From Wikipedia:

As a researcher at the Institute for High Energy Physics in Protvino, Bugorski used to work with the largest Soviet particle accelerator, the Synchrotron U-70.[2] On July 13, 1978, Bugorski was checking a malfunctioning piece of equipment when an accident occurred due to failed safety mechanisms. Bugorski was leaning over the piece of equipment when he stuck his head in the part through which the proton beam was running. Reportedly, he saw a flash “brighter than a thousand suns”, but did not feel any pain. The beam measured about 200,000 rads when it entered Bugorski’s skull, and about 300,000 rads when it exited after colliding with the inside of his head.

The left half of Bugorski’s face swelled up beyond recognition, and over the next several days started peeling off, showing the path that the proton beam (moving near the speed of light) had burned through parts of his face, his bone, and the brain tissue underneath. As it was believed that about 500 to 600 rads is enough to kill a person, Bugorski was taken to a clinic in Moscow where the doctors could observe his expected demise. However, Bugorski survived and even completed his Ph.D..[3] There was virtually no damage to his intellectual capacity, but the fatigue of mental work increased markedly.[2] Bugroski completely lost hearing in the left ear and only a constant, unpleasant internal noise remained. The left half of his face was frozen, due to the destruction of nerves, and does not age.[1] He is able to function perfectly well, save the fact that he has occasional petit mal seizures and very occasional grand mal seizures.