The two-day Nuclear Security Summit in Washington ended on Tuesday, with leaders from 47 nations signing a document calling for joint efforts to ensure nuclear security.

The first multilateral summit in the 21st century on global nuclear security consolidated consensus among world members to keep terrorists, criminals and other unauthorized actors from acquiring nuclear material, including highly enriched uranium and plutonium.

In the 12-point document, 47 participating countries pledged "sustained and effective international cooperation" to secure all vulnerable nuclear material in four years. Global nuclear security requires the peaceful and secure use of nuclear power, and for nuclear weapons to be possessed by countries only with reason. Despite increasing energy options, any improper use of nuclear technology is likely to cause enormous harm to the global community.

The world has been shrouded with the cloud of nuclear weapons and nuclear wars since the Cold War. But during those decades, nuclear weapons served mainly as an effective tool of deterrence by two ideologically divided camps. It was a security privilege for only a few countries. Nuclear deterrence worked in a series of international disputes, from the Cuban Missile Crisis in 1962 to the signing of the treaty between the United States and the erstwhile Soviet Union on the elimination of their mid- and short-range missiles in 1987. In any case, the two strategic rivals always remained cautious about a possible nuclear war and carefully managed their nuclear stockpiles.

The end of the Cold War failed to reverse the world's nuclear armament process, although enormous changes have occurred since then on the global nuclear landscape.

As a world nuclear power, China has made unremitting efforts toward global nuclear disarmament. But the country's commitment of not being the first to use nuclear weapons has not led other members in the "Nuclear Club" to follow suit, or pushed them to take a more rational and self-restrained approach toward developing nuclear weapons.

The rapid development of nuclear technology has resulted in the rapid spread of nuclear material worldwide and in a wider variety of fields, putting the world in a very dangerous position. More than 100 countries are currently building or preparing to build nuclear facilities of their own. The 50 tons of weapons-grade enriched uranium in the world, together with other nuclear material, are sufficient to make 120,000 atomic bombs.