The Navy is investigating cheating allegations against about one-fifth of its trainers at a school for naval nuclear power reactor operators.

It is the second exam-cheating scandal to hit the military this year, on top of disclosures of ethical lapses at all ranks in the military as it transitions from more than a decade of war-fighting.

An Air Force cheating probe has implicated nearly 100 officers responsible for land-based nuclear missiles. Those implicated in the Navy investigation have no responsibility for nuclear weapons.

The Navy says at least 30 sailors are accused of having cheated on written tests they must pass to become instructors at a nuclear propulsion school at Charleston, S.C. The Navy uses two nuclear reactors there to train sailors for duty on U.S. submarines and aircraft carriers.