The Los Alamos Accident, December 1958:
Acute effects of massive radiation doses on humans

    The following text is taken verbatim from Shipman (1961). In summary, an industrial accident occurred in which approximately 3kg of plutonium dissolved in solvent was accidentally brought together in a critical configuration. This resulted in an "excursion"  of ca. 1.5 x 1017 fissions. The industrial worker received an acute, whole-body dose of neutrons and gamma radiation in excess of 10,000 rad or 100 Gy (10mSv = rem), where 5 Gy is considered a lethal dose . The immediate cause of death was heart failure, due to the massive radiation dose to the chest. The report describes the consequences of neutron irradiation of biological tissue. This remains the highest dose of radiation every received by an individual in a peace-time nuclear accident.


           On the 30th of December 1958, an accident occurred at the Los Alamos Scientific Laboratory which was of particular interest because of the extremely high dose of radiation delivered to the principal victim. The accident occurred in a complex of buildings known as DP West, situated some thousands of feet from any housing areas or from any other concentration of work. DP West is primarily concerned with the chemical and metallurgical processing of plutonium. The procedure being carried out when the accident occurred was the recovery of plutonium from liquid wastes, a lengthy process involving many steps. Not more than a few hundred grams of plutonium were normally processed at any one time. At the time of the accident, the operation was nearing the final step, with plutonium in a tank containing water and a solvent, tributyl phosphate. The solvent and aqueous phases were in separate layers but were to be mixed by stirring.

            This was an extremely complicated accident resulting from the fortuitous conjunction of several quite unrelated factors. In the first place, the process was not the normal routine one that had been carried out many times over a three-year period; it was the end-of-the-year cleanup in preparation for the annual inventory of plutonium. It is difficult to imagine that the simple action of a stirring device in a tank could draw a sub-critical configuration of fissionable material into a truly critical geometry. The system had been in operation for a number of years and many batches of plutonium had been processed. With each batch a little more went in than came out, and it was assumed that the deficit was irrecoverable loss which had gone down the drain. What was not realized was that over the years the system had actually retained, bit by bit, a total of almost 3.0 kg of plutonium.

            The chemical operator K was a man of no great technical education but with many years of practical experience in this and related operations. He was repeating a process he had carried out many times before. It is possible that over the years he had introduced a few short-cuts in the process without the knowledge of his supervisors. On the afternoon of the accident, K was standing on a short stepladder, looking through a viewing port into the tank (where the plutonium was). Within seconds after the stirrer was started there was a muffled boom and K fell backwards off the stepladder. The blades of the stirrer drew material down in the center and forced it up the outer sides of the tank, and for an unfortunate instant the geometry in the solvent layer brought the material together in a critical configuration.

            There was only a single critical excursion, without subsequent oscillations, such as the one that later occurred at Oak Ridge National Laboratory. Later calculations showed that there had been a burst of 1.5 x 1017 fissions. Fortunately, K was the only man in the room, but there were two men in the adjacent room. There were a great number of tanks of various sizes which fortunately shielded the other two men, D and R. Both these men heard the boom of the critical excursion. In a matter of seconds D had left his work station to see what had happened in the next room. By the time he got there, K had already picked himself up off the floor and had gone to and opened the outside doors. When D reached him, K was standing outside in the snow. D found K ataxic and disoriented. He needed support to remain erect, and all he could say was: "I'm burning up, "I'm burning up". K's face appeared flushed even at this early time. Thinking that K had been the victim of alpha contamination, D guided and supported K back into the room, where they were met by R, and the three continued on to an emergency shower. D and R stripped off his outer clothes and held him under the shower, because he could not stand unaided. Perhaps 5 minutes after the accident, he was virtually unconscious. While R called for assistance, D returned to the room of the accident. He certainly passed within a few feet of the tank at least two or more times.

            The plant nurse arrived on the scene approximately 10 minutes after the accident and was puzzled to find a patient obviously in shock and unconscious, but with nice, rosy-pink cheeks; she did not realize that his color was due to radiation-induced erythema. The patient was nearly pulseless. The man was admitted to the emergency room of the Los Alamos Medical Center 25 minutes after the accident.

