Robot retrieves radioactive material from damaged Fukushima nuclear power plant

Scientists at Tokyo Electric Power Company Holdings (TEPCO), the company that operates the Japanese nuclear power plant in Fukushima, which was destroyed by a tsunami in 2011, have succeeded in retrieving a tiny piece of highly radioactive material from one of the three reactor cores using a specially developed robot. This was announced by TEPCO on Saturday. Among other things, the sample should provide information on how quickly the radioactive material needs to be removed.

The robot cut the sample, which is around 5 millimeters in size and weighs 3 grams, out of a pile of melted fuel elements after it had entered the Daiichi 2 reactor via a multipart pipe (PDF) through an access point in the primary containment. The robot was lowered through the pipe on a rope and then advanced about 6 meters into the interior. The robot removed the sample with a pair of tongs and placed it in a safety container. The container was then retrieved by TEPCO employees wearing safety equipment.

It must now be checked whether the sample can be used at all. This is because a previously defined radioactive limit value must not be exceeded in order for the sample to be analyzed in different laboratories. However, scientists from the nuclear power plant operating company are certain that the sample is small enough that the limit value will not be exceeded.

The recovery mission was not under a good star at the beginning. In August, the robot was sent on its two-week tour, but had to be stopped due to an error. Workers wearing radiation protection equipment were unable to place the robot quickly enough without being exposed to radiation for too long due to incorrectly assembled pipes. During a second attempt, both of the robot's cameras failed, meaning that the robot operators were unable to control it by sight. The robot therefore had to be completely replaced. Only then did the successful start-up take place.

Findings expected on nuclear power plant decommissioning

TEPCO expects the radioactive sample to provide more precise information about the course of the disaster. In addition, an analysis of the composition should provide important data for planning the decommissioning of the nuclear power plant and the development of the necessary techniques and robots.

TEPCO estimates that there are around 880 tons of radioactive material in the three damaged reactors at Fukushima. This would have to be recovered and disposed of in stages. The Japanese government expects this work to take around 30 to 40 years. However, independent experts consider a period of around 100 years to be realistic.

Fukushima cannot be sealed as an entire complex, like Chernobyl. The reactors are located too close to the sea and in a flood zone with high seismic activity. It would therefore be negligent to simply seal the plant and do nothing more.

(olb)