Radioactive histories Part 2 - The SL-1 disaster
Did you know... 3 mile island was not the first major nuclear reactor disaster on American soil. some 18 years before, near a small town called Idaho Falls a small experimental low powered nuclear reactor exploded killing all its operators and coating almost 30 miles of desert and highway in mild doses of cesium. To date it is the only reactor explosion in the US to cause instant death, and remains the only nuclear accident in US history to product Corium. This is the story of Stationary Low powered reactor 1 Or SL1 for short.
- Stationary Low Power Reactor
- SL-1 site design and operations
- The Accident
- Human Dynamics
- The Discovery
- The Aftermath
- The long term affects
- Lessons learned
Stationary Low Power Reactors
A Stationary Low Power Reactor (SLPR) is a type of nuclear reactor designed for small-scale power generation, research, or other specialized applications. These reactors typically have a power output of less than 10 megawatts and are designed to be compact, safe, and easy to operate.
SLPRs are often used for remote or off-grid locations, such as military bases, small communities, or industrial sites, where traditional power sources may not be available or practical. They can also be used for research purposes, such as testing new reactor designs or fuel types.
One of the key features of SLPRs is their passive safety systems. Unlike larger nuclear reactors, which require active cooling and emergency backup systems to prevent accidents, SLPRs are designed to shut down automatically and cool down passively in the event of a malfunction or power outage. This makes them inherently safer and more reliable than traditional nuclear reactors.
Overall, SLPRs offer a flexible and reliable source of low-carbon energy that can be used in a variety of applications. However, like all nuclear power sources, they require careful design, construction, and operation to ensure safety and prevent accidents.
Design and Operation
The Stationary Low-Power Reactor 1 (SL-1) was a small nuclear reactor located at the National Reactor Testing Station in Idaho, USA. It was designed and built by the United States Army in the late 1950s as a prototype for a portable nuclear power plant that could be used in remote locations such as military bases and radar installations.
The SL-1 was a boiling water reactor that used a core of highly enriched uranium fuel. It had a thermal power output of 3 megawatts and was designed to operate for up to five years without refueling. The reactor was housed in a steel pressure vessel that was surrounded by a concrete shield to protect against radiation.
The SL-1's control systems were designed to be simple and easy to operate, with manual controls and a small crew of three operators. The reactor was shut down and started up manually, and the control rods that regulated the nuclear reaction were raised and lowered using a manual crank.
The Accident
The SL-1 accident occurred on January 3, 1961. At the time of the accident, three nuclear operators were on duty: John Byrnes, Richard McKinley, and Richard Legg.
The accident began during a routine maintenance procedure. The operators were preparing to replace a control rod in the reactor's core. The control rod was being removed using a manual crank when it suddenly became stuck. In an attempt to free the rod, one of the operators, Richard McKinley, stood on top of the reactor vessel and used a pry bar to try to loosen the rod.
As McKinley was working on the control rod, the reactor suddenly went critical. The exact cause of the criticality is still debated, but it is believed that the control rod was withdrawn too quickly, causing an uncontrolled nuclear reaction.
The sudden burst of energy caused a steam explosion in the reactor vessel, lifting the reactor core out of its support structure. The explosion released a burst of steam and radiation, which fatally injured all three operators.
The force of the explosion was so great that it lifted the 1,400-pound reactor core nearly nine feet into the air. The core then fell back into the vessel, causing a second burst of steam and radiation. The explosion also damaged the reactor building and caused a small fire.
Human Dynamics
While the exact cause of the accident is still debated, there were several human factors that contributed to the disaster. These factors include:
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Inadequate Training: The operators at SL-1 were military personnel who had limited experience with nuclear reactors. They had received only a few months of training and were not fully qualified to operate the reactor. This lack of experience and training may have contributed to the accident.
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Poor Procedures: The operators at SL-1 were using outdated and poorly written procedures for starting up and shutting down the reactor. The procedures were not clear and did not provide sufficient guidance for the operators. This may have led to confusion and mistakes during the startup procedure.
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Overconfidence: The operators at SL-1 may have been overconfident in their abilities to operate the reactor safely. They had successfully operated the reactor several times before the accident and may have become complacent or overly confident in their abilities.
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Lack of Oversight: The Army had limited oversight and control over the operation of the reactor. The operators at SL-1 were not required to follow the same strict safety procedures as civilian operators, and there were no independent inspections or audits of the reactor's operation.
The discovery
At the time of the accident, heat sensors above the reactor triggered an alarm at the NRTS security facility at 9:01 pm MST. False alarms had occurred earlier in the morning and afternoon that same day, leading the response team of six firefighters, led by Ken Dearden, assistant chief, to arrive nine minutes later, expecting another false alarm.
Initially, the firefighters noticed nothing unusual, with only a little steam rising from the building, which was normal for the cold 6 °F (−14 °C) night. Unable to contact anyone inside the SL-1 facility, the firefighters had a security guard open the gate for them. They donned their Scott Air-Paks and arrived at the Support Facilities Building to investigate.
