Cecil Kelley criticality accident
Encyclopedia
The Cecil Kelley criticality accident was a nuclear accident that took place on December 30, 1958, at the Los Alamos National Laboratory
in Los Alamos, New Mexico, in the United States. It is one of only ten such events
to ever occur outside of a nuclear reactor, though it was the third such event to take place in 1958 (the others having taken place on 16 June at the Y-12 Plant
in Oak Ridge, Tennessee, and on 15 October at the Vinča Nuclear Institute
in Vinča, Yugoslavia). The accident involved plutonium
compounds dissolved in liquid chemical reagents
, and it caused the death of one man – Cecil Kelley, a chemical operator – from severe radiation poisoning
within 35 hours.
remaining from other experiments and applications, along with various organic solvents and acids in an aqueous solution for the purpose of recovering it for reuse. In pure form and under normal temperature and pressure conditions, plutonium – a mostly man-made element existing in trace amounts in nature – is a solid silvery metal. However, it tarnishes quickly when exposed to air and readily dissolves in concentrated hydrochloric
, hydroiodic and perchloric acids
as well as others. On the day of the accident the mixing tank was supposed to contain what nuclear chemists call a "lean" concentration of dissolved plutonium (≤0.1g of plutonium per liter of solution) in a bath of highly corrosive nitric acid
and a caustic stabilized aqueous organic emulsion. However, as a result of what were later determined to be at least two "improper transfers" of plutonium waste to the tank (the sources for which were never determined or at least never publicly disclosed), the concentration of plutonium in the mixing tank on this particular occasion was nearly 200 times higher, and was distributed unevenly. The upper layers of solution had especially high concentrations, and were already close to criticality
before Kelley acted. When Kelley switched on the mixing tank, the lower and more-aqueous layers within the tank immediately pushed outward and upward forming a vortex
"bowl" and the higher plutonium-rich layers swirled toward the vortex's bottom and center.
Among other ideal characteristics, the ideal shape or "geometry" for any radioactive substance to become supercritical is a sphere. While the solution in the center of the vortex was not spherical, it did become thicker in the center and this, along with the corresponding increase in density and the neutron reflectivity of the aqueous layer surrounding it, caused the dissolved plutonium to reach and cross the criticality threshold in approximately one second: neutrons
within the mixture began to bombard the nuclei of the solution's plutonium atoms with sufficient frequency that these atoms broke apart and released other neutrons in a sustained nuclear chain reaction
lasting only 200 microseconds but releasing a huge burst of neutrons and gamma radiation. Such an uncontrolled release of nuclear energy is often referred to as an excursion
.
Within three seconds the layers in the mixture had become dispersed and no further excursions were possible.
followed by the sound of a thud. The power burst either caused Kelley to collapse or knocked him off the ladder, and he had fallen to the ground. He arose disoriented, and apparently switched the mixer off and then back on again before running outside of the building. The other technicians found him there in the snow in a state of ataxia
and only able to say to them, "I'm burning up! I'm burning up!"
Because the possibility of an excursion taking place in a mixing tank had been considered virtually impossible, the technicians decided that Kelley must have somehow been exposed to either alpha radiation
, the acid bath, or both, and one of them took him to a chemical shower while the other switched off the mixer. Additional staff members arrived on the scene within minutes to find Kelley virtually unconscious. The skin color of his face indicated erythema
brought on by cutaneous radiation syndrome.
Any accident at Los Alamos involving a radioactive substance requires an immediate investigation by a team of radiation monitoring staff. Even before Kelley was taken to an emergency room, these staff members began an examination of the mixing room with radiation detectors capable of assessing the alpha radiation indicative of plutonium decay
. This radiation should have been widespread if any of the plutonium mixture had escaped the tank. Nothing unusual was initially found. Eighteen minutes later, however, the team began searching for gamma radiation
– they unexpectedly found this kind of radiation in abundance near the mixing tank, on the order of tens of rads
per hour. Such intense gamma radiation could only have been produced during an excursion; this, combined with the otherwise inexplicable flash of light reported by the other two technicians, was sufficient to identify the event as a criticality accident.
from fast neutrons
and 2,700 rad from gamma ray
s, for a total of 3,600 rad. For an adult human, exposure to 200 rad from a spherical (unfocused) radiation source such as an excursion will cause radiation sickness but is not considered definitely lethal; 240–340 rad is the median lethal dose; a dose of 500 rad is almost always deadly. Kelley had received more than seven times the adult human lethal dose. Although the medical staff in the emergency room took steps to ease his pain with Demerol and morphine
, previous research on radiation exposure in animals indicated Kelley's death would be inevitable. Within six hours his lymphocytes were all but gone. A bone biopsy performed 24 hours after the incident produced bone marrow that was watery and contained no red blood cells. Numerous intravenous blood transfusions had no lasting helpful effect: 35 hours following his initial exposure and after a final bout of intense restlessness, agitation, sweating, becoming ashen-skinned, and having an irregular pulse, Cecil Kelley died of heart failure.
on Cecil Kelley. The case alleged the misconduct of doctors, the hospital, and the administration of Los Alamos in removing organs from the deceased without consent from next-of-kin over a span of many years (1958–1980). Kelley's autopsy was the first instance of this type of post-mortem analysis, but there were many more performed by Dr. Lushbaugh and others in later years at Los Alamos. During a deposition for the case, Dr. Lushbaugh, when asked who gave him the authority to take 8 pounds of organs and tissue from Kelley's body, said, "God gave me permission." The class action suit was settled by the defendants for about $9.5 million in 2002 and an additional $800,000 in 2007. None of the defendants admitted any wrongdoing.
