Tritium detected four times in a week since the second discharge of contaminated water by Japan

On October 3 (local time), authorities collect samples before the second discharge of contaminated water (treated water according to the Japanese government) from the first unit of the Fukushima-Daiichi Nuclear Power Plant in Okuma, Fukushima, Japan. Courtesy of the Tokyo Electric Power Company (TEPCO)

In the week following the second discharge of radiation-contaminated water from the first unit of the Fukushima-Daiichi Nuclear Power Plant, four times, authorities detected tritium at a level that exceeded the detection limit near the waterway from which the water was released. This was unusual compared to the previous situation, when tritium levels only surpassed the limit once in a month after the contaminated water was first discharged. The latest discovery raises concerns that tritium may be regularly found in nearby waters now due to the release of contaminated water.

According to the analysis of the tritium concentration disclosed by the Tokyo Electric Power Company (TEPCO) on October 15, authorities found tritium at levels that exceeded the detection limit four times in a week (Oct. 7-14) after the contaminated water was discharged a second time at T-0-1A, the monitoring location closest to the waterway through which the water was released. The monitoring point was approximately 200 meters away from the waterway.

The detection limit is the minimum level that can be detected using measuring equipment, and it is slightly different at each monitoring point. When the amount of tritium released is smaller than the detection limit, authorities cannot measure the exact amount of tritium. If the level of tritium falls short of the detection limit, authorities conclude that there is practically no tritium, but if it exceeds the limit, they conclude that there are traces of the radioactive substance.

According to the information, on October 8, three days after the second discharge of contaminated water, authorities found 9.4 becquerels (Bq) of tritium per liter at T-0-1A, exceeding the detection limit. The tritium level climbed to 11 Bq on October 10 and 14 Bq on October 13. TEPCO has yet to announce specific numbers, but according to the graph, on October 14, the amount of tritium appears to have surpassed 10 Bq. Tritium levels in other monitoring points did not reach the detection limit.

The latest phenomenon is unusual when we consider that tritium levels hardly exceeded the detection limit after the contaminated water was discharged for the first time on August 24. Before the second release of contaminated water, tritium levels only exceeded the detection limit once on September 1 (10 Bq). Thus, tritium has been found in the sea a total of five times so far.

This is different from the prediction by some experts, who did not expect tritium levels in a particular location to constantly increase, since the contaminated water would spread out in the ocean currents after being released. However, TEPCO explained that the flow of the ocean current in the waters in question could regularly shift and that this could lead to changes in numbers. The company also said that even if tritium was detected, the level was far less than 700 Bq per liter--the standard to recognize an anomaly--and posed no safety problems.

But if tritium is found more often in a sea where the radioactive isotope of hydrogen has never been detected before the discharge of contaminated water, it could make nearby fishermen and the citizens of neighboring countries nervous. Tritium could have a harmful influence on living creatures when they are constantly exposed to the substance.

Despite such changes in tritium levels, in a daily briefing on the discharge of contaminated water on October 16, Park Ku-yeon, first assistant director in the Office for Government Policy Coordination conveyed the opinion of the International Atomic Energy Agency (IAEA), which claimed there was nothing unusual. As for the tritium levels, Park said, “There is no problem since the levels are lower than the standard used to determine anomalies.” The Korean government gave a shorter explanation than the briefing by TEPCO, which shared information on tritium levels that exceeded the detection limit as well as on their analysis of the cause.

Meanwhile, according to TEPCO, on October 6, shortly after the second discharge of contaminated water, the pressure in the transfer pump used to release the water into the ocean dropped. The power company believed this was caused by foreign substances in the pump’s metal filter and said they cleaned the filter in question. They also added that the problem would not affect the future discharge of contaminated water.