Robot Probes Show Japan Reactor Cleanup Worse Than Expected

Earlier this month, another robot, designed for cleaning debris for the main "scorpion" probe, had to return midway through because two of its cameras became inoperable after two hours when its total radiation exposure reached a maximum tolerance of 1,000 Sievert -- a level that can kill a human within seconds. The original duration planned for the robot was 10 hours, or 100 Sievert per hour.