If a healthy adult male received minor shrapnel wounds from an explosion in a cold environment, what are the chances of him getting tetanus?

Immunized?: Hopefully the only context in which one would receive shrapnel wounds is during military service. All US military members are immunized against tetanus, so you should not be too concerned about tetanus. Whether military or not, check immunization history. Other skin infections would be more likely with puncture wounds, so maintain medical care and monitoring until resolved.