Analysis of Two Nuclear Accidents in the USA and Ukraine - Case Study Example

ACCIDENT AND CATASTROPHE Name Course Institution Instructor’s name Date Introduction Nuclear Power plant accidents are probably the rarest forms of accidents that happen anywhere in the world. However, if they happen to occur their effects are felt for generations. The Chernobyl disaster is one of such incidents that happened several almost three decades ago but still affects thousands of people today. The extent at which nuclear power plant accidents happen is linked to human mistakes as well as plant design. In this report we are looking into depth the cases of two nuclear accidents, the Three Mile Island Nuclear accident in the state of Pennsylvania in the United Sates and the Chernobyl disaster in Ukraine. The report attempts to explore the cause of each accident, how it happened and why, similarities and differences between the two accidents as well as the lessons learnt. In addition, we will seek to establish whether the latter accident could be avoided from the lessons learnt from the first accident and also look at possibilities of a repeat of the same. Case Studies Three Mile Island Accident The Three Mile Island Nuclear power plant accident occurred near Middletown, Dauphin county Pennsylvania on the 28th of March, 1979 (World Nuclear Association, 2012). The accident was termed as the most critical in the United States nuclear power plant operating history, despite not having caused any injuries or deaths to the workers at the plant and the surrounding community. The accident unfolded on March 28, 1979 at around 4.00 am, when the plant experienced a breakdown in the minor non nuclear part of the plant (Nuclear Regulatory Commission, 2011). The main feed water pumps ceased running a problem believed to have been caused by either electrical or mechanical breakdown, which abstracted the steam generators from taking away heat. The turbine, then the reactor automatically stopped. This led to an immediate build up of pressure in the primary system (the nuclear part of the plant) (Walker, 2004). To minimize the pressure, the Pilot Operated Relieve Valve opened and was expected to close when the pressure went down by a significant amount, but unfortunately it did not close (World Nuclear Association, 2012). More worse, signals to show the operator that the valve was still open failed to execute their purpose. This resulted the cooling water to pour out from the open valve causing the core of the reactor to overheat. As cooling water flowed from the core of the plant through the pressurizer, the equipments available to the operator of the reactor gave confusing information. There was actually no equipment that showed the level of the water in the core (World Nuclear Association, 2012). The operators therefore relied on the level of water in the pressurizer to determine the level of the coolant at the core. This confused them as the pressurizer showed high levels of water which made them assume that the coolant was sufficient at the core. Besides there was no signal that showed that the pilot operated valve was still open. This resulted the warning lights to flash and alarms to ring but the operators could not realize that the plant was facing a loss of coolant accident. The operators made various attempts to respond to the alarms but worsened the situation when they reduced the flow of the coolant through the core (Walker, 2004). Since there was no adequate cooling, the nuclear fuel overheated to a level at which the zirconium covering (the long metal pipes which hold the nuclear fuel pellets) disintegrated and the fuel pellets started to melt. It was discovered that, about 50 percent of the core melted during the initial stages of the accident (World Nuclear Association, 2012). Despite the TMI-2 plant experiencing a severe core meltdown, the most hazardous form of nuclear plant accident; it did not result to worst case effects as anticipated by the reactor experts. In a worst case disaster, nuclear fuel melting would cause a breach of the walls of the containment structure and release large amounts of radiation to the environment (Nuclear Regulatory Commission, 2011). Fortunately, this did not happen in the case of the Three Mile Island incident. The federal and state authorities were caught by surprise by the accident. They concentrated on the small portions of radioactive gases releases that were measured off the site by late morning of March 28 and were also concerned over the potential hazard that the plant posed to the surrounding environment. The authorities did not even realize that the core had melted, but they tried all they could to put the reactor under control and restore the cooling of the core. The NRC regional office immediately dispatched a team of inspectors to the plant. Other agencies such as the Environment Protection Agency and Department of Energy dispatched their teams. A team from the Brookhaven National Laboratory was as well sent to help in the monitoring