It is called a research center, but the Pakistan Institute of Nuclear Research looks more like a fortress. Layers of barbed wire surround the sprawling complex in the dusty hills at Kahuta, 20 miles southeast of Pakistan's capital, Islamabad. Much of the facility is buried beneath the earth, a precaution against accident -- or perhaps surprise attack. Paratroopers guard the installation, and tanks block all routes into Kahuta. Crotale surface-to- air missiles and antiaircraft guns bristle toward the skies, through which Pakistani air force planes fly round-the-clock patrols. Unauthorized entry to Kahuta is impossible, sightseeing in the vicinity ill advised.
Precise information about what goes on inside Kahuta is virtually unobtainable; the site is one of Pakistan's most closely held defense secrets. Nonetheless, over the past decade the world has been catching occasional, disturbing glimpses of clandestine dealings and espionage coups that have left trails of suspicion leading inexorably back to Kahuta. All those James Bond operations have conveyed the same unsettling message: even though the government of President Mohammed Zia ul-Haq firmly denies it, Pakistan appears to be developing the capacity to build an atom bomb.
But Kahuta is just one outcropping of a far bigger nightmare: nuclear proliferation, the spread of atomic weaponry, has entered a new and ever more ominous phase. As the 40th anniversary of the A-bomb explosion over Hiroshima approaches, the world has special reason to view what is happening with trepidation, at the very least. On the Asian subcontinent, in the Middle East, in southern Africa and, to a lesser degree, in South America, a number of countries have acquired or are in the process of acquiring the capacity to build atomic weapons. At the same time, the fragile international system of self-restraint that the world has built around its most deadly Pandora's box of technology, a system that has worked surprisingly well so far, is under growing strain. Says a senior official of the Vienna-based International Atomic Energy Agency: "Proliferation has already happened. The main problem of the late 1980s is not so much preventing the spread of nuclear weapons, but making it survivable."
. Among the signs that illustrate proliferation's disquieting reach:
-- In Moscow on an official visit last week, Indian Prime Minister Rajiv Gandhi charged that Pakistan's development of an atom bomb was "very close" to fruition. Earlier this month, the Indian leader had affirmed that such an achievement by his country's chief regional rival "will completely change the present military balance on the subcontinent. At no cost will we allow our integrity and security to be compromised." In 1974, India shocked the world with a "peaceful" underground nuclear explosion in the Rajasthan Des- ert; Gandhi's pronouncements hold out the threat that India might resume testing, perhaps even begin to build and stockpile nuclear arms.