Fri, Jul 14, 2023 page8

• Tritium discharge is safe: the evidence

  • By Lin Ji-shing 林基興
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  Radioactively contaminated water is soon to be discharged from Japan’s Fukushima Dai-ichi nuclear power plant into the Pacific Ocean after being treated by an Advanced Liquid Processing System (ALPS). This decision has drawn protests from neighboring countries as the water contains radioactive tritium.

  Tritium is a hydrogen isotope that also occurs in nature because it is produced when cosmic rays collide with air molecules in the atmosphere. Tritiated water has chemical features almost identical to water with an ordinary hydrogen atom. Tritium has a radioactive half-life of 12.32 years. Tritiated water has a relatively short half-life of about 10 days in the human body. Tritium emits weak beta particles, which are electrons and cannot penetrate the human body through the skin. A Canadian study showed that tritium is not associated with an increased risk of cancer for people who live near nuclear power stations.

  Nuclear power plants around the world release low concentrations of tritium into the environment. In China, Japan, Taiwan and South Korea, they emit more than 1,400 trillion becquerels (Bq) of tritium radioactivity each year, but the tritium radioactivity in the water of the western part of the north Pacific Ocean remains below 0.3 becquerels per liter (Bq/l), which is within the range of natural background radiation.

  The tritium radioactivity of water discharged from the Fukushima Dai-ichi plant between March and June 2011 as an emergency measure following the March 11, 2011, nuclear accident was about 3,400 trillion becquerels, but none of it was detected in Taiwan.

  The radioactivity of tritium-containing water discharged into the sea by the Fukushima Dai-ichi plant would be kept below 1,500Bq/l, which is far less than Japan’s tritium discharge standard of 60,000Bq/l and the WHO’s limit of 10,000Bq/l. After being diluted by rapidly mixing it with a huge amount of seawater, the radioactivity of the discharged water would very soon be the same as that of the surrounding background level.

  The average amount of liquid tritium discharged by the Ma-anshan Nuclear Power Plant in Pingtung County over the past decade was 35.8 trillion becquerels per year, which is 1.6 times higher than the 22 trillion becquerels of tritium that is to be discharged annually from the Fukushima Dai-ichi nuclear power plant. Nonetheless, the results of environmental impact assessments carried out over the years show that it is hard to detect any tritium in South Bay (南灣), which is adjacent to the Ma-anshan plant.

  Japanese models of the planned discharge show that the human exposure radiation dose from discharging the tritium would be a mere 1/100,000 of the average annual radiation dose of 2.1 millisierverts that people in Japan receive from the natural environment. This is a negligible amount, so the discharges of tritium-containing wastewater would hardly pose any risk to marine organisms or humans.

  The International Atomic Energy Agency in 2021 set up a task force comprising 11 internationally recognized experts from the UK, the US, Canada and several other countries. They independently examined the radiological characteristics of water treated at the Fukushima Dai-ichi plant, and monitored the environment. This work is done openly and transparently, and it is to continue for the foreseeable future.

  Taiwanese should act according to the scientific evidence, rather than mimick the opposition of some Japanese fishers or governments such as China and South Korea. Imagine, if China, South Korea or Taiwan needed to carry out such discharges. Would it be right for neighboring countries to protest without the support of scientific evidence?

  Lin Ji-shing is a university professor.

  Translated by Julian Clegg
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