of the radiation in the atmosphere. At 9.15 am, the White House was informed of the incident and at 11.00 am all workers who were not directly related to the technical team were ordered to vacate the premises of the nuclear plant (Nuclear Regulatory Commission, 2011). In the evening, the core seemed to be adequately cooled and the reactor seemed to be stable. However, new fears emerged by Friday march 30 in the morning. There was a significant release of radiation from the auxiliary structure of the plant done to relieve pressure on the core system and prevent curtailing the course of the coolant to the core, which caused a major confusion. With the uncertainty of the plant’s condition, Richard L. Thornburgh, the governor of Pennsylvania consulted with NRC regarding evacuation of the population in the affected area. The area was evacuated with pregnant women and young children within five mile radius of the nuclear plant being advised to vacate (Nuclear Regulatory Commission, 2011). In the meantime, there was a huge hydrogen bubble in the dome of the pressure container (the container which holds the reactor core) which raised new worries. It was feared that the hydrogen bubble might explode or burn and burst the pressure vessel. In that scenario, the core would descend into the containment structure and cause a breach of the containment. This caused panic among the authorities and the experts but on April 1, 1979 this anxiety was ended after experts determined that the bubble would not burn since there was no oxygen at the pressure vessel (Nuclear Regulatory Commission, 2011). Besides, the utility had by then managed to reduce the size of the bubble. Thorough studies of the radiological effects of the disaster have been carried out by NRC, Department of health, Health and Human Service (former Education and Welfare), Environmental Protection Agency and other independent organizations. It was estimated that the average dose to around two million residents in the area was just 1 millirem. This is minute considering that radiation from chest X-ray is about 6 millirem, and the annual millirem for the area which is between 100-125 millirem, hence the collective dose from the accident was insignificant (Nuclear Regulatory Commission, 2011). Various agents came to a conclusion that, even though the nuclear reactor was highly damaged, most of the radiation was managed and the actual release has insignificant effects on individuals’ health or that of the environment. The Three Mile Island accident was as a result of a combination of personal error, faulty design as well as component failure. The accident cost the US government about $1 billion. The incident however changed the entire nuclear industry in the United States as Nuclear Regulation Commission established serious and tight regulations to curb future accidents. Chernobyl Nuclear Power Disaster The Chernobyl Nuclear accident famously referred to as the Chernobyl disaster is considered one of the worst nuclear power plant catastrophes in history. It is also one of the only two disasters categorized as a level 7 event the other one being the Fukushima Daiichi nuclear disaster on the International Nuclear Event Scale (World Nuclear Association, 2011). The accident occurred on April 26, 1986 in Ukraine at the Chernobyl nuclear Power Plant. An explosion and a fire disbursed massive quantities amounts of radioactive pollutants into the air which spread over much of Europe and Western USSR. The accident occurred when reactor four experienced a dangerous power increase which led to explosion of the inner core at 1.23 am. This released massive quantities of radioactive fuel and materials of the core into the air and ignited the graphite moderator which is combustible. The burning graphite moderator raised the emission of radioactive particles conveyed by the smoke as the reactor was not covered with any form of hard containment vessel (World Nuclear Association, 2011). The fire which resulted sent a cloud of highly radioactive smoke into the air and over a large geographical coverage including Pripyat. This accident happened during an experiment that was planned to test a potential safety emergency core cooling aspect which happened during routine shutdown procedure. Nuclear power reactors require cooling even after being shut down. The management of the reactor wished to carry out an important experiment regarding safety of reactor 4. At the moment of the experiment at Chernobyl reactor, the power backup from generators were not well designed as they were expected to have a 15 seconds interval to pump water cooling water into the reactor. Unfortunately, this target had not been achieved and they were taking between 60-75 seconds to provide effective power of 5.5 MW to run one major cooling water pump to full potential. The lapse time was considered unsafe as it would lead to the heating up of the reactor causing disaster. The plant had been running for 2 years with this shortcoming which was a breach of safety rule. The