            The patient was a powerfully-built man of 38; he weighed approximately 170 lb. and was 71 inches tall. By the time he arrived at the hospital he was semiconscious, but disoriented. He was moving around restlessly on the stretcher and all visible skin areas were of a dusky purplish color. He seemed to be in severe pain, apparently abdominal. His conjunctivae were markedly reddened, but his excessive restlessness made careful examination difficult. He retched frequently but vomited only small amounts of watery fluid. About 10 minutes after admission he had an episode of explosive watery diarrhea. Some of this fecal fluid was radio-assayed and showed a significant content of 24Na, indicating a copious passage of fluids into the gastrointestinal tract.

            His blood pressure was found to be 80/40 mm Hg with a pulse rate of 160 per minute. He had repeated mild shaking chills, and his restlessness was so great that he had to be restrained An indication that the dose had been massive was the fact that a portable gamma survey instrument held to the surface of the body gave a reading of 15 mRem/hour.

            The patient was placed in an oxygen tent. His hypotension and his rapid pulse still persisted and his rectal temperature was found to be 103 oF. Physical examination did not reveal impressive findings. His optic fundi were normal, but the conjunctivae were intensely injected. His eyes looked as though they should have been painful, but the patient denied any discomfort. There was definite erythema over the anterior surface of the body down to the level of the knees.

            About 5 hours after the accident the patient appeared to be in a satisfactory condition. He was rational, comfortable, and emotionally at ease. By this time it was also apparent from the dosimetric studies that his radiation exposure had unquestionably been supra-lethal and of greater magnitude than in any of the cases previously reported. The total white cell counts reflected this very definitely. The total white cell count rose steadily to a peak of 28,000 mm3, but the lymphocytes had virtually disappeared from the circulating blood in less than 6 hours. This we regarded as a very grave prognostic sign.

            A very dramatic finding was the marked degree of urinary retention. There was a total urinary output of less than 600 ml with a total fluid intake of approximately 14 liters!

            On the second evening, more than 30 hours after the accident, the patient's condition deteriorated rather abruptly. He developed increasing abdominal cramps and fairly heavy sedation failed to control his restlessness. Despite administration of oxygen by mask he showed increasing cyanosis. Sedation was given and he lapsed into a coma from which he never roused. Death supervened from cardiac arrest 34 3/4 hours after the accident, his heart having been the target of nearly 12,000 RAD of ionizing radiation.

            The neutron dose was determined by measurement of induced 24Na activity in the blood, in selected body tissues, and in the whole body, as well as from induced activity in other materials such as brass overall buttons and nearby chemicals. It now appears that the combined neutron and gamma dose delivered to K's anterior chest wall, and thus to the right side of the heart and the anterior wall of the stomach, was approximately 12,000 rad. The total dose to the face and to the front of the skull was less, but still in excess of 10,000 rad. The dose to the lower legs was probably less that 1,000 rad.

            At autopsy the most striking finding was the edematous, water-logged appearance of practically all tissues except the lungs. The general picture was quite characteristic of acute right heart failure resulting from right-sided myocarditis, complicated by excessive fluid intake. The first loop of the jejunum, the gastric pyloric bulb and the surface of the left lobe of the liver contained numerous petechial hemorrhages. The spleen was wrinkled and flabby. The right side of the heart was dilated and filled with blood, while the left heart was in systole. Externally the right auricle and the anterior portion of the right atrium also showed hemorrhages similar to those in the pericardium.

            This man had received more than enough radiation to this bone marrow to kill him in 3 or 4 weeks, if he had no other injuries. The injury to his gastrointestinal tract would have killed him in 1 or 2 weeks had not a more vital insult killed him first. In our case the man received at the same time another and quite distinct injury to his heart, which, physiologically, was quite overwhelming. It seems clear that the injury to the heart muscle in this case must be regarded as the primary cause of death.


Shipman, T.L. 1961. A radiation fatality resulting from massive over-exposure to neutrons and gamma rays. In "Diagnosis and treatment of acute radiation injury." International Documents Service, New York, pp. 113-133.