Three Mile Island Accident

On March 28, 1979, the three mile island accident occurred. Unit 2 reactor near Middletown, Pennsylvania, partially melted down. Although the tiny radioactive leaks had no apparent health consequences on plant workers or the general public, this was the most significant three mile nuclear accident in the history of commercial nuclear power plant operations in the United States. Emergency service planning, reactor operator training, human factors engineering, radiation protection, and many other aspects of nuclear power plant operations have all been significantly revised as a result of the three mile island disaster. 

The NRC also tightened and increased its regulatory control as a result of it. All these modifications improved reactor safety in the United States dramatically. TMI-2's partial meltdown and extremely tiny off-site radioactive leaks were caused by a mix of faulty equipment, design-related difficulties, and careless mistakes by workers.

Events of Three Mile Island Accident

The catastrophe began around 4 a.m. on Wednesday, March 28, 1979, when a malfunction in the plant's secondary, non-nuclear component occurred (one of the two reactors on the site). The primary feedwater pumps were unable to send water to the steam generators, which remove heat from the reactor core, due to either a mechanical or electrical failure. The turbine-generator at the plant, as well as the reactor itself, were both automatically shut down due to this. The pressure in the prion increased immediately.

When the pressure dropped to acceptable levels, the valve should have closed, but it remained open. The valve, however, was closed, according to instruments in the control room, which informed the plant employees. As a result, the plant's crew was unaware that the stuck-open valve was leaking cooling water in the form of steam. The operators were unaware that the facility was suffering from a loss-of-coolant. The three mile island accident deaths as alarms rang and warning lights flashed.

Other tools available to plant employees provided inaccurate or misleading data. The huge pressure tank containing the reactor core was always filled to the brim with water during normal operations. As a result, there's no need for a water-level device to determine if the vessel's water level reached the core. As a consequence, plant personnel thought that because long sensors showed that the pressurizer level of water was sufficient, the core was also adequately flooded. That was not the case at all. There were so many three mile island accident deaths.

The personnel executed a sequence of activities that exposed the core, unaware of the stuck-open relief-valve and unable to detect if the core was covered with cooling water. The blocked valve reduced the main pressure gradient to the point where the cooling water pumps began to shake and had to be shut off. They cut back on the flow of water because the emergency cooling water being pushed into the primary system threatened to entirely fill the pressurizer - a dangerous situation. The water level in the pressure vessel declined as a result of the reactor coolant pumps not circulating water and the primary system being deprived of emergency cooling water.

(Image will be uploaded soon)

Health Consequences Post-three-mile Island Accident

The NRC, as well as the Environmental Protection Agency, the Department of Health, Education, and Employment, the Department of Energy, and the Commonwealth of Pennsylvania, conducted extensive examinations of the three mile nuclear accident radioactive implications.

Several other independent groups researched the details of the accident as well. During the three mile island disaster, the two million people (approximately) who were in the vicinity of TMI-2 achieved an overall radiation exposure of only around 1 millirem above the ordinary level.

To put this in perspective, a chest X-ray exposes you to roughly 6 millirems of radiation, whereas the area's natural radioactive ambient dose is around 100-125 millirem each year. At the property line, the maximum exposure of a human would have been less than 100 millirems above the ordinary level.

Although questions regarding probable ill effects of radiation on humans, animals, and plants in the TMI area were raised in the months following the three mile nuclear accident, none could be linked to the three mile island accident deaths. Various government agencies monitoring the area collected hundreds of samples including air, water, milk, plants, soil, and edibles.

Releases from the event may have resulted in very low amounts of radionuclides. Despite the catastrophic damage to the reactor, rigorous studies and analyses by various organizations, including Columbia University and the University of Pittsburgh, have concluded that the actual leak had little consequences on people's physical health or the environment.

The Three mile Island Accident After Effects 

The three mile island accident nuclear disaster had several causes like human error, design flaws, and component failures, and it forever impacted the nuclear power industry and the NRC. Anxiety and distrust among the public grew, the NRC's rules and oversight grew to be more rigorous, and the facilities' management was inspected more closely. After a thorough investigation of the three mile island disaster occurrences, the NRC made permanent and significant modifications to how it supervises its licensees, lowering the danger to public health and safety.

Below are some of the most significant changes after the three mile island accident nuclear disaster. 

• Plant design and equipment requirements are being upgraded and strengthened. Fire protection, piping systems, supplementary feed water structures, confinement structure isolation, component dependability, and the ability of plants to shut down automatically are all included in the changes.

• The importance of human performance in plant safety led to changes in operator training and staffing requirements, as well as enhanced instrumentation and controls for plant operation and the implementation of fitness-for-duty programs for plant personnel to prevent alcohol and drug misuse.

• Enhancing emergency readiness, including requirement of plants to immediately alert the NRC of significant events and establishing a 24-hour NRC Operations Center. Licensees now test exercises and response plans multiple times a year. State and local agencies participate in drills with the Federal Emergency Management Agency and the National Nuclear Security Administration.

• Including the NRC's observations, findings, and recommendations about licensee’s performance and managerial effectiveness in a published paper on a regular basis.

• Having senior NRC managers assess plant progress on a daily basis to identify plants that require considerable additional regulatory attention.

• Expanding the NRC's resident inspection program, which was first approved in 1977, to include at least two inspectors who live nearby and work entirely at each facility in the United States and provide daily monitoring of licensee compliance with NRC laws.

• Expanding both performance and safety inspections, as well as the use of risk assessment to detect any plant's susceptibility to major incidents.

• Creating a separate office inside the NRC to strengthen and reorganize enforcement personnel.

• Creating the Institute of Nuclear Power Operations, the industry's own "policing" group, and the Nuclear Power Institute to give a uniform industry approach to generic nuclear regulatory hurdles, as well as contact with the NRC and other government entities.

The three mil island concluded that it’s pertinent to not just maintain the nuclear safety but to also have competent, skilled and informed people to act under any circumstances. At TMI though there were malfunctions of equipment but the vital safety equipment was up and about and this was made possible with a good combination of sound nuclear safety protocols and competent people.