China's polar research vessel and ice-breaker Xuelong (Snow Dragon) is anchored in Shanghai, East China, on April 16, 2013. On Tuesday, technicians from Jiangnan Shipyard started renovation and maintenance work on its engines, deck machinery and environmental protection equipment. The maintenance is expected to be done by September. [Photo/Xinhua]

China's polar research vessel and ice-breaker Xuelong (Snow Dragon) is anchored in Shanghai, East China, on April 16. On Tuesday, technicians from Jiangnan Shipyard started renovation and maintenance work on its engines, deck machinery and environmental protection equipment. The maintenance is expected to be done by September. [Photo/Xinhua]