previous tests carried out to correct this mistake were unsuccessful. The station managers presumably wanted to correct this issue at the first opportunity, which is probably the reason why they carried on with the test amid serious problems being experienced and is the reason why procedural approval for the test was not obtained from the Soviet nuclear regulator despite the presence of a representative at the complex 4 reactor (World Nuclear Association, 2011). In addition, it is believed that the night staff that later came to execute the experiment after the day’s attempt being interrupted by loss of power supply, were not ready for the experiment. They were not familiar with the procedures laid down for the experiment. Day time shift workers were the one that were familiar with the experiment. Therefore, when there was a problem, the workers at one point continued to insert metal rods in an effort to restore the system. This is believed to have fueled the situation from bad to worse hence the explosion. The effort to contain the disaster involved more than half a million workers and cost about 18 million rubles which crippled the Soviet economy. Two workers died instantly from the explosion while several others were affected later. Since the occurrence of the accident in 1986 to the year 2000 an estimated 350,400 people from the most hit areas of Russia, Ukraine, and Belarus were evacuated and resettled. About 60 percent of the fallout is said to have been in Belarus. The affected countries, Russia, Ukraine and Belarus have been overwhelmed by the burden by the healthcare and decontamination costs that have been continuing since the incidence. According to the International Atomic Energy Agency the actual number of deaths from the accident varies significantly. The number of deaths attributed directly to the accident is 31 all among the workers in the plant reactor and emergency workers. Estimates from the World Health Organization puts the number of deaths at around 4000 civilians while the association of Concerned scientists estimate the effect to the broader population to hit 50000 cancer cases causing over 25000 cancer deaths. Comparison and contrast between the two accidents The two accidents, the Chernobyl accident and the Three Mile Island accident are similar in a number of ways. First they both involve nuclear reactors. The two accidents are also attributed to the design of the nuclear reactors. In the case of the Three Mile Island in the United States, the reactor was not well covered with a hard containment and there was also an issue of coordination in the system whereby the computer interface did not display all the processes as required (Walker, 2004). When the valve failed to close, the operator was not able to realize due to system failure. Consequently, in the Chernobyl incident, design played a significant role in the accident. The interval between the power lapses (time interval between power failure and generator power to move the pump to the maximum speed for effective cooling) was not controlled to the minimal requirement of 15-20 seconds despite the plant having run for 2 years without this important aspect of safety. The time lapse was very high running up to 75 seconds. This mistake had been corrected several times without success. Consequently, the workers and firefighter in the Chernobyl MTI-2 plant responded to the accident by pouring water to the plant to cool it down. They did not understand the extent and the danger that they were exposing themselves to (Dyatlov, 2003). As a result several of them suffered radiation attack and died weeks later from the radiation they exposed themselves to. This shows that they did not have adequate safety measures and training to deal with the disaster. The role of human error is also prevalent in the two accidents. In the first accident involving Three Mile Island Nuclear Power Plant, there was an aspect of human fault. The staff that controlled the plant were said to be less experienced on the operation of a nuclear plant. This was evident in the way the operators ignored the alarm bells and the light flashes and just made assumptions that there was a minor problem with the coolant (Walker, 2004). Since the computer system was not also showing the errors in the core of the coolant, the operator relied on the level of water in the pressurizer which suggested that there was still more water. Hence the operator assumed that the coolant had sufficient water which led him to let go of excess water. This made the reactor to overheat as there was no sufficient water for cooling the reactor. It is very clear that, the human error in this case was prominent to cause the accident. The two accidents are also linked with the leak of harmful radiation. Radiation was released to the environment in both cases and evacuation was done in both areas. However, the Three Mile Island accident was not as serious as the Chernobyl disaster. The main difference in the two accidents is the seriousness of the