China has played an important role in international nuclear security cooperation, a US nuclear expert told Xinhua in a recent interview.

"China has made significant progress on its nuclear security system and significant contributions to global nuclear security," said Hui Zhang, senior research associate with the Belfer Center for Science and International Affairs at Harvard University.

Zhang made the remarks shortly before the fourth Nuclear Security Summit (NSS), which is scheduled to take place in Washington, D.C., from March 31 to April 1.

Zhang noted that as active participants of the NSS, Chinese leaders have showed strong awareness of the significance of the nuclear security cooperation between countries.

"At the 2014 Nuclear Security Summit, President Xi Jinping stressed that increased cooperation regarding the nuclear security of one country is beneficial to all nations," Zhang said.

He said that, as Xi pointed out, "The amount of water a bucket can hold is determined by its shortest plank. The loss of nuclear material in one country can be a threat to the whole world."

The NSS, initiated by US President Barack Obama, first took place in Washington in 2010 with an aim to prevent nuclear terrorism around the globe. It was followed by additional summits in Seoul of South Korea in 2012, and The Hague of the Netherlands in 2014.

Xi pledged at The Hague Summit that China will unswervingly enhance its nuclear security capabilities, contribute to the establishment of an international nuclear security system, support international cooperation and safeguard regional and world peace and stability.

Zhang pointed out that the great achievements China has made in nuclear security during the past few years were in accordance with the Chinese president's words.

China has established "a security approach based on a design basis threat (DBT)" and "an application of modern concepts of physical protection, based on systems-engineering approaches to analyzing vulnerabilities and designing defenses to address them," said Zhang, who is currently working with Project on Managing the Atom at Harvard.

The country has also established the use of modern physical protection, material control and material accounting technologies as well as requirements for in-depth vulnerability assessments of security systems, according to the expert.

Earlier this year, China released its first white paper on Nuclear Emergency Preparedness, detailing policies and measures relating to nuclear emergency preparedness and highlighting a "rational, coordinated and balanced" nuclear security approach.

The white paper reviewed China's safety record since nuclear activities began in the mid-1950s, saying that nuclear facilities and activities had always been "in a safe and stable state" and safety at nuclear power stations was in a state of constant improvement.

Meanwhile, the nuclear security cooperation between China and major countries has also been greatly strengthened over the past decade, Zhang said.

He emphasized China-US cooperation in particular, saying it comprises "in-depth training and discussion workshops on everything from approaches to the design of physical protection systems, to steps to strengthen security culture, and cooperation to build a Center of Excellence (CoE) on Nuclear Security."

The CoE, whose construction started in 2013, will be the biggest nuclear security international exchange, training and demonstration center in the Asia-Pacific Region once completed this year, according to official documents.

Looking into the future, Zhang said such bilateral cooperation "should continue and grow stronger" against the background of a world that remains haunted by the specter of nuclear proliferation and even nuclear terrorism.

Figures from the International Atomic Energy Agency, the world's nuclear watchdog, showed that more than 100 cases of loss or theft of radioactive substances are reported every year.

Zhang believed China could take greater responsibilities in global nuclear security with growing capacities.

"It is imperative (for China) to maintain and further strengthen the global nuclear security cooperation. For example, China and the United States can launch in-depth discussion and best practice exchanges on how to increase international assurance about nuclear security conditions," Zhang said.

"They can also conduct joint exercises to strengthen coordinated response in the event of a nuclear terrorism or nuclear smuggling event," the expert added.