BEIJING, March 11 -- China has never stopped improving nuclear security and the safety of its nuclear power plants can be assured, the National Nuclear Safety Administration (NNSA) said on Tuesday.

Tuesday is the third anniversary of Japan's nuclear meltdown in 2011, when a massive quake and tsunami crippled the Fukushima Daiichi reactor and left more than 18,000 people dead or missing.

Like other countries, China has stepped up nuclear checks since the Fukushima crisis to avoid similar accidents. In the past three years, more than 300 specialists have overhauled nuclear power plants and assessed their security situations. The results of the assessment indicate that China's nuclear power plants are safe, but work still needs to be done in responding to and handling extreme natural events like Fukushima.

Despite the satisfactory state of affairs, the NNSA has put forward 24 requirements for improvements to safety, both in operational plants and in the construction of new plants.

China has 17 nuclear power stations in operation with a total installed capacity of 14.8 million kilowatts. A further 28 units are under construction.

In 2012, a medium-term nuclear safety plan was passed, curbing nuclear pollution as well as raising security at nuclear facilities. The plan includes better anti-seismic and radioactive substance control designs for new plants.