Ten researchers spent more than two years and 1.3 million yuan (US$157,000) to build what they believe is one of the tiniest leak detectors ever invented.

The micro-robot is smaller in diameter than a 1-yuan coin and is about as tall as a typical dictionary. Propelled by motorized wheels, it can move up and down inside the slimmest pipes and work in highly radioactive environments.

"Some of the pipes used in nuclear power plants are extremely narrow -with diameters as small as 2 centimeters - and contaminated with radioactive material, a threat for inspection workers," said Qian Jinwu, one of the university's project leaders. "It's important to locate the leaks because if we don't, radiation could escape to the environment."

The robot passed inspection by the nation's Ministry of Science and Technology in October, and it will soon be put to use in China's four nuclear power plants. So far, no significant release of radiation has been reported at any of the nuclear power stations.

When put on the job, the robot will be able to move in all directions at a maximum speed of more than 1 meter per minute. It is equipped with an electronic sensor that can measure even the smallest pipe breaks. On finding a leak, it sends an alarm to an operator, pinpointing the spot where repairs are needed.

"Current methods for detecting pipe leaks are pretty ineffective," said Li Minqian, a nuclear technology researcher at the Chinese Academy of Sciences. "This new robot will bring a higher level of safety."

The robot project was sponsored by the National Natural Science Foundation, National High-Technology Research and Development Program, the city's Commission of Science and Technology and its Commission of Education.

Developers say their slender inspector can be applied across a wide range of operations, including gas, water and oil pipes.

Meanwhile, the university is developing another micro-robot equipped with a camera to allow for visual inspections to detect surface rust and other imperfections.

(www.eastday.com.cn)