Inside the building, everything appeared normal, but it was unoccupied. Three mugs of warm coffee were in the break room, and three jackets were hanging nearby. Upon entering the reactor control room, the firefighters noticed a radiation warning light. As they climbed the stairs to SL-1's reactor operating floor level, their handheld radiation detector suddenly jumped sharply above its maximum range, prompting a retreat for a second radiation detector. However, the second radiation detector also maxed out at its 200 röntgens per hour (R/hr) scale as they ascended again. They peered into the reactor room before withdrawing.
At 9:17 pm, a health physicist arrived at the scene, and he and Assistant Chief Moshberger, both wearing air tanks and masks with positive pressure in the mask to force out any potential contaminants, approached the reactor building stairs. Their detectors read 25 röntgens per hour (R/hr) as they started up the stairs, and they withdrew. The pair then found a higher-scale ion chamber detector and reached the top of the stairs to look inside the reactor room for the three missing men. Their Jordan Radector AG-500 meter pegged at 500 R/hr on the way up. When they reached the top, they saw a dim, humid, wet operating floor strewn with rocks and steel punchings, twisted metal, and scattered debris.
The Aftermath
After the SL-1 accident, the immediate priority was to determine the cause of the explosion and recover the bodies of the three victims. Recovery efforts began the day after the accident, on January 4, 1961. Due to the hazardous conditions inside the reactor building, recovery crews could only work for short periods of time and were limited to using remote-controlled equipment.
The first recovery team was sent in on January 5, but they had to withdraw due to high radiation levels. On January 6, a second team managed to retrieve the bodies of John Byrnes and Richard McKinley, who had been killed instantly by the explosion. However, the body of Richard Legg, who was impaled on a control rod and stuck in the reactor, was much more difficult to recover.
Over the next several weeks, workers used remote-controlled equipment to carefully remove debris and cut the control rod that impaled Legg's body. On February 9, 1961, Legg's body was finally recovered and removed from the reactor building.
The recovery operation was a difficult and dangerous task that required careful planning and execution. The workers who participated in the recovery efforts were exposed to high levels of radiation, and some of them suffered from radiation sickness as a result. Despite the risks, the recovery crews worked tirelessly to retrieve the bodies of the victims and ensure that the reactor was safe to enter again.
Long term affects
The aftermath of the SL-1 accident had long-term impacts on the surrounding area and the nuclear industry as a whole. The radioactive contamination at the site was significant, and the cleanup efforts continued for years after the accident.
The immediate area around the SL-1 reactor building was heavily contaminated with radioactive materials. The soil and groundwater were contaminated, and the buildings on the site had to be decontaminated or demolished. In addition, the nearby town of Arco, Idaho, experienced a great deal of anxiety and fear over the potential health effects of the accident.
After the accident, the SL-1 reactor was decommissioned and dismantled. The reactor was first disassembled and placed in storage containers. The containers were then shipped to the Idaho National Laboratory, where they were stored in an underground radioactive waste storage facility.
In the years following the accident, the SL-1 site was the subject of numerous studies and investigations. The results of these studies helped to shape new safety protocols and regulations for nuclear facilities. The SL-1 accident also served as a cautionary tale for the nuclear industry, reminding engineers and operators of the potential dangers of nuclear power.
Today, the site of the SL-1 accident is still monitored for radiation levels, and access to the site is restricted. The Idaho National Laboratory continues to store the contaminated materials from the site, and the surrounding area remains a reminder of the risks associated with nuclear power.
Poster depecting the damaged reactor used to remind engineers that safety is the number 1 focus in nuclear engineering.
Lessions learnt
The SL-1 accident serves as a reminder of the importance of strict adherence to safety protocols and procedures in the nuclear industry. The accident was caused by a combination of human error, design flaws, and inadequate safety procedures. Some of the key lessons that can be learned from the SL-1 accident include:
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The importance of proper training: The accident at SL-1 was caused in part by a lack of training for the reactor operators. This underscores the importance of proper training and education for anyone working in the nuclear industry.
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The need for clear communication: Communication breakdowns between different groups of workers contributed to the SL-1 accident. Clear communication channels and protocols are essential in order to ensure that everyone involved in a nuclear facility understands their role and responsibilities.
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The importance of safety culture: A strong safety culture is essential in any industry, but it is particularly critical in the nuclear industry. The SL-1 accident highlights the need for a culture that prioritizes safety above all else.
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The need for robust safety systems and procedures: The design flaws and inadequate safety procedures at SL-1 contributed to the severity of the accident. Robust safety systems and procedures are essential to minimize the risk of accidents and to ensure that any accidents that do occur are contained and mitigated as much as possible.
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The need for transparency and accountability: The SL-1 accident was largely caused by a lack of transparency and accountability within the organization. The nuclear industry must prioritize transparency and accountability in order to build public trust and to ensure that safety concerns are taken seriously.
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