Just remember, however your day goes, chances are very good it won't be as bad as May 21, 1946 was for Louis Slotin

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On May 21, 1946, with seven other colleagues watching, Slotin performed an experiment that involved the creation of one of the first steps of a fission reaction by placing two half-spheres of beryllium (a neutron reflector) around a plutonium core. The experiment used the same 6.2-kilogram (13.7 lb) plutonium core that had irradiated Harry K. Daghlian, Jr., later called the "Demon core" for its role in the two accidents. Slotin grasped the upper beryllium hemisphere with his left hand through a thumb hole at the top while he maintained the separation of the half-spheres using the blade of a screwdriver with his right hand, having removed the shims normally used.^[2] Using a screwdriver was not a normal part of the experimental protocol.

At 3:20 p.m., the screwdriver slipped and the upper beryllium hemisphere fell, causing a "prompt critical" reaction and a burst of hard radiation.^[9] At the time, the scientists in the room observed the "blue glow" of air ionization  and felt a "heat wave". In addition, Slotin experienced a sour taste in his mouth and an intense burning sensation in his left hand.^[2] Slotin instinctively jerked his left hand upward, lifting the upper beryllium hemisphere and dropping it to the floor, ending the reaction. However, he had already been exposed to a lethal dose (around 2100 rems, or 21 Sv) of neutron and gamma radiation.^[14] Slotin's radiation dose was about four times the lethal dose, equivalent to the amount that he would have been exposed to by being 1500 m (4800 ft) away from the detonation of an atomic bomb.^[15]

As soon as Slotin left the building, he vomited, a common reaction from exposure to extremely intense ionizing radiation.^[2] Slotin's colleagues rushed him to the hospital, but irreversible damage had already been done. His parents were informed of their son's inevitable death and a number of volunteers donated blood for transfusions, but the efforts proved futile.^[2] Louis Slotin died nine days later on May 30,^[16] in the presence of his parents. He was buried in Winnipeg on June 2, 1946.^[2]

At first, the incident was classified and not made known even within the laboratory; Robert Oppenheimer and other colleagues later reported severe emotional distress at having to carry on with normal work and social activities while they secretly knew that their colleague lay dying.

The core involved was subject to a number of experiments shortly after the end of the war and was used in the ABLE detonation, during the Crossroads series of nuclear weapon testing. Slotin's experiment was set to be the last conducted before the core's detonation and was intended to be the final demonstration of its ability to go critical.^[15]

The accident ended all hands-on critical assembly work at Los Alamos. Future criticality testing of fissile cores was done with special remotely controlled machines, such as the "Godiva" series, with the operator located a safe distance away in case of accidents.

That should make you a teeny bit grateful. Maybe.  I remember hearing about this in my freshman physics class, but the professor never revealed the whole story.