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Tougher rules for Japanese nuclear plants

Over two years after the Fukushima disaster, Japan's nuclear watchdog has approved new safety guidelines. Nuclear expert Michael Maqua explains how this may pave the way for the country's offline reactors to restart.

DW: According to media reports, the new guidelines issued by the Nuclear Regulation Authority (NRA) for the first time make it compulsory that Japanese nuclear plants take steps to guard against radiation leaks in the case of severe accidents. Such safety standards were previously adopted by operators on a voluntary basis. What aspects do the new regulations cover?

Michael Maqua: Without having analyzed the new guidelines in detail, it can be stated that the new safety regulations emphasize on two main aspects. The first one is a review of the existing design of the nuclear power plants, in particular with respect to external natural hazards such as tsunamis and earthquakes.

The second key aspect is that the new guidelines demand technical backfitting to implement additional measures in the area of the so-called severe accident management. This includes for instance technical components to prevent hydrogen explosions or venting lines equipped with filters for certain radionuclides to lower pressure inside the reactor building in case of a core melt accident.

Is the NRA tackling the issues that led to the meltdown in Fukushima?

In dealing with tsunamis and earthquakes as well as with the enhancement of severe accident management, Japan's Nuclear Regulation Authority is addressing two of the main factors that influenced the development of the Fukushima accident. However, the effectiveness of the new requirements in this regard can only be assessed after their implementation.

Michael Maqua is head of the Plant Engineering Department of the Cologne-based GRS (Photo: Michaela Schaefer)

Maqua says Japan's NRA is addressing aspects that influenced the Fukushima disaster

High levels of a toxic substance called strontium-90 were recently found in groundwater at the devastated Fukushima nuclear power plant. What are the main risks involved?

Strontium-90 is potentially harmful to human health as it accumulates in the bones if it is ingested for example with drinking water or food. Once in the body, it can cause bone cancer or leukemia. To estimate the potential health risk in this case, we would not only need to know the amount of strontium reaching the environment but also whether there is a possibility of ingestion.

As far as we know, the groundwater at the Fukushima site is not used as drinking water, so the risk of ingestion in this way seems very limited. However, it has to be made sure that also in a broader region drinking water is not contaminated. The same applies for ingestions by consuming fish or seafood. Since we do not know if or how much of the contaminated groundwater reaches the sea, it cannot be excluded that strontium might accumulate in saltwater fish in that area.

Most of Japan's 50 nuclear plants remain closed after they were shut down for safety checks following the March 2011 earthquake and tsunami that triggered multiple meltdowns and massive radiation leaks at the Fukushima Dai-ichi nuclear power plant. How much of Japan's energy needs were covered by nuclear plants before the tsunami disaster stroke?

According to statistics of the World Nuclear Association, nuclear power plants covered close to 30 percent of the overall electricity production in Japan in the years before the Fukushima accident. The same source claims that in 2012, this share amounted only to about 2 percent.

The new Japanese government under Prime Minister Shinzo Abe has been pushing to restart some of the country's nuclear reactors. The new NRA requirements are expected to take effect on July 8. Could the implementation of these safety standards pave the way for restarting some of the offline reactors?

We assume that the restart of the plants will only be allowed if the utilities can demonstrate that they have implemented the new requirements. However, if a plant is found to be situated in an area with an active seismic fault that exceeds the limits of the new regulations, it will have to be finally shut down. The respective investigations of the sites are still ongoing.

Michael Maqua is head of the plant engineering department at GRS, a German-based organization specializing in the fields of nuclear safety and radioactive waste management.

The interview was conducted by Gabriel Domínguez