The unnamed Nuclear Physics Professor teaches Nuclear Physics at Springfield University. From his accent, he seems to be of German origin.
Homer is required to take training in nuclear physics after inspectors from the Nuclear Regulatory Commission conduct a surprise evaluation at the nuclear plant and Homer mysteriously manages to cause a meltdown even though the simulator in the inspectors' van doesn't have any nuclear material in it. The inspectors determine that Homer is dangerously underqualified for his own job, and Mr. Burns isn't able to bribe his way out of the situation. Burns is able, however, to pull some strings and get Homer admitted to Springfield University, where he enrolls in Nuclear Physics 101.
The Professor has apparently taught the class at least once before Homer takes it, as he says that there are a few new faces in the class and jokingly says, "Out with the old, in with the nucleus." (Everyone except Homer gets the joke.) The Professor is shown as being very knowledgeable about the subject matter he teaches, and also very patient as an instructor: He's willing to go the extra mile to make sure his students learn the material. For example, after class the Professor holds extended review sessions on the day's lecture. While the extra sessions aren't required, they are very helpful, so the Professor advises everyone to participate.
The Professor's only flaw is that he's prone to occasional clumsiness, as seen when he drops his lecture note cards on the first day of class. Homer, who previously missed the "in with the nucleus" joke, finds the Professor's dropping his notes to be hysterically funny, and laughs uproariously at the Professor, shocking the rest of the class. Homer also loudly announces that he's blowing off the review sessions as soon as he learns that they aren't required ("Then kiss my curvy butt good-bye!"), opting instead to go outside and chase squirrels.
Homer tests the Professor's patience again when the Professor is lecturing about proton accelerators and Homer arrogantly interrupts: "Excuse me, Professor Brainiac, but I worked in a nuclear power plant for ten years, and I think I know how a proton accelerator works." The Professor keeps his cool and graciously invites Homer to "please come down and show us." Homer's demonstration causes another meltdown, resulting in his being assigned supplemental tutoring (this time mandatory) with Benjamin, Doug, and Gary. The tutoring is in addition to the class, so Homer stays in Nuclear Physics 101 with the Professor for the rest of the semester.