addition of that brick caused the reaction to go immediately into the prompt critical region of neutronic behavior. This resulted in a criticality accident. Daghlian reacted immediately after dropping the brick and attempted to knock the brick off the assembly without success. He was forced to disassemble part of the tungsten-carbide pile in order to halt the reaction. Daghlian was estimated to have received a dose of 510 rem (5.1 Sv) of neutron radiation, from a yield of 1016 fissions. Despite intensive medical care, he developed symptoms of severe radiation poisoning, and his sister and widowed mother were flown out to care for him. He fell into a coma and died 25 days after the accident. He was the first known fatality caused by a criticality accident. His body was returned to New London, where he was buried at Cedar Grove Cemetery. Legacy As a result of the incident, safety regulations for the project were scrutinized and revised. A special committee was established to review any similar experiments and recommend appropriate safety procedures. This change of procedures included needing a minimum of two people involved in such an experiment, using at least two instruments monitoring neutron intensities with audible alerts, and preparing a plan for operating methods and any contingencies that might occur during similar experiments. Additionally, discussions and designs for remote-controlled test devices were initiated, eventually leading to the creation of the Godiva device. These changes did not prevent another criticality accident from happening at Los Alamos the following year. Louis Slotin, a colleague of Daghlian's, was killed in 1946 while performing criticality tests on the same plutonium core. After these two incidents it became known as the "demon core", and all similar criticality experiments were halted until remote-controlled assembly devices were more fully developed and available. In 2000, the city of New London erected a memorial stone and flagpole in Calkins Park to honor Daghlian. The monument bears an inscription: "though not in uniform, he died in service to his country." References External links 1921 births 1945 deaths Accidental deaths in New Mexico American nuclear physicists American people of Armenian descent Armenian physicists Deaths from laboratory accidents Manhattan Project people People from Los Alamos, New Mexico People from Waterbury, Connecticut People from New London, Connecticut Plutonium Purdue University alumni Victims of radiological poisoning Burials at Cedar Grove Cemetery (New London, Connecticut)