SHORTLY after an atomic bomb burst overhead 50 years ago, turning human beings into wisps of smoke and bricks into melted lumps, Hiroshima declared itself a city of peace.
Since then, the word ''peace'' has become something of a local brand name. In a half-hour's stroll, a visitor can see the Peace Bridge, the Peace Park, the Peace Memorial Museum, the Flame of Peace, the Pond of Peace, the Figure of the Merciful Goddess of Peace, the Children's Peace Monument, the Peace Clock Tower, and so on.
One can even mail a postcard from the Peace Memorial Mailbox.
The vision of peace articulated here is sweeping: ''We dedicate this bell,'' says an inscription, ''as a symbol of Hiroshima's aspiration: Let all nuclear arms and wars be gone, and the nations live in true peace!''
Yet some activists say the Hiroshima peace movement - made up of councils sponsored by political parties, parts of the city government, and small independent groups - has little to show after decades of effort.
Especially troubling to some is that the movement has largely ignored the potential dangers posed by Japan's own nuclear-power industry. To some extent, these critics suggest, the anguish endured in Hiroshima has inspired more banalities than action.
Hiroshi Hara was 13 years old on Aug. 7, 1945, when he made his way past corpses toward his junior high school to tell the authorities that he had survived.
Now a retired railway engineer who has traveled the world to talk about his experience of the atomic bomb, his long-term assessment is grim: ''It's disappointing,'' says Mr. Hara. ''Not much has been done to eliminate nuclear weapons in the past 50 years.''
Hara faults world governments for this more than the local peace movement. Even so, he says, the movement has been dulled by internal divisions and because the affluence of modern-day Japan has made people less interested in activism and political action.
Satomi Oba, a former schoolteacher who heads a 200-member group called Plutonium Action Hiroshima, is more critical. ''The peace movement in Hiroshima,'' she says, ''has always focused on Aug. 6, 1945 - only on the past.''
As a result, Ms. Oba argues, more immediate issues have been overlooked: Japan's massive accumulation of ''peaceful'' plutonium, the potential for nuclear-weapons proliferation in Japan and other nearby countries, and the dangers of the commercial use of nuclear power.
Indeed, during the postwar era Japan has grown increasingly reliant on nuclear energy, now the source of a third of its electricity. Although the government insists its motives are entirely peaceful, Japan is also one of the few countries still developing reactors that generate and burn plutonium - the key ingredient in nuclear weapons and a substance that is said to pose extreme health hazards even without being detonated.
Jinzaburo Takagi, a Tokyo-based activist who is a nuclear physicist, estimates that Japan had a supply of 11 metric tons of plutonium at the end of 1993. He calculates that the nuclear-energy industry now has the capacity to use just 2 metric tons, resulting in a sizable surplus. ''I don't see any concrete military nuclear program in Japan,'' Dr. Takagi observes, ''but still there is some potential risk'' that the political climate would change and that a military program could emerge. It takes as little as 14 pounds of plutonium to make a bomb.
OFFICIALS in several Asian countries have frequently wondered why Tokyo insists on pursuing its plutonium program, the likes of which most other countries with nuclear-energy industries have abandoned as too dangerous and costly. Some Asian governments worry that Japan, with its technological sophistication and growing space program, could assemble a nuclear weapon and the means to deliver it in short order.
To raise these speculations with Japanese officials is to invite stiff, righteous denials. They defend the plutonium program on the grounds that it is a renewable resource, which cannot be said for uranium, the material used in most nuclear-power plants.
There is also evidence that Hiroshima's image as a peace city is being manipulated by the Japanese nuclear-energy industry.
In late July the Pugwash Conference on Science and World Affairs, an international gathering of scientists opposed to nuclear weapons, held its annual conference in Hiroshima. Pugwash organizers were embarrassed by revelations that they had accepted funding from a regional nuclear-power company and an industry association. They argued that no strings had been attached to the money.
Even so, Mitsuo Okamoto, a peace studies professor who publicized the sources of the funding, worries that in underwriting the opponents of nuclear weapons, the industry is trying to win allies among the people most likely to scrutinize the safety of nuclear power.
The Hiroshima peace movement has been compromised by political division ever since the 1960s, when the city's major antinuclear organization began to splinter over cold-war ideological controversies.
Communists and socialists fought over whether they should oppose the nuclear weapons being developed by the Soviet Union.
In the aftermath of the Chernobyl disaster in 1986, the movement coalesced for a time, mounting protests in Hiroshima against nuclear-power plants. But today the various groups cannot agree on a common stand on nuclear energy, so there is no unified advocacy on the plutonium issue in Hiroshima.
The city government, too, has sidestepped questions about the safety of nuclear power, emphasizing instead the physical and human effects of the bomb in its activism.
''We want to show how destructive the A-bomb was,'' says Hiroshi Harada, director of the Peace Memorial Museum, explaining the goals that his institution clearly meets. ''We want to show to the whole world why nuclear weapons shouldn't be used again.''
Harada notes that the museum is the most popular in Japan, with 1.5 million visitors a year. A third of them are children, since very few Japanese students can avoid a field trip to Hiroshima.
Thanks to the museum and the efforts of Hiroshima's fragmented peace movement, says Naomi Shohno, a retired nuclear- physics professor and self-avowed pacifist, ''People the world over have learned the horrible effects of the bomb. But not much else.''
Professor Okamoto says Hiroshima's contribution to activist causes may simply be as a symbol: ''It's an eternal place, which means that the bomb should never have been used.''