(from "Operational Accidents and Radiation Exposure Experience Within the United States Atomic Energy Commission, 1943-1970," (WASH 1192), U. S. Government Printing Office, Washington, D.C., 1971.)
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After placing emulsion in a tank, the operator was believed to have added a dilute plutonium solution from a second tank. Solids containing plutonium were probably washed from the bottom of the second tank with nitric acid and the resultant mixture of nitric acid and plutonium-bearing solids added to the tank containing the emulsion. Shortly after starting the stirrer motor to initiate an expected mild nonnuclear reaction between the emulsion and the acid, the operator observed a "blue flash", also observed by an employee in an adjoining room.
The employee died 35 hours later from the effects of a radiation exposure tentatively estimated at 12,000 rem (±50%).
Two other employees received radiation exposures of 134 rem and 53 rem, respectively. Property damage was reported as negligible. (See TID-5360, Suppl. 2, p. 30; USAEC Serious Accidents Issue #113, 1-22-59.)
A nuclear accident occurred in a 55-gallon stainless steel drum in a processing area in which enriched uranium is recovered from various materials by chemical methods in a complex of equipment. This recovery process was being remodeled at the time of the accident.
The incident occurred while they were draining material thought to be water from safe 5-inch storage pipes into an unsafe drum.
Eight employees were in the vicinity of the drum carrying out routine plant operations and maintenance. A chemical operator was participating in the leak testing which inadvertently set off the reaction. He was within three to six feet of the drum, while the other seven employees were from 15 to 50 feet away.
Using special post hoc methods for determining the neutron and gamma exposures of the employees involved, it was estimated that the eight men received: 461 rem, 428 rem, 413 rem, 341 rem, 298 rem, 86 rem, 86 rem, and 29 rem.
Area contamination was slight, with decontamination costs amounting to less than $1,000.
During this incident 1.3 X 1018 fissions occurred. (See TID-5360, Suppl. 2, p. 25; USAEC Serious Accidents Issue #136, 8-25-59; USAEC Health and Safety Information Issue #82, 9-5-58; 1959 Nuclear Safety, Vol. 1, #2, p. 59.)
Manual withdrawal of a control rod from a critical assembly caused in accidental supercriticality.
The operation being conducted was the comparison of a series of newly-manufactured control rods. The assembly had been operated with the standard control rod. It was then shut down by inserting all control rods and draining the water moderator, a standard safe method of shutting down the assembly when core changes are to be made. The standard rod was removed and the first of a. series of control rods to be tested was inserted.
The, reactor was filled with water with the test control rod fully in and the standard type control rods fully inserted. Withdrawal of one of the standard control rods 32 centimeters caused the assembly to become critical and the power was leveled off while the desired measurements were made. The control rod was then reinserted into the original "in" position.
With the water still in the assembly, the four members of the crew then went into the assembly room for the purpose of replacing the control rod which they had just tested. The group leader went up on the platform, reached out with his right hand and started to pull out the tested rod. As soon as he had withdrawn it about one foot, the center of the assembly emitted a bluish glow and a large bubble formed. Simultaneously, there was a muffled explosive noise. The group leader let go of the control rod which he was removing and it fell back into position. The crew left the assembly room immediately and went to the control room.
Four employees received radiation exposures ranging from 12 to 190 rem. (See TID-5360, p. 23.)
All employee's badge indicated a radiation exposure had occurred over a period of several weeks while he was engaged in his routine duties at a linear accelerator.
Investigation indicated that the film badge did receive an estimated radiation exposure of 150 rem; however, there was no evidence that the employee had actually received the exposure.
An unplanned nuclear excursion occurred in a plutonium processing facility due to the inadvertent accumulation of approximately 1500 grams of plutonium in 45-50 liters of dilute nitric acid solution in a 69-liter glass transfer tank. The sequence of events which led to the accumulation of the plutonium in the tank cannot be stated positively. However, it is believed that, when a tank valve was opened, the solution from another vessel overflowed to a sump and was drawn into the transfer tank through a temporary line between this tank and the sump.
When the excursion occurred, radiation and evacuation alarms sounded. All but three employees left the building immediately, according to well-prepared and -rehearsed evacuation plans. Fortunately, they were not in close proximity to the involved system nor in a high radiation field.
Of the 22 persons in the building at the time, only four employees, those who were in the room with the system, were hospitalized for observation. Three of them were the system operators, who were in close proximity to the excursion, and who received estimated radiation doses of 110, 43 and 19 rem. None, of them showed symptoms definitely referable to their radiation exposures. The fourth was sent to the hospital only because he was in the room at the time of the incident.
Some fission product activity, airborne via, the vent system and the exhaust stack, was detected in the atmosphere for a brief period after the accident.
The physical damage amounted to less than $1,000. (See TID-5360, Suppl. 4, p. 17.)
Seven employees were accidentally exposed to radiation from irradiated fuel elements when a crane operator mistakenly thought he had been given the all-clear signal to move a rack of hot fuel elements into a position against the aluminum window which separates the exposure room from the reactor pool. The room was to be vacated and the shield door closed before positioning the fuel elements against the window. The gamma room door could not be seen from the crane operator's position.
When the crane operator began moving the fuel elements into the window position, the 10-millirem monitor near the gamma room door tripped an alarm. The reactor supervisor immediately ordered the fuel elements moved away from the window, terminating the incident.
The estimated exposure time of the individuals was 1 1/4 seconds. The seven employees'
exposures were 100 rem, 58 rem, 24 rem, 18 rem, 18 rem, 8 rem, and 4 rem. There were no
radiation injuries as a result of the accident. (See TID-5360, Suppl. 4, p. 21.)
An employee received an exposure to radiation for less than one minute when he mistakenly entered a room containing tanks of radioactive residues used in processing irradiated fuel elements.
The exposure was first discovered when a pocket dosimeter was examined at the end of the day's shift and was confirmed when the employee's film badge was processed. He apparently suffered no ill effects and continued working; however, he was transferred to other duties. (See TID-5360, Suppl. 2, p. 23.)
An employee's film badge indicated a radiation exposure had occurred over a period of approximately 14 days while he was engaged in his routine duties at a linear accelerator.
Although neither proved nor disproved, since the employee's film badge showed an estimated external whole-body cumulative radiation exposure of 50 rem, it was charged to his record.
A physicist was exposed while a series of adjustments were being made on beam-defining plates in a new electron linear accelerator. Radiation surveys were made with negative results when personnel entered the cell after the first three adjustment runs. No survey was made after the fourth and fifth runs. A survey made after the sixth run showed a 1,000 rem/hr level.
During all entries to the cell, the key which was designed to lock all controls in the "OFF" position was removed from the control panel. It was determined that the film badges had been exposed to about 200 Kev energy gamma radiation. An exposure dose of 41 rem was assigned to physicist "A". This dose was received in a period of about one minute, which was the established time he worked alone on plates 3 and 4 and entered the cell to measure very high radiation levels. The next highest reading of 400 millirem was received by physicist "B". All others received less than 50 millirem. (See TID-5360, Suppl. 3, p. 8.)
A security guard was to accompany the radiation safety monitors into the exclusion area, after a. weapons test and establish surveillance of equipment. The guard had his own vehicle.
When he arrived at the place where he was to meet the monitors, the guard found that they had already left and started out after them. Somehow, he lost his way and drove beyond the established safety point. When it became apparent that he could not find the radiation safety monitors, he contacted his headquarters by radio and notified them of his position. He was immediately ordered out of the area.
The guard's film badge indicated he had received a dose of 39 rem. (See TID-5360, p. 72.)
When the prescribed time after a shot had elapsed, four employees, dressed in the proper protective clothing, were recovering samples from a nuclear test area.
It had been prearranged to have a. monitor enter the area. in advance of the men; however, they entered the area to redeem the samples without the monitor.
The four men received external radiation exposures of 28, 19, 14 and 4 rem, respectively. Upon medical examination, the men showed no signs of ill effects. (See TID-5360, Suppl. 1, p. 4.)
An employee unknowingly worked and slept in close proximity to highly contaminated equipment while it was in transport between testing sites. He received a 24 rem whole-body exposure in 24 hours; his total yearly exposure was 27.8 rem.
A nuclear excursion occurred within the reactor vessel, resulting in extensive damage of the reactor core and room, and in high radiation levels (approximately 500-1000 rem/hr) within the reactor room.
At the time of the accident, a three-man crew was on the top of the reactor assembling the control rod drive mechanisms and housing. The nuclear excursion, which resulted in an explosion, was caused by manual withdrawal, by one or more of the maintenance crew, of the central control rod blade from the core considerably beyond the limit specified in the maintenance procedure.
Two members of the crew were killed instantly by the force of the explosion and the third-man died within two hours following the incident as a result of an injury to the head. Of the several hundred people engaged in recovery operations, 22 persons received radiation exposures in the range of three to 27 rem gamma radiation total-body exposure. The maximum whole-body beta radiation was 120 rem.
Some gaseous fission products, including radioactive iodine, escaped to the atmosphere outside the building and were carried downwind in a narrow plume. Particulate fission material was largely confined to the reactor building, with slight radioactivity in the immediate vicinity of the building.
The total property loss was $4,350,000. (See TID-5360, Suppl. 4, p. 8; 1962 Nuclear Safety, Vol. 3, #3, p. 64.)
Two employees were following through the routine involved in the calibration of photocell detectors. The detectors were placed in the radiation beam area, 30" in front of the 340-curie cobalt 60 source unit. Currents were being recorded for each detector with the source exposed. Three detectors had previously been calibrated; the fourth was placed in position; both employees returned to the console; the source was exposed and the current output of the detector was recorded. After recording the current value, employee "A" noted that the warning lights were out and assumed that the source was no longer exposed. He approached the detector located in front of the source, without making a precautionary radiation survey, and started making mechanical adjustments on the photodiode. Employee "B" followed "A" and aided him in the adjustments.
"A" received a, total-body dose of 18 rem as determined by film badge reading. "B" received a
total whole-body dose of 5 rem. (See TID-5360, Suppl. 3, p. 23.)
During a shutdown operation for scheduled refueling, six employees were working on the reactor top adjacent to the reactor tank opening, while two men were present as observers and advisors. All were exposed to radiation when a highly radioactive reactor component was placed in a position where it was not adequately shielded because of lowered water level in the reactor tank. The moving of the component and the coincident lowering of the water level were done to facilitate insertion and removal of experiments in the reactor.
The eight employees received radiation exposures, ranging from 2.5 rem to 21.5 rem. (See
TID5360, Suppl- 1, p. 18.)
Four employees, who were handling fission samples improperly, received whole-body exposures ranging from 1.7 rem to 17 rem.
While handling 55-gallon drums, whose greasy surfaces had trapped considerable amounts of radioactive fallout, an employee received 13 rem whole-body exposure during one working day. His total yearly exposure was 15.14 rem.
Construction employees, who wore no dosimeters, were inadvertently exposed to a lost 27-curie iridium 192 radiography source during the construction of a new production reactor. Exposures were estimated based upon radiation surveys and interviews with the personnel involved. The exposures ranged from 3.9 rem to 15.2 rem.
An employee was in a shielded X-ray room using a portable X-ray unit. The circumstances indicated that the employee was not exposed to the radiation shown by his film badge. However, investigation could not prove this; therefore, it was assumed that the employee was exposed.