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...
in Los Alamos, New Mexico, in the United States. It is one of only ten such events
Criticality accident
A criticality accident, sometimes referred to as an excursion or a power excursion, is an accidental increase of nuclear chain reactions in a fissile material, such as enriched uranium or plutonium...
to ever occur outside of a nuclear reactor, though it was the third such event to take place in 1958 (the others having taken place on 16 June at the Y-12 Plant
Y-12 National Security Complex
The Y-12 National Security Complex is a United States Department of Energy National Nuclear Security Administration facility located in Oak Ridge, Tennessee, near the Oak Ridge National Laboratory...
in Oak Ridge, Tennessee, and on 15 October at the Vinča Nuclear Institute
Vinča Nuclear Institute
Vinča Nuclear Institute is a nuclear physics research institution near Belgrade, in Serbia.-History:The Institute was originally established in 1948 as the Institute for Physics. In 1953 it was renamed in favour of Boris Kidrič. Several different research groups started in the 1950s, and two...
in Vinča, Yugoslavia). The accident involved plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
compounds dissolved in liquid chemical reagents
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
, and it caused the death of one man – Cecil Kelley, a chemical operator – from severe radiation poisoning
Radiation poisoning
Acute radiation syndrome also known as radiation poisoning, radiation sickness or radiation toxicity, is a constellation of health effects which occur within several months of exposure to high amounts of ionizing radiation...
within 35 hours.
Context of the accident
Cecil Kelley was a 38-year-old chemical operator with 11 years of experience, more than half of those while at the Los Alamos lab where one of his duties was to operate a large (1,000 liter capacity) stainless steel mixing tank. The tank contained residual radioactive plutonium-239Plutonium-239
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...
remaining from other experiments and applications, along with various organic solvents and acids in an aqueous solution for the purpose of recovering it for reuse. In pure form and under normal temperature and pressure conditions, plutonium – a mostly man-made element existing in trace amounts in nature – is a solid silvery metal. However, it tarnishes quickly when exposed to air and readily dissolves in concentrated hydrochloric
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
, hydroiodic and perchloric acids
Perchloric acid
Perchloric acid is the inorganic compound with the formula HClO4. Usually encountered as an aqueous solution, this colourless compound is a strong acid comparable in strength to sulfuric and nitric acids. It is a powerful oxidizer, but its aqueous solutions up to appr. 70% are remarkably inert,...
as well as others. On the day of the accident the mixing tank was supposed to contain what nuclear chemists call a "lean" concentration of dissolved plutonium (≤0.1g of plutonium per liter of solution) in a bath of highly corrosive nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
and a caustic stabilized aqueous organic emulsion. However, as a result of what were later determined to be at least two "improper transfers" of plutonium waste to the tank (the sources for which were never determined or at least never publicly disclosed), the concentration of plutonium in the mixing tank on this particular occasion was nearly 200 times higher, and was distributed unevenly. The upper layers of solution had especially high concentrations, and were already close to criticality
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...
before Kelley acted. When Kelley switched on the mixing tank, the lower and more-aqueous layers within the tank immediately pushed outward and upward forming a vortex
Vortex
A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...
"bowl" and the higher plutonium-rich layers swirled toward the vortex's bottom and center.
Among other ideal characteristics, the ideal shape or "geometry" for any radioactive substance to become supercritical is a sphere. While the solution in the center of the vortex was not spherical, it did become thicker in the center and this, along with the corresponding increase in density and the neutron reflectivity of the aqueous layer surrounding it, caused the dissolved plutonium to reach and cross the criticality threshold in approximately one second: neutrons
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
within the mixture began to bombard the nuclei of the solution's plutonium atoms with sufficient frequency that these atoms broke apart and released other neutrons in a sustained nuclear chain reaction
Nuclear chain reaction
A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. The specific nuclear reaction may be the fission of heavy isotopes or the fusion of light isotopes...
lasting only 200 microseconds but releasing a huge burst of neutrons and gamma radiation. Such an uncontrolled release of nuclear energy is often referred to as an excursion
Criticality accident
A criticality accident, sometimes referred to as an excursion or a power excursion, is an accidental increase of nuclear chain reactions in a fissile material, such as enriched uranium or plutonium...
.
Within three seconds the layers in the mixture had become dispersed and no further excursions were possible.
