Demon core ( Eng. Demon core ) - the name given to the subcritical volume of plutonium weighing 6.2 kg, which participated in two accidents in the laboratory of Los Alamos in 1945 and 1946. In both cases, radiation exposure as a result of an unplanned transition to a critical state led to the death of scientists, after which the assembly got its name. The design consisted of two halves of plutonium balls in the delta phase, coated with a layer of nickel , with a total mass of 6.2 kg, with a density of 15.7 g / cm³ [1] [2] . In 1946, this charge was used in the Able bomb at the Crossroads atomic weapon tests on the Bikini Atoll.
Content
- 1 First incident
- 2 Second incident
- 3 Consequences
- 4 notes
First Incident
On August 21, 1945, the young scientist Harry Daglyan alone conducted an experiment to study neutron reflection. The core was placed inside a block structure made of tungsten carbide , a neutron reflector . The addition of each new block weighing 4.4 kg (the total mass of the blocks was to be 236 kg) brought the assembly closer to a critical state. When trying to install the next block, Daglyan dropped it directly on plutonium, which transferred the assembly to a supercritical state . Despite the fact that the block was immediately removed, Daglyan received a lethal dose of radiation (about 5-8 Sv ) and died of radiation sickness after 25 days [1] [2] .
The second person also suffered during the incident, guard Robert J. Hemmerley, who was not involved in the experiment, received a dose of approximately 0.2 Sv. Hemmerli died in 1978 (32 years after the accident) from leukemia at the age of 62 years [3] .
During the incident, approximately 10 16 divisions occurred, the nickel cover on the plutonium ball did not collapse [2] .
Second Incident
On May 21, 1946, physicist Louis Zlotin conducted an experiment in the laboratory of Los Alamos to study the properties of nuclear fission by installing a neutron reflector in a subcritical assembly, while he demonstrated the experience of seven other scientists. For its extreme danger, the experiment was called "pulling the dragon's tail." The experimenter placed the core between two beryllium hemispheres (playing the role of a reflector) and manually lowered the upper hemisphere onto the core, holding it with the thumb at the hole in the upper part. When the hemisphere was moved up and down, sensors recorded changes in assembly activity. The only object that prevented the hemispheres from closing was a flat screwdriver sting, which the scientist held in his right hand [1] . Zlotin conducted this experiment more than ten times, previously Enrico Fermi told him and other employees who participated in the experiments that if they did not stop their dangerous experiments, they would "die within a year" [4] .
While lowering the upper hemisphere, the Zlotin screwdriver slid and the hemispheres closed, completely surrounding plutonium. The assembly instantly went into a supercritical state, but Zlotin quickly knocked the upper hemisphere to the floor, stopping the chain reaction, which probably saved the lives of other people in the laboratory. Zlotin received a large dose of radiation - about 1000 rad (mainly from fast neutrons ) and died after 9 days from acute radiation sickness in intestinal form. The rest of those present received doses, estimated by the 40s, at 0.4-3.6 Sv [1] [2] [5] . Two of them died 18 and 20 years after the accident, from leukemia (aged 42 years) and myocardial infarction (aged 54 years), respectively; one died after 29 years at the age of 83 (bacterial endocarditis); one died during the Korean War after 6 years. Three were alive in 1977-1978, 31-32 years after the incident [3] .
Consequences
The plutonium ball was used in the ABLE nuclear test, which took place as part of Operation Crossroads on July 1, 1946. Thanks to the experiments of Daglyan and Zlotin, the effectiveness of the weapons used in the tests was increased compared to those used in the bombing of Japan [1] [6] .
Notes
- ↑ 1 2 3 4 5 Hubbell MW The Fundamentals of Nuclear Power Generation: Questions & Answers . - Bloomington: AuthorHouse , 2011 .-- P. 119. - 537 p. - ISBN 978-1-4634-2658-3 .
- ↑ 1 2 3 4 William R. Stratton. A Review of Crticality Accidents . LANL (September 26, 1967). Date of treatment February 16, 2012. Archived September 10, 2012. ;
2000 Edition , pp. 74-76;
Overview of nuclear accidents with the occurrence of SCR (LA-13638) - translation into Russian in 2003 - 1. Los Alamos National Laboratory, August 21, 1945; May 21, 1946 - ↑ 1 2 WHAT HAS HAPPENED TO THE SURVIVORS OF THE EARLY LOS ALAMOS NUCLEAR ACCIDENTS page 22 table 2
- ↑ Welsome, Eileen. The Plutonium Files . - 1999. - P. 184. - ISBN 978-0385314022 .
- ↑ Radiation doses in the Pajarito accident of may 21, 1946 // LANL, LA-687, May 26, 1948
- ↑ Miller, Richard L. Under the Cloud: The Decades of Nuclear Testing. - The Woodlands, Texas : Two Sixty Press, 1991 .-- P. 69, 77. - ISBN 0029216206 .