into the atmosphere and the surrounding ocean. These isotopes are formed as a by-product of the nuclear fission reactions occurring within a nuclear power plant. During a fission chain reaction in a containment vessel, uranium-235 or plutonium-239 breaks down into an extensive array of deadly radioactive isotopes. These isotopes undergo further radioactive decay until they become stable, releasing harmful particles and damaging energy radiation in the process. While beta particles travel short distances and affect skin and soft tissues, gamma radiation is capable of travelling even greater distance and impacts the entire body.

Cesium-137 and-134, and Iodine- 131 are the most notable and abundant radioactive contaminants released in any nuclear disaster, but news of fresh spikes in other radionuclides such as strontium -90 and tritium are doing the rounds in the case of the Fukushima disaster and may even prove to be even more threatening. How does nuclear radiation emanating from these radionuclides affect us and what are the potential risks when we are exposed to so-called low levels of radioactivity over the long-term?

Health impact of Cesium -137 and 134

Cs-137 and Cs-134 are highly unstable radionuclides that keep releasing beta particles and gamma radiation as they decay. These radiations can penetrate tissues – killing cells and practically destroying DNA strands and knocking out sections of gene sequences. Chronic, long-term exposure to these nuclear radiations can lead to DNA mutations, thereby increasing life-time cancer risks.

What is even more threatening is that children are more vulnerable to the adverse effects of ionizing radiations than adults and exposure to Cs-134 and Cs-137 adversely impacts neonatal and infant health. In fact, studies even show that humans can manifest neurological effects when they are exposed to nuclear radiation during the development of the central nervous system.

With a half-life of 30 years, Cesium-137 is one of the most long-lasting radionuclides and can persist in the ecosystem for 180-300 years. Cesium-137 quickly enters the ecosystem and leads to the contamination of water, soil, plants and animals. It bio-accumulates and bio-magnifies and gets even more dangerous as it moves up the food chain. Studies show that regular consumption of food that has been contaminated with cesium radionuclides leads to its accumulation in endocrine tissues, heart, kidneys, small intestines, pancreas, liver and spleen.

Health impact of Iodine-131

In our body, iodine plays a critical role in proper functioning of the thyroid gland and in production of thyroid hormones. These hormones are essential for life and particularly responsible for regulating the body’s metabolic functions as well other vital functions including heart rate, digestion, central nervous system, muscle strength, growth and development. When a person is already deficient in iodine, the thyroid gland will utilize iodine in any chemical form – whether it is a regular or radioactive iodine – in order to produce thyroid hormones. 

So, what happens when iodine-131 is ingested? I-131 stays in the body where it emits radioactive energy in the form of beta particles and gamma radiations – causing damage to internal organs that results in internal damage mainly localized to the thyroid and parathyroid glands. While it is true that iodine-131 has a relatively shorter half-life, of only 8 days, it has the potential to cause tremendous damage to the thyroid tissues, especially if the body is deficient in iodine. Studies conducted in the wake of Chernobyl incident show us that when people are exposed to I-131, especially during childhood, they increase the risk of developing thyroid related ancillary diseases, including thyroid cancer. This is pretty much evident in the health toll inflicted on as many as 40 percent of children in Fukushima prefecture. 

In developing adolescents, it can lead to stunted physical and mental growth. In fact, the adverse health effects of iodine-131 is of major concern to pregnant women, foetus, infants and children up to 10 years of age. With tiny thyroid glands and overall smaller body mass, this section of population is far more sensitive to the damaging energy radiation than the adults.

Health impact of Strontium-90

It is important to closely monitor the sustained release of radionuclides from groundwater and leaking tanks at the Fukushima nuclear power plants site. The mix and the intensity of different radionuclides is changing. It has been reported that in June 2015 “Tepco reported the highest-ever readings of strontium-90 outside of the Fukushima plant ports. The readings were 1,000,000 Bq/m3 of strontium-90 at two locations near water intakes for Reactors 3 and 4. Tepco has not been able to explain the spike in readings. The prior highest readings were 700,000 Bq/m3.” [3]

Strontium-90 is not found in nature. It is a by-product of the nuclear fission reactions taking place in the nuclear power plants. Reports of higher levels of strontium-90 present in groundwater and storage tanks and washing into the ocean is of immediate concern. A potential carcinogen, it can damage the cellular DNA and raise cancer risks. What makes it potentially more dangerous is that strontium-90 mimics calcium and as such it is utilized by the bones and becomes concentrated there. With a half-life as long as 30 years, it remains lodged there for long periods, causing constant damage. 

While these radiation levels are considered far below what would be considered dangerous to human health, marine life and the associated ecosystem, “the risk of long-term exposure to low-level radiation is unclear. Studies of radiotherapy patients and others indicate that there is a significant increase in cancer risk if lifetime exposure exceeds 100,000 microsieverts, according to the World Health Organization. A person exposed daily to radiation at the high end of the levels now seen (in some areas) would reach that lifetime exposure level in fewer than 23 years,” as published in National Geographic [4].

Next in this series: Who was affected and the potential risks: Murky questions?

References:

  1. Jonathan M. Samet, Dayana Chanson. 2015. Fukushima Daiichi Power Plant Disaster: How many people were affected? Green Cross.
  2. Hiromi Kumagai. December 2015. TEPCO confronts new problem of radioactive water at Fukushima plant. The Asahi Shimbun.
  3. Robert Hunziker. June 2015. Is Fukushima Getting Worse? Counter Punch.
  4. Patrick J. Kiger. April 2014. Fukushima Return: At Nuclear Site, How Safe is “Safe?”.  National Geographic.