Blind Spot in Nuclear Safety

Dossier 10

http://www3.nhk.or.jp/nhkworld/newsline/201404301311.html

Nuclear Watch: Blind Spot in Nuclear Safety

Aired on Apr. 30

Experts are still struggling to clarify what happened at Fukushima Daiichi during the venting process at the time of the disaster, in order to establish how much radioactivity was actually released in the environment.

But NHK’s  investigation team has discovered quite another story.

5.6 km away from the plant, there is a radiation monitoring post which studied the dispersion of radioactive particles and it contains data which are very surprising : it shows a strange spike of radiation at 14.40 on March 12, i.e. one hour before the first hydrogen explosion and shortly after a crucial operation was carried out at the plant (i.e. the opening of vents to release pressure)

At the time nuclear engineers declared that there would only be a very small release of radioactivity from the steam while venting (0.1% emission of radioactive particles).

But NHK’s investigation has revealed that this may not have been the case!

Through an Italian nuclear euipmen testing centre (SIET), two simulation experiments were carried out to see if the reality tallied out with the 0.1% estimation of radiation risk.

The first experiment was carried out at normal temperature. Most radioactive particles would have been trapped in the water. The results were consistent withe the 0.1% theory.

However the temperature of the water could already have been quite high. So the second simulation raised the temperature in the upper layer of water. The experiment showed that UP TO 50% radioactive elements could have escaped with the steam released.  That is 500 times more than suggested by the previous simulation.

Conclusions:

“Crucial safety features can fail to function as expected.”

This “also reminds us that what we know about what happened at Fukushima Daiichi remains very limited.”