Generally, it's only possibly to delay the development of the atomic bomb, not to prevent it entirely. There were enough people aware of the possibility atomic bomb already when WWII broke out, however, the main incentive for the US to develop the atomic bomb was to develop it first because it was feared that Germany was working on it, too. This however, as we know, didn't happen, and the first atomic bomb wasn't ready until after Germany already had surrendered.
Now, the repercussions from the absence of the atomic bomb would probably the following:
- without the bomb, an invasion of Japan will become necessary. This will be an extremely costly affair, and possibly could lead to a divided Japan because the Soviets are able to grab a sizable amount of Latin from the north.
- without the bomb, there'll be less of a deterrent towards Stalin, and the Soviets would be more likely to attack Western Europe after WWII.
- it's also doubtful that the Soviets would have had an atomic bomb in a similar time frame if they didn't have the Manhattan project to spy on.