accident. Even though the Three Mile Island accident is termed as the worst commercial nuclear power accident in the US, it cannot be compared to the Chernobyl accident. Chernobyl accident involved an explosion that left massive of nuclear radiation into the environment affecting a massive area in Eastern Europe and Russia. The countries affected include Russia, Ukraine Belarus (Dyatlov, 2003). Evacuation took quite a long time up to year 2000 about 350400 people had been evacuated and resettled from the affected areas. In the Three Mile Island accident in Pennsylvania, there was no explosion or fire hence there was very minimal radiation released to the air. Evacuation was done within 5 miles radius from the plant and targeted pregnant women and pre-school children. Consequently there was no death reported or associated with the accident at Three Mile Island. The radiation was too minimal to cause any harm. In the case of Chernobyl disaster, 2 people died instantly from the explosion and about 30 more died a few weeks from the radiation. Several others continue to suffer from the effects of the radiation attributed to the Chernobyl disaster. Could the later incident have been avoided if the lessons from the first incident would have been acted upon? The first incident happened in 1979 in the United States at Three Mile Island Nuclear Power Plant. The mistakes that led to the accident were very clear and the Nuclear Regulatory Commission used this incident to formulate new policies and tightened the requisites for licensing of nuclear plants including training of the workers. These measures made the Three Mile Island a world class nuclear plant which has never experienced any hiccup ever since (World Nuclear Association, February 2012). The later incident in Chernobyl occurred 6 years later. The same mistakes of design and human error were evident in the accident which is one of the two most serious nuclear accidents in the world. If the lessons learnt from the former disaster in the US were considered in other industries internationally including at Chernobyl, the accident would not have occurred. The issues are mainly plant or reactor design and human fault. This could have prevented the losses that were caused by the Chernobyl disaster. Possibility of another nuclear accident Nuclear power plants are very vulnerable and there is a high possibility that nuclear accidents can be repeated. Despite most of the hazards being termed as “Beyond Design basis Event” such as those triggered by natural calamities such as earthquake and tsunami, like nuclear meltdown that occurred in Japan at Fukushima No. 1 Nuclear power plant on March 2011, the issue of design and human fault are still likely to cause nuclear plant disasters (Stephanie, 2011). This is mainly because of the issue of transparency and ethics associated with nuclear generation. Most of the plants are established with lots of secrecy such as in Iran and it is very difficult to establish exactly what goes on inside these containment buildings. Therefore the role of Nuclear Regulatory Authority may not be realized in regulating all the nuclear power plants. Political issues are also a significant hindrance to safety of nuclear power plants. Issues concerning nuclear plants are surrounded by controversy and political interference all over the world which may put innocent people at risk of hazardous plants. Conclusion Nuclear power plants are sensitive to safety issues. The occurrence of various nuclear power plant accidents such as the Three Mile Island accident in the US in 1979 and the Chernobyl disaster of 1986 have proved the seriousness related to nuclear plants. The two accidents are similar in various ways including being caused by faulty design and human mistakes. They involved nuclear meltdown that caused evacuation at different levels. Several lessons were learnt from the two disasters and the second disaster could definitely be avoided if lessons from the first disaster were considered. Nevertheless there is still likelihood of occurrence of similar accidents due to the controversy and ethics issues surrounding the establishment and running of nuclear power plants. References Dyatlov, A. 2003. Chernobyl. How did it happen? Nauchtechlitizdat: Moscow. Nuclear Regulatory Commission, March 2011. Backgrounder on the Three Mile Island Accident, retrieved February 28, 2012 Stephanie C. March 19, 2011. "Nuclear power is on trial". CNN.com. Walker, J. 2004. Three Mile Island: A Nuclear Crisis in Historical Perspective. Berkeley: University of California Press. World Nuclear Association February 2012. Safety of Nuclear Power Reactors retrieved February 28, 2012 < http://www.world-nuclear.org/info/inf06.html> World Nuclear Association January 2012. Three Mile Island Accident, retrieved February 27, 2012 http://www.world-nuclear.org/info/inf36.html World Nuclear Association September 2011. The Chernobyl Disaster 1986, retrieved February 27, 2012 < http://www.world-nuclear.org/info/chernobyl/inf07.html> Read More