RamscoopRaider
Donor
A number of possibilities. You have to make the USSR/Russia unwilling or unable to make a bomb
Unable would require them not being able to afford the cost of a bomb, which is an issue as science marches on and each successive country to get the bomb spends less, a USSR unable to afford the cost of their program in the '40s is one thing, a USSR unable to afford what South Africa or Israel spent, much less North Korea, is another thing and much, much harder for a country the size of Russia with their natural resources
Unwilling means that for some reason they are not willing to spend the bomb. It being within their means but considered too costly for the benefit is one possibility, but that would basically require they not see themselves as a great power, not be threatened by any neighbors, and not care that the US and UK have them, very unlikely. Another possibility is them being bound by treaty not to make them and unwilling to face the consequences for doing so, possible if they lose WWIII and face nuclear attack if they violate treaty terms. A final possibility would be an ideological opposition to nukes, either a Pacifist or Green type government, the likeliness of this is debateable
Unable would require them not being able to afford the cost of a bomb, which is an issue as science marches on and each successive country to get the bomb spends less, a USSR unable to afford the cost of their program in the '40s is one thing, a USSR unable to afford what South Africa or Israel spent, much less North Korea, is another thing and much, much harder for a country the size of Russia with their natural resources
Unwilling means that for some reason they are not willing to spend the bomb. It being within their means but considered too costly for the benefit is one possibility, but that would basically require they not see themselves as a great power, not be threatened by any neighbors, and not care that the US and UK have them, very unlikely. Another possibility is them being bound by treaty not to make them and unwilling to face the consequences for doing so, possible if they lose WWIII and face nuclear attack if they violate treaty terms. A final possibility would be an ideological opposition to nukes, either a Pacifist or Green type government, the likeliness of this is debateable