Even six years after a nuclear crisis struck Fukushima in Japan, radiation levels at Fukushima continued to reach the extreme levels. While most of this data is collected through cameras and robots, there is now a shadow of doubt about the future of these robots.

Tokyo Electric Power Company Holdings Inc. (TEPCO), the operator of the Fukushima Daiichi plant, failed to get a comprehensive report in its attempt to find nuclear debris in a containment vessel with the help of the PMORPH survey robot – developed by Hitachi-GE Nuclear Energy and the International Research Institute for Nuclear Decommissioning (IRID) – on Thursday.

Read: Fukushima Is A Nuclear Radiation Nightmare, In Pictures

This was the latest in the spate of robot failures in the process of decommissioning the plant. Last month, a Toshiba “scorpion” robot, built to tolerate up to 1,000 sieverts of radiation, was unable to withstand the high levels of nuclear toxicity in nuclear reactor No. 2. There have been a number of other instances, causing authorities to think of alternative approaches to the clean-up.

To address the issue, members of Japan’s Nuclear Regulation Authority (NRA) said the reliance on robots needs to be limited, with the job of collecting the vital data from the locations of melted nuclear fuel being passed on to newer, possibly more successful, technology.

“We should come up with a method that will allow us to investigate in a short period of time and in a more sensible way,” a senior member of the NRA, the government agency, was quoted as saying by local publication Asahi Shimbun on Friday.

While TEPCO and the Japanese government hope to start the process of removing molten nuclear fuel from 2021, they have faced great difficulty in gauging the location, amount and condition of the fuel because of the extreme levels of radiation.

Many suggest redirecting funds to “safe containment” through chemistry and biology, whereas there have also been discussions over the use of artificial intelligence to handle the robots for more precise working. However, it must be noted that whatever little progress has been made in the direction of decommissioning has been a result of the robot usage.