Robot can't find fuel debris

March 24, 2017

Robot probe into reactor failed to find debris

https://www3.nhk.or.jp/nhkworld/en/news/20170324_02/*

The operator of the crippled Fukushima Daiichi nuclear plant says a robot probe into the No.1 reactor failed to locate where the fuel debris is.

It says it will work to find it by analyzing radiation data obtained by the probe.

Tokyo Electric Power Company, or TEPCO, did a 5-day robotic investigation through Wednesday inside the reactor's containment vessel. It measured radiation and tried to take images of fuel debris -- a mixture of melted nuclear fuel and reactor parts.

TEPCO says the probe didn't get any images of the debris, but that at 10 locations under water, it measured radiation levels at various heights.

Officials say that at one of the points where they were expecting debris to be, at 90 centimeters from the floor, the radiation was 9.4 sieverts an hour. That is very strong. They say at that location the levels remained high even as the dosimeter got further away from the floor.

At another point the radiation was 11 sieverts an hour at 30 centimeters from the floor. But the radiation levels got lower further away from the floor.

TEPCO engineers plan to use the data and images to analyze the spread of debris, which is essential to decommission the reactor.

See also : http://www.japantimes.co.jp/news/2017/03/24/national/tepco-robot-failed-capture-images-melted-fuel-reactor-1/