Given the continuing threat that nuclear weapons pose for humanity and the global environment, is it ever ethically acceptable for scientists to engage in research and development work on such weapons?  

Given the continuing threat that nuclear weapons pose for humanity and the global environment, is it ever ethically acceptable for scientists to engage in research and development work on such weapons?

Discuss the conditions, if any, under which it would be acceptable.
Explain and defend your position, and then explain how your ethical philosophy helped you or affected how you answered this question.