The difficulty of dealing with the crisis as seen in the accident at the "Santaszana Outdoor Laboratory" concealed despite the largest nuclear accident in the United States' first meltdown

In order to avoid the occurrence of a serious accident, a number of safety measures are prepared at nuclear power plants, and thorough measures for safety are taken. Even such a thorough countermeasure occurred in California state in the United States that it can not say absolute as long as manipulated by human beings "Santaszana field workshop"The largest nuclear power plant accident in the US is taught.

Nuclear Plant Accidents: Sodium Reactor Experiment - All Things Nuclear
http://allthingsnuclear.org/dlochbaum/nuclear-plant-accidents-sodium-reactor-experiment

In nuclear power plants where nuclear power generation is performed, a number of safety measures are taken to ensure safety when an accident should happen. For example, if the external power supply is lost, a diesel power supply that generates electricity in the event of an emergency may assist or the emergency pump automatically moves and supplies cooling water when the pipe through which the cooling water passes ruptures , A multilayered defense system is adopted.

However, Dave Lakbaum, a nuclear power expert and director of UCS Nuclear Safety Project, says, "The disadvantage of defense in defense is that no countermeasures are 100% reliable." And, each of the unreliable defense layers included indeterminate and unreliable elements of "human behavior" in the "Santaszana Outdoor Laboratory" that occurred in Los Angeles, USA I will explain the accident of nuclear power generation as an example.


The Sodium Reactor Facility (SRE) was built at the Santaszana field laboratory, a comprehensive research facility in the Simi Valley on the outskirts of Los Angeles. In 1955, the core of SRE reached its first criticality, and we started generating electricity from April 25, 1957. As indicated by its name in SRE, we used liquid sodium for primary cooling and secondary cooling of the heat generated in the fission reaction.


In May 1959 SRE engineers at the Santa Susana field laboratory found troublesome signs. The temperature of liquid sodium in the primary cooling loop gradually rose from 285 degrees to 304 degrees over 3 days. It was confirmed by the thermocouple that the temperature of the fuel element in the core rose from 460 degrees to 507 degrees.

On June 2, 1959 workers concluded that the system was out of order, and responsible for sealing the sodium pump causeTetralin(Tetrahydronaphthalene) seal was found to be defective and liquid sodium leaked. I shut down the SRE completely on June 3 and replaced the pump's tetra - ringin seals.

The SRE was resumed at 6:50 on July 12 when the repair was completed, but at 15:30 I found that the level of radioactivity in the nuclear reactor was clearly rising. We suspected radioactive leakage from the upper part of the nuclear reactor, stopped the nuclear reactor and replaced it with a solid plug from the water level probe. After that, on July 13, despite detecting the abnormal value of the power level, I decided to resume SRE. I know that I started inserting the control rod after the unintended increase in the output level started.

After that, as a result of unexpected accidents and inappropriate measures against it, 13 nuclear fuel rods of SRE that had been subjected to multiple safety measures had melted, 13 of iodine 131 and cesium 137 It caused a nuclear accident to release into the atmosphere.


According to Mr. Rakbaum, though SRE saw many opportunities to solve accidents that occurred in the early stages, they missed everything. The first cause of tetralin leakage in the primary loop in the latter half of 1958 was the design problem of the flow path of liquid sodium. But in June 1959 this design problem was not handled until another tetralin leak occurred. When tetralin leakage occurred in June 1959, although the possibility that tetralin covered the surface of the fuel and the heat exchanger was strongly inferred, only the tetralin was removed from the liquid sodium, I did not make sure it did not cover it.

In addition, Mr. Rakbaum points out evils of "backward wisdom". For example, it is concluded that the control rod had to be pulled out to an unexpected position in order to achieve criticality after visually inspecting the fuel and removing the residue, but accident occurred on common sense after the accident occurred It is impossible to bring it to the point before it is done, and also points out the difficulty of understanding the situation at the time of the accident after the accident.

Even if we take safety measures that seem perfect, we can tell you that the meltdown accident at the "Santaszana Outdoor Laboratory" is more difficult to completely avoid danger than human beings operate, This accident did not appear on the table after being hidden thoroughly by the US government even after it occurred. After that, the existence of the accident was revealed in 1979 by the student of the University of California, Los Angeles, and the Environmental Protection Agency (EPA) finally hears local hearings in 2012 in response to requests from the surrounding residents who complain of health concerns It was announced that cesium 137 of 1,000 times the reference value was detected. thisThree Mile Island nuclear power plant accidentFor the largest nuclear power plant accident in the USA, the complete removal of radioactive materials has not been completed.