Events of the excursion
Kelley had been standing on a foot ladder looking at the contents of the mixing tank through a viewing window when the excursion event occurred. Two other technicians working within the laboratory witnessed a bright flash of blue lightIonized air glow
The ionized-air glow is the emission of characteristic blue–purple–violet light, of color called electric blue, by air subjected to an energy flux. -Processes:...
followed by the sound of a thud. The power burst either caused Kelley to collapse or knocked him off the ladder, and he had fallen to the ground. He arose disoriented, and apparently switched the mixer off and then back on again before running outside of the building. The other technicians found him there in the snow in a state of ataxia
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
and only able to say to them, "I'm burning up! I'm burning up!"
Because the possibility of an excursion taking place in a mixing tank had been considered virtually impossible, the technicians decided that Kelley must have somehow been exposed to either alpha radiation
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
, the acid bath, or both, and one of them took him to a chemical shower while the other switched off the mixer. Additional staff members arrived on the scene within minutes to find Kelley virtually unconscious. The skin color of his face indicated erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
brought on by cutaneous radiation syndrome.
Any accident at Los Alamos involving a radioactive substance requires an immediate investigation by a team of radiation monitoring staff. Even before Kelley was taken to an emergency room, these staff members began an examination of the mixing room with radiation detectors capable of assessing the alpha radiation indicative of plutonium decay
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
. This radiation should have been widespread if any of the plutonium mixture had escaped the tank. Nothing unusual was initially found. Eighteen minutes later, however, the team began searching for gamma radiation
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
– they unexpectedly found this kind of radiation in abundance near the mixing tank, on the order of tens of rads
Rad (unit)
The rad is a unit of absorbed radiation dose. The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the malignant mammalian cells in question..." It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by...
per hour. Such intense gamma radiation could only have been produced during an excursion; this, combined with the otherwise inexplicable flash of light reported by the other two technicians, was sufficient to identify the event as a criticality accident.
Kelley's clinical course
For the first hour and forty minutes following the accident Kelley had been incoherent, and had gone through waves of intense vomiting and retching. He then stabilized, was able to once again converse normally, and was able to have his pulse taken and his blood drawn. The blood draw indicated that Kelley had been exposed to approximately 900 radRad (unit)
The rad is a unit of absorbed radiation dose. The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the malignant mammalian cells in question..." It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by...
from fast neutrons
Neutron temperature
The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature. The neutron energy distribution is...
and 2,700 rad from gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s, for a total of 3,600 rad. For an adult human, exposure to 200 rad from a spherical (unfocused) radiation source such as an excursion will cause radiation sickness but is not considered definitely lethal; 240–340 rad is the median lethal dose; a dose of 500 rad is almost always deadly. Kelley had received more than seven times the adult human lethal dose. Although the medical staff in the emergency room took steps to ease his pain with Demerol and morphine
Morphine
Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
, previous research on radiation exposure in animals indicated Kelley's death would be inevitable. Within six hours his lymphocytes were all but gone. A bone biopsy performed 24 hours after the incident produced bone marrow that was watery and contained no red blood cells. Numerous intravenous blood transfusions had no lasting helpful effect: 35 hours following his initial exposure and after a final bout of intense restlessness, agitation, sweating, becoming ashen-skinned, and having an irregular pulse, Cecil Kelley died of heart failure.
Implications
An investigation into the circumstances of the accident never resulted in a public explanation of how the mixing tank became filled with such a high concentration of plutonium—initially the blame was placed on Kelley himself. The US government had been waiting for an accident like this to happen so that theories about the progression of radiation poisoning and the eventual distribution of radioactive plutonium in a human could be examined (although Kelley had neither ingested nor inhaled any plutonium during the accident, he, like many laboratory technicians at Los Alamos, had been exposed to minute particles of airborne plutonium over the course of several years). An event such as this was therefore considered an "experiment of opportunity:" Careful records were kept of every moment of Kelley's life from accident through death and onto the autopsy table. His organs were ground up and their plutonium levels analyzed. The results of these tissue analyses were considered fundamental to understanding what would happen to a population during a nuclear attack and impossible to obtain any other way. Although the bone marrow biopsy of Kelley's sternum was performed under the premise that the physicians wished to determine if he were a candidate for a bone marrow transplant, Kelley's death was of such certainty that an actual transplant was never seriously considered.Court case
In 1996, Doris E. Kelley and Mareau Katie Kelley, relatives of Cecil Kelley, filed a lawsuit against Dr. Clarence Lushbaugh, the pathologist who performed the autopsyAutopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...
on Cecil Kelley. The case alleged the misconduct of doctors, the hospital, and the administration of Los Alamos in removing organs from the deceased without consent from next-of-kin over a span of many years (1958–1980). Kelley's autopsy was the first instance of this type of post-mortem analysis, but there were many more performed by Dr. Lushbaugh and others in later years at Los Alamos. During a deposition for the case, Dr. Lushbaugh, when asked who gave him the authority to take 8 pounds of organs and tissue from Kelley's body, said, "God gave me permission." The class action suit was settled by the defendants for about $9.5 million in 2002 and an additional $800,000 in 2007. None of the defendants admitted any